a The C bond angle in ethylene is close to 180.0. true false b Cis-trans isomerism is possible only among appropriately substituted alkenes. true false Cis-trans isomerism in alkenes exists because of the restricted rotation about a carbon-carbon double bond. true false Cis-2-butene and trans-2-butene can be interconverted by free rotation about the carbon-carbon double bond. true false e) 1-Chloropropene can exist as a pair of cis-trans isomers. true false