Prussian Blue/NaNO₂as an Efficient Reagent for the Nitration of Phenols in Aqueous Bisulfate and Acetonitrile Medium: Synthetic and Kinetic Study

Abstract

The reaction kinetics of Prussian blue (PB)/NaNO2 initiated for the nitration of phenols by in aqueous bisulfate and acetonitrile medium indicated first‐order dependence on [phenol], [NaNO2], and [PB]. An increase in [KHSO4] accelerated the rate of nitration under otherwise similar conditions. The rate of nitration was faster in the solvent of higher dielectric constant (D). Observed results were in accordance with Amis and Kirkwood plots [log k′ vs. (1/D) and [(D − 1)/(2D + 1)]. These findings together with the linearity of plots, log k′ versus (vol% of acetonitrile (ACN)) and mole fraction of (nx) ACN, probably indicate the importance of both eloctrostatic and nonelctrostatic forces, solvent–solute interactions during nitration of phenols. Reaction rates accelerated with the introduction of electron‐donating groups and retarded with electron‐withdrawing groups, which are interpreted by Hammett's theory of linear free energy relationship. Hammett's reaction constant (ρ) is a fairly large negative (ρ < 0) value, indicating attack of an electrophile on the aromatic ring. Furthermore, an increase in temperature decreased the reaction constant (ρ) values. This trend was useful in obtaining isokinetic temperature (β) from Exner's plot of ρ versus 1/T. Observed β value (337.8 K) is above the experimental temperature range (303–323 K), indicating that the enthalpy factors are probably more important in controlling the reaction.

Synthetic Protocols for Aromatic Nitration: A Review

“…Reaction rates accelerated with the following sequence: p −Me> m −Me>H> o −OH> m ‐OH> m −Cl due to the electron donating groups. Selective method for nitration of phenol and use of eco‐friendly catalyst under mild condition make this approach wide synthetic with commercial utility [48] …”

“…Selective method for nitration of phenol and use of eco-friendly catalyst under mild condition make this approach wide synthetic with commercial utility. [48] Chaudhary et al reported an efficient protocol for nitration of N-alkyl anilines using tert-butyl nitrite (Scheme 40). For comparative study authors employed various solvents such as acetonitrile, tetrahydrofuran, methanol & 1,4-dioxane.…”

Interdependence of the Hammett and isokinetic relationships: a numerical simulation approach

“…It can be observed that the deviations of the enthalpy increased linearly with those of the entropy, the slope (T) being dimensionally a temperature. This and other statistical parameters were systematically analyzed for 10 homologous reaction series searched in the chemical literature [59][60][61][62][63][64]. Since it has been demonstrated [35][36][37] that the random errors of the activation enthalpy are directly proportional to those of the entropy, according to the equation:…”