3.7 Alcohols

We think of alcohol as one specific substance, but in fact any molecule with a C-OH group is an alcohol. We have already met phenol, and now we see that it is an alcohol, hence the -ol in its name. Even sugars are alcohols; they're polyols since they have multiple C-OH groups on the same molecule. The -OH group is called a hydroxy group.

A primary alcohol is one where the carbon atom is bonded to at most one other carbon atom. Examples include ethanol, butanol, and phenethyl alcohol C₆H₅CH₂CH₂OH.

A secondary alcohol has two carbon atoms bonded to its carbon atom. An example is isopropyl alcohol or isopropanol, (CH₃)₂CHOH. Isopropyl alcohol is an isomer of propyl alcohol or propanol, but the name isopropyl is anomalous, since there is no such thing as isopropane. Nevertheless it is in common use to mean a (CH₃)₂CH- group. Propanol is also called n-propanol, short for "normal" propyl alcohol, to distinguish it from its isomer.

A tertiary alcohol is one with three carbon atoms bonded to its alcoholic carbon. A good example is tert-butyl alcohol, (CH₃)₃COH.

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