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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3nc219

Which statements about azo coupling are correct?

  1. ACoupling of benzenediazonium chloride with phenol is fastest in strongly acidic medium (pH about 1) because the diazonium ion concentration is highest.
  2. BMethyl orange is obtained by coupling diazotised sulfanilic acid with N,N-dimethylaniline.
  3. CCoupling with phenols is carried out at pH 9-10.
  4. DCoupling with aromatic amines is carried out at pH 4-5.

Answer: B, C, D

Phenols couple best as phenoxide in mild alkali, and amines couple as the free base in weakly acidic medium. In strong acid the phenol is not ionised and the amine is protonated, so the ring is deactivated and coupling is very slow. Methyl orange is made from the stated components.
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