Question

Which of the following is the correct structure of tyrosine?
A.

B.

C.

D.

Answer 1

Hint: Amino acids include amino\[\;(NH2)\] and carboxyl \[\left( { - COOH} \right)\] functional groups. It also has a side-chain attached to it.

The amino acids, which can be made within the body are non-essential amino acids. The amino acids which cannot be prepared inside the body are essential amino acids.

Tyrosine: is a kind of non-essential amino acid.

Complete Step by Step Solution:
The general formula of Amino acids is as follows


Image: General formula of Amino acids

The IUPAC name of Tyrosine is 4-hydroxyphenylalanine. In this case, the side chain is the
\[( - CH2 - C6H5 - OH)\] group.

Here, the \[( - OH)\] or hydroxyl group is attached to the para position of the phenyl ring.

All the options have the general structure of Amino acids.
Only the side-chain structure is different. Hence, we just have to check whether the structures contain the correct formula for the side group or not.

Image: Option A
If we take option A, we see that it has the \[( - C3H6 - C6H5 - OH)\]group as the side chain. The hydroxyl group is attached to the para position of the benzene ring. Hence, this is not the correct structure of Tyrosine.


Image: Option B
If we take option B, we see that It has the \[( - C6H5 - OH)\] group as the side chain. The hydroxyl group is attached to the meta position of the benzene ring. Hence, this is not the correct structure of Tyrosine.

Image: Option C
If we take option C, we see that the \[( - CH2 - C6H4 - OH)\] group is the side chain. The hydroxyl group is attached to the benzene ring's para position. Hence, this is the correct structure of Tyrosine.


Image: Option D
If we take option D, we see that It has the \[( - C3H6 - C6H4 - OH)\] group as the side chain. The hydroxyl group is attached to the meta position of the benzene ring. Hence, this is not the correct structure of Tyrosine.

So, option C is correct.

Note: While attempting the question, one must have an idea about the formula of the side-group of Tyrosine. He/she must pay attention to the position of the hydroxyl group on the given options. The IUPAC name of Tyrosine is 4-hydroxyphenylalanine which makes it clear that the position of the hydroxyl group substituent is fourth on the phenyl ring.