Common/trivial names

As organic chemistry developed historically, a new compound was typically given its own individual, one-off name as soon as it was discovered or isolated, well before any systematic naming scheme existed at all; these older, informally-assigned names are what we now call common (or trivial) names. A trivial name usually carries some genuine story or historical reason behind it, and has simply stuck through long-established usage -- so even once IUPAC's fully systematic method (developed in the sections that follow) became available, trivial names did not disappear. They remain genuinely useful, and for many well-known, commercially important organic compounds they are still the names actually used day to day, in preference to the more cumbersome systematic name. Table 14.5 collects the trivial names of a representative set of such compounds, alongside their structural formulae, for reference. Closely related to naming (since it feeds directly into how branched alkyl chains get numbered and named in the sections that follow), the book's 'Remember' box at this point defines four classes of saturated (sp3-hybridised) carbon, purely by counting how many OTHER carbon atoms it is directly, singly bonded to: a PRIMARY (1°) carbon is bonded to only one other carbon (for example, both carbons of ethane, CH3-CH3, are primary, since each is bonded to just the other one); a SECONDARY (2°) carbon is bonded to two other carbons (for example, the middle carbon of propane, CH3-CH2-CH3); a TERTIARY (3°) carbon is bonded to three other carbons (for example, the middle, branch-bearing carbon of isobutane, CH3-CH(CH3)-CH3); and a QUATERNAR …