Organic reaction
Organic reactions are
chemical reactions involving
organic compounds. The basic
organic chemistry reaction types are
addition reactions,
elimination reactions,
substitution reactions,
pericyclic reactions,
rearrangement reactions and
redox reactions. In
organic synthesis, organic reactions are used in the construction of new organic molecules.
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.
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.
Factors governing organic reactions are essentially the same as that of any
chemical reaction. Factors specific to organic reactions are the 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 as many
isomers. Selectivity in terms of
regioselectivity,
diastereoselectivity and
enantioselectivity is therefore an important criterium 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.
The number of possible organic reactions is basically infinite. 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.
Addition reactions include such reactions as
halogenation,
hydrohalogenation and
hydration. The main addition reactions are:#
electrophilic addition or EA#
nucleophilic addition or NA#
radical addition or RA
Elimination reactions include processes such as
dehydration and are found to follow a E1, E2 or
E1cB reaction
reaction mechanismSubstitution reactions are divided into:#
nucleophilic aliphatic substitution with
SN1,
SN2 and
SNi reaction mechanisms#
nucleophilic aromatic substitution or NAS#
nucleophilic acyl substitution#
electrophilic substitution or ES#
electrophilic aromatic substitution or EAS#
radical substitution or RS
Organic redox reactions are
redox reactions specific to
organic compounds and very common.
Rearrangement reactions are divided into:#
1,2-rearrangements#
pericyclic reactions#
metathesisIn
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.
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:
*
Acyl halides:
preparation -
reactions *
Aldehydes:
preparation -
reactions*
Acyloins:
preparation -
reactions*
Alkanes:
preparation -
reactions*
Alkenes:
preparation -
reactions*
Alkynes:
preparation -
reactions*
Alkyl halides:
preparation -
reactions*
Alcohols:
preparation -
reactions*
Azides:
preparation -
reactions*
Aziridines:
preparation -
reactions*
Amides:
preparation -
reactions*
Amines:
preparation -
reactions*
Benzenes:
preparation -
reactions*
Carboxylic acids:
preparation -
reactions*
cyclopropanes:
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*
Phenols:
preparation -
reactionsOrganic 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.
In
heterocyclic chemistry, organic reactions are classified by the type of heterocycle formed.
*
List of organic reactions* Other chemical reactions:
inorganic reactions,
biochemical reactions,
organometallic reactions,
polymerization reactions.
*
Important publications in organic chemistry*
Organic reaction flashcards from OSU*
list of named reactions from UConn*
organic reactions
