${\mathrm{C}}_6{\mathrm{H}}_5-{\mathrm{CH}}_2-{\mathrm{NH}}_2+\mathrm{RX}\to {\mathrm{C}}_6{\mathrm{H}}_5-{\mathrm{CH}}_2-\mathrm{NH}-\mathrm{R}$

Which of the following alkyl halides is best suited for this reaction by ${\mathrm{SN}}_1$ mechanism?

${\mathrm{C}}_6{\mathrm{H}}_5-{\mathrm{CH}}_2-\mathrm{Br}$ is best suited for this reaction through a ${\mathrm{SN}}^1$ mechanism as the carbocation(benzyl carbocation) formed in the reaction is resonance stabilized. The benzyl carbocation formed is ${\mathrm{C}}_6{\mathrm{H}}_5-{\mathrm{CH}}_2^{+}$. Reactivity in these reactions depends upon the stability of the carbocation intermediate.

Hence, the correct answer is option C) ${\mathrm{C}}_6{\mathrm{H}}_5-{\mathrm{CH}}_2-\mathrm{Br}$.