NEET 2003 Chemistry question

Which of the following statements is not correct for sigma- and pi- bonds formed between two carbon atoms :

(1)Sigma-bond is stronger than a pi-bond
(2)Bond energies of sigma- and pi-bonds are of the order of 264 KJ/mol and 347 KJ/mol, respectivelyCorrect
(3)Free rotation of atoms about a sigma bond is allowed but not in case of a pi-bond
(4)Sigma-bond determines the direction between carbon atoms but a pi-bond has no primary effect in this regard

Answer: (2)

Solution

A sigma bond is formed by head-on (axial) overlap, which is more effective than the sideways overlap of a pi bond, so a sigma bond is stronger than a pi bond (statement 1 is correct). In C-C bonds the sigma bond energy is about 347 kJ/mol while the pi bond is about 264 kJ/mol. Statement (2)

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Question ID VK-089188