Aromatic Compounds Containing Nitrogen - Result Question 7
####7. Coupling of benzene diazonium chloride with 1-naphthol in alkaline medium will give
(2019 Main, 8 April I)
(a)
(c)
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Answer:
Correct Answer: 7. (d)
Solution:
- Coupling of benzene diazonium chloride with 1-naphthol in alkaline medium will give the following coupling reaction.
In the presence of $O \overline{H}$ ion, $Ar \stackrel{+}{N} _2$ exists in equilibrium with an unionised compound ( $Ar-N=N-OH)$ and salts $\left[ArN=N^{+}\right\rceil-\stackrel{\ominus}{O} H$ derived from it, which do not couple.
$$ \begin{aligned} {[Ar-N \equiv N]^{+} } & \stackrel{\ominus}{O H} \stackrel{NaOH}{\underset{H^{+}}{\rightleftharpoons}} Ar-\underset{\text { Does not couple }}{N=N-OH} \ & \underset{H^{+}}{\stackrel{NaOH}{\rightleftharpoons}} Ar \underset{\text { Does not couple }}{N}=N-\stackrel{O}{Na} \end{aligned} $$
Following conditions are very useful for coupling reaction to take place.
(a) The solution must be so alkaline that the concentration of diazonium ion is too low.
(b) It must not be so acidic that the concentration of free phenoxide ion is too low.
