Which of the following is the major solute species in a solution of glutamic acid at pH = 1.3?

Options

A.
B.
C.
D.

Explanation

To determine the major solute species in a solution of glutamic acid at pH = 1.3, we can follow these steps:

### Step 1: Understand the Structure of Glutamic Acid
Glutamic acid is an alpha-amino acid with the following structure:
- It contains two carboxylic acid groups (–COOH) and one amino group (–NH2).
- The structure can be represented as HOOC-CH(NH2)-CH2-COOH.

### Step 2: Identify the Ionization States
At different pH levels, glutamic acid can exist in various forms:
- **At low pH (acidic conditions)**: The amino group (–NH2) can accept a proton (H+) to become positively charged (–NH3+), and the carboxylic acid groups can remain protonated (–COOH).
- **At neutral pH**: Glutamic acid typically exists in its zwitterionic form, where one carboxylic acid group is deprotonated (–COO-) and the amino group is protonated (–NH3+).
- **At high pH (basic conditions)**: Both carboxylic acid groups can lose protons, resulting in a negatively charged form.

### Step 3: Analyze the Given pH
Given that the pH is 1.3, this indicates an acidic environment. In such conditions:
- The carboxylic acid groups will predominantly remain protonated (–COOH).
- The amino group will be protonated (–NH3+).

### Step 4: Determine the Major Species
In an acidic medium (pH = 1.3), glutamic acid will exist primarily in its cationic form:
- The structure will be: HOOC-CH(NH3+)-CH2-COOH.

### Step 5: Evaluate the Options
Now, we need to identify which option corresponds to the cationic form:
- **Option A**: Represents the cationic form.
- **Option B**: Represents the anionic form.
- **Option C**: Represents the zwitterionic form.
- **Option D**: Represents the double anionic form.

### Conclusion
The major solute species in a solution of glutamic acid at pH = 1.3 is represented by **Option A**, which is the cationic form of glutamic acid.

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