Question

does xanthoproteic confirm the presence of specific amino acid residues in the proteins? explain?

Answer 1

Xanthoproteic reactions are generally used to determine the functional group in amino acids. In Xanthoproteic test amino acids containing phenyl group interact with nitric acid and undergoes nitration of phenyl ring. Normally amino acids such as Tyrosine and Tryptophan forms yellow coloured nitration product which in turn gives orange colour upon addition of alkali in the Xanthoproteic test.

Using this test we cannot specifically tell which amino acid is present. for Eg. Tyrosine and Tryptophan will give a positive test. The amino acid phenylalanine generally shows a negative result even though it contains a phenyl group. In phenylalanine, the phenyl group is very stable and it will not undergo nitration.