Organic Chemistry MCAT Practice Exam

What type of alcohol cannot be produced through hydride reduction of carbonyl compounds?

1. Primary alcohols

2. Tertiary alcohols

3. Secondary alcohols

4. None of the above

The correct answer is: Tertiary alcohols

The correct answer indicates that tertiary alcohols cannot be produced through hydride reduction of carbonyl compounds. This is because hydride reduction involves the addition of hydrogen (in the form of a hydride ion) to a carbonyl group (such as aldehydes and ketones) to form an alcohol. When considering the structure of carbonyl compounds, aldehydes can be reduced to primary alcohols, and ketones can be reduced to secondary alcohols. Tertiary alcohols, on the other hand, require a carbon source that is already branched or has three substituents connected to the carbon atom that would be the new alcohol group. The carbonyl carbon in both aldehydes and ketones is only bonded to one or two substituents, meaning that after reduction they can only yield primary alcohols from aldehydes and secondary alcohols from ketones. In the case of tertiary alcohols, their structure necessitates a carbon atom that is bonded to three other carbon atoms—something that cannot result from the direct reduction of a carbonyl compound, since the carbonyl group can only provide one additional hydrogen to a carbon structure that originally is less substituted. Therefore, the pathway to creating tertiary alcohols does not involve a direct