In aqueous solution amino acids moslty exit as

Options

A. `NH_(2)-CHR-COOH`
B. `NH_(2)-CHR-COO^(-)`
C. `overset(+)(N)H_(3)CHRCOOH`
D. `H_(3)overset(+)NCHRCOO^(-)`

Explanation

To solve the question "In aqueous solution amino acids mostly exist as", we can follow these steps:

### Step 1: Understand the Structure of Amino Acids
Amino acids have a general structure represented as:
\[ \text{NH}_2 - \text{CHR} - \text{COOH} \]
where:
- \(\text{NH}_2\) is the amino group,
- \(\text{CHR}\) is the side chain that varies among different amino acids,
- \(\text{COOH}\) is the carboxylic acid group.

**Hint:** Recall the basic structure of amino acids and their functional groups.

### Step 2: Consider the Behavior of Amino Acids in Aqueous Solution
In an aqueous solution, amino acids can undergo protonation and deprotonation. The amino group (\(\text{NH}_2\)) can gain a proton (H⁺) to become \(\text{NH}_3^+\), and the carboxylic acid group (\(\text{COOH}\)) can lose a proton to become \(\text{COO}^-\).

**Hint:** Think about how acids and bases behave in water.

### Step 3: Write the Ionic Form of Amino Acids
When amino acids are in an aqueous solution, they typically exist in the zwitterionic form, which can be represented as:
\[ \text{NH}_3^+ - \text{CHR} - \text{COO}^- \]
This indicates that the amino group is positively charged, and the carboxylate group is negatively charged.

**Hint:** Remember that zwitterions have both positive and negative charges but are overall neutral.

### Step 4: Identify the Correct Answer
Given the options, the correct representation of amino acids in aqueous solution is:
\[ \text{NH}_3^+ - \text{CHR} - \text{COO}^- \]
This corresponds to option D.

**Hint:** Look for the option that matches the zwitterionic form.

### Final Answer
Thus, the correct answer is:
**Option D: \(\text{NH}_3^+ - \text{CHR} - \text{COO}^-\)**