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Rubber

Rubber

:This article is about the material rubber, for other uses see Rubber (disambiguation) Rubber is an elastic hydrocarbon polymer which occurs as a milky emulsion (known as latex) in the sap of a number of plants but can also be produced synthetically. The major commercial source of natural latex used to create rubber is the Para rubber tree, Hevea brasiliensis (Euphorbiaceae). This is largely because it responds to wounding by producing more latex. Other plants containing latex include figs (Ficus elastica), euphorbias, and the common dandelion. Although these have not been major sources of rubber, Germany attempted to use such sources during World War II when it was cut off from rubber supplies. These attempts were later supplanted by the development of synthetic rubber. Its density is 920 kg/m³. density In places like Kerala, where coconuts are in abundance, the shell of half a coconut is used as the collection container for the latex. The shells are attached to the tree via a short sharp stick and the latex drips down into it overnight. This usually produces latex up to a level of half to three quarters of the shell. The latex from multiple trees are then poured into flat pans and this is mixed with formic acid, which serves as a coagulant. After a few hours, the very wet sheets of rubber are wrung out by putting them through a press before they are sent onto factories where vulcanization and further processing is done. Aside from a few natural product impurities, natural rubber is essentially a polymer of isoprene units, a hydrocarbon diene monomer. Synthetic rubber can be made as a polymer of isoprene or various other monomers. Rubber is believed to have been named by Joseph Priestley, who discovered in 1770 that dried latex rubbed out pencil marks. The material properties of rubber make it an elastomer.

History

In its native Central America and South America, rubber has been collected for a long time. The Mesoamerican civilizations used rubber mostly from Castilla elastica. The Ancient Mesoamericans had a ball game using rubber balls (see: Mesoamerican ballgame), and a few Pre-Columbian rubber balls have been found (always in sites that were flooded under fresh water), the earliest dating to about 1600 BCE. According to Bernal Díaz del Castillo, the Spanish Conquistadores were so astounded by the vigorous bouncing of the rubber balls of the Aztecs that they wondered if the balls were enchanted by evil spirits. The Maya also made a type of temporary rubber shoe by dipping their feet into a latex mixture. Rubber was used in various other contexts, such as strips to hold stone and metal tools to wooden handles, and padding for the tool handles. While the ancient Mesoamericans did not have vulcanization, they developed organic methods of processing the rubber with similar results, mixing the raw latex with various saps and juices of other vines, particularly Ipomoea alba, a species of Morning glory. In Brazil the natives understood the use of rubber to make water-resistant cloth. A story says that the first European to return to Portugal from Brazil with samples of such water-repellent rubberized cloth so shocked people that he was brought to court on the charge of witchcraft. Portugal When samples of rubber first arrived in England, it was observed that a piece of the material was extremely good for rubbing out pencil marks on paper. This was the origin of the material's English name of 'rubber'. Blocks of the material are still used for this purpose, and known as 'rubbers' in British English, causing occasional amusement to speakers of American English, to whom a 'rubber' is a condom (usually made from latex). (American English uses 'eraser' to refer to the rubber block.) The para rubber tree initially grew in South America, where it was the main source of what limited amount of latex rubber was consumed during much of the 19th century. About 100 years ago, the Congo Free State in Africa was a significant source of natural rubber latex, mostly gathered by forced labor. The Congo Free State was forged and ruled as a personal colony by the Belgian King Leopold II where millions of Africans died as a result of lust for rubber and rubber profits. After repeated efforts (see Henry Wickham) rubber was successfully cultivated in Southeast Asia, where it is now widely grown. Rubber, natural or synthetic substance characterized by elasticity, water repellence, and electrical resistance. Natural rubber is obtained from the milky white fluid called latex, found in many plants; synthetic rubbers are produced from unsaturated hydrocarbons.

Current sources of rubber

Today Asia is the main source of natural rubber. Over half of the rubber used today is synthetic, but several million tonnes of natural rubber are still produced annually, and is still essential for some industries, including automotive and military. Hypoallergenic rubber can be made from Guayule. Early experiments in the development of synthetic rubber led to the invention of Silly Putty. Natural rubber is often vulcanized, a process by which the rubber is heated and sulfur is added to improve resilience and elasticity. The process of vulcanization greatly improved the durability and utility of rubber from the 1830s on. The successful development of vulcanisation is most closely associated with Charles Goodyear. Carbon black is often used as an additive to rubber to improve its strength, especially in vehicle tires.

External links

- [http://www.irrdb.com/IRRDB/NaturalRubber/Default.htm International Rubber Research & Development Board]
- [http://astlettrubber.com/bulletins.shtml Astlett Rubber Inc]
- [http://www.sicom.com.sg Singapore Commodity Exchange] Category:Natural materials Category:Organic polymers Category:Terpenes and terpenoids ja:ゴム

Rubber (disambiguation)

Rubber has several uses including:
- The material rubber, originally from the rubber tree
- The rubbery domain of polymers
- A rubber in contract bridge is two 100-point games
- In baseball the rubber is the thin white slab on the pitcher's mound from which the pitcher throws, or at times the pitcher's mound in general
- A slang term for a condom
- The British term for an eraser
- In some sports, especially cricket, a series of matches between two (usually international) sides is known as a rubber.
- Rubber is a solo album by former Guns N' Roses guitarist Gilby Clarke

Hydrocarbon

In chemistry, a hydrocarbon is any chemical compound that consists only of the elements carbon (C) and hydrogen (H). They all contain a carbon backbone, called a carbon skeleton, and have hydrogen atoms attached to that backbone. (Often the term is used as a shortened form of the term aliphatic hydrocarbon.)

Examples

aliphaticFor example, methane (swamp/marsh gas) is a hydrocarbon with one carbon atom and four hydrogen atoms: CH₄. Ethane is a hydrocarbon (more specifically, an alkane) consisting of two carbon atoms held together with a single bond, each with three hydrogen atoms bonded: C₂H₆. Propane has three C atoms (C₃H₈) and so on (C_nH_2n+2).

Three types of hydrocarbons

PropaneThere are essentially three types of hydrocarbons: #aromatic hydrocarbons, which have at least one aromatic ring #saturated hydrocarbons, also known as alkanes, which don't have double, triple or aromatic bonds #unsaturated hydrocarbons, which have one or more double or triple bonds between carbon atoms, are divided into: #
- alkenes #
- alkynes #
- dienes diene

The number of hydrogen atoms

The number of hydrogen atoms in hydrocarbons can be determined, if the number of carbon atoms is known, by using these following equations:
- Alkanes: C_nH_2n+2
- Alkenes: C_nH_2n (assuming only one double bond)
- Alkynes: C_nH_2n-2 (assuming only one triple bond) Each of these hydrocarbons must follow the 4-hydrogen rule which states that all carbon atoms must have the maximum number of hydrogen atoms that it can hold (the limit is four). Note, an extra bond removes 2 hydrogen atoms and only saturated hydrocarbons can attain the full four. This is because of the unique positions of the carbon's four electrons.

Molecular graph

Usually carbon backbone is represented as molecular graph in which only carbon atoms are represented as vertices and bonds as edges. Molecular graphs contain the structure of the hydrocarbon in which missing hydrogen atoms can be added in a unique way. Hydrocarbons are extensively studied in mathematical chemistry.

Petroleum

Liquid geologically-extracted hydrocarbons are referred to as petroleum (literally "rock oil") or mineral oil, while gaseous geologic hydrocarbons are referred to as natural gas. All are significant sources of fuel and raw materials as a feedstock for the production of organic chemicals and are commonly found in the Earth´s subsurface using the tools of petroleum geology. Oil reserves in sedimentary rocks are the principal source of hydrocarbons for the energy, transport and chemicals industries. The production of liquid hydrocarbon fuel from a number of sedimentary basins has been integral to modern energy development. Hydrocarbons are of prime economic importance because they encompass the constituents of the major fossil fuels (coal, petroleum, natural gas, etc.) and biofuels, as well as plastics, waxes, solvents and oils. In urban pollution, these components--along with NOx and sunlight--all contribute to the formation of tropospheric ozone.

