An optically inactive compound (A) having molecular formula `C_(4)H_(11)N` on treatment with `HNO_(2)` gave an alcohol (B) which on heating with conc. `H_(2)SO_(4)` at 440 K gave an alkene ( C) . ( C) on treatment with HBr gave an optically active compound (D ) having molecular formula `C_(4)H_(9)Br` Identify (A) ,(B) ,(C) and (D).

Explanation

Since compound (A) is optically inactive and contains nitrogen which gives alcohol with `HNO_(2)`, it is primary amine. The reactions may be given as :
`underset("1-Aminobutane")underset("(A)")(CH_(3)CH_(2)CH_(2)CH_(2)NH_(2)) overset(HNO_(2))(to) underset("Butan-1-ol")underset("(B)")(CH_(3)CH_(2)CH_(2)CH_(2)OH) + N_(2) + H_(2)O`
`underset("(B)")(CH_(3)CH_(2)CH_(2)CH_(2)OH) underset(-H_(2)O)overset(H_(2)SO_(4), 440 K)(to) underset("But-1-ene")underset("(C)")(CH_(3)CH_(2)CH=CH_(2))`
`underset("(C)")(CH_(3)CH_(2)CH=CH_(2)) overset(HBr)(to) underset("2-Bromobutane(optically active)")underset("(D)")(CH_(3)CH_(2)underset(Br)underset(|)CH-CH_(3)`