Trans vs. cis, or Z vs. E I am new to organic chemistry and am confused regarding the following question:

Does the geometrical isomerism of 3-methyl-2-heptene fall into the category of trans vs. cis, or the category of Z vs. E? And what is the rule that determines whether it falls into the first or the second category?

My textbook is not clear on this.

Many thanks!
(Z) is the same like cis

(E) is the same like trans

BUT cis and trans is usually only for double bonds with 2 different substituents. Confusion can arise when, for instance, you have 2-halobut-2-enes, because some take the highest priority when determining if this is cis or trans whereas others may take the identical groups.

You can use (Z) and (E) for more than 2 substituents, for those with higher priority. Like in your example.

In general it is better to use (Z) and (E) nomenclature to avoid these ambiguities.