Question

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

• A. 1
• B. 3
• C. 5
• D. 4

Answer 1

Answer: (C)

$R-\underset{M}{N H_{2}}+CH_{3}COCl \rightarrow \underset{M + 42}{R N H C O C H_{3}}+HCl$

If the increase in molecular mass is 42, the reactant has one $NH_{2}$ group.

Actual increase in molecular mass $=390-180=210$

Number of $NH_{2}$ groups $=\frac{210}{42}=5$