Ultrasonic irradiation of p-nitrophenol in aqueous solution

Abstract

ionization potentials, electron affinities, and charge distribution, and that of Mulliken,25 which is related to ionization potentials and electron affinities. None provides a linear free energy relationship for the reactions under discussion here. Typically, the enhancement of the rate constant caused by CH3 substitution is underestimated compared to the predicted reduction of reactivity caused by the substitution of the electron-withdrawing halogen atoms.The reaction transition state in the R + HI reactions, whether formed directly from the reactants or formed from a rearrangement of an R.1-H complex,' involves an H atom with a partial positive charge located in the region between the I atom and the methyl radical. Enhanced electron density (as provided by methyl (25) Mullikcn, R. S. J . Chem. Phys. 1934, 2, 782.substitution for H) at the methyl radical carbon would stabilize such a transition state and facilitate reaction, while diminished electron density (such as that caused by halogen atom substitution for H) would destabilize such a transition state. This is the behavior that is observed.Additional studies of the kinetics of R + HI and R + HBr reactions are in progress to understand more fully the factors controlling reactivity. Acknowledgment.The kinetics and mechanism of the sonochemical reactions of p-nitrophenol have been investigated in oxygenated aqueous solutions. In the presence of ultrasound (20 W z , 84 W) pnitrophenol was degraded primarily by denitration to yield NO2-, NOf, benzoquinone, hydroquinone, 4nitrocatecho1, formate, and oxalate. These reaction products and the kinetic observations are consistent with a model involving high-temperature reactions of pnitrophenol in the interfacial region of cavitation bubbles. The main reaction pathway appears to be carbon-nitrogen bond cleavage. Reaction with hydroxyl radical provides a secondary reaction channel. The average effective temperature of the interfacial region surrounding the cavitation bubbles was estimated to be T 800 K.

N-Sulfonylation of amines, imides, amides and anilides using p-TsCl in presence of atomized sodium in EtOH–THF under sonic condition

“…These accomplishments by ultrasound are attributed to the phenomenon of acoustic cavitation [26], and the primary chemical reactions are due to the transient state of high temperatures and pressures generated during the acoustic cavitation [27]. Cavitation depends on whether the system is liquid-liquid or liquid-solid.…”

Ultrasonic removal of pyridine from wastewater: optimization of the operating conditions

“…This dependence of degradation on pH compared well with existing literature. Kotronarou et al (1991) and Jain et al (2004) investigated the influence of the changes in the initial pH of the pnitrophenol (PNP) solutions on the decay of PNP. PNP decayed exponentially with time at all pH values.…”

“…Therefore, many researchers deliberately bubble gas through a sonochemical reaction to facilitate uniform cavitation (Kotronarou et al 1991). To determine the effect of dissolved gas, experiments were carried out in air saturated solutions.…”

Ultrasonically Enhanced Voltammetric Analysis and Applications: An Overview

“…For example in bulk solution, sonolysis in water leads to the hydroxyl radical bought about by dissociation of water inside the cavitation bubble. Simple tests for such radicals include the Weissler test [43,44] solution and the Fricke [45], terphthalate [46,47] and nitrophenol dosimeters [48,49]. Evidence of the degradation products induced by ultrasound was investigated in pioneering work by Riesz et al [50 ± 53] who utilized EPR spin trapping of the non-volatile nitrone.…”