Question

Which of the following on reactions with nitrous acid, followed by treatment with $NaOH$ produces a blue coluration?

• A. $RCH_{2}NO_{2}$
• B. $R_{3}CNO_{2}$
• C. $R_{2}CHNO_{2}$
• D. $PhNO_{2}$

Answer 1

Answer: (C)

$R-\underset{N O_{2}}{\underset{\left|\right.}{C} H_{2}}+O=N-OH \rightarrow \underset{\underset{\underset{\text{blood red colouration}}{\text{Dissolve in NaOH to give}}}{\left(\text{Nitrolic acid}\right)} \, \, \, }{R - \underset{N O_{2} \, \, \, }{\underset{\left|\right.}{C} = N} - O H + H_{2} O}$
$R-\underset{N O_{2} \, \, \, }{\overset{R}{\overset{\left|\right.}{\underset{\left|\right.}{C}}} - R}+HNO_{2} \rightarrow $ No reaction
$\text{R} - \underset{\left(\text{NO}\right)_{\text{2 }}}{\overset{\text{R}}{\overset{\text{|}}{\underset{\text{|}}{\text{C}}}} - \text{H}} + \text{HO} - \text{N} = \text{O} \rightarrow \underset{\underset{\underset{\text{but gives blue colouration}}{\text{Does not dissolve in NaOH,}}}{\left(\text{Pseudo} \text{ } \text{nitrole}\right)} \, }{\text{R} - \underset{\left(\text{NO}\right)_{\text{2}} \, \, }{\overset{\text{R}}{\overset{\text{|}}{\underset{\text{|}}{\text{C}}}} - \text{N}} = \text{O} + \left(\text{H}\right)_{\text{2}} \text{O}}$
$PhNO_{2}+HNO_{2} \rightarrow $ No reaction