Carboxylic acids can be converted to 1o alcohols using Lithium aluminum hydride (LiAlH4)
Note that NaBH4 is not strong enough to convert carboxylic acids or esters to alcohols. An aldehyde is produced as an intermediate during this reaction, but it cannot be isolated because it is more reactive than the original carboxylic acid.
For example, butanoic acid can be reduced to butanol when reacted with lithium aluminum hydride as shown below.
There is not complete agreement on the mechanism for this reaction. However, the mechanism below is considered probable by many chemists.
2) Nucleopilic reaction by the hydride anion
3) Leaving group removal
4) Nucleopilic reaction by the hydride anion
5) The alkoxide is protonated