A<unk>  or glycol is a chemical compound containing two hydroxyl groups (-OH groups).  Vicinal<unk> s have hydroxyl groups attached to adjacent atoms.  Examples of vicinal<unk>  compounds are ethylene glycol and propylene glycol.  Geminal<unk> s have hydroxyl groups bonded to the same atom.  In general, organic geminal<unk> s readily dehydrate to form a carbonyl group.  For example, carbonic acid ((HO)2C=O) is unstable and has a tendency to convert to carbon dioxide (CO2) and water (H2O).  Nevertheless, in rare situations the chemical equilibrium is in favor of the geminal<unk> .  For example, when formaldehyde (H2C=O) is dissolved in water the geminal<unk>  (H2C(OH)2) is favored.
Examples of<unk> s in which the hydroxyl functional groups are more widely separated include 1,4-butanediol and bisphenol A.
Diol
Haloalkane
Glycerin
Saturated fat
Hydrocarbon
Unsaturated fat
Polyphenol
Cholesterol