Addition reaction

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Addition of chlorine to ethylene

An addition reaction, in organic chemistry, is in its simplest terms an organic reaction where two or more molecules combine to form a larger one.[1][2]

Addition reactions are limited to chemical compounds that have multiple bonds, such as molecules with carbon-carbon double bonds (alkenes), or with triple bonds (alkynes). Molecules containing carbon—hetero double bonds like carbonyl (C=O) groups, or imine (C=N) groups, can undergo addition as they too have double bond character.

An addition reaction is the opposite of an elimination reaction. For instance the hydration reaction of an alkene and the dehydration of an alcohol are addition-elimination pairs.

There are two main types of polar addition reactions: electrophilic addition and nucleophilic addition. Two non-polar addition reaction exists as well called free radical addition and cycloadditions. Addition reactions are also encountered in polymerizations and called addition polymerization. Based on the number of lines and their slopes obtained by plotting alkene ionization potentials versus logs of their relative rates of additions, Donna Nelson and her students have identified patterns in alkene addition reactions and in their mechanisms.

Addition reactions general overview. Top to bottom: electrophilic addition to alkene, nucleophilic addition of nucleophile to carbonyl and free radical addition of halide to alkene

Addition-elimination reaction[edit]

In the related addition-elimination reaction an addition reaction is followed by an elimination reaction. In the majority of reactions it involves addition of nucleophiles to carbonyl compounds in what is called nucleophilic acyl substitution.[3]

Other addition-elimination reactions are the reaction of an aliphatic amine to an imine and an aromatic amine to a Schiff base in alkylimino-de-oxo-bisubstitution. The hydrolysis of nitriles to carboxylic acids is also a form of addition-elimination.

References[edit]

  1. ^ Morrison, R. T.; Boyd, R. N. (1983). Organic Chemistry (4th ed.). Boston: Allyn and Bacon. ISBN 0-205-05838-8. 
  2. ^ March, Jerry (1985), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (3rd ed.), New York: Wiley, ISBN 0-471-85472-7 
  3. ^ Reaction-Map of Organic Chemistry Murov, Steven. J. Chem. Educ. 2007, 84, 1224 Abstract