Question

Rank substituents in order of their priority when assigning the E or Z label to an alkene.

CH₂I, Br, H, CH₂CH₂Cl, NH₂

Answer 1

Concepts and reason

This problem is based on the concept of priority order while assigning the substituents for E/Z designation in an alkene.

Alkenes can be classified as the E alkenes and Z alkenes depending on the arrangement of groups, atoms or substituents attached to the olefinic carbons across the double bond.

Fundamentals

Substituents are given priority number on the basis of atomic number. Substituents having high atomic number are prior to the ones having less atomic number.

The substituents are as follows:

${\rm{C}}{{\rm{H}}_2}{\rm{I}},\;{\rm{Br}},\;{\rm{H}},\;{\rm{C}}{{\rm{H}}_2}{\rm{C}}{{\rm{H}}_2}{\rm{Cl}},\;{\rm{N}}{{\rm{H}}_2}$

The decreasing rank order is given below:

${\rm{Br}}\; > \;{\rm{N}}{{\rm{H}}_2}\; > \;{\rm{C}}{{\rm{H}}_2}{\rm{I}}\; > \;{\rm{C}}{{\rm{H}}_2}{\rm{C}}{{\rm{H}}_2}{\rm{Cl}}\; > \;{\rm{H}}$

Ans:

The priority order of the substituents is given below:

${\rm{Br}}\; > \;{\rm{N}}{{\rm{H}}_2}\; > \;{\rm{C}}{{\rm{H}}_2}{\rm{I}}\; > \;{\rm{C}}{{\rm{H}}_2}{\rm{C}}{{\rm{H}}_2}{\rm{Cl}}\; > \;{\rm{H}}$