The given structure of `alpha` - amino acid will exist at which pH ?
`overset(o+)(N)H_3-underset(R)underset(|)overset(COOH)overset(|)C-H`

Options

A. 7
B. 14
C. 6
D. 12

Answer

To determine the pH at which the given structure of the alpha-amino acid exists, we need to analyze the structure and the charges present.

### Step-by-Step Solution:

1. **Identify the Structure**: The structure provided shows an amino group (`NH3^+`), a carboxylic acid group (`COOH`), and a generic R group. The amino group is positively charged, indicating it has accepted a proton.

2. **Understanding the pH Influence**: The pH of a solution affects the ionization of amino acids. At low pH (acidic conditions), the amino group is protonated (as shown in the structure), and the carboxylic acid group is also likely to be in its protonated form (COOH).

3. **Neutral Form of Amino Acids**: Typically, amino acids exist in a zwitterionic form (where the amino group is protonated and the carboxylic group is deprotonated) at a neutral pH (around 7). However, in acidic conditions (pH < 7), the amino group remains protonated, and the carboxylic acid group does not lose its proton.

4. **Conclusion on pH**: Since the structure shows a positively charged amino group, this indicates that the amino acid is in an acidic environment where it has accepted a proton. Therefore, the amino acid will exist at a pH less than 7.

5. **Final Answer**: The alpha-amino acid will exist at a pH less than 7, which corresponds to option C.