Question

A dibromo derivative (A) on treatment with KCN followed by acid hydrolysis and heating gives a monobasic acid (B) along with the liberation of CO₂. (B) on heating with liquid ammonia followed by treating with Br₂/KOH gives (C) which on treating with NaNO₂ and HCl at low temperature followed by oxidation gives a monobasic acid (D) having molecular mass 74. Identify A to D.

Answer 1

(i) \[\begin{array}{cc}
\ce{CH3 - CH2 - CH - CH2 ->[KCN] CH3 - CH2 - CH - CH2 ->[(i) H^+/H2O][(ii) Heat] CO2 + \underset{\underset{(B)}{(Butanoic acid)}}{CH3 - CH2 - CH2} - COOH}\\
\phantom{....}|\phantom{.....}|\phantom{.........................}|\phantom{......}|\phantom{......................................}\\
\phantom{}\ce{\underset{\underset{(A)}{(1, 2-dibromobutane)}}{Br\phantom{...}Br}}\phantom{.................}\ce{\underset{(1, 2-dicyanobutane)}{CN\phantom{...}CN}}\phantom{..................................}
\end{array}\]

(ii) \[\ce{\underset{\underset{(B)}{(Butanoic acid)}}{CH3 - CH2 - CH2 - COOH} ->[liq. NH3][\Delta] \underset{(Butanamide)}{CH3 - CH2 - CH2 - CONH2} ->[Br2/KOH] \underset{\underset{(C)}{(1-Aminopropane)}}{CH3 - CH2 - CH2 - NH2}}\]

(iii) \[\ce{\underset{\underset{(C)}{1-Aminopropane}}{CH3 - CH2 - CH2 - NH2} ->[NaNO2/HCl][Low temperature] \underset{(1-propanol)}{CH3 - CH2 - CH2 - OH} ->[K2Cr2O7/H^+][2(O)] \underset{\underset{(D)}{(Propanoic acid)}}{CH3 - CH2 - COOH}}\]

(iv) Molecular mass of propanoic acid is 74.

A	\[\begin{array}{cc} \ce{CH3 - CH2 - CH - CH2 - Br}\\ |\\ \phantom{.}\ce{Br} \end{array}\]	1, 2-dibromo butane
B	\[\begin{array}{cc} \ce{CH3 - CH2 - CH - CH2 - CN}\\ |\phantom{.}\\ \phantom{.}\ce{CN} \end{array}\]	1, 2-dicyano butane
C	\[\ce{CH3 - CH2 - CH2 - NH2}\]	1-amino propane
D	\[\ce{CH3 - CH2 - COOH}\]	propanoic acid