Kinetics and mechanism of quinolinium dichromate mediated oxidation of sugar alcohols in Bronsted acid media

Bronsted acid catalyzed oxidation of certain sugar alcohols (polyols) has been studied by quinolinium dichromate (QDC) using aqueous sulfuric, perchloric, and hydrochloric acids at different temperatures. At constant acidity, reaction kinetics revealed the second‐order kinetics with a first order in [Alcohol] and [QDC]. Zucker‐Hammett, Bunnett, and Bunnett‐Olsen criteria were used to analyze acid‐dependent rate accelerations. Bunnett‐Olsen plots of (log k + Hν) versus (Hν + log [H+]), and (log k) versus (Hν + log [H+]) afforded slope values (ϕ and ϕ*, respectively) > 0.47, suggesting that a water molecule acts as a prton transfer agent in the slow step of the mechanism in the oxidation of alcohols by QDC in the presence of aqueous sulfuric, perchloric, and hydrochloric acids.