Question

Which of the following has the shortest C-Cl bond? 

(1) Cl–CH=CH–OCH₃ 

(2) Cl–CH=CH–CH₃ 

(3) Cl–CH=CH₂ 

(4) Cl–CH=CH–NO₂

Answer 1

Answer is (4)

Due to –M effect of –NO₂ and + M effect of Cl more D.B. character between C – Cl bond. So shortest bond length.

Answer 2

Answer is (4)

Resonance form of Cl – CH = CH – NO₂ is more stable than resonance form of any other given compounds. Hence, double bond characters in C – Cl bond is maximum and bond length is shortest. 

So, the answer should be 2