Question

1.
Which of the following statement is CORRECT for
[3]
FC3 - CF2 - CF3
(A) All C-F bond lengths are identical
(B)Two C-F bonds attached to middle Carbon-atom are longer compared to other C-F bonds at the terminal
Carbon-atoms
(C) Two C-F bonds attached to middle Carbon-atom are shorter compared to other C-F bonds at the terminal
Carbon-atoms
(D) None is correct
21
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Answer 1

Answer:

trying to predict different C−F bond lengths of octafluoropropane, CF3−CF2−CF3 :

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Applying Bent's rule here, we see that

For C2, we have C3 and C1 towards which s-character of sp3 orbitals is richer. Hence sp3 orbital of C2 has lesser s-character directed towards F.

For C1 (or C3), we have only C2 toward which s-character of sp3 orbitals is richer. Hence sp3 orbital of C1 has greater s-character directed towards F.

Using this I think C2−F bond length is greater than C1−F.