Question

Which of the following tests is suitable to differentiate between aniline and benzylamine?

• A. Aniline gives dye test on diazotisation and reaction with $\beta$-naphthol while benzylamine gives alcohol
• B. Benzylamine gives green dry with $\beta$-naphthol after diazotisation while aniline gives orange dye
• C. Aniline gives carbylamine reaction while benzylamine does not
• D. Benzylamine gives carbylamine reaction while aniline does not

Answer 1

Answer: (A)

Aniline forms stable diazonium salts when reacted with nitrous acid $HNO _{2}$, and no $N _{2}$ gas is evolved.
$NaNO _{2}+ HCl \rightarrow HNO _{2}+ NaCl$
$C _{6} H _{5} NH _{2} \xrightarrow{ NaNO _{2}+ HCl }C _{6} H _{5} N _{2} Cl ^{-}+ NaCl +2 H _{2} O$
Benzylamine on reaction with $HNO _{2}$ yeilds Benzyl alcohol and Nitrogen gas.
$C _{6} H _{5} CH _{2} NH _{2} \xrightarrow{HNO _{2}}\left[ C _{6} H _{5} CH _{2} N _{2}^{+} Cl ^{-}\right] \xrightarrow{ H _{2} O}C _{6} H _{5} CH _{2} OH + HCl + N _{2}( g )$