T1 T2* Relaxation Time Correlation NMR Monitoring of the Mechanochemical Formation of Quinoxaline Derivatives

Despite the increased use of mechanochemistry for chemical reactions few options for reaction monitoring or solid state analysis are available. This work explores using T1 T2* 1H NMR to monitor the reaction between benzil or 4,4’ dimethybenzil with o phenylenediamine. For both reactions, the T1 T2* correlation plots show differences in relaxation times throughout the reaction. This work demonstrates using two different strageties to monitor the reaction progression. In the first case the reaction is monitered by the appearance of signals corresponding to the product, and side product water. In the second case the reaction is monitored by the replacement of the signals corresponding to the starting material, by signals corresponding to the product. This magnetic resonance correlation measurement provides an excellent option for whole sample solid state analysis by virtue of its simplicity and versatility.