Question

The alkene that exhibits optical isomerism is:

• A. 2-methyl-2-pentene
• B. 3-methyl-2-pentene
• C. 3-methyl-1-pentene
• D. 4-methyl-1-pentene
• E. 2-methylpentane

Hint:

For optical isomerism in alkenes, look for a chiral center formed by a carbon atom attached to four different substituents. This occurs when the alkene is asymmetric and leads to non-superimposable mirror images (enantiomers).

Answer 1

The Correct Option is C

Step 1: Optical isomerism occurs when a molecule has a chiral center, i.e., a carbon atom attached to four different substituents. For alkenes, this can occur if the double bond leads to non-superimposable mirror images (enantiomers).

Step 2: To check for optical isomerism, we examine each option:

- Option (A) \( \text{2-methyl-2-pentene} \): This molecule has no chiral centers because the two substituents on the second carbon (the methyl groups) are identical, preventing optical isomerism.

- Option (B) \( \text{3-methyl-2-pentene} \): This also lacks a chiral center due to the symmetry of the double bond, so it does not exhibit optical isomerism.

- Option (D) \( \text{4-methyl-1-pentene} \): This compound also does not have a chiral center because the substituents on the carbon atom with the double bond are not different enough to create optical isomerism.

- Option (E) \( \text{2-methylpentane} \): This is an alkane, not an alkene, and lacks a double bond, so it cannot exhibit optical isomerism.

Step 3: Option (C) \( \text{3-methyl-1-pentene} \) has a chiral center at the third carbon due to the different substituents attached to it: a hydrogen atom, a methyl group, and two different alkyl groups. This makes the molecule optically active and capable of exhibiting optical isomerism.

Thus, the correct answer is option (C).