Final answer:
Treatment of an aldehyde or ketone with NaBH4 or LiAlH4 and water forms primary alcohols from aldehydes and secondary alcohols from ketones through nucleophilic addition of hydride ions.
Step-by-step explanation:
The treatment of an aldehyde or ketone with either NaBH4 or LiAlH4 followed by water will result in the reduction of the carbonyl group to a hydroxyl (-OH) group. In these reactions, NaBH4 or LiAlH4 act as hydride donors that lead to the nucleophilic addition of a hydride ion to the carbonyl carbon of aldehydes and ketones. Consequently, this process transforms aldehydes into primary alcohols and ketones into secondary alcohols.
Though both reagents can be used for this purpose, NaBH4 is more commonly used since it is tolerant to water and therefore easier to handle in a laboratory setting. However, LiAlH4 is more reactive and can reduce a broader range of compounds, including carboxylic acids and their derivatives, whereas NaBH4 is mainly used for aldehydes, ketones, and acid halides.