Final answer:
Lithium aluminum hydride (LiAlH4) reduction of carboxylic acids, esters, acyl chlorides, and amides typically results in the formation of alcohols, following hydrolysis.
Step-by-step explanation:
The expected products of lithium aluminum hydride reduction of carboxylic acids and their derivatives typically involve the conversion of these functional groups into alcohols. LiAlH4 (lithium aluminum hydride) is a strong reducing agent that is capable of reducing carboxylic acids, esters, acyl chlorides, and amides to their corresponding alcohols upon subsequent hydrolysis.
During the reduction of a carboxylic acid, the LiAlH4 donates a hydride ion (H-) to the carbonyl carbon, converting the carboxylic acid into an aldehyde intermediate, which is then further reduced to an alcohol. Ester reduction proceeds via a similar mechanism, first forming an aldehyde and then reducing it further to an alcohol. With acid halides, the reduction bypasses the aldehyde stage and directly gives the corresponding primary alcohol. Amides, upon reduction with LiAlH4, yield amines, which can be further hydrolyzed under the reaction conditions to form alcohols and ammonia.
To illustrate, the reduction of an ester with LiAlH4 followed by hydrolysis would proceed as follows:
- R-COOR' + 4[H] (from LiAlH4) → R-CHOH-R' (Primary alcohol)
The hydrolysis step, typically performed with water or a weak acid, is crucial because the aluminohydride complex formed during the reduction reaction is decomposed by water, liberating hydrogen and forming complexes such as Na[Al(OH)4] that can be easily removed from the reaction mixture.