Burning Hydrocarbons

Hydrocarbons are currently the main source of the world’s electric energy and heat sources (such as home heating) because of the energy produced when burnt. Hydrocarbons are all substances with low entropy (meaning they hold a lot of energy potential), which can be released and harnessed by burning them. Often this energy is used directly as heat such as in home heaters, which use either oil or natural gas. The hydrocarbon is burnt and the heat is used to heat water, which is then circulated in pipes around the building heating every room. A similar principle is used to create electric energy in power plants. Hydrocarbons (usually coal) are burnt and the energy released in this way is used to turn water in to steam, which is used to turn a turbine that generates energy much like a windmill does. In an ideal reaction the byproducts would be only water and carbon dioxide but because the coal is not pure or cleaned there are often many toxic byproducts such as mercury and arsenic. Also, incomplete combustion causes the production of carbon-monoxide which is toxic because it will bind with hemoglobin more readily than oxygen, so if it is breathed in oxygen can not be absorbed, causing suffocation. Clean coal technology is currently under development.

External links

- [http://www.gasresources.net/DisposalBioClaims.htm Dismissal of the Claims of a Biological Connection for Natural Petroleum.]
- [http://www.gasresources.net/Introduction.htm An introduction to the modern petroleum science, and to the Russian-Ukrainian theory of deep, abiotic petroleum origins.]
- [http://www.aapg.org/explorer/2002/11nov/abiogenic.cfm Abiogenic Gas Debate 11:2002 (EXPLORER)]

Polymer

Polymer is a generic term used to describe a very long molecule consisting of structural units and repeating units connected by covalent chemical bonds. The key feature that distinguishes polymers from other molecules is the repetition of many identical, similar, or complementary molecular subunits in these chains. These subunits, the monomers, are small molecules of low to moderate molecular weight, and are linked to each other during a chemical reaction called polymerization. Instead of being identical, similar monomers can have varying chemical substituents. The differences between monomers can affect properties such as solubility, flexibility, and strength. In proteins, these differences give the polymer the ability to adopt a biologically-active conformation in preference to others. (See self-assembly.) Identical monomers with nonreactive side groups result in a polymer chain that will tend to adopt a random coil conformation, as described by an ideal chain mathematical model. Although most polymers are organic, with carbon-based monomers, there are also inorganic polymers; for example, the silicones, with a backbone of alternating silicon and oxygen atoms. Polymers are typically classified according to three main groups:
- thermoplastics (linear or branched chains)
- thermosets (crosslinked chains)
- elastomers The term polymer covers a large, diverse group of molecules, including substances from proteins to stiff, high-strength Kevlar fibres. For example, the formation of polyethene (also called polyethylene) involves thousands of ethene molecules bonded together to form a straight (or branched) chain of repeating -CH₂-CH₂- units (with a -CH₃ at each terminal): image:example_polymerization.png Polymers are often named in terms of the monomer from which they are made. Because it is synthesized from ethene in a process during which all the double bonds in the vinyl monomers are lost, polyethene has the unsaturated structure: image:polyethene_monomer.png If it were named according to its final structure, it would have the alkane designation "polyethane". Because synthetic polymer formation is governed by random assembly from the constituent monomers, polymer chains within a solution or substance are generally not of equal length. This is unlike basic, smaller molecules in which every atom is stoichiometrically accounted for, and each molecule has a set molecular mass. An ensemble of differing chain lengths, often obeying a normal (Gaussian) distribution, occurs because polymer chains terminate during polymerization after random amounts of chain lengthening (propagation). Proteins are polymers of amino acids. Typically, hundreds of the (nominally) twenty different amino acid monomers make up a protein chain, and the sequence of monomers determines its shape and biological function. (There are also shorter oligopeptides which function as hormones.) But there are active regions, surrounded by, as is believed now (Aug 2003), structural regions, whose sole role is to expose the active regions. (There may be more than one on a given protein.) So the exact sequence of amino acids in certain parts of the chains can vary from species to species, and even given mutations within a species, so long as the active sites are properly accessible. Also, whereas the formation of polyethylene occurs spontaneously under the right conditions, the synthesis of biopolymers such as proteins and nucleic acids requires the help of enzyme catalysts, substances that facilitate and accelerate reactions. Unlike synthetic polymers, these biopolymers have exact sequences and lengths. (This does not include the carbohydrates.) Since the 1950s, catalysts have also revolutionised the development of synthetic polymers. By allowing more careful control over polymerization reactions, polymers with new properties, such as the ability to emit coloured light, have been manufactured. The characterization of a polymer requires several parameters which need to be specified. This is because a polymer actually consists of a statistical distribution of chains of varying lengths, and each chain consists of monomer residues which affect its properties. Some of these parameters are described below.

Physical properties of polymers

Physical properties of polymers include the degree of polymerization, molar mass distribution, crystallinity, as well as the thermal phase transitions:
- T_g, glass transition temperature
- T_m, melting point (for thermoplastics).

Branching

During the propagation of polymer chains, branching can occur. In free-radical polymerization, this occurs when a chain curls back and bonds to an earlier part of the chain. When this curl breaks, it leaves small chains sprouting from the main carbon backbone. Branched carbon chains cannot line up as close to each other as unbranched chains can. This causes less contact between atoms of different chains, and fewer opportunities for induced or permanent dipoles to occur. A low density results from the chains being further apart. Lower melting points and tensile strengths are evident, because the intermolecular bonds are weaker and require less energy to break. Besides branching, polymers can have other topologies: linear, network (cross-linked 3D structure), IPN (integrated polymer network), comb, or star as well as dendrimer and hyperbranched structures.

Stereoregularity

Stereoregularity or tacticity describes the isomeric arrangement of functional groups on the backbone of carbon chains. Isotactic chains are defined as having substituent groups aligned in one direction. This enables them to line up close to each other, creating crystalline areas and resulting in highly rigid polymers. In contrast, atactic chains have randomly aligned substituent groups. The chains do not fit together well and the intermolecular forces are low. This leads to a low density and tensile strength, but a high degree of flexibility. Syndiotactic substituent groups alternate regularly in opposite directions. Because of this regularity, syndiotactic chains can position themselves close to each other, though not as close as isotactic polymers. Syndiotactic polymers have better impact strength than isotactic polymers because of the higher flexibility resulting from their weaker intermolecular forces.

Constitution of polymers

Copolymers

Copolymerization with two or more different monomers results in chains with varied properties. There are twenty amino acid monomers whose sequence results in different shapes and functions of protein chains. Copolymerising ethene with small amounts of 1-hexene (or 4-methyl-1-pentene) is one way to form linear low-density polyethene (LLDPE). (See polyethylene.) The C₄ branches resulting from the hexene lower the density and prevent large crystalline regions from forming within the polymer, as they do in HDPE. This means that LLDPE can withstand strong tearing forces whilst remaining flexible. A block copolymer is formed when the reaction is carried out in a stepwise manner, leading to a structure with long sequences or blocks of one monomer alternating with long sequences of the other. There are also graft copolymers, in which entire chains of one kind (e.g., polystyrene) are made to grow out of the sides of chains of another kind (e.g., polybutadiene), resulting in a product that is less brittle and more impact-resistant. Thus, block and graft copolymers can combine the useful properties of both constituents and often behave as quasi-two-phase systems. The following is an example of step-growth polymerization, or condensation polymerization, in which a molecule of water is given off and nylon is formed. The properties of the nylon are determined by the R and R' groups in the monomers used. nylon The first commercially successful, completely synthetic polymer was nylon 6,6, with alkane chains R = 4C (adipic acid) and R' = 6C (hexamethylene diamine). Including the two carboxyl carbons, each monomer donates 6 carbons; hence the name. In naming nylons, the number of carbons from the diamine is given first and the number from the diacid second. Kevlar is an aromatic nylon in which both R and R' are benzene rings. Copolymers illustrate the point that the repeating unit in a polymer, such as a nylon, polyester or polyurethane, is often made up of two (or more) monomers.

