Abstract
The acid-catalyzed reversible etherification of the allelotrope of p-nitrosophenol (PNP) with ethanol in dioxane was studied kinetically togather with its reverse reaction, the acid-catalyzed reversible hydrolysis of p-nitrosophenetole (PNPT) in dioxane. Both reactions have another rate equation at more or less than 0.4 M water as follows : In the case of CH2O⪈0.4M and CH2SO4=0.1N ; Rateforward=(k2-kf-3hCH2O+k3CPNP)CPNPCEtOH Ratereverse=(k-2-kf3hCH2O+k-3CPNPT)CPNPTCH2O In the case of CH2O≨0.4 M and CH2SO4=0.1N ; Rate'forward={k2-0.4kf-3h+kf3h(CH2O-0.4)+k3CPNP-k-4hCPNP(CH2O-0.4)}CPNPCEtOH Rate'reverse={k-2-0.4kr3h+kr-3h(CH2O-0.4)+k3CPNPT-k4hCPNPT(CH2O-0.4)}CPNPTCH2O When the concentration of water is constant, the rate equation of the forward reaction was simplified in the following way. Rateforward=(k2'+k3'CPNP)CPNPCEtOH Isotope Effects on these rate constants were k2'H/k2'D=0.83 and k3'H/k3'D=2.58, respectively. Apparent activation parameters, ΔEa and ΔS=⃥ were obtained to be 2.1 kcal/mol, -72.4 e.u. for the forward reaction expressed by k2' and 27.0 kcal/mol, 4.4 e.u. for the forward one expressed by k3', respectively. Nucleophilic attack of oxygen atom of ethanol on the ring carbon attached to hydroxyl group of the allelotrope, is discussed as a probable mechanism.
