Which statement is/are correct.

Options

A. No primary kinetic isotope effect is observed during nitration of benzene
B. `K_H//K_D`=1 for halogenation of benzene
C. `K_H//K_D`=1 for sulphonation of benzene
D. `K_H//K_D` is >greater than 1 for alkylation of benzene

Answer

To determine which statements are correct regarding the kinetic isotope effects in the nitration, halogenation, sulfonation, and alkylation of benzene, we will analyze each statement step by step.

### Step 1: Analyze the first statement
**Statement:** No primary kinetic isotope effect is observed during nitration of benzene.

**Analysis:**
In the nitration of benzene, the rate-determining step does not involve the breaking of a carbon-hydrogen bond. Since the primary kinetic isotope effect (KIE) is observed when there is a bond breaking involving hydrogen, the absence of such a bond breaking in the rate-determining step means that no primary KIE is observed.

**Conclusion:** This statement is correct.

### Step 2: Analyze the second statement
**Statement:** kH/kD = 1 for halogenation of benzene.

**Analysis:**
Similar to nitration, the halogenation of benzene does not involve the breaking of a carbon-hydrogen bond in the rate-determining step. Therefore, the ratio of the rate constants for the reaction with hydrogen (kH) to that with deuterium (kD) will also be equal to 1, indicating no primary kinetic isotope effect.

**Conclusion:** This statement is correct.

### Step 3: Analyze the third statement
**Statement:** kH/kD = 1 for sulfonation of benzene.

**Analysis:**
In the sulfonation of benzene, the first step involves the breaking of a carbon-hydrogen bond, which is the rate-determining step. This means that the primary kinetic isotope effect will be observed, and thus kH/kD will be greater than 1, not equal to 1.

**Conclusion:** This statement is incorrect.

### Step 4: Analyze the fourth statement
**Statement:** kH/kD > 1 for alkylation of benzene.

**Analysis:**
In the alkylation of benzene, similar to halogenation, the rate-determining step does not involve the breaking of a carbon-hydrogen bond. Therefore, the ratio kH/kD will be equal to 1, not greater than 1.

**Conclusion:** This statement is incorrect.

### Final Summary of Correct Statements
The correct statements are:
1. No primary kinetic isotope effect is observed during nitration of benzene (Correct).
2. kH/kD = 1 for halogenation of benzene (Correct).
3. kH/kD = 1 for sulfonation of benzene (Incorrect).
4. kH/kD > 1 for alkylation of benzene (Incorrect).

Thus, the correct statements are the first and second statements.

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