Write the structural formulas for each of the following groups: (i) `n`-butyl, (ii) isobutyl, (iii) `sec`-butyl, (iv) tertbutyl, (v) isopentyl (isomyl), and (vi) tert-pentyl (`t`-amyl).
Strategy: In `n`-alkyl groups, all `C` atoms form a continous `C` chain with no branching. In isoalkyl group, there is a `CH_(3)`-group on the next-to-end carbon in the chain. Prefixes sec and tert-indicate secondary and tertiary, respectively, i.e., the `H` atom is removed from `2^(@) and 3^(@)C` atoms.