Geometrical isomers result due to the

Geometrical isomerism Activation energy for the rotation about carbon–carbon double bond is very high (250 kJ mol–1). This is the contribution of pie bond to the total C = C bond energy of 605 kJ mol–1. Because of high activation energy, rotation about C = C is restricted. As a result, two spatial arrangements of groups are possible at C = C. They are named as cis and trans isomers or geometrical isomers