Question

A compound with molecular mass 180μ is acylated with CH₃COCl, to get a compound with molecular mass 390μ. The number of amino groups present per molecule of the former compound is 

(a) 6 

(b) 2 

(c) 5 

(d) 4

Answer 1

The correct option is (c) 5.

Explanation:

Acylation of an amine group is represented as follows:

RNH₂ + CH₃COCl ---> RNHCOCH₃ + HCl

Mass of product = 390 g 

Mass of amine = 180 g 

Increase in mass = 390- 180 g = 210 g 

Mass of one molecule of CH₃CO = 12 + 3 + 12 + 16 = 43 

Since, one hydrogen atom of NH₂ group is replaced mass added per molecule = 43 - 1 = 42 g

So, number of  aceryl groups introduced = 210/42 = 5

Thus, number of amino groups in the original compound = 5