An organic compound A having molecular formula `C_(2)H_(5)O_(2)N` on treatment with `HNO_(2)` gives a blue coloured compound B having molecular formula `C_(2)H_(4)O_(3)N_(2)`. On reduction, A gives a compound C having molecular formula `C_(2)H_(7)N`. C on treatment with nitrous acid gives D which gives positive iodoform test. Identify the compounds A, B, C and D.

Explanation

Since, the compound C having molecular formula `C_(2)H_(7)N` reacts with nitrous acid to give D which gives positive iodoform test, the compound C should be ethanamine. Ethanamine reacts with `HNO_(2)` to give ethanol which gives a positive iodoform test.Hence, the compound D is ethanol.
`underset("Ethanamine"(C ))(CH_(3)CH_(2)NH_(2)) + HNO_(2) rarr underset("Ethanol (D) (gives positive iodoform test)")(CH_(3)CH_(2)OH) + N_(2) uarr + H_(2)O`
Since, C is obtained by the reduction of A having molecular formula `C_(2)H_(5)O_(2)N`, the compound A should be nitroethane.

Compound A will react with `HNO_(2)` as follows

Hence the compound B is nitrosonitroethane.