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

Options

A. 6
B. 2
C. 5
D. 4

Answer

C

Explanation

During acetylation, one H atom (at mass=1amu) of the `NH_(2)` group is replaced by an acetyl group, i.e.., `CH_(3)CO` (mol. Mass=43amu).
`-NH_(2)+CH_(3)COCl to -NHCOCH_(3)+HCl`
In other words, acetylation of each `NH_(2)` group increases the mass by 43-1=42 amu. now since the mol. mass of the organic compound is 180 while that of the acetylated product is 390, therefore, increase in the mass due to acetylation=390-180=210amu.
`therefore`No. of `-NH_(2)` groups`=(210)/(42)=5`