Gabriel phthalimide synthesis can be used for the preparation of amine from

$\mathrm{C}{\mathrm{H}}_3\mathrm{C}{\mathrm{H}}_2\mathrm{B}\mathrm{r}$ is more reactive in ${\mathrm{S}}_{\mathrm{N}}2$ reactions. In $(\mathrm{C}{\mathrm{H}}_3{)}_3\mathrm{C}\mathrm{B}\mathrm{r}$ , steric hindrance at the carbon of $\mathrm{C}-\mathrm{B}\mathrm{r}$ is very high, therefore, the nucleophilic attack of phthalimide anion is mechanically hindered.

The $-\mathrm{C}{\mathrm{H}}_3$ and $-\mathrm{O}\mathrm{C}{\mathrm{H}}_3$ are electron-donating groups, which do not activate Br atom for nucleophilic substitutions reactions. Hence, compounds C and D are not also used for the preparation of amines.