Question

Looking at figure 4.2 here, we can see experimentaly that cyclohexane is more polarizable than benzene.

Why is this the case?

Intuitively, I would think that because the orbitals in benzene are more delocalized, the electrons in benzene could move farther in reaction to an applied electric field, thus creating a larger dipole and being more polarized than what is possible in the localized orbitals of cyclohexane.

The only counter argument I can think of is that the carbons in benzene are SP2, and thus more electronegative than the SP3 carbons in cyclohexane so that even though the electrons have more space to react to an applied field in benzene, they are held tighter to the nuclei and therefore form less of a dipole. However, something about this argument doesn’t seem convincing to me.

Answer 1

Cyclohexane is more polarizable than benzene due to its sp3 hybridized carbons being less electronegative and therefore holding their electrons more loosely, allowing for greater distortion in an electric field, unlike the stable delocalized electrons in sp2 hybridized benzene.

Step-by-step explanation:

The question of why cyclohexane is more polarizable than benzene, despite benzene's delocalized electrons, can be addressed by considering the nature of electron delocalization and the effect of hybridization on electronegativity. In benzene, the delocalized pi electrons are stabilized due to aromatic stabilization, making them less prone to distortion in an electric field.

Additionally, benzene's carbons are sp2 hybridized, which increases their electronegativity compared to the sp3 hybridized carbons of cyclohexane, leading to a tighter hold on the shared electrons. Understanding the electronegativity difference and electron distribution is key.

While benzene's electron-rich regions might suggest greater polarizability, the stability of these delocalized electrons reduces their response to external fields. Cyclohexane, although it lacks the delocalized nature of benzene, has sp3 carbon atoms that are less electronegative, allowing its electrons to be more easily distorted, rendering it more polarizable.