Which type of alcohol has two alkyl groups attached to the carbon with the OH group?

The correct classification of the alcohol in question is based on the connectivity of the carbon atom that bears the hydroxyl (OH) group. In a secondary alcohol, the carbon with the OH group is attached to two other carbon atoms. This means that this carbon is located in the middle of the carbon chain, surrounded by two alkyl groups.

For example, if you take the alcohol isopropanol (propan-2-ol), the central carbon has the OH group and is connected to two other carbon groups on either side, fulfilling the definition of a secondary alcohol.

In contrast, a primary alcohol has the OH group attached to a carbon that is connected to only one other carbon atom, while a tertiary alcohol has the OH group attached to a carbon that is connected to three other carbon atoms. Quaternary alcohols, while not typically discussed in the same category, would refer to structures that are not standard in conventional alcohol classification, as they involve a carbon bonded to four carbon substituents, which cannot logically attach an -OH group in a stable manner. Understanding these distinctions helps in accurately categorizing alcohols based on their structures.