Nomenclature of Alcohols, Phenols and Ethers

Naming alcohols. The IUPAC (substitutive) name of an alcohol is built by identifying the

longest continuous carbon chain that includes the carbon bearing $-\text{OH}$, replacing that

chain's '-ane' alkane ending with '-ol', and numbering the chain from whichever end gives the

$-\text{OH}$ group the lower locant (the $-\text{OH}$ position takes priority over any other

substituent's locant when the two directions are compared). The locant is cited immediately

before the '-ol' suffix, e.g. $\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}$ is propan-1-ol

(not propan-3-ol), and $\text{CH}_3\text{CH(OH)CH}_3$ is propan-2-ol. Any other substituents are

named and located exactly as for alkanes, e.g. 3-methylbutan-1-ol for

$(\text{CH}_3)_2\text{CHCH}_2\text{CH}_2\text{OH}$. For a diol or triol, the terminal 'e' of the

parent alkane name is retained before the multiplying-prefixed suffix, e.g. ethane-1,2-diol.

Classifying alcohols. Independently of its IUPAC name, every alcohol is also classified by how

many other carbons are bonded to the $-\text{OH}$-bearing carbon: primary (1°) if that carbon

is attached to only one other carbon (or none, as in methanol), secondary (2°) if attached to

two, and tertiary (3°) if attached to three. This classification, distinct from the numbering

used in the name, is what actually controls how fast and by what mechanism the alcohol reacts, as

later sections on the Lucas test and dehydration show.

Naming phenols. 'Phenol' itself is a retained IUPAC name for hydroxybenzene and is used as the

parent name for substituted derivatives, with the $-\text{OH}$ carbon fixed as C-1 and the ring

numbered to give the lowest locants to the substituents, e.g. 4-methylphenol (also called

p-cresol) for a methyl group on the carbon directly opposite the $-\text{OH}$. Several dihydroxy

and trihydroxy phenols keep long-established common names rather than fully systematic ones --

catechol (1,2-dihydroxybenzene), resorcinol (1,3-) and hydroquinone (1,4-) -- which remain in

routine use alongside the systematic names.

Naming ethers. IUPAC substitutive nomenclature treats an ether as an alkane substituted by an

'alkoxy' group: the smaller of the two R groups (attached through oxygen) becomes the

'-oxy' prefix, and the larger R group becomes the parent chain, e.g.

$\text{CH}_3\text{--O--CH}_2\text{CH}_3$ is methoxyethane (methoxy prefix on an ethane parent), and …