Amides are one member of the group of compounds that are referred to as carboxylic acid derivatives. As shown by the examples of the various classes of carboxylic acid derivatives below, these have the general formula RCOX where the group X has an electronegative atom bonded to the carbonyl carbon.
Acyl chlorides are the most reactive of these compounds. As shown in the the scheme, acyl chlorides are converted, on reaction with an amine (or ammonia) to an amide or on reaction with water to a carboxylic acid. The overall reaction is substitution with HCl being a co-product of the reaction.
Acyl chlorides may be prepared from the reaction of a carboxylic acid with SOCl2. Unlike the other reactions shown at the right of the scheme, this reaction converts a carboxylic acid to a more reactive carboxylic acid derivative. This is because SOCl2 activates the OH on the carboxylic acid so that it is displaced by Cl.
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| acid chloride | amide | propanoic acid |
Acyl chlorides are the most reactive of these compounds. As shown in the the scheme, acyl chlorides are converted, on reaction with an amine (or ammonia) to an amide or on reaction with water to a carboxylic acid. The overall reaction is substitution with HCl being a co-product of the reaction.Acyl chlorides may be prepared from the reaction of a carboxylic acid with SOCl2. Unlike the other reactions shown at the right of the scheme, this reaction converts a carboxylic acid to a more reactive carboxylic acid derivative. This is because SOCl2 activates the OH on the carboxylic acid so that it is displaced by Cl.
Thus an amide can be prepared from a carboxylic acid if it is first converted to an acyl chloride.