Question

A compound with molecular mass $180$ is acylated with $C{H}_{3}COCl$ to get a compound with molecular mass $390$. The number of amino groups present per molecule of the former compound is

• A. $5$
• B. $6$
• C. $4$
• D. $2$

Answer 1

The correct option is A $5$

$\underset{\text{M}}{R-N{H}_2}+C{H}_{3}COCl⟶\underset{\text{M+42}}{RNHCOC{H}_3}+HCl$
If the increase in molecular mass is $42$, the reactant has one $N{H}_2$ group.
Actual increase in molecular mass $=390–180$
$=210$
Number of $N{H}_2$ groups $=\frac{210}{42}=5$