The number of mono chloro derivatives that the compound ‘D’ can give ${\mathrm{CH}}_3\mathrm{CN}\stackrel{{\mathrm{H}}_2\mathrm{O}/{\mathrm{H}}^{+}}{\to }\mathrm{A}\stackrel{\mathrm{Ca}}{\to }\mathrm{B}\underset{\mathrm{distillation}}{\overset{\mathrm{dry}}{\to }}\mathrm{C}\underset{\mathrm{HCl}}{\overset{\mathrm{Zn}-\mathrm{Hg}}{\to }}\mathrm{D}$

$\therefore {\mathrm{CH}}_3\mathrm{CN}\stackrel{{\mathrm{H}}_2\mathrm{O}/{\mathrm{H}}^{+}}{\to }{\mathrm{CH}}_3-\mathrm{COOH}\stackrel{\mathrm{Ca}}{\to }{\left({\mathrm{CH}}_3\mathrm{COO}\right)}_2\mathrm{Ca}\underset{\mathrm{distillation}}{\overset{\mathrm{dry}}{\to }}$ 

Hence propane upon monochlorination gives

${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{Cl}$ and ${\mathrm{CH}}_3-\stackrel{\underset{\mathrm{I}}{\overset{.}{\mathrm{Cl}}}}{\mathrm{CH}}-{\mathrm{CH}}_3$