Two groups are said to be trans if they are bonded to the opposite side of the same double bond or ring, as in trans-1,2-dichlorobut-2-ene, or trans-1,2-dimethylcyclohexane. trans– isomers cannot be converted into the cis isomers through rotation of bonds without destruction of the double bond or ring. This form of isomerism is known as geometric isomerism.