Which of the following compounds is an amino acid

Options

A. `CH_(3)-CH_(2)-overset(O)overset(|)(C)-O-NH_(4)`
B. `CH_(3)-underset(NH_(2))underset(|)(CH)-overset(O)overset(||)(C)-OH`
C. `CH_(3)-CH_(2)-overset(O)overset(||)(C)-NH_(2)`
D. `CH_(3)-underset(NH_(2))underset(|)(CH)-overset(O)overset(||)(C)-Cl`

Explanation

To determine which of the given compounds is an amino acid, we need to understand the general structure of amino acids and analyze each option accordingly.

### Step-by-Step Solution:

1. **Understand the Structure of Amino Acids**:
- Amino acids have the general formula: NH2-CHR-COOH.
- This means they contain an amino group (-NH2), a carboxylic acid group (-COOH), and a side chain (R) which can be a hydrogen atom, alkyl group, or other functional groups.

2. **Analyze the Options**:
- We will evaluate each option to see if it fits the amino acid structure.

3. **Option 1**: CH3CH2C(=O)O^- NH4^+
- This compound appears to be an ammonium salt formed from an acid-base reaction. It does not contain a free amino group (-NH2) attached to a carbon that is also attached to a carboxylic acid group. **Not an amino acid.**

4. **Option 2**: CH3CH2COOH
- This compound is propanoic acid (a carboxylic acid) and does not contain an amino group (-NH2). **Not an amino acid.**

5. **Option 3**: CH3CH2C(=O)NH2
- This compound is an amide because it has a carbonyl group (C=O) directly attached to the nitrogen atom. It does not have a carboxylic acid group (-COOH). **Not an amino acid.**

6. **Option 4**: CH3CH(NH2)COCl
- This compound contains an amino group (-NH2) and a carbon that is also attached to a carboxylic acid group (-COCl, which can be converted to -COOH). This structure fits the criteria for an amino acid. **This is an amino acid.**

7. **Conclusion**:
- The correct answer is **Option 4** as it contains both an amino group and a carboxylic acid group.