Carboxylic Acids and their Derivatives 2 Question 9
9. A compound with molecular mass 180 is acylated with $\mathrm{CH}_{3} \mathrm{COCl}$ to get a compound with molecular mass 390 . The number of amino groups present per molecule of the former compound is
(2013 Main)
(a) 2
(b) 5
(c) 4
(d) 6
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Answer:
Correct Answer: 9. (d)
Solution:
- $R-\mathrm{NH}{2}+\mathrm{CH}{3}-\mathrm{C}-\mathrm{Cl} \underset{(-\mathrm{HCl})}{\longrightarrow} R-\mathrm{NH}-\mathrm{C}-\mathrm{CH}_{3}$
Since, each $-\mathrm{COCH}{3}$ group displace one $\mathrm{H}$ atom in the reaction of one mole of $\mathrm{CH}{3}-\stackrel{\mathrm{C}}{\mathrm{O}}-\mathrm{Cl}$ with one $-\mathrm{NH}_{2}$ group, the molecular mass increases with 42 unit.
Since the mass increases by $(390-180)=210$, hence the number of $-\mathrm{NH}_{2}$ group is $\frac{210}{42}=5$.
