- Organic reaction
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Organic reactions are chemical reactions involving organic compounds.[1] The basic organic chemistry reaction types are addition reactions, elimination reactions, substitution reactions, pericyclic reactions, rearrangement reactions, photochemical reactions and redox reactions. In organic synthesis, organic reactions are used in the construction of new organic molecules. The production of many man-made chemicals such as drugs, plastics, food additives, fabrics depend on organic reactions.
The oldest organic reactions are combustion of organic fuels and saponification of fats to make soap. Modern organic chemistry starts with the Wöhler synthesis in 1828. In the history of the Nobel Prize in Chemistry awards have been given for the invention of specific organic reactions such as the Grignard reaction in 1912, the Diels-Alder reaction in 1950, the Wittig reaction in 1979 and olefin metathesis in 2005.
Contents
Classifications
Organic chemistry has a strong tradition of naming a specific reaction to its inventor or inventors and a long list of so-called named reactions exists, conservatively estimated at 1000. A very old named reaction is the Claisen rearrangement (1912) and a recent named reaction is the Bingel reaction (1993). When the named reaction is difficult to pronounce or very long as in the Corey-House-Posner-Whitesides reaction it helps to use the abbreviation as in the CBS reduction. The number of reactions hinting at the actual process taking place is much smaller, for example the ene reaction or aldol reaction.
Another approach to organic reactions is by type of organic reagent, many of them inorganic, required in a specific transformation. The major types are oxidizing agents such as osmium tetroxide, reducing agents such as Lithium aluminium hydride, bases such as lithium diisopropylamide and acids such as sulfuric acid.
Fundamentals
Factors governing organic reactions are essentially the same as that of any chemical reaction. Factors specific to organic reactions are those that determine the stability of reactants and products such as conjugation, hyperconjugation and aromaticity and the presence and stability of reactive intermediates such as free radicals, carbocations and carbanions.
An organic compound may consist of many isomers. Selectivity in terms of regioselectivity, diastereoselectivity and enantioselectivity is therefore an important criterion for many organic reactions. The stereochemistry of pericyclic reactions is governed by the Woodward-Hoffmann rules and that of many elimination reactions by the Zaitsev's rule.
Organic reactions are important in the production of pharmaceuticals. In a 2006 review [2] it was estimated that 20% of chemical conversions involved alkylations on nitrogen and oxygen atoms, another 20% involved placement and removal of protective groups, 11% involved formation of new carbon-carbon bond and 10% involved functional group interconversions.
Organic reactions by mechanism
There is no limit to the number of possible organic reactions and mechanisms.[3] However, certain general patterns are observed that can be used to describe many common or useful reactions. Each reaction has a stepwise reaction mechanism that explains how it happens, although this detailed description of steps is not always clear from a list of reactants alone. Organic reactions can be organized into several basic types. Some reactions fit into more than one category. For example, some substitution reactions follow an addition-elimination pathway. This overview isn't intended to include every single organic reaction. Rather, it is intended to cover the basic reactions.
Reaction type Subtype Comment Addition reactions electrophilic addition include such reactions as halogenation, hydrohalogenation and hydration. nucleophilic addition radical addition Elimination reaction include processes such as dehydration and are found to follow an E1, E2 or E1cB reaction mechanism Substitution reactions nucleophilic aliphatic substitution with SN1, SN2 and SNi reaction mechanisms nucleophilic aromatic substitution nucleophilic acyl substitution electrophilic substitution electrophilic aromatic substitution radical substitution Organic redox reactions are redox reactions specific to organic compounds and are very common. Rearrangement reactions 1,2-rearrangements pericyclic reactions metathesis In Condensation reactions a small molecule, usually water, is split off when two reactants combine in a chemical reaction. The opposite reaction, when water is consumed in a reaction, is called hydrolysis. Many Polymerization reactions are derived from organic reactions. They are divided into addition polymerizations and step-growth polymerizations.
In general the stepwise progression of reaction mechanisms can be represented using arrow pushing techniques in which curved arrows are used to track the movement of electrons as starting materials transition to intermediates and products.
