Question

Among the following the achiral amino acid is
A. 2- Ethylalanine
B. 2- Methylglycine
C. 2- Hydroxymethyl serine
D. Tryptophan

Answer 1

Hint: In order to solve this question we should know that achirality is present in those compounds in which two or more groups are present on the same atom.

Complete Step by Step Solution:
Chiral and achiral compounds are a part of stereochemistry. Chiral centres or compounds are those which have an atom which has all different groups attached to it and on the other hand achiral compounds are those which have all the atoms to which two or more same constituents or functional groups are attached. According to the given question, the structure of 2-Ethylalanine is given as:
 
We can see there are four different groups (that are\[-COOH\],$-N{{H}_{2}}$,$-{{C}_{2}}{{H}_{5}}$,$-C{{H}_{3}}$) attached to the same carbon and thus we can say that this carbon is a chiral carbon and thereby this compound is a chiral compound. For the compound, 2-Methylglycine, the structure is given as:

Here, we can see that there are four different groups attached to the carbon (that are\[-COOH\],$-N{{H}_{2}}$,$-H$,$-C{{H}_{3}}$) and thus again it is a chiral carbon and this compound is a chiral compound. The next structure given is 2-Hydroxylmethyl serine, the structure of the compound is given as:

The groups attached to the carbon are$-COOH$, $-N{{H}_{2}}$, $-C{{H}_{2}}OH$. Here, we can see that there are two similar groups are attached to the carbon and when two similar groups are attached to the carbon it’s said to be achiral carbon and the compound is achiral compound. The next compound is tryptophan and its structure is given by

Here, there are four different groups attached to the carbon and thus the compound is said to be a chiral compound.
So, the correct option is c. 2-hydroxymethyl serine.

Note: The thing to remember is that a chiral compound is the one in which any of the carbon or any atom of the main chain has four different groups attached to it so achiral compound is the one in which all the atoms of the main chain have two or more same groups attached to it.