Reaction of HBr with propene in absence of peroxide is a/an:

Options

A. electrophilic addition
B. electrophilic substitution
C. nucleophilic addition
D. nucleophilic substitution

Answer

To determine the nature of the reaction between HBr and propene in the absence of peroxide, we can follow these steps:

### Step 1: Identify the Reactants
The reactants in this reaction are propene (C3H6) and hydrogen bromide (HBr). The structure of propene is CH3-CH=CH2.

### Step 2: Understand the Mechanism
In the absence of peroxide, the reaction proceeds via an electrophilic addition mechanism. HBr can dissociate into H⁺ (a proton) and Br⁻ (bromide ion).

### Step 3: Electrophilic Attack
The double bond in propene acts as a nucleophile and attacks the electrophilic H⁺ ion. This leads to the formation of a carbocation intermediate.

### Step 4: Formation of Carbocations
When H⁺ adds to propene, two possible carbocations can form:
1. **Primary Carbocation**: CH3-CH2-CH2⁺ (1° carbocation)
2. **Secondary Carbocation**: CH3-CH⁺-CH3 (2° carbocation)

### Step 5: Stability of Carbocations
The secondary carbocation is more stable than the primary carbocation because it is more substituted. Therefore, the reaction will favor the formation of the secondary carbocation.

### Step 6: Nucleophilic Attack
The bromide ion (Br⁻), which is a nucleophile, will then attack the more stable secondary carbocation, leading to the formation of the major product.

### Step 7: Identify the Products
The major product formed will be:
- CH3-CH(Br)-CH3 (bromopropane)

The minor product, formed from the primary carbocation, will be:
- CH3-CH2-CH2Br (1-bromopropane)

### Conclusion
The reaction of HBr with propene in the absence of peroxide is an example of an **electrophilic addition reaction**.

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