Question

which of the following are optically active? check all that apply.

Explanation:

Step1: Recall optical - activity condition

A compound is optically active if it has a chiral center (a carbon atom bonded to four different groups) or lacks a plane of symmetry.

Step2: Analyze first structure

The first structure has a carbon atom bonded to four different groups (two different halogen - containing groups and two different alkyl - like groups), so it is chiral and optically active.

Step3: Analyze second structure

The second structure has a chiral center as it has a carbon atom with four different groups attached, so it is optically active.

Step4: Analyze third structure

The third structure has a plane of symmetry passing through the two methyl - substituted carbons, so it is not chiral and not optically active.

Step5: Analyze fourth structure

The fourth structure has a carbon atom bonded to four different groups (chlorine, methyl, and two other different groups on the ring), so it is chiral and optically active.

Step6: Analyze fifth structure

The fifth structure has a plane of symmetry passing through the two methyl - substituted carbons, so it is not chiral and not optically active.

Step7: Analyze sixth structure

The sixth structure has a plane of symmetry passing through the two methyl - substituted carbons, so it is not chiral and not optically active.

Step8: Analyze seventh structure

The seventh structure has a chiral center as it has a carbon atom with four different groups attached, so it is optically active.

Step9: Analyze eighth structure

The eighth structure has a plane of symmetry passing through the two methyl - substituted carbons, so it is not chiral and not optically active.

Answer:

The optically active structures are the first, second, fourth, and seventh ones.