Question

Determine the stereoconfiguration (E or Z) for each double bond in the following alkenes, as applicable.

Determine the stereoconfiguration (E or Z) for each double bond in the following alkenes, as applicable b. d. a. Br C. он CI H-N HO Br

Answer 1

a. According to Cahn Ingold Prelog rules the atoms which are connected to double bond are given priority according to their atomic number if they are different and if they are isotopes then according to atomic mass. in this compound, in the left side of double bond the atoms are Br and C since atomic number of bromine is more than carbon so it is given more priority. On the right side of the double bond the atoms connected are C and H, therefore C has more priority. Since both more priority groups are on the same side then it is of Z configuration.

b. Going down top to bottom in the diagram, the first bond cannot be classified into E or Z because the two groups attached to the left carbon atoms are same so it will not give a different configuration after rotating the double bond. In second bond, it is E configuration and in the third bond it will not show E or Z.

c. According to CIP rules when atoms connected to double bonds are same, we compare next atoms connected to them. so in this compound the right carbon is connected to to oxygen but the oxygen which is connected to carbon is given more priority. Therefore it is an E configuration.

d. It is of E configuration because O and Cl are on opposite sides.

e. Going from left to right, first double bond is Z, second is also Z and third is E (because high priority groups NCH3CH3 and CH3CHCHCH2CH2CHCHCH2 are on opposite sides).