The Newman−Kwart Rearrangement:  A Microwave Kinetic Study

Abstract

The kinetic profile of the Newman-Kwart rearrangement has been evaluated using microwave heating. After first demonstrating equivalence between conventional convective heating and microwave heating, data was gathered and analyzed to determine the effects of substituent, solvent, and concentration on the reaction order. Reaction rate constants, Arrhenius constants, and activation energies have been determined. The reaction rate shows strong sensitivity to the substituent and modest sensitivity to the solvent. At high concentrations, the reaction order increases from the previously reported first-order to a mixed first/second-order reaction. Overall, this re-evaluation of the Newman-Kwart rearrangement has shown the reaction rate order to be more complex than previously thought. In addition, microwave heating has proven ideal for the rapid collection of data to facilitate this type of kinetic study.

Conversion of Phenols into Selenophenols: Seleno Newman–Kwart Rearrangement

“…To gain insight to the course of the reaction the kinetics for the rearrangement of 4-nitro-O-aryl selenocarbamate (2 c) was studied and compared with previously reported results obtained with 4-nitro-O-arylthiocarbamate. [18] It was found that both the O Ar !S Ar and the experimental O Ar !Se Ar rearrangement proceeds with first-order kinetics and a comparison of the kinetic parameters are presented in Figure 2. Here it is shown how the O Ar !Se Ar proceeds significantly faster than the O Ar !S Ar rearrangement.…”

High Temperature Initiator-Free RAFT Polymerization of Methyl Methacrylate in a Microwave Reactor

“…the non-existence of non-thermal microwave effects. [35][36][37][38][39][40] In addition, comparable polydispersity indices were obtained for the thermal and microwave polymerizations, indicating a similar control over the polymerizations.…”

Conversion of Phenols into Selenophenols: Seleno Newman–Kwart Rearrangement

“…Furthermore, the O Ar →Se Ar rearrangement reaction also proceeds at significantly lower temperatures than does the O Ar →S Ar rearrangement when the same phenols are used. To gain insight to the course of the reaction the kinetics for the rearrangement of 4‐nitro– O ‐aryl selenocarbamate ( 2 c ) was studied and compared with previously reported results obtained with 4‐nitro‐ O‐ arylthiocarbamate 18. It was found that both the O Ar →S Ar and the experimental O Ar →Se Ar rearrangement proceeds with first‐order kinetics and a comparison of the kinetic parameters are presented in Figure 2.…”