|| Chapter 20: Carboxylic
Acid Derivatives. Nucleophilic Acyl Substitution
Reactions of Nitriles
Reaction type: Nucleophilic
- Nitriles typically undergo nucleophilic
addition to give products that often undergo a further reaction.
- The chemistry of the nitrile
functional group, C≡N,
is very similar to that of the carbonyl, C=O of aldehydes and ketones.
Compare the two schemes:
- However, it is convenient to
describe nitriles as carboxylic acid derivatives because:
- the oxidation state of the
C is the same as that of the carboxylic acid derivatives.
- hydrolysis produces the carboxylic
- Like the carbonyl containing
compounds, nitriles react with nucleophiles via two scenarios:
- Strong nucleophiles (anionic)
add directly to the C≡N to form an intermediate imine salt that
protonates (and often reacts further) on work-up with dilute acid.
Examples of such nucleophilic systems are : RMgX, RLi, RC≡CM,
- Weaker nucleophiles (neutral)
require that the C≡N be activated prior to attack of the Nu.
This can be done using a acid catalyst which protonates
on the Lewis basic N and makes the system more electrophilic.
Examples of such nucleophilic systems are : H2O, ROH
of a nitrile gives a structure that can be redrawn in another resonance
form that reveals the electrophilic character of the C since it is a