Which sequence is the best way to prepare pent-2-yne from propyne?

Sodamide converts propyne to sodium propynide, $\mathrm{CH}{}_3-\mathrm{C}\equiv \mathrm{C}{}^{-}\mathrm{Na}{}^{+}$, which attacks a primary alkyl halide in an ${\mathrm{S}}_{\mathrm{N}}2$ reaction. With $\mathrm{CH}{}_3\mathrm{CH}{}_2\mathrm{Br}$ the product is $\mathrm{CH}{}_3-\mathrm{C}\equiv \mathrm{C}-\mathrm{CH}{}_2\mathrm{CH}{}_3$, pent-2-yne. Aqueous NaOH is too weak a base, methyl bromide would give but-2-yne, and a tertiary halide gives elimination instead.