Chemical properties of polymers

Intermolecular forces

The attractive forces between polymer chains play a large part in determining a polymer's properties. Because polymer chains are so long, these interchain forces are amplified far beyond the attractions between conventional molecules. Also, longer chains are more amorphous (randomly oriented). Polymers can be visualised as tangled spaghetti chains - pulling any one spaghetti strand out is a lot harder the more tangled the chains are. These stronger forces typically result in high tensile strength and melting points. The intermolecular forces in polymers are determined by dipoles in the monomer units. Polymers containing amide groups can form hydrogen bonds between adjacent chains; the positive hydrogen atoms in N-H groups of one chain are strongly attracted to the oxygen atoms in C=O groups on another. These strong hydrogen bonds result in, for example, the high tensile strength and melting point of kevlar. Polyesters have dipole-dipole bonding between the oxygen atoms in C=O groups and the hydrogen atoms in H-C groups. Dipole bonding is not as strong as hydrogen bonding, so ethene's melting point and strength are lower than kevlar's, but polyesters have greater flexibility. Ethene, however, has no permanent dipole. The attractive forces between polyethene chains arise from weak van der Waals forces. Molecules can be thought of as being surrounded by a cloud of negative electrons. As two polymer chains approach, their electron clouds repel one another. This has the effect of lowering the electron density on one side of a polymer chain, creating a slight positive dipole on this side. This charge is enough to actually attract the second polymer chain. Van der Waals forces are quite weak, however, so polyethene melts at low temperatures.

Polymer characterization

A variety of lab techniques are used to determine the properties of polymers. Techniques such as wide angle X-ray scattering, small angle X-ray scattering, and small angle neutron scattering are used to determine the crystalline structure of polymers. Gel permeation chromatography is used to determine the number average molecular weight, weight average molecular weight, and polydispersity. FTIR is used to determine composition. Thermal properties such as the glass transition temperature and melting point can be determined by differential scanning calorimetry and dynamic mechanical analysis. Pyrolysis followed by analysis of the fragments is one more technique for determining the possible structure of the polymer. Polymer known as polymer substrate is used for everyday banknotes in Australia and New Zealand, and is also used in commemorative notes in other countries. See also: Polymerization -- Biopolymer -- Condensation polymer -- Addition polymer -- Synthetic polymer -- Glass transition temperature -- Polymer physics -- Important publications in polymer chemistry

External links

- [http://www.borealisgroup.com/public/dictionary/Dictionary.jsp Polymer dictionary]
- [http://www.vivamer.com/ Responsive Biopolymers for Drug Delivery and Imaging]
- [http://web.umr.edu/~wlf/ Polymer Chemistry Hypertext, Educational resource]
- [http://www.polychemistry.com/ Polymer Chemistry Innovations]
- [http://www.odcad.com/html/organicdevice_appearance1.HTM Materials for Organic devices]
- [http://www.pslc.ws/macrog/index.htm The Macrogalleria - a cyberwonderland of polymer fun!] Category:Polymers Category:Polymer chemistry ko:중합체 ms:Polimer ja:重合体 th:โพลีเมอร์

LaTeX

L^AT_EX, written as LaTeX in plain text, is a document preparation system for the TeX typesetting program. It offers programmable desktop publishing features and extensive facilities for automating most aspects of typesetting and desktop publishing, including numbering and cross-referencing, tables and figures, page layout, bibliographies, and much more. LaTeX was originally written in 1984 by Leslie Lamport and has become the dominant method for using TeX —few people write in plain TeX anymore. The current version is LaTeX2ε.

Pronunciation

LaTeX is usually pronounced "LAY-tech" or "LAH-tech" (IPA: , ), where ch represents the sound of ch in German Bach or Scottish loch: the last character in the name is actually a capital chi, as the name of TeX derives from the Greek τεχνη (skill, art, technique). While TeX's creator Donald Knuth promoted the "tech" pronunciation, Lamport has said he doesn't favor or deprecate any pronunciation for LaTeX. It is traditionally printed with the special typographical logo shown on this page. In media where the logo cannot be precisely reproduced in running text, the word is typically given the unique capitalization LaTeX to avoid confusion with the word "latex".

The typesetting system

latex.]] LaTeX is based on the idea that authors should be able to concentrate on writing within the logical structure of their document, rather than spending their time on the details of formatting. It encourages the separation of formatting from content, whilst still allowing manual typesetting adjustments where needed. By keeping the formatting details in a separate file from the text, it is often regarded as superior to word processors and most other desktop publishing systems, which allow trivially easy visual layout changes but tend to intertwine content and form so tightly that consistency and automation are often difficult. LaTeX also provides great flexibility in formatting while maintaining the identity of structure, which purely structural systems like SGML and XML do not directly address. LaTeX can be arbitrarily extended by using the underlying macro language for developing custom formats. For example, there are numerous commercial implementations of the whole TeX system (which includes LaTeX), and vendors may offer extra features like phone support and additional typefaces. LyX is a free visual document processor that uses LaTeX for a back-end. TeXmacs is a free, WYSIWYG editor with similar functionalities as LaTeX, but a different typesetting engine. A number of popular commercial DTP systems use modified versions of the original TeX typesetting engine. The recent rise in popularity of XML systems and the demand for large-scale batch production of publication-quality typesetting from such sources has seen a steady increase in the use of LaTeX. The example below shows an example of a LaTeX input (left) and output (right): [http://sciencesoft.at/index.jsp?link=latex&lang=en&wiki=1 Online LaTex], which uses this example.

Community

batch production LaTeX was originally most commonly used by mathematicians and scientists, amongst whom it remains the favored tool for writing papers, preprints, and books. Because of the underlying TeX system, originally developed for documents with mathematics, laying out mathematical expressions is considered to be easier, and the resulting typesetting of higher quality, than any competing document-processing systems. Many scientific journals and other publishers provide free LaTeX packages which implement their "in-house" typesetting styles. The popularity of LaTeX in the technical and academic communities is perhaps partly due to its early availability on Unix systems, and the comparative unavailability of competing word processors on those platforms until recently. But from an early stage LaTeX was available on a wider range of hardware and software than any other program, and versions are now available for almost any system from PDAs to desktop PCs to supercomputers. LaTeX is less popular than mainstream desktop publishing software outside the technical communities for several reasons. It is regarded as hard to learn for people with no previous experience of markup languages. Although it is very easy to customise the appearance of articles, books, and reports, using only a handful of instructions, it remains basically a typesetter for automating document production, not a manual page design program, so performing complex visual layouts incorporating multiple images is difficult. Another barrier to usage for many is the asynchronous interface used in most free versions, where editing is done in a different window from the typeset display. Inverse search can be used to bridge this problem partially. Several commercial implementations, however, use a synchronous typographic display like other DTP systems (as does the non-commercial and open source LyX). Alternatively, GNU TeXmacs is a free WYSIWYG editor which offers features similar to LaTeX, but is based on a different typesetting engine.

Licensing issues

LaTeX is free software. It has a peculiar license called LPPL, not compatible with the GNU General Public License, that allows redistribution and modification, but requires that modified files carry a modified filename. This ensures that files that depend on other files will produce the expected behavior and avoids problems similar to DLL hell. A new version of the LPPL that will be compatible with the GPL is in the works.

