HH /stereogenic centre C-H centre H H Rule 4:Multiple bonds are treated as if they are an equal number of single bonds -CH=CH2 is counted as -CH三O is counted as C C H H H H H stereogenic centre C H H H stereogenic centre > Rule 4 : Multiple bonds are treated as if they are an equal number of single bonds CH CH2 is counted as C H C CH2 C CH O is counted as O H C O C