# chem

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The average bond enthalpy for a C=C double bond is 614kj/mol and that of a C-C single bond is 348kj/mol . Estimate the energy needed to break the pi bond in 2-butene.

CH3 CH3 CH3 H
\ / \ /
C=C ------> C=C
/ \ / \
H H H CH3
Cis-2-butene Trans-2-butene

• chem -

Think about this. A single bond C-C is a sigma bond. The double bond is a sigma bond + a pi bond. So would the difference between energy of double bond and single bond be the pi bond?

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