Thursday, October 17, 2013

E/Z notation

E   ==>  Entgegen ( German word ). Two groups of higher priority are on opposite sides of double bond.
Z   ==>  Zusammen ( German word ). Two groups of higher priority are on same sides of double bond.
Example :
       Now we start with the cis isomer, the left end of the double bond has C and H. By the CIP priority rules, C is higher priority than H. ( Due to its higher atomic number ). In cis isomers the right end of the double bond also the same priority. Since the two priority groups are both on the same side of the double bond. Therefore this is (z) 2- butene.
        Now we look at the trans isomer, the higher priority group are on the opposite sides of the double bond. Therefore this is (E) 2- butene.

Example:

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