Q9-10 Pb - Organic Chemistry (Mcmurry)

Question

Show the terminal alkyne and alkyl halide from which the following products can be obtained. If two routes look feasible, list both.

$\mathbf{b}\mathbf{.}\mathbf{ }{\left({\mathrm{CH}}_3\right)}_{\mathbf{2}}\mathbf{CHC}\mathbf{\equiv }{\mathbf{CCH}}_{\mathbf{2}}{\mathbf{CH}}_{\mathbf{3}}$

Step-by-Step Solution

Answer

Answer

$\mathrm{b}. {\left({\mathrm{CH}}_3\right)}_2\mathrm{CHC}\equiv \mathrm{CH} + {\mathrm{CH}}_3{\mathrm{CH}}_2\mathrm{Br}\to {\left({\mathrm{CH}}_3\right)}_2\mathrm{CHC}\equiv {\mathrm{CCH}}_2{\mathrm{CH}}_3$

Step 1: Alkylation

Migration of the alkyl group from one molecule to another via carbanion or carbocation formation

Step 2: Alkylation of acetylide ion

Acetylide ion is a strong nucleophile that reacts with the electrophile like alkyl halide that replaces the halide and forms alkyne. Hence new C-C bond is formed, and the old C-Br bond is broken.