Effects of temperature on the ESR and ENDOR spectra of the DMPO–OBut spin adduct; the problems of identifying the trapped radical

Honeywill, J. D.; Mile, B.

doi:10.1002/1097-458x(200006)38:6<423::aid-mrc666>3.3.co;2-n

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“…6 Gas phase catalytic oxidation can also be used. 9 In order to sidestep these limitations, we used a tubular fixed bed reactor, with the reactor effluents cooled to room temperature immediately after leaving the catalytic bed, and collected them in a toluene solution containing a spin trap. 5,7 The principle of the spin-trapping methodology relies on the fast selective addition (trapping) of short-lived radicals to a diamagnetic spin trap, usually a nitrone or a nitroso compound, such as 5,5-dimethyl-1-pyrroline-N-oxide (DMPO).…”

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Spin trapping of radical intermediates in gas phase catalysis: cyclohexane oxidation over metal oxides

