Experimental and theoretical approaches on the reaction mechanism and kinetics of dimethyl 2-(6-oxopyridazin-1(6H)-yl)fumarate: Micelle and salt effects

A one-pot diastereospecific reaction between DMAD (dimethyl acetylenedicarboxylate) (1) and 3-(2H) pyridazinone (2) in the presence of AsPh3 (3) as an efficient catalyst was studied kinetically. The effect of different salts was considered on the reaction velocity in methanol. The results highlighted that NaBr and CaCl2 salts – in 5 × 10−2 M and 10−2 M concentrations, respectively – raised the reaction rate near four times. Sodium dodecyl sulfate (SDS) as an anionic micelle was added to the solution, and the reaction rate decreased by half. The first and second steps (k1 and k2) of the reaction mechanism become observable in the UV – Vis spectrum when SDS was added to the reaction medium, this observation creates new information regarding the reaction mechanism. Activation energy and its related parameters were determined for the reaction, hence associative mechanism, chemically and enthalpy-controlled being of the reaction documented. A computational study was carried out (for the reaction in the absence of SDS) employing DFT method at the B3LYP/6-31 + G(2d,p) level of theory and fourth step, approved as RDS (rate determining step). Job’s method was used to determine the stoichiometry ratio among the reactants (1), (2) and (3) and the relevant plot exhibited the 1:1:1 stoichiometric ratio.