Organic reaction
Organic reactions are
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.
Classifications
Organic chemistry has a strong tradition of naming a specific reaction to its inventor or inventors and a long
Another approach to organic reactions is by type of
Finally, reactions are also classified by mechanistic class. Commonly these classes are (1) polar, (2) radical, and (3) pericyclic. Polar reactions are characterized by the movement of electron pairs from a well-defined source (a nucleophilic bond or lone pair) to a well-defined sink (an electrophilic center with a low-lying antibonding orbital). Participating atoms undergo changes in charge, both in the formal sense as well as in terms of the actual electron density. The vast majority of organic reactions fall under this category. Radical reactions are characterized by species with unpaired electrons (radicals) and the movement of single electrons. Radical reactions are further divided into chain and nonchain processes. Finally, pericyclic reactions involve the redistribution of chemical bonds along a cyclic transition state. Although electron pairs are formally involved, they move around in a cycle without a true source or sink. These reactions require the continuous overlap of participating orbitals and are governed by orbital symmetry considerations. Of course, some chemical processes may involve steps from two (or even all three) of these categories, so this classification scheme is not necessarily straightforward or clear in all cases. Beyond these classes, transition-metal mediated reactions are often considered to form a fourth category of reactions, although this category encompasses a broad range of elementary organometallic processes, many of which have little in common and very specific.
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
Organic reactions are important in the production of
By mechanism
There is no limit to the number of possible organic reactions and mechanisms.[5][6] 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 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
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.
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 |
Lactones | preparation | reactions |
Nitriles | preparation | reactions |
Nitro compounds | preparation | reactions |
Phenols | preparation | reactions |
Thiols | preparation | reactions |
Other classification
In
Organic reactions can also be classified by the type of bond to carbon with respect to the element involved. More reactions are found in
See also
- List of organic reactions
- Other chemical reactions: polymerization reactions.
- Important publications in organic chemistry
References
- ISBN 0-12-429785-4
- ^ J. Clayden, N. Greeves & S. Warren "Organic Chemistry" (Oxford University Press, 2012)
- ^ Robert T. Morrison, Robert N. Boyd, and Robert K. Boyd, Organic Chemistry, 6th edition, Benjamin Cummings, 1992
- doi:10.1039/b602413k
- doi:10.1021/ed070p14
- ISBN 0-471-60180-2