EFFECTS OF THE SUBSTITUENT GROUPS ON THE REACTION MECHANISM OF THE THERMAL DECOMPOSITION OF DIAZO ALDEHYDES: A COMPUTATIONAL STUDY

A computational study on the decomposition reaction of a series of diazo aldehydes (CHO-CRN₂), with the groups R=H, CH₃, phenyl, i-C₃H₇, cyclo-C₃H₅, NH₂, Cl and OH has been carried out. Optimization and frequency calculations on anti and syn isomers have been performed at the MP2/6-31G(d) level of theory. Based on the results, the reaction mechanism for each compound was interpreted from the possible interactions of the substituent groups with the intermediate and its influence on the reaction rate. The reaction for almost all substituents used proceeded by Wolff rearrangement in two steps, the first of them being the rate-determining step. Substituents groups with a giver capacity of π charge, such as NH₂ and OH, improve the rate of decomposition of diazo aldehydes. The bonding characteristics of all the species involved in some of the studied reactions have been investigated by the natural bond orbital (NBO) analysis.