First 155 words of the document:
E/Z isomerism is one type of stereoisomerism.
In stereoisomerism, the atoms are bonded in the same order but are arranged differently
in space in each isomer.
Because of lack of rotation around the double bond, some alkenes have stereoisomers.
This happens when the two double-bonded carbon atoms each have different atoms or
groups attached to them.
Then you get an E isomer and a Z isomer.
When the same groups are across the double bond then it's the E -isomer = trans
When the same groups are both above or both below the double bond then it's the Z
isomer = cis
Name Type Where
Cis Z Same groups are both
above or both below the
Trans C Same groups are opposite
the double bond