Question

Which of the following is the correct order of C—C bond lengths among these compounds :-
(I) CH3–O–CH=CH–NO2 (II) CH2=CH–NO2
(III) CH2=CH–CH3 (IV) CH2=CH2

(1) I > III > II > IV
(2) IV > III > II > I
(3) I > II > III > IV
(4) II > III > I > IV

Answer 1

Answer:(3)

Explanation In (I) O and N are nore electro negative than C so C-C bond length increase and is maximum in given examples

In (II) N is attached

Answer 2

The correct option is (3)  I > II > III > IV.

• The first compound we have is CH3–O–CH=CH–NO2, here the bond order is further decreased as a result of the resonance of the oxygen lone pair with the carbon-carbon double bond and the electron-withdrawing properties of the nitro group.
• The second compound we have is CH2=CH–NO2, the carbon-carbon double bond's electron density, and bond order are both decreased by the powerfully electron-withdrawing nitro group.
• The third compound we have is CH2=CH–CH3, here the electron-donating group -CH3 provides more electron density towards the double bond and due to repulsion bond order is reduced.
• In the fourth compound, we have no electron-donating or an electron-withdrawing group, hence bond order remains intact.
• Therefore the correct order is I > II > III > IV.

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