The E - Z System for Designating Alkene Diastereomers

In Section 4.5 we learned to use the terms cis and trans to designate the stereochemistry of alkene diastereomers. These terms are unambiguous, however, only when applied to di-substituted alkenes. If the alkene is trisubstituted or tetrasubstituted, the terms cis and trans are either ambiguous or do not apply at all. Consider the following alkene as an example  

It is impossible to decide whether A is cis or trans since no two groups are the same. 

A system that works in all cases is based on the priorities of groups in the Cahn-lngold-Prelog convention (Section 5.7). This system, called the (E)-(Z) system, applies to alkene diastereomers of all types. In the (E)-(Z) system, we examine the two 

The two stereoisomers of l-bromo-l,2-dichloroethene cannot be designated as cis and trans in the normal way because the double bond is trisubstituted. They can, however, be given (E) and (Z) designations. Write a structural formula for each isomer and give each the proper designation. 

Using the ( )-(Z) designation [and in parts (e) and (f) the R)-iS) designation as well] give lUPAC names for each of the following  

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