Classification

Alcohols, phenols and ethers are each classified along their own set of criteria, developed in the two sub-sections that follow. Alcohols and phenols are first classified by how MANY hydroxyl groups their molecule carries -- one (monohydric), two (dihydric), three (trihydric), or more (polyhydric) -- and, within the monohydric class specifically, by the HYBRIDISATION of the carbon atom that the -OH group is actually bonded to: an ordinary sp3-hybridised carbon (giving the familiar primary/secondary/tertiary alcohols, and their allylic/benzylic sub-types) versus an sp2-hybridised carbon that is itself part of a carbon-carbon double bond (giving the less common vinylic alcohols). Ethers, having no -OH group of their own to count, are instead classified purely by whether the two groups flanking their oxygen atom are identical (symmetrical/simple ethers) or different (unsymmetrical/mixed ethers). These three classification schemes -- by -OH count, by -OH- …