The prefixes “cis” and “trans” are from Latin. In the context of chemistry, cis indicates that the functional groups are on the same side of the carbon chain while trans conveys that functional groups are on opposing sides of the carbon chain. Cis-trans isomers are stereoisomers, that is, pairs of chemistry contexts 2 pdf which have the same formula but whose functional groups are rotated into a different orientation in three-dimensional space. Z isomerism, which is an absolute stereochemical description, and only to be used with alkenes.
In general, stereoisomers contain double bonds that cannot rotate, or they may contain ring structures, where the rotation of bonds is restricted or prevented. Cis and trans isomers occur both in organic molecules and in inorganic coordination complexes.
When the substituent groups are oriented in the same direction, the diastereomer is referred to as cis, whereas, when the substituents are oriented in opposing directions, the diastereomer is referred to as trans. Cis and trans isomers often have different physical properties. Differences between isomers, in general, arise from the differences in the shape of the molecule or the overall dipole moment.
C in the trans isomer. The differences between cis and trans isomers can be larger if polar bonds are present, as in the 1,2-dichloroethenes. The cis isomer in this case has a boiling point of 60. C, while the trans isomer has a boiling point of 47.