Concept Explanation: Electrophilic Addition Reaction of Alkenes

This question involves predicting the major product of an electrophilic addition reaction where an alkene reacts with HBr. The key concept here is Markovnikov's Rule, which states that in the addition of a protic acid (like HBr) to an unsymmetrical alkene, the hydrogen atom attaches to the carbon with more hydrogen atoms, and the halogen attaches to the carbon with fewer hydrogen atoms.

Step-by-Step Solution:

Step 1: Analyze the Alkene Structure

The reactant is an unsymmetrical alkene (1-methylcyclopentene). The double bond is between two carbons: one is a tertiary carbon (attached to three alkyl groups) and the other is a secondary carbon (attached to two alkyl groups).

Step 2: Apply Markovnikov's Rule

When HBr adds across the double bond, the hydrogen (H⁺) will add to the less substituted carbon (the secondary carbon), and the bromide (Br⁻) will add to the more substituted carbon (the tertiary carbon). This occurs because the tertiary carbocation intermediate is more stable than the secondary carbocation.

Step 3: Determine the Major Product

The major product is 1-bromo-1-methylcyclopentane. The structure shows a bromine atom attached to the tertiary carbon of the cyclopentane ring.

Final Answer:

The correct option is: Major product structure

Related Topics:

Electrophilic Addition Reactions
Carbocation Stability
Anti-Markovnikov Addition (in presence of peroxides)
Hydration of Alkenes

Important Formulae and Theory:

Markovnikov's Rule: "The rich get richer" - the carbon with more hydrogens gets the hydrogen.

Carbocation Stability Order:

3° > 2° > 1° > methyl

General Reaction:

R - CH = CH 2 + HBr \to R - CHBr - CH 3