Kinetics and reactivity correlation in diol oxidation by tetramethyl-ethylenediammonium dichromate across acetic acid–water mole fractions

The present investigation focuses on the oxidation kinetics of four vicinal diols, four non-vicinal diols, and one monoether by tetramethyl-ethylenediammonium dichromate (TMEDADC) in water–acetic acid mixtures of different molar ratios. All the selected diols resulted in the formation of corresponding hydroxyaldehyde as a main product of the oxidation. The reaction follows first-order kinetics with respect to TMEDADC and shows a fractional order (between 1 and 2) in diol concentration. Oxidation of [1,1,2,2- ² H ₄ ] ethane diol exhibits a noticeable primary kinetic isotope effect ( k _H / k _D = 5.58 at 298 K). A strong linear correlation is observed between the rate constants for vicinal diols and the Taft polar substituent constants (Σσ*), and the negative polar reaction constant (ρ* = − 2.19 at 298 K) indicates the development of an electron-deficient center in the rate-determining step. A plausible process involving the pre-equilibrium generation of chromate ester has been postulated.