Frontends

Because LaTeX markup code can be hard to remember and/or time consuming to learn, there are a few front ends to help:
- Kile: IDE designed mainly for KDE ([http://kile.sourceforge.net/ homepage]).
- LEd: A free environment for rapid TeX/LaTeX document development under MS Windows ([http://www.latexeditor.org homepage]).
- LyX: WYSIWYM (What you see is what you mean) IDE ([http://www.lyx.org/ homepage]).
- Scientific Letter: Commerce mail software with export to TeX/LaTeX ([http://www.sciletter.com/ homepage]).
- Texmaker: Free cross-platform LaTeX editor. Runs on Windows, Mac OS X and Unix (GNU/Linux binary). Is released under the GPL license ([http://www.xm1math.net/texmaker/index.html homepage]).
- TeXnicCenter: IDE designed for MS Windows users under GPL ([http://www.toolscenter.org/ homepage]).
- TeXShop: A free front end for Mac OS X, with editor and output window ([http://www.uoregon.edu/~koch/texshop/texshop.html homepage]).
- WebTex: A free MiKTeX/CGI driven web front end ([http://dev.baywifi.com/latex/ homepage]).
- WinEdt: Shareware IDE for Windows 9x/NT4.0/2000/XP ([http://www.winedt.com/ homepage]).
- WinShell: Freeware IDE for Windows 9x/NT4.0/2000/XP ([http://www.winshell.de/ homepage]).

External links

Community

- [http://www.latex-project.org/ Official LaTeX project site] web site for open development of LaTeX (you can also obtain a CVS snapshot of LaTeX3, the next version of LaTeX which is not yet released)
- [http://www.tug.org/ The TeX Users Group]
- [news:comp.text.tex comp.text.tex]. A Usenet newsgroup for (La)TeX related questions, comp.text.tex is an invaluable resource for (La)TeX. Search the archives with [http://groups.google.com/group/comp.text.tex Google Groups] before posting.
- [irc://irc.freenode.net/#latex #latex] IRC chat room on Freenode

Periodicals

- The PracTeX Journal. Online journal of the TeX Users Group.
- TUGBoat. Print journal of the TeX Users Group.

Tutorials/FAQs

- [http://www.lecb.ncifcrf.gov/~toms/latexforbeginners.html LaTeX for Beginners]
- [http://people.ee.ethz.ch/~oetiker/lshort/lshort.pdf The Not So Short Introduction to LaTeX2e], or LaTeX2e in 133 minutes (2.21 MiB PDF file).
- [http://www.tex.ac.uk/cgi-bin/texfaq2html?introduction=yes The UK TeX FAQ] List of questions and answers that are frequently posted at comp.text.tex.
- [http://www.ctan.org/tex-archive/info/beginlatex/ Formatting Information] Online book for beginners available in [http://www.ctan.org/tex-archive/info/beginlatex/html/index.html HTML] and [http://www.ctan.org/tex-archive/info/beginlatex/beginlatex-3.6.pdf PDF]
- [http://www.maths.tcd.ie/~dwilkins/LaTeXPrimer/ LaTeX Primer] A basic guide to LaTeX.
- [http://www.tug.org.in/tutorials.html Tutorials in LaTeX] Free manual distributed by the India TeX Users Group (TUG).
- [ftp://ftp.ams.org/pub/tex/doc/amsmath/short-math-guide.pdf The AMS Short Math Guide for LaTeX] A concise summary of math formula typesetting features (PDF file).
- [http://www.rna.nl/tex.html TeX on Mac OS X] Guide to using TeX and LaTeX on a Mac.
- [http://www-h.eng.cam.ac.uk/help/tpl/textprocessing/ Text Processing using LaTeX]
- [http://tex.loria.fr/index.html The (La)TeX encyclopaedia]
- [http://www.giss.nasa.gov/latex/ Hypertext Help with LaTeX]
- [http://www-h.eng.cam.ac.uk/help/tpl/textprocessing/ltxprimer-1.0.pdf LaTeX Tutorials: a Primer] (PDF file)
- [http://www.andy-roberts.net/misc/latex/index.html Getting to Grips with LaTeX] Latex tutorials taking you from the very basics towards more advanced topics.
- [http://www.math.auc.dk/~dethlef/Tips/preparation.html LaTeX, Emacs etc. for your PC] A useful and step-by-step guide to getting Miktex and Emacs working together on a Windows PC.

Add-on Packages

- [http://latex-beamer.sourceforge.net/ LaTeX-beamer] Create sophisticated, structured presentations and slides using LaTeX.
- [http://www.ctan.org/tex-archive/macros/latex/contrib/powerdot/ powerdot] Another very good class for presentations.
- [http://www.phil.cam.ac.uk/teaching_staff/Smith/LaTeX/nd.html bussproofs.sty (and others)] Setting natural deduction tree proofs.
- [http://www.mcnabbs.org/andrew/linux/latexres/ Making a Resume in LaTeX] A LaTeX template with instructions for making an easily-maintained resume.
- [http://latex2rtf.sourceforge.net/ LaTeX2RTF] Translator program which is intended to convert a LaTeX document into the RTF format.

Reference

- [http://www.ctan.org The Comprehensive TeX Archive Network] Latest (La)TeX-related packages and software
- [http://www.tug.org/tds/ TeX Directory Structure], used by many (La)TeX distributions
- [http://www.math.missouri.edu/~stephen/naturalmath/ Natural Math] converts natural language math formulas to LaTeX representation
- [http://www.ctan.org/tex-archive/info/l2tabu/english/l2tabuen.pdf Obsolete packages and commands]
- [http://www.miktex.org/ MiKTeX] A popular and up-to-date TeX (including LaTeX) implementation for Windows.
- . The Companion is an excellent resource for intermediate to advanced LaTeX users. For those already somewhat familiar with LaTeX, this is probably the single most useful available book on the subject. The book website has the complete Table of Contents and a sample chapter available for download. Category:Domain-specific programming languages Category:Free software Category:Page description languages Category:TeX Category:Typesetting programming languages Category:Typesetting ja:LaTeX ko:LaTeX

Para rubber tree

:This article is about the main commercial source of latex. For the common ornamental plant, see Ficus elastica. The Pará rubber tree (Hevea brasiliensis), often simply called rubber tree, is a tree belonging to the family Euphorbiaceae and the most important member of the genus Hevea. It is of major economical importance because its sap-like extract (not sap however) (known as latex) can be collected and is the primary source of natural rubber. The tree can reach a height of over 30m. The white or yellow latex occurs in latex vessels in the bark, mostly outside the phloem. These vessel spiral up the tree in a righthanded spiral which forms an angle of about 30 degrees with the horizontal. Once the trees are 5-6 years old, the harvest can begin: incisions are made orthogonal to the latex vessels, just deep enough to tap the vessels without harming the tree's growth, and the sap is collected in small buckets. Older trees yield more latex. angle The Pará rubber tree initially grew only in Amazonia. Increasing demand and the discovery of the vulcanization procedure in 1839 lead to a boom in that region, enriching the cities of Manaus and Belém. The name of the tree derives from Pará, the Brazilian state that contains Belém. There had been an attempt made, in 1873, to grow rubber outside Brazil. After some effort, twelve seedlings were germinated at the Royal Botanic Gardens, Kew. These were sent to India for cultivation, but died. A second attempt was then made, some 70,000 seeds being sent to Kew in 1875. About 4% of these germinated, and in 1876 about 2000 seedlings were sent, in Wardian cases, to Ceylon, and 22 sent to the Botanic Gardens in Singapore. Once established outside its native country, rubber was extensively propagated in the British colonies. By 1898, a rubber plantation had been established in Malaya, and today most rubber tree plantations are in Southeast Asia and some also in tropical Africa. Efforts to cultivate the tree in its native South America were unsatisfactory.

