For a carbon-carbon double bond, we predict a value of 120o for the bond angles about each carbon. Section 5. 2: nomenclature of alkenes: to form iupac names for alkenes, change the suffix "-ane" of the parent alkane to "-ene" Some alkenes, particularly those of low molecular weight, are known almost exclusively by their common names: ex. If the groups of higher priority are on the same side of the double bond, the configuration of the alkene is z. If they are on opposite sides of the double bond, the alkene is e. For alkenes containing two or more double bonds, the suffix "-ene" is changed to "-adiene", "- atriene", and so on: those alkene that contain several double bonds are also referred to more generally as polyenes. For an alkene with one carbon-carbon double bond that can show cis, trans isomerism, two stereoisomers are possible.