What term describes diols with hydroxyl groups on the same carbon?

The term used to describe diols—compounds with two hydroxyl groups—on the same carbon is "geminal diols." In a geminal diol, the two -OH groups are attached to the same carbon atom, which distinguishes them from vicinal diols, where the hydroxyl groups are located on adjacent carbons.

Geminal diols are often formed from the hydration of carbonyl compounds, such as aldehydes and ketones. In these cases, the carbonyl carbon is attacked by water, resulting in the addition of two hydroxyl groups to that same carbon. This structural arrangement often leads to the formation of unstable intermediates because they can easily dehydrate back to the carbonyl compound.

Understanding the definitions of vicinal and geminal diols is crucial in organic chemistry. Vicinal diols have their two hydroxyl groups on two different adjacent carbon atoms, while geminal diols concentrate them on one carbon. Recognizing these terms helps in identifying different molecular structures and understanding their chemical reactivity.