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Which of the following amino acid will give violet coloured complex with neutral ferric chloride solution?

Options

  1. AThreonine
  2. BSerine
  3. CTyrosine
  4. DCysteine

Correct answer

C. Tyrosine

Step-by-step solution

Neutral ferric chloride ( FeCl ₃ ) solution gives a characteristic violet coloured complex with compounds containing a phenolic hydroxyl group. Among the given amino acids, Tyrosine contains a phenolic - OH group in its side chain. Threonine and Serine contain aliphatic - OH groups, and Cysteine contains a thiol ( - SH ) group, none of which give a positive neutral FeCl ₃ test. Therefore, Tyrosine will give a violet coloured complex with neutral ferric chloride solution. Answer: Tyrosine

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