Answer to Question #102102 in Chemistry for Abhishek

Question

a) What is primary isotope effect? How is it different from the secondary isotope effect? Explain with the help of an example of electrophilic substitution in aromatic compounds


b) What do you understand by ortho directing activator and deactivator and meta directing deactivators.

Answer 1

(a)Primary kinetic isotope effects are rate changes due to isotopic substitution at a site of bond breaking in the rate determining step of a reaction.

Primary isotope effects involve isotopic substitution at the bond being broken in a reaction, while secondary isotope effects involve isotopic substituion on bonds adjacent to the bond being broken.

Aromatic compounds react by electrophilic aromatic substitution reactions, in which the aromaticity of the ring system is preserved. For example, benzene reacts with bromine to form bromobenzene. Many functional groups can be added to aromatic compounds via electrophilic aromatic substitution reactions.

(b)A ortho para directing activator is a functional group which when bonded with benzene rings induces negative charge on its ortho and para position by resonance or hyperconjugation.

A meta directing deactivator is a functional group which when bonded with benzene rings takes away negative charge from its ortho and para position by resonance or hyperconjugation.