Synonyms

The genus Hevea is also known as:
- Caoutchoua J.F.Gmel.
- Micrandra Benn. & R.Br.
- Siphonanthus Schreb. ex Baill.
- Siphonia D.Richard ex Schreb. Schreb. Category:Euphorbiaceae simple:Rubber tree

Fig

About 800, including:
Ficus altissima
Ficus americana
Ficus aurea
Ficus benghalensis - Indian Banyan
Ficus benjamina - Weeping Fig
Ficus broadwayi
Ficus carica - Common Fig
Ficus citrifolia
Ficus drupacea
Ficus elastica
Ficus godeffroyi
Ficus grenadensis
Ficus hartii
Ficus lyrata
Ficus macbrideii
Ficus macrophylla - Moreton Bay Fig
Ficus microcarpa - Chinese Banyan
Ficus nota
Ficus obtusifolia
Ficus palmata
Ficus prolixa
Ficus pumila
Ficus racemosa
Ficus religiosa - Sacred Fig
Ficus rubiginosa - Port Jackson Fig
Ficus stahlii
Ficus sycomorus
Ficus thonningii
Ficus tinctoria
Ficus tobagensis
Ficus triangularis
Ficus trigonata
Ficus ulmifolia
Ficus vogelii Figs (Ficus) are a genus of about 800 species of woody trees, shrubs and vines in the family Moraceae, native throughout the tropics with a few species extending into the warm temperate zone. temperate The genus includes one species, the Common Fig F. carica, that produces a commercial fruit called a fig; the fruit of many other species are edible though not widely consumed. Other examples of figs include the banyans and the Sacred Fig (Peepul or Bo) tree. Most species are evergreen, while those from temperate areas, and areas with a long dry season, are deciduous. A fig fruit is derived from a specially adapted flower. The fruit (an accessory fruit called a syconium) has a bulbous shape with a small opening (the ostiole) in the end and a hollow area inside lined with small red edible seeds. The fruit/flower is pollinated by small wasps that crawl through the opening to fertilise the fruit. Figs come in two sexes: hermaphrodite (called caprifigs because only goats eat them) and female. Fig wasps grow in caprifigs; when they mature, they mate, and the females leave in search of immature figs to lay their eggs in. When the wasp finds one, she pollinates the female flowers but will not lay eggs in the edible fig, only in the caprifig. Thus the edible fig ripens without any wasp frass in it. When a caprifig ripens, another caprifig must be ready to be pollinated. Tropical figs bear continuously, enabling fruit-eating animals to survive the time between masts. In temperate climes, wasps hibernate in figs, and there are distinct crops. Caprifigs have three crops per year; edible figs have two. The first of the two is small and is called breba; the breba figs are olynths. There is typically only one species of wasp capable of fertilizing the flowers of each species of fig, and therefore plantings of fig species outside of their native range results in effectively sterile individuals. For example, in Hawaii, some 60 species of figs have been introduced, but only four of the wasps that fertilize them have been introduced, so only four species of figs produce viable seeds there. Figs are also easily propagated from cuttings. An extraordinarily large self-rooted Wild Willowleaf Fig in South Africa is protected by the Wonderboom Nature Reserve. Michael Moore ran a ficus tree against Republican Congressman Rodney Frelinghuysen from New Jersey in the year 2000.

Symbolism

New Jersey In the Book of Jeremiah in the Old Testament rotten figs are used as a symbol for destruction, and in the New Testament Jesus rebukes an unfruitful fig tree. The Fig is one of the two sacred trees in Islam. Many Muslims consider Fig trees sacred. Because of the peculiar form of the flower of figs, ancient Indians regarded the fig as a flowerless tree. Buddhist and Hindu texts sometimes refer to 'seeking flowers in a fig tree' to indicate something that is pointless or impossible, or to indicate the total absence of some quality (compare the Australian English language expression 'why search for the bunyip?'). References to the flowers of a fig may also be used to indicate great rarity- roughly comparable to the English expression 'rare as hen's teeth'. Pāli scholar K.R. Norman collected references to fig flowers in the Pāli canon in his translation of the Samyutta Nikaya, as well as writing an article entitled Rare as Fig Flowers that was published with his collected papers by the Pāli Text Society.

External links

- [http://www.figweb.org/Ficus/index.htm Figweb] Major reference site for the genus Ficus
- [http://www.figweb.org/Interaction/Video/index.htm Video: Interaction of figs and fig wasps] Multi-award-winning documentary
- [http://www.thefruitpages.com/figs.shtml Fig Fruit Information]
- [http://www.hort.purdue.edu/newcrop/morton/fig.html Fruits of Warm Climates: Fig]
- [http://www.crfg.org/pubs/ff/fig.html California Rare Fruit Growers: Fig Fruit Facts]
- [http://www.nafex.org/figs.htm North American Fruit Explorers: Fig] Category:Accessory fruit Category:Moraceae Category: plant morphology ja:イチジク ko:무화과나무 simple:Fig

Euphorbia

:Selected species:
- Euphorbia aaron-rossii - Marble Canyon spurge
- Euphorbia acanthothamnos - Greek spiny spurge
- Euphorbia agraria - urban spurge
- Euphorbia albomarginata - rattlesnake weed
- Euphorbia alluaudii
- Euphorbia amygdaloides - wood spurge
- Euphorbia antisyphilitica - wax plant, candelilla
- Euphorbia bicolor - snow-on-the-prairie
- Euphorbia bilobata - blackseed spurge
- Euphorbia bifurcata - forked spurge
- Euphorbia biumbellata
- Euphorbia brachycera - horned spurge
- Euphorbia brittingeri
- Euphorbia caunculata - waterfall
- Euphorbia chamaesula - mountain spurge
- Euphorbia characias
- Euphorbia commutata - tinted woodland spurge
- Euphorbia coralloides - coral spurge
- Euphorbia corollata - flowering spurge
- Euphorbia cotinifolia - Mexican shrubby spurge, red spurge
- Euphorbia crenulata - Chinese caps
- Euphorbia cuphosperma
- Euphorbia curtisii - Curtis' spurge
- Euphorbia cyathophora - wild poinsettia
- Euphorbia cyparissias - cypress spurge
- Euphorbia damarana
- Euphorbia davidii - David's spurge
- Euphorbia dendroides - tree spurge
- Euphorbia dentata - toothed spurge
- Euphorbia discoidalis - summer spurge
- Euphorbia dulcis - sweet spurge
- Euphorbia epithymoides - cushion spurge
- Euphorbia eriantha - beetle spurge, Mexican pointsetta
- Euphorbia esula - leafy spurge
- Euphorbia exigua - dwarf spurge
- Euphorbia exserta - coastal sand spurge
- Euphorbia exstipulata - square-seed spurge
- Euphorbia falcata - sickle spurge
- Euphorbia floridana - greater Florida spurge
- Euphorbia fulgens - scarlet plume
- Euphorbia gaudichaudii
- Euphorbia gayeri
- Euphorbia graminea - grassleaf spurge
- Euphorbia haeleeleana - akoko, Kauai spurge
- Euphorbia helioscopia - Sun Spurge
- Euphorbia helleri - Heller's spurge
- Euphorbia hernariifolia
- Euphorbia heterophylla - painted euphorbia, kaliko
- Euphorbia hexagona - sixangle spurge
- Euphorbia hyberna - Irish spurge
- Euphorbia incisa - Mojave spurge
- Euphorbia innocua - velvet spurge
- Euphorbia inundata - Florida Pineland spurge
- Euphorbia ipecacuanhae - American ipecac
- Euphorbia josei - Jose spurge
- Euphorbia lactea - mottled spurge
- Euphorbia lancifolia - ixbut
- Euphorbia lathyris - caper spurge
- Euphorbia leucocephala - pascuita, white-laced euphorbia
- Euphorbia leuconeura
- Euphorbia longicruris - wedgeleaf spurge
- Euphorbia lucida - shining spurge
- Euphorbia macropus - Huachuca mountain spurge
- Euphorbia maculata - spotted spurge
- Euphorbia marginata - variegated spurge, white-margined spurge
- Euphorbia mellifera - honey spurge
- Euphorbia mercurialina - mercury spurge
- Euphorbia milii - crown-of-thorns, christplant
- Euphorbia misera - cliff spurge
- Euphorbia myrsinites - myrtle spurge
- Euphorbia nephradenia - Pana spurge
- Euphorbia neriifolia - Indian spurgetree
- Euphorbia nudicaulis
- Euphorbia oblongata - eggleaf spurge, oblong spurge
- Euphorbia oerstediana - West Indian spurge
- Euphorbia palmeri - wood spurge, woodland spurge
- Euphorbia palustris - marsh spurge
- Euphorbia paralias - sea spurge
- Euphorbia peplidion - low spurge
- Euphorbia peplis - purple spurge
- Euphorbia peplus - petty spurge
- Euphorbia petiolaris - Manchineel berry
- Euphorbia pinea
- Euphorbia pinetorum - Pineland spurge
- Euphorbia plagiantha
- Euphorbia platyphyllos - broad-leaved spurge
- Euphorbia poisonii
- Euphorbia polyphylla - lesser Florida spurge
- Euphorbia portlandica - Portland spurge
- Euphorbia pseudocactus - "Zigzag" Cactus
- Euphorbia pubentissima - false flowering spurge
- Euphorbia pulcherrima - poinsettia
- Euphorbia purpurea - Darlington's glade spurge
- Euphorbia radians - sun spurge
- Euphorbia resinifera - resin spurge
- Euphorbia rigida
- Euphorbia roemerana
- Euphorbia roemeriana - Roemer's spurge
- Euphorbia segetalis - grainfield spurge
- Euphorbia seguieriana
- Euphorbia serrata - serrated spurge, toothed spurge
- Euphorbia serrulata - upright spurge
- Euphorbia spathulata - roughpod spurge, warty spurge
- Euphorbia spinosa
- Euphorbia strictior - Panhandle spurge
- Euphorbia supine
- Euphorbia telephioides - Telephus spurge
- Euphorbia terracina - Geraldton carnation weed
- Euphorbia tetrapora - weak spurge
- Euphorbia texana - Texas spurge
- Euphorbia tirucalli - milkbush, Indian tree spurge
- Euphorbia trichotoma - sanddune spurge
- Euphorbia villosa
- Euphorbia virosa
- Euphorbia wrightii - Wright's spurge :See full list. Spurges (genus Euphorbia) are a very large and variable worldwide plant taxon, belonging to the namesake family (spurge family, or Euphorbiaceae). The name "Euphorbia" comes from a Greek surgeon named Euphorbus, who supposedly used the milky latex of these plants in his potions.

