Question

Which species exhibits a plane of symmetry?

Answer 1

Molecule (D) has a plane of symmetry.

Explanation:

(A)

A plane of symmetry would have to be a vertical plane that includes the carboxyl group, `"C1"`, and the midpoint of the `"C3-C4"` bond.

However, the methyl group on `"C2"` is "down" while the one on `"C5"` is "up",

Molecule (A) has no plane of symmetry..

(B)

Even with a "flat" projection, Molecule (B) has no plane of symmetry.

(c)

A plane of symmetry would have to include `"C1, C4"`, and the two carboxyl groups.

However, the groups on `"C2"` and `"C3"` do not have mirror-image counterparts on `"C6"` and `"C5"`.

Molecule (C) has no plane of symmetry.

(D)

There is a vertical plane of symmetry passing through the midpoints of the `"C1-C2"` and `"C3-C4"` bonds.

Molecule (D) has a plane of symmetry.