Comment on the C-C bond length for ${\mathrm{C}}_6{\mathrm{H}}_6 \mathrm{and} {\mathrm{C}}_2{\mathrm{F}}_6$ compounds.

The structure of C₂H₆ is:

The structure of C₂F₆ is:

In C₂H₆, there is no electronegativity difference between C and H whereas in C₂F₆, there is electronegativity difference between C and F. As a result, partial positive charge is generates on both C atoms of C₂F₆. This results in shortening of C-C bond length of C₂F₆ so that the electrons between two carbon atoms becomes close and try to stabilize the positive charge on carbon atoms.