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JEE Advanced levelSingle correct optionDifficulty 3 of 3nc090

Benzenediazonium chloride (1 equiv.) is allowed to couple with resorcinol (benzene-1,3-diol) in mildly alkaline solution. The major monoazo product is

  1. A2-(phenylazo)benzene-1,3-diol (azo group between the two OH groups)
  2. B5-(phenylazo)benzene-1,3-diol (azo group meta to both OH groups)
  3. C4-(phenylazo)benzene-1,3-diol (azo group ortho to one OH and para to the other)
  4. Dno coupling, since resorcinol is not activated

Answer: C

Both phenoxide oxygens activate positions 2, 4 and 6; position 5 is meta to both. Position 4 (equivalent to 6) is ortho to one oxygen and para to the other, and is less hindered than position 2, which lies between two oxygens. The major monoazo product is therefore the 4-isomer.
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