Question

Which of the following molecule has highest electron density in the phenyl ring?

• A.
• B.
• C.
• D.

Answer 1

The correct option is A

In (a), maximum hyperconjugation takes place thereby increasing the electron density in the phenyl ring to the most.
In (c), the two methyl groups bring negative charge on the same carbon by hyperconjugation, hence opposes one another and decreases the extent of hyperconjugation.
In (b) and (d), there is either no or very less electron donation to phenyl ring by hyperconjugation effect because in (b), there is only one $\alpha$-H and in (d), there is no $\alpha$-H.