Sodium perborate/NaNO2/KHSO4-triggered synthesis and kinetics of nitration of aromatic compounds

• Published in: Research on chemical intermediates 2018-10, Vol.44 (10), p.6023-6038
• Main Authors: Rajanna, K. C., Muppidi, Suresh, Pasnoori, Srinivas, Saiprakash, P. K.
• Format: Article
• Language: English
• Subjects: Acetonitrile; Aromatic compounds; Catalysis; Chemistry; Chemistry and Materials Science; Entropy of activation; Inorganic Chemistry; Interaction parameters; Nitration; Phenols; Physical Chemistry; Reaction kinetics; Resonant interactions; Sodium nitrite; Sodium perborate; Solvation; Synthesis
• ISSN: 0922-6168; 1568-5675
• DOI: 10.1007/s11164-018-3473-2

Sodium perborate (SPB) was used as efficient green catalyst for NaNO 2 /KHSO 4 -mediated nitration of aromatic compounds in aqueous acetonitrile medium. Synthesis of nitroaromatic compounds was achieved under both conventional and solvent-free microwave conditions. Reaction times were comparatively shorter in the microwave-assisted than conventional reaction. The reaction kinetics for nitration of phenols in aqueous bisulfate and acetonitrile medium indicated first-order dependence on [Phenol], [NaNO 2 ], and [SPB]. Reaction rates accelerated with introduction of electron-donating groups but retarded with electron-withdrawing groups. Kinetic results did not fit well quantitatively with Hammett’s equation. Observed deviations from linearity were addressed in terms of exalted Hammett’s constants ( σ ¯ or σ eff ), para resonance interaction energy (ΔΔ G p ) parameter, and Yukawa–Tsuno parameter ( r ). This term provides a measure of the extent of resonance stabilization for a reactive structure that builds up charge (positive) in its transition state. The observed negative entropy of activation (−Δ S # ) suggests greater solvation and/or cyclic transition state before yielding products.