Electron spin resonance

Janzen, Edward G.

doi:10.1021/ac60341a023

Cited by 14 publications

(4 citation statements)

References 63 publications

(72 reference statements)

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“…Therefore, because the bond energy for Cl-C12H9 is lower (397 kJ mol -1 ) than that of C6H5-C6H4Cl (418 kJ mol -1 ), dechlorination is expected to occur more rapidly than recombination of the biphenyl. The ESR data cannot be used to differentiate between these two pathways, however, because Cl• is difficult to detect directly by ESR, due to its high reactivity (34). The following pathways are proposed for the formation of other compounds in the first group.…”

Section: Resultsmentioning

confidence: 99%

Cavitation Chemistry of Polychlorinated Biphenyls: Decomposition Mechanisms and Rates

Zhang

Hua

2000

Environ. Sci. Technol.

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Polychlorinated biphenyls (PCBs) are pollutants of environmental concern due to their widespread presence and persistence. The sonolytic destruction of aqueous polychlorinated biphenyls (PCBs) is reported in this article. The kinetics and transformation pathways were investigated at multiple frequencies and with various analytical tools. The pseudo-first-order rate constants for 2-PCB (4.6 μM), 4-PCB (5.4 μM), and 2,4,5-PCB (7.6 × 10-2 μM) were 2.1 × 10-3 ± 2.8 × 10 -5 s-1, 1.6 × 10-3 ± 3.4 × 10-5 s-1, and 2.6 × 10-3 ± 9.4 × 10 -5 s-1, respectively, when Ar-saturated solutions were sonicated at 20 kHz and an acoustic intensity of 30.8 W cm-2. Chlorine recovery as chloride ion was 77%, 79%, and 70% for 2-PCB, 4-PCB, and 2,4,5-PCB under the same conditions. Electron spin resonance (ESR) experiments demonstrated that phenyl radical was formed during sonolysis of 2-PCB and 4-PCB. The formation of biphenyl, which was detected by mass spectroscopy, also indicates PCB dechlorination during sonication. Ethyl benzene, diethylbiphenyl, dibutylbiphenyl, phenol, propylphenol, and di-tert-butyl phenol were also detected by mass spectroscopy as products of PCB sonication. The kinetics of 2-PCB composition as well as the role of aqueous hydroxyl radical were examined at 20, 205, 358, 618, and 1071 kHz. The ultrasonic frequency significantly impacted the reaction rate and chloride recovery.

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Section: Resultsmentioning

confidence: 99%

Cavitation Chemistry of Polychlorinated Biphenyls: Decomposition Mechanisms and Rates

Zhang

Hua

2000

Environ. Sci. Technol.

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“…The use of dtc to measure quantitatively inorganic cupric ions using ESR has been reviewed by Janzen (35). The source of a copper ESR signal previously observed in fatty tissues has been identified as Cu(dtc)2.…”

Section: Esr Investigations Of Tetradentate Cupric Complexesmentioning

confidence: 99%

ESR of Copper and Iron Complexes with Antitumor and Cytotoxic Properties

Antholine¹,

Kalyanaraman²,

Petering³

1985

Environmental Health Perspectives

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The relatively few iron and copper metal complexes which have been examined in cells and tissues for their redox properties, radical generation properties, and antitumor activity are discussed for studies which utilized electron spin resonance spectroscopy (ESR). A common property of a number of metal complexes, which include bleomycin, adriamycin, and thiosemicarbazones described in this review, is that they are readily reduced by thiol compounds and oxidized by oxygen or reduced species of oxygen to produce radicals. Structural features ofthese reactions are identified by ESR spectroscopy in model systems and-often in cells. Furthermore, ESR spectroscopy has been most useful to probe the environment of the complexes in cells and to measure the rate of reduction of their oxidized forms. As a result of these studies, it is anticipated that more attention will be given to the exploration of redox-active metal complexes as drugs.

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“…Even choosing Cl as the target element, some authors have admitted that the mass balance (even defining the mass balance related to chlorinated compound disappeared [31], and not related to the initial amount of starting material) after sonolysis is found to be as low as 50% [41] and frequently in the range [70-100%] [30,31,54]. The Cl · radical presents such a high reactivity that it is difficult to detect it directly by ESR [133], which could be a reasonable explanation.…”

Section: Mass Balance and Speciation Technical And Environmental Viamentioning

confidence: 99%

Sonochemical Treatment of Water Polluted by Chlorinated Organocompounds. A Review

González-Garcı́a

Sáez

Tudela

et al. 2010

Water

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As one of several types of pollutants in water, chlorinated compounds have been routinely subjected to sonochemical analysis to check the environmental applications of this technology. In this review, an extensive study of the influence of the initial concentration, ultrasonic intensity and frequency on the kinetics, degradation efficiency and mechanism has been analyzed. The sonochemical degradation follows a radical mechanism which yields a very wide range of chlorinated compounds in very low concentrations. Special attention has been paid to the mass balance comparing the results from several analytical techniques. As a conclusion, sonochemical degradation alone is not an efficient treatment to reduce the organic pollutant level in waste water.

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Electron spin resonance

Cited by 14 publications

References 63 publications

Cavitation Chemistry of Polychlorinated Biphenyls: Decomposition Mechanisms and Rates

Cavitation Chemistry of Polychlorinated Biphenyls: Decomposition Mechanisms and Rates

ESR of Copper and Iron Complexes with Antitumor and Cytotoxic Properties

Sonochemical Treatment of Water Polluted by Chlorinated Organocompounds. A Review

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