A geminal diol (or gem-diol for short) is any organic compound having two hydroxyl functional groups (-OH) bound to the same carbon atom. Geminal diols are a subclass of the diols, which in turn are a special class of alcohols. Most of the geminal diols are considered unstable.
The simplest geminal diol is methanediol CH
4O
2 or H
2C(OH)
2. Other examples are:
- dihydroxymalonic acid (HOOC)
2C(OH)
2 - decahydroxycyclopentane (C(OH)
2)
5 - chloral hydrate (Cl
3C)HC(OH)
2.