An activated amino acid `A(H_(2)NCHRCOX)` reacts with an amino acid `B(H_(2)NCHR'CO_(2)H)`. Which statement is correct about this reaction ?

Options

A. The amino acids are cpupled by a peptide link of form `- CONH-`
B. Activation prevents reaction between two molecules of A
C. The reaction involves elimination of HX
D. A dipeptide is formed

Explanation

To determine which statement is correct about the reaction between the activated amino acid A (H₂NCHRCOX) and the amino acid B (H₂NCHR'CO₂H), we can analyze the reaction step-by-step.

### Step 1: Identify the Components
- **Amino Acid A**: H₂NCHRCOX
- Functional groups: Amino group (NH₂), R group (side chain), Carboxyl group (COX, where X is a leaving group).

- **Amino Acid B**: H₂NCHR'CO₂H
- Functional groups: Amino group (NH₂), R' group (side chain), Carboxyl group (CO₂H).

### Step 2: Understand the Reaction
When these two amino acids react, the amino group of amino acid A will attack the carboxyl group of amino acid B, leading to the formation of a peptide bond. During this process, the leaving group X from amino acid A and the hydroxyl group (OH) from the carboxyl group of amino acid B will be eliminated as water (H₂O) or HX, depending on the specific reaction conditions.

### Step 3: Write the Reaction
The reaction can be summarized as follows:
1. The amino group of A attacks the carbonyl carbon of the carboxyl group of B.
2. Elimination of HX (where X is the leaving group) occurs.
3. A peptide bond is formed between the two amino acids.

The resulting product is a dipeptide:
- **Dipeptide Structure**: H₂NCHRCO-NHCHR'CO₂H

### Step 4: Analyze the Statements
1. **Amino acid pulled by a peptide link off from CONS**: This statement is correct because the peptide bond formed is indeed a link between the two amino acids, and the product contains a peptide bond (C-N bond).

2. **Activation prevents reaction between two molecules away**: This statement is incorrect. Activation of the amino acid does not prevent the reaction; rather, it facilitates the formation of the peptide bond.

3. **Reaction involved elimination of HX**: This statement is correct. The reaction involves the elimination of HX during the formation of the peptide bond.

4. **A dipeptide is formed**: This statement is correct. The product of the reaction is indeed a dipeptide.

### Conclusion
Based on the analysis, the correct statements about the reaction are:
- Statement 1: Correct
- Statement 2: Incorrect
- Statement 3: Correct
- Statement 4: Correct

Thus, the correct options are 1, 3, and 4.