Illustrated Glossary of Organic Chemistry

Geminal (gem): Describes two functional groups bonded to the same carbon. The prefix gem may be added to the molecule's name to indicate the geminal relationship.

A geminal diol.		A vicinal diol.

In a geminal diol, the two OH groups are bonded to the same carbon. In a vicinal diol, the two OH groups are on adjacent carbons.


This acetal contains geminal alkoxy groups.