13.4.5—Chiral centres and geometrical (cis/trans)

To find a chiral centre, inspect each tetrahedral carbon for four different attached groups. To find geometrical isomerism, inspect each C=C—or suitable ring—for restricted rotation and two different groups at each relevant position.

Compare the paths around a ring as well as the atoms directly attached. A drawing can hide equivalence, so trace each substituent until the first point of difference.

A substituted cycloalkane can have cis and trans forms even without a C=C because the ring restricts rotation. A carbon with two identical ring paths is not a chiral centre.

Do not count every wedge/dash bond as a chiral centre, and do not call a double bond geometrically isomeric when one end has identical substituents.