Question

Which of the following is not an example of cross-conjugation?

• A.
• B.
• C.
• D.

Answer 1

The correct option is D

(a) The first molecule has a keto group attached to two phenyl rings. The $C=O$ double bond is in cross conjugation with the double bonds of the two phenyl rings.

(b) In the second molecule, the middle double bond is in cross-conjugation with the other two side double bonds.

(c) In the third molecule, the lone pair of oxygen atom is in cross-conjugation with the two double bonds.

(d) The fourth molecule does not show any type of cross-conjugation. It shows extended conjugation.

Hence option (d) is the correct answer.