Among the following, the achiral amino acids is

Options

A. 2-ethylalanine
B. 2-methylglycine
C. 2-hydroxymethyl serine
D. Tryptophan

Answer

To determine which of the given amino acids is achiral, we need to analyze the structure of each amino acid and identify whether they possess a chiral center. A chiral center is typically a carbon atom that is bonded to four different groups.

### Step-by-Step Solution:

1. **Identify the Amino Acids**: We have four amino acids to analyze:
- 2-Ethylalanine
- 2-Methylglycine
- 2-Hydroxy-methylglycine
- Tryptophan

2. **Analyze 2-Ethylalanine**:
- Structure: NH2-CH(C2H5)-COOH
- The central carbon is attached to:
- NH2 (amino group)
- COOH (carboxyl group)
- C2H5 (ethyl group)
- CH3 (methyl group)
- Since this carbon is attached to four different groups, **2-Ethylalanine is chiral**.

3. **Analyze 2-Methylglycine**:
- Structure: NH2-CH(CH3)-COOH
- The central carbon is attached to:
- NH2 (amino group)
- COOH (carboxyl group)
- CH3 (methyl group)
- H (hydrogen)
- This carbon is also attached to four different groups, so **2-Methylglycine is chiral**.

4. **Analyze 2-Hydroxy-methylglycine**:
- Structure: NH2-CH(CH2OH)-COOH
- The central carbon is attached to:
- NH2 (amino group)
- COOH (carboxyl group)
- CH2OH (hydroxymethyl group)
- H (hydrogen)
- This carbon is attached to four different groups, making **2-Hydroxy-methylglycine chiral**.

5. **Analyze Tryptophan**:
- Structure: NH2-CH(C8H6N)-COOH
- The central carbon is attached to:
- NH2 (amino group)
- COOH (carboxyl group)
- C8H6N (indole side chain)
- H (hydrogen)
- This carbon is also attached to four different groups, so **Tryptophan is chiral**.

6. **Conclusion**:
- After analyzing all four amino acids, we find that all of them are chiral. However, if we consider the possibility of a mistake in the options or the naming of the amino acids, we can conclude that **2-Hydroxy-methylglycine** is the one that stands out as it has a repeating group (CH2OH) which may lead to confusion, but it is indeed chiral.

### Final Answer:
None of the given amino acids are achiral based on the analysis. However, if we strictly consider the options, **2-Hydroxy-methylglycine** is the one that may be perceived as less chiral due to its structure, but it is still chiral.