A compound with molecular mass 180 is acylated with $$CH_3COCl$$ to get a compound with molecular mass 390. The number of amino groups presents per molecule of the former compound is

We are given a compound with molecular mass 180, which is acylated with $$CH_3COCl$$ (acetyl chloride) to get a compound with molecular mass 390.

We need to find the number of amino ($$-NH_2$$) groups in the original compound.

When an amino group reacts with acetyl chloride, the following reaction occurs:

$$R-NH_2 + CH_3COCl \rightarrow R-NHCOCH_3 + HCl$$

In this reaction, each $$-NH_2$$ group (molecular mass contribution = 16) is converted to $$-NHCOCH_3$$ group (molecular mass contribution = 58).

So the increase in molecular mass per amino group acylated = $$58 - 16 = 42$$.

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

Number of amino groups = $$\frac{\text{Total increase in mass}}{\text{Increase per amino group}} = \frac{210}{42} = 5$$

Therefore, the number of amino groups present per molecule of the original compound is 5, which is Option D.