What defines a diol?

A diol is specifically defined as an alcohol that contains two hydroxyl groups (-OH) in its molecular structure. This characteristic is what sets diols apart from other types of alcohols, which may contain only one hydroxyl group. Because diols have two hydroxyl groups, they exhibit different chemical properties compared to monohydric alcohols, which have only one hydroxyl group.

The presence of two hydroxyl groups means that diols can participate in a wider range of chemical reactions, such as forming hydrogen bonds, which can affect their physical properties like boiling points and solubility. In addition, diols can exist in various structural forms, such as vicinal diols (where the hydroxyl groups are on adjacent carbon atoms) or geminal diols (where both hydroxyl groups are attached to the same carbon atom).

By contrast, other options describe different categories of alcohols. For example, alcohols containing one hydroxyl group would describe monohydric alcohols, while processes involving oxidation of aldehydes or the structure of tertiary alcohols highlight other distinct chemical classifications that do not pertain to the specific requirement of having two hydroxyl groups.