Why dipole moment of cyclopentanone is greater than cyclopentadienone?please help me.
Here is my explanation.
In addition to the bond dipole caused by the C-O electronegativity difference, there is also a resonance contributor
The combination of the two effects gives cyclopentanone a dipole moment of 3.28 D.
The corresponding resonance contributor in cyclopentadienone is
In this case, generating a positive charge on the carbonyl carbon generates a highly unstable antiaromatic 4π system.
The relative importance of this contributor will therefore be less, and the dipole moment will be decreased (to 3.13 D).