Organic reactions by functional groups
Organic reactions can be categorized based on the type of functional group involved in the reaction as a reactant and the functional group that is formed as a result of this reaction. For example in the Fries rearrangement the reactant is an ester and the reaction product an alcohol.
An overview of functional groups with their preparation and reactivity is presented below:
Functional group Preparation Reactions Acid anhydride preparation reactions Acyl halides preparation reactions Acyloins preparation reactions Alcohols preparation reactions Aldehydes preparation reactions Alkanes preparation reactions Alkenes preparation reactions Alkyl halides preparation reactions Alkyl nitrites preparation reactions Alkynes preparation reactions Amides preparation reactions Amine oxide preparation reactions Amines preparation reactions Arene compounds preparation reactions Azides preparation reactions Aziridines preparation reactions Carboxylic acids preparation reactions Cyclopropanes preparation reactions Diazo compounds preparation reactions Diols preparation reactions Esters preparation reactions Ethers preparation reactions Epoxide preparation reactions Haloketones preparation reactions Imines preparation reactions Isocyanates preparation reactions Ketones preparation reactions Lactams preparation reactions Nitriles preparation reactions Nitro compounds preparation reactions Phenols preparation reactions Thiols preparation reactions Other organic reaction classification
In heterocyclic chemistry, organic reactions are classified by the type of heterocycle formed with respect to ring-size and type of heteroatom. See for instance the chemistry of indoles.
Organic reactions can also be classified by the type of bond to carbon with respect to the element involved. More reactions are found in organosilicon chemistry, organosulfur chemistry, organophosphorus chemistry and organofluorine chemistry. With the introduction of carbon-metal bonds the field crosses over to organometallic chemistry.
CH He CLi CBe CB CC CN CO CF Ne CNa CMg CAl CSi CP CS CCl CAr CK CCa CSc CTi CV CCr CMn CFe CCo CNi CCu CZn CGa CGe CAs CSe CBr CKr CRb CSr CY CZr CNb CMo CTc CRu CRh CPd CAg CCd CIn CSn CSb CTe CI CXe CCs CBa CHf CTa CW CRe COs CIr CPt CAu CHg CTl CPb CBi CPo CAt Rn Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Uut Uuq Uup Uuh Uus Uuo ↓ CLa CCe CPr CNd CPm CSm CEu CGd CTb CDy CHo CEr CTm CYb CLu Ac Th Pa CU Np Pu Am Cm Bk Cf Es Fm Md No Lr Chemical bonds to carbon Core organic chemistry Many uses in chemistry Academic research, but no widespread use Bond unknown / not assessed See also
- List of organic reactions
- Other chemical reactions: inorganic reactions, metabolism, organometallic reactions, polymerization reactions.
- Important publications in organic chemistry
External links
- Organic reactions @ Synarchive.com
- Organic reaction flashcards from OSU
- list of named reactions from UConn
- organic reactions
- Organic chemistry help-Best of the Web 2008
- Organic chemistry help-Electronic Flashcards
- Study-Organic-Chemistry.com
- organic-reaction.com
References
- ^ Strategic Applications of Named Reactions in Organic Synthesis Laszlo Kurti, Barbara Czako Academic Press (March 4, 2005) ISBN 0-12-429785-4
- ^ Analysis of the reactions used for the preparation of drug candidate molecules John S. Carey, David Laffan, Colin Thomson and Mike T. Williams Org. Biomol. Chem., 2006, 4, 2337 - 2347, doi:10.1039/b602413k
- ^ Is This Reaction a Substitution, Oxidation-Reduction, or Transfer? / N.S.Imyanitov. J. Chem. Educ. 1993, 70(1), 14 – 16.
Topics in Organic Reactions Addition reaction - Elimination reaction - Polymerization - Reagents - Rearrangement reaction - Redox reaction - Regioselectivity - Stereoselectivity - Stereospecificity - Substitution reaction - List of organic reactions
Concepts in organic chemistry Aromaticity · Covalent bonding · Functional groups · Nomenclature · Organic compounds · Organic reactions · Organic synthesis · Publications · Spectroscopy · Stereochemistry · List of organic compoundsCategories:
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