Which of the following is correct structure of tyrosine?

Solution

Chemistry ma’am · 3 steps

Tyrosine is phenylalanine with an OH at the para position, so check two things: one CH₂ and para OH.

1. Build tyrosine. Start from phenylalanine, C₆H₅-CH₂-CH(NH₂)-COOH. Tyrosine has an extra OH on the ring, para (position 4) to the side chain: HO-C₆H₄-CH₂-CH(NH₂)-COOH, that is, 2-amino-3-(4-hydroxyphenyl)propanoic acid.
2. Two checks. First, only one CH₂ links the ring to the α-carbon that carries NH₂ and COOH. Second, the OH sits para to that CH₂, directly across the ring.

   Option	CH₂ groups between ring and α-carbon	OH position on ring	Tyrosine?
   (a)	1	meta	no
   (b)	2	para	no
   (c)	2	meta	no
   (d)	1	para	yes

3. So. Only (d) has a single CH₂ and a para OH, so (d) is the correct structure of tyrosine.

The idea to keep. Learn tyrosine as phenylalanine plus a para OH. For any aromatic amino acid, check the chain length to the α-carbon and where the ring substituent sits.

Answer from the NTA final answer key. Solution by PrepWiser.