Addition of ammonia derivative to carbonyl compounds is done in presence of weakly acidic medium because.

IUPAC name of the compound

The compounds $\mathrm{A}$ and $\mathrm{B}$ in the reaction sequence

$\mathrm{A}\stackrel{\mathrm{Phenol}}{⟵}{\mathrm{CH}}_3\mathrm{COCl}\stackrel{{\mathrm{CH}}_3\mathrm{COONa}}{⟶}\mathrm{B}$

The decreasing order of the ratio of $\mathrm{HCN}$ addition to compounds $\mathrm{a}$ to $\mathrm{d}$ is:

$\left(\mathrm{a}\right) \mathrm{HCHO}$

$\left(\mathrm{b}\right) {\mathrm{CH}}_3{\mathrm{COCH}}_3$

$\left(\mathrm{c}\right) {\mathrm{PhCOCH}}_3$

$\left(\mathrm{d}\right) \mathrm{PhCOPh}$