Question

1. Fluorene is essentially non-polar. Briefly explain, with respect to atoms that are present and absent in fluorene, and their relative electronegativities, why fluorene is non-polar.

Answer 1

The fluorene, as shown in the figure, only has four types of bonds:

H--Csp2

H--Csp3

C=C

C--C

The values of relative electronegativity according to the Pauling scale for C and H are:

X_C= 2.5 and X_H= 2.1

Thus the difference between a C--C bond and C = C is:

While the difference between an H - C bond is:

Following the Pauling scale, when the difference is <0.4 the link is covalent character apolar. For this reason, in addition to the system of conjugated rings that the molecule possesses, the electronic cloud is not significantly displaced, consequently the molecule is apolar.