Description

The genus ranges from small trees, shrubs, vines to herbaceous plants. A significant percentage of these are succulent plant, some of which remarkably resemble cacti despite being unrelated, an example of convergent evolution. To the exception of a few species (i.e. Euphorbia hedytoides or Euphorbia curtisii), this genus is composed of monoecious species. Spurges have a highly specialized inflorescence: the cyathium, which are reduced unisexual flowers grouped into characteristic pseudanthia. It consists of a central pistillate flower surrounded by five groups of staminate flowers. All flowers are enclosed within an involucre with four marginal glands. The central flower develops before the surrounding male ones, thus each cyathium functions like a protogynous hermaphrodite flower. The glands of the cyathium usually produce nectar, and pollination is mainly zoophilous. Indeed, the cyathium looks so much like a hermaphrodite flower that Linnaeus and other authors interpreted it as a true flower. Lamarck however interpreted the cyathium as an inflorescence and this is now recognized. Spurges contain an acrid, poisonous milky latex, and some of them are armed with thorns. Most of the spurges yield powerful emetic and cathartic products.

Distribution

The genus is primarily found in the tropical regions of Africa and the Americas, but also in temperate zones. Succulent species are mostly originated from Africa and Madagascar.

Taxonomy

The genus Euphorbia is one of the largest and most complex genera of flowering plants; several botanists have made attempts to subdivide the genus into numerous smaller genera, but to date, these segregate genera have not generally been recognised:
- Ademo Post & Kuntze
- Adenopetalum Klotzsch & Garcke
- Adenorima Raf.
- Agaloma Raf.
- Aklemia Raf.
- Alectoroctonum Schltdl.
- Allobia Raf.
- Anisophyllum Haw.
- Anthacantha Lem.
- Aplarina Raf.
- Arthrothamnus Klotzsch & Garcke
- Bojera Raf.
- Ceraselma Wittst.
- Chamaesyce Raf.
- Characias Gray
- Chylogala Fourr.
- Ctenadena Prokh.
- Cyathophora Raf.
- Cystidospermum Prokh.
- Dactylanthes Haw.
- Dematra Raf.
- Desmonema Raf.
- Dichrophyllum Klotzsch & Garcke
- Dichylium Britton
- Diplocyathium Heinr.Schmidt
- Ditritra Raf.
- Endoisila Raf.
- Epurga Fourr.
- Esula (Pers.) Haw.
- Euforbia Ten., orth. var.
- Eumecanthus Klotzsch & Garcke
- Euphorbiastrum Klotzsch & Garcke
- Euphorbiodendron Millsp.
- Euphorbiopsis H.Lév.
- Euphorbium Hill
- Galarhoeus Haw.
- Kanopikon Raf.
- Kobiosis Raf.
- Lacanthis Raf.
- Lathyris Trew
- Lepadena Raf.
- Leptopus Klotzsch & Garcke
- Lophobios Raf.
- Lyciopsis (Boiss.) Schweinf.
- Medusea Haw.
- Nisomenes Raf.
- Ossifraga Rumph.
- Peccana Raf.
- Petalandra F.Muell. ex Boiss.
- Pleuradena Raf.
- Poinsettia Graham
- Pythius B.D.Jacks.
- Sclerocyathium Prokh.
- Sterigmanthe Klotzsch & Garcke
- Tithymalopsis Klotzsch & Garcke
- Tithymalus Gaertn.
- Torfasadis Raf.
- Treisia Haw.
- Tricherostigma Boiss.
- Tumalis Raf.
- Vallaris Raf.
- Xamesike Raf.
- Zalitea Raf.
- Zygophyllidium (Boiss.) Small

Reference

[http://www.itis.usda.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=28032 ITIS - Euphorbia]
as of 2002-07-13 Category:Euphorbiaceae
-

Synthetic rubber

Synthetic rubber is a type of artificially-made polymer material which acts as an elastomer. An elastomer is a material with the mechanical (or material) property that it can undergo much more elastic deformation under stress than most materials and still return to its previous size without permanent deformation. Synthetic rubber serves as a substitute for natural rubber in many cases, especially when improved material properties are needed. Natural rubber coming from latex is mostly polymerized isoprene with a small percentage of impurities in it. This will limit the range of properties available to it. Also, there are limitations on the proportions of cis and trans double bonds resulting from methods of polymerizing natural latex. This also limits the range of properties available to natural rubber, although addition of sulfur and vulcanization are used to improve the properties. However, synthetic rubber can be made from the polymerization of a variety of monomers including isoprene (2-methyl-1,3-butadiene), 1,3-butadiene, chloroprene (2-chloro-1,3-butadiene), and isobutylene (methylpropene) with a small percentage of isoprene for cross-linking. Furthermore, these and other monomers can be mixed in various desirable proportions to be copolymerized for a wide range of physical, mechanical, and chemical properties. The monomers can be produced pure and addition of impurities or additives can be controlled by design to give optimal properties. Polymerization of pure monomers can be better controlled to give a desired proportion of cis and trans double bonds. See also:
- Butyl rubber
- Styrene-butadiene Category:Polymers Category:Organic polymers

Formic acid

Formic acid (systematically called methanoic acid) is the simplest carboxylic acid. Its formula is C H₂ O₂ or HCOOH. Its structure is shown at right. In nature, it is found in the stings and bites of many insects of the order Hymenoptera, including bees and ants. It is also the principal irritant in the leaves of the stinging nettle. It is also a significant combustion product resulting from alternative fueled vehicles burning methanol (and ethanol, if contaminated with water) when mixed with gasoline. Its name comes from the Latin word for ant, formica, referring to its early isolation by the distillation of ant bodies. A chemical compound such as a salt from the neutralization of formic acid with a base, or an ester derived from formic acid, is referred to as formate (or methanoate). The formate ion has the formula HCOO^-.

History

As early as the 15th century, some alchemists and naturalists were aware that ant hills gave off an acidic vapor. The first person to describe the isolation of this substance (by the distillation of large numbers of dead ants) was the English naturalist John Ray, in 1671. It was first synthesized from hydrocyanic acid by the French chemist Joseph Gay-Lussac. In 1855, another French chemist, Marcellin Berthelot, developed a synthesis from carbon monoxide that is similar to that used today. In the chemical industry, formic acid was long considered a chemical compound of only minor industrial interest. In the late-1960s, however, significant quantities of it became available as a byproduct of acetic acid production. With its growing use as a preservative and antibacterial in livestock feed, it is now produced for its own sake.

Properties

Formic acid is miscible with water and most polar organic solvents, and somewhat soluble in hydrocarbons. In hydrocarbons and in the vapor phase, it actually consists of hydrogen-bonded dimers rather than individual molecules. In the gas phase, this hydrogen-bonding results in severe deviations from the ideal gas law. Liquid and solid formic acid consists of an effectively infinite network of hydrogen-bonded formic acid molecules. Formic acid shares most of the chemical properties of other carboxylic acids, although under normal conditions it will not form either an acyl chloride or an acid anhydride. Until very recently, all attempts to form either of these derivatives have resulted in carbon monoxide instead. It has now been shown that the anhydride may be produced by reaction of formyl fluoride with sodium formate at -78^oC, and the chloride by passing HCl into a solution of 1-formimidazole in monochloromethane at -60^oC^[1]. Heat can also cause formic acid to decompose to carbon monoxide and water. Formic acid shares some of the reducing properties of aldehydes. Formic acid is unique among the carboxylic acids in its ability to participate in addition reactions with alkenes. Formic acids and alkenes readily react to form formate esters. In the presence of certain acids, including sulfuric and hydrofluoric acids, however, a variant of the Koch reaction takes place instead, and formic acid adds to the alkene to produce a larger carboxylic acid. Most simple formate salts are water-soluble.

Production

A significant amount of formic acid is produced as a byproduct in the manufacture of other chemicals, especially acetic acid. However, this production is insufficient to meet the present demand for formic acid, and some formic acid must be produced for its own sake. When methanol and carbon monoxide are combined in the presence of a strong base, the formic acid derivative methyl formate results, according to the chemical equation :CH₃OH + CO → HCOOCH₃ In industry, this reaction is performed in the liquid phase at elevated pressure. Typical reaction conditions are 80°C and 40 atm. The most widely-used base is sodium methoxide. Hydrolysis of the methyl formate produces formic acid: :HCOOCH₃ + H₂O → HCOOH + CH₃OH However, direct hydrolysis of methanol requires a large excess of water to proceed efficiently, and so some producers perform it by an indirect route, first reacting the methyl formate with ammonia to produce formamide, and then hydrolyzing the formamide with sulfuric acid to produce formic acid: :HCOOCH₃ + NH₃ → HCONH₂ + H₂O :HCONH₂ + H₂O + ½H₂SO₄ → HCOOH + ½ (NH₄)₂SO₄ This technique has problems of its own, particularly disposing of the ammonium sulfate byproduct; so, recently, some manufacturers have developed energy-efficient means of separating formic acid from the large excess of water used in direct hydrolysis. In one of these processes, used by BASF, the formic acid is removed from the water by liquid extraction with an organic base.

Uses

The principal use of formic acid is as a preservative and antibacterial agent in livestock feed. When sprayed on fresh hay or other silage, it arrests certain decay processes and causes the feed to retain its nutritive value longer, and so it is widely use to preserve winter feed for cattle. In the poultry industry, it is sometimes added to feed to kill salmonella bacteria. Some beekeepers use formic acid as a miticide against the Varroa mite. Formic acid is of minor importance in the textile industry and in the tanning of leather. Some formate esters are artificial flavorings or perfumes. In synthetic organic chemistry, formic acid is often used as a source of hydride ion. The Eschweiler-Clarke reaction and the Leuckart-Wallach reaction are famous examples of this. Fuel cells that use modified [http://www.tekion.com/business/index.htm formic acid] are promising.

Safety

The principle danger from formic acid is from skin or eye contact with liquid formic acid or with the concentrated vapors. Any of these exposure routes can cause severe chemical burns, and eye exposure can result in permanent eye damage. Inhaled vapors may similarly cause irritation or burns in the respiratory tract. Since carbon monoxide may be also be present in formic acid vapors, care should be taken wherever large quantities of formic acid fumes are present. The US OSHA Permissible Exposure Level (PEL) of formic acid vapor in the work environment is 5 parts per million parts of air (ppm). Formic acid is readily metabolized and eliminated by the body. Nonetheless, some chronic effects have been documented. Some animal experiments have demonstrated it to be a mutagen, and chronic exposure may cause liver or kidney damage. Another possibility with chronic exposure is development of a skin allergy that manifests upon re-exposure to the chemical. The hazards of solutions of formic acid depend on the concentration. The following table lists the EU classification of formic acid solutions: EU classification

External links

- [http://64.233.167.104/search?q=cache:TsUEX0W9jsAJ:etd.rau.ac.za/theses/available/etd-09082004-124908/restricted/MScJAWillemse.pdf+%22CARBON+MONOXIDE+AS+REAGENT+IN+THE+FORMYLATION+OF+AROMATIC+COMPOUNDS%22&hl=en Carbon monoxide as reagent in the formylation of aromatic compounds]
- [http://www.hazard.com/msds/f2/bkp/bkpnl.html MSDS (Material Safety Data Sheet)]
- [http://ecb.jrc.it/ European Chemicals Bureau]
- [http://www.ilo.org/public/english/protection/safework/cis/products/icsc/dtasht/_icsc04/icsc0485.htm International Chemical Safety Card 0485]
- [http://www.cdc.gov/niosh/npg/npgd0296.html NIOSH Pocket Guide to Chemical Hazards]
- [http://www.compchemwiki.org/index.php?title=Formic_acid Computational Chemistry Wiki] Category:Carboxylic acids Category:Solvents ja:ギ酸 th:ฟอร์มิก แอซิด

Isoprene

Isoprene
Chemical name	2-Methyl-1,3-butadiene
Chemical formula	C₅H₈
Molecular mass	68.11 g/mol
Density	0.681 g/ml
Melting point	-145.95 °C
Boiling point	34.067 °C
CAS number	78-79-5
SMILES	CC(=C)C=C
Image:Isoprene-Structure.png
200px

Isoprene is a common synonym for the chemical compound 2-methyl-1,3-butadiene. It is commonly used in industry, is an important biological material, and can be a harmful environmental pollutant and toxicant when present in excess quantities. At room temperature, isoprene is a colorless liquid which is highly flammable and easily ignited. It can form explosive mixtures in air and is highly reactive, capable of polymerizing explosively when heated. The United States Department of Transportation considers isoprene a hazardous material and requires special marking, labeling, and transportation for it. It is most readily available industrially as a by-product of the thermal cracking of naphtha or oil. About 95% of isoprene production is used to produce cis-1,4-polyisoprene - a synthetic version of natural rubber. Natural rubber is a polymer of isoprene - most often cis-1,4-polyisoprene - with a molecular weight of 100,000 to 1,000,000. Typically, a few percent of other materials, such as proteins, fatty acids, resins and inorganic materials are found in high quality natural rubber. Some natural rubber sources are composed of trans-1,4-polyisoprene, a structural isomer which has similar, but not identical properties.

Biological roles and effects

Isoprene is formed naturally in plants and animals and is generally the most common hydrocarbon found in the human body. The estimated production rate of isoprene in the human body is 15 µmol/kg/h, equivalent to approximately 17 mg/day for a 70 kg person. Isoprene is also common in low concentrations in many foods. Isoprene is produced in the chloroplasts of leaves of certain tree species through the DMAPP pathway; the enzyme isoprene synthase is responsible for its biosynthesis. The amount of isoprene released from isoprene-emitting vegetation depends on leaf mass, leaf area, light (particularly photosynthetic photon flux density), and leaf temperature. Thus, during the night, little isoprene is emitted from tree leaves while daytime emissions are expected to be substantial (~5 ppbV) during hot and sunny days. With a global biogenic production in the range of 350–500 Tg of carbon/year, isoprene has a large impact on atmospheric processes and is thus an important compound in the field of Atmospheric Chemistry. Isoprene affects the oxidative state of large air masses, is an important precursor for ozone, a pollutant in the lower atmosphere. Furthermore, isoprene forms secondary organic aerosols through photooxidation with OH radicals which also have wide-ranging health effects, particularly for the respiratory tract, and reduce visibility due to light scattering effects. Because of its atmospheric importance, much work has been devoted to emission studies from isoprene-emitting vegetation, and, kinetic and mechanistic studies of isoprene oxidation via OH radicals, ozone, and NO₃ radicals. It is a common structural motif in biological systems. The terpenes (for example, the carotenes are tetraterpenes) are derived from isoprene, as are the terpenoids and coenzyme Q. Also derived from isoprene are phytol, retinol (vitamin A), tocopherol (vitamin E), dolichols, and squalene. Heme A has an isoprenoid tail, and lanosterol, the sterol precursor in animals, is derived from squalene and hence from isoprene. The functional isoprene units in biological systems are dimethylallyl pyrophosphate (DMAPP) and its isomer isopentenyl pyrophosphate (IPP), which are used in the biosynthesis of terpenes and lanosterol derivatives. In virtually all organisms, isoprene derivatives are synthetised by the HMG-CoA reductase pathway. Addition of these chains to proteins is termed isoprenylation. According to the United States Department of Health and Human Services Eleventh Edition Report on Carcinogens, isoprene is reasonably expected to be a human carcinogen. Tumors have been observed in multiple locations in multiple test species exposed to isoprene vapor. No adequate human studies of the relationship between isoprene exposure and human cancer have been reported.

Biosynthesis and Its Inhibition by Statins

HMG-CoA reductase inhibitors, also known as the group of cholesterol-lowering drugs called statins, inhibit the synthesis of mevalonate. Mevalonate is a precursor to isopentenyl pyrophosphate, which combines with its isomer, dimethyl allyl pyrophosphate, in repeating alternations to form isoprene (or polyprenyl) chains. Statins are used to lower cholesterol, which is synthesized from the 15-carbon isoprenoid, farnesyl pyrophosphate, but also inhibit all other isoprenes, including coenzyme Q10. This [http://www.cholesterol-and-health.com/Synthesis-Of-Cholesterol.html flow chart]shows the biosynthesis of isoprenes, and the point at which statins act to inhibit this process.

Reference

Merck Index, Eleventh Edition, ISBN 911910-28-X. Poisson, N., M. Kanakidou, and P. J. Crutzen, "Impact of nonmethanehydrocarbons on tropospheric chemistry and the oxidizing power of the global troposphere: 3-dimensional modelling results," Journal of Atmospheric Chemistry, vol. 36, pp. 157–230, 2000. Monson, R. K., and E. A. Holland, "Biospheric trace gas fluxes and their control over tropospheric chemistry," Annual Review of Ecological Systems, vol. 32, pp. 547–+, 2001. Claeys, M., B. Graham, G. Vas, W. Wang, R. Vermeylen, V. Pashynska, J. Cafmeyer, P. Guyon, M. O. Andreae, P. Artaxo, and W. Maenhaut, "Formation of secondary organic aerosols through photooxidation of isoprene," Science, vol. 303, pp. 1173–1176, 2004. Pier, P. A., and C. McDuffie, "Seasonal isoprene emission rates and model comparisons using whole-tree emissions from white oak," Journal of Geophysical Research, vol. 102, pp. 23,963–23,971, 1997. Poschl, U., R. von Kuhlmann, N. Poisson, and P. J. Crutzen, "Development and intercomparison of condensed isoprene oxidation mechanisms for global atmospheric modeling," Journal of Atmospheric Chemistry, vol. 37, pp. 29–52, 2000.

External link

[http://www.cholesterol-and-health.com/Synthesis-Of-Cholesterol.html Flow Chart Showing the Biosynthesis of Isoprenes] [http://ntp.niehs.nih.gov/ntp/roc/toc11.html Report on Carcinogens, Eleventh Edition; U.S. Department of Health and Human Services, Public Health Service, National Toxicology Program] Category:Dienes ja:イソプレン

Diene

Dienes are hydrocarbons which contain two double bonds. Dienes are intermediate between alkenes and polyenes.

Classes

Dienes can divided into three classes: #Unconjugated dienes have the double bonds separated by two or more single bonds. #Conjugated dienes have conjugated double bonds separated by one single bond #Cumulated dienes have the double bonds sharing a common atom as in a group of compounds called allenes. In organic chemistry a conjugated diene is also a functional group.

Common dienes

The simplest conjugated diene is 1,3-butadiene. Cyclopentadiene is another example of a diene. Cyclopentadiene

Reactions with dienes

The 1,3 configuration of double bonds found in 1,3-butadiene (conjugated double bonds) make these types of dienes capable of participating in more reaction types than is the case for molecules with either just a single alkene functional group or with multiple, but non-alternating, alkene groups. One possible reaction for such dienes is the Diels-Alder reaction. Category:functional groups Category:Hydrocarbons

Joseph Priestley

Joseph Priestley (March 13 1733–February 8 1804) was an English chemist, philosopher, dissenting clergyman, and educator. He is known for his investigations of carbon dioxide and the co-discovery of oxygen.

Early life and education

He was born in Birstall parish, six miles from Leeds, Yorkshire. He learned a variety of languages, both classical and modern, in his youth, including several Semitic languages; he also studied what was then called natural history. The school he attended was called Batley Grammar School which still exists, and now has a junior and infants section for children between the ages of 2-10, named Priestley House. In 1751 he entered Daventry, a school under Nonconformist auspices, and there his religious views took shape. He became an adherent of Arianism and a fervent abolitionist. In September, 1755, he started as a parish minister in Needham Market, Suffolk, though he was not officially ordained until May 18, 1762. Because he stammered and the parish was not suited to his heterodox ideas, nor did they want a bachelor for their minister, he was unpopular in his Suffolk parish and he ultimately went to Nantwich, Cheshire. He established a private school in connection with the church in Nantwich where he preached, and derived his income from that school.

Warrington

Subsequently he went to Warrington, the biggest of the dissenting academies in England, as a tutor in belles-lettres. By this time his religious ideas had matured to Socinianism, a form of Unitarianism. At Warrington, he associated with other liberal-minded tutors. A sympathetic printer, William Eyres, was willing to publish his work. It was here that he published his grammar book in 1761 (a remarkably liberal grammar for its day) and other books on history and educational theory. He taught anatomy and astronomy and led field trips for his students to collect fossils and botanical specimens. Both modern history and the sciences were subjects which had not been taught in any schools before Priestley.

Leeds

On June 23 1762, Priestley married Mary Wilkinson of Wrexham, and by September 1767 the combination of his finances and her health caused him to relocate to Leeds. He there took charge of the Mill Hill congregation. In Leeds Priestley also published two political works, Essay on the First Principles of Government 1768 and The Present State of Liberty in Great Britain and her Colonies 1769, and also in 1769 Remarks on Dr Blackstone's Commentaries where he defended constitutional rights of dissenters against William Blackstone. Priestley's house was next to a brewery and Priestley began to experiment with the gas given off by fermenting beer. His first experiments involved demonstrating that the gas would extinguish lighted wood chips. He then noticed that the gas appeared to be heavier than normal air as it remained in the vats and did not mix with the air in the room. The gas, which Priestley called "fixed air" and had already been discovered and named "mephitic air" by Joseph Black, was carbon dioxide. Priestley discovered a method of impregnating water with the carbon dioxide by placing a bowl of water above a vat of fermenting beer. The carbon dioxide soon became dissolved in the water and Priestley found that the impregnated water developed a pleasant sweet acidic taste. He began to offer the treated water to friends as a refreshing drink. In 1772 Priestley published a paper entitled Impregnating Water with Fixed Air in which he described a process of dripping sulfuric acid (or oil of vitriol