[ILoveISO]

When does one use E/Z instead of CIS/Tran vise versa? Thanks and an example would be great

[sjb]

E and Z is a more general system, whereas cis and trans often leads to more ambiguities, consider the attached structure -this could be cis if we were looking for identical groups, or trans if looking for highest CIP priority, but it has a unique E/Z style name. Naming it in all three styles is left as an exercise for the reader.