Question

For the Nucleophilic substitution of sodium saccharin, our proudct resulted in O-Ethylsaccharin as the minor product and N-Ethylsaccharin was the major product. I do not understand why N-Ethylsaccharin is the thermodynamic product and O-Ethylsaccharin is the kinetic product. To my understanding N-Ethyl has a higher activation energy and O-Ethyl has a lower activation energy yet O-Ethylsaccharins forms faster. I cant wrap my head around which product will be thermo or kinetic product, can you please help me understand this topic ?  

Answer 1

Thermodynamic or Kinetic products depends on the stability of intermediate. As per reaction mechanism rules, if most stable intermediate formed, it leads to the formation of the Thermodynamic product. The lesser stable intermediate reacts fastly with a nucleophile and forms a kinetic product.

In the above case, the most stable intermediate formed in case of formation of N-ethyl saccharine and hence it yields a thermodynamic product.

N-ethyl saccharine is a thermodynamic product because of acidic hydrogen that is attached to Nitrogen. Immediately in the reaction, it looses and ethyl group will be substituted.