IUPAC nomenclature of substituted benzene

Naming a substituted benzene ring follows its own set of conventions, layered by how many substituents are present. For a MONOsubstituted benzene (exactly one substituent on the ring), the IUPAC name is formed simply by placing that substituent's own name as a prefix directly in front of 'benzene' -- giving names such as chlorobenzene, nitrobenzene, bromobenzene, iodobenzene, and tert-butylbenzene. A handful of monosubstituted benzenes, however, keep entirely separate, long-accepted trivial names that bear no obvious resemblance at all to the attached substituent's own name, and IUPAC itself formally accepts and universally uses these trivial names right alongside (or even in preference to) the fully systematic ones: methylbenzene is universally called toluene, aminobenzene is aniline, hydroxybenzene is phenol, methoxybenzene is anisole, and the -CHO and -COOH derivatives of benzene are benzaldehyde and benzoic acid respectively. If the substituent chain attached to the ring itself has MORE carbon atoms than the benzene ring does (that is, 7 or more carbons), the whole compound is instead named as a phenyl-SUBSTITUTED alkane -- the ring becomes the substituent, not the parent -- giving names such as 2-phenylheptane and hexylbenzene; this same 'benzene ring as substituent, not parent' naming is also used whenever the benzene ring happens to be attached to an alkane chain that ALREADY carries the compound's own principal functional group, as in 1-chloro-3-phenylpropane, phenylmethanol (also called benzyl alcohol), and 1-phenylethanone (also called acetophenone). For DIsubstituted benzenes (exactly two substituents), the three geometrically distinct substitution patterns have long-standing trivial prefixes -- ortho (o-, adjacent substituents), meta (m-, one carbon apart), and para (p-, directly opposite) -- while the formal IUPAC system instead numbers the ring directly: 1,2-dichlorobenzene (= o-dichlorobenzene), 1,3-dichlorobenzene (= m-dichlorobenzene), 1,4-dichlorobenzene (= p-dichlorobenzene). Where the two substituents on the ring are DIFFERENT from each other, they are cited in strict alphabetical order together with the lowest possible pair of locant numbers, e.g. 1-bromo-4-iodobenzene (= p-bromoiodobenzene) and 1-chloro-3-nitrobenzene (= m-chloronitrobenzene); and if one of the two substituents happens to be one that already gives the ring its own special trivial parent name (as aniline, toluene, or phenol do), the whole compound is instead named as a derivative of THAT special trivial parent rather than of plain 'benzene' -- e.g. 2-chloroaniline (= o-chloroaniline), 3-nitrotoluene (= m-nitrotoluene), 4-bromophenol (= p-bromophenol). For TRIsubstituted (and more highly substituted …