Pi Bond Sideways overlap of parallel p orbitals. No rotation is possible without breaking the pi bond (63 kcal/mole). Cis isomer cannot become trans without a chemical reaction occurring. CH3 CH3 CH cis no overlap with the ends perpendicular trans Chapter 7 5 Chapter 7 5 Pi Bond • Sideways overlap of parallel p orbitals. • No rotation is possible without breaking the pi bond (63 kcal/mole). • Cis isomer cannot become trans without a chemical reaction occurring. =>