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

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.