Investigation of electronic effects in diazine rings. Linear free energy relationships in the reactivity of diazine mono- and di-carboxylates

Abstract

Rate constants for the reaction of six possible diazine monocarboxylates with diazodiphenylmethane (DDM) in ethanol, and also for the hydrolysis of the corresponding methyl carboxylate esters, have been determined at four selected temperatures. Correlations with sums of the Hammett σ constants for ring nitrogens treated as substituents, which are fairly satisfactory for the reaction with DDM at 30 °C (ρ_DDM= 0.64, log k₀=–1.54, r= 0.92, s= 0.12) and for ester hydrolysis (ρ_EH= 2.28, log k₀=–3.36, r= 0.94, s= 0.36) are, however, excellent for the intercorrelation of the two reaction series (ρ_DDM/ρ_EH= 0.34, r= 0.99, s= 0.12). The reactivity of ortho- and para-diazine dicarboxylates in the reaction with DDM, in ethanol and dimethylformamide, has been investigated and compared with the corresponding reactions of ortho- and para-benzene- and pyridine-dicarboxylates.