Question

If isomerization requires breaking the pi bond, what minimum energy is required for isomerization in j/mol?

Answer 1

The minimum energy required for isomerization is 267 000 J/mol 

The isomerization of cis-but-2-ene to trans-but-2-ene requires breaking of the π bond.

The bond energy of a C-C σ bond is 347 kJ/mol.

The bond energy of a C=C double bond (σ + π) is 614 kJ/mol.

So the bond energy of a π bond is (614 – 347) kJ/mol = 267 kJ/mol =
267 000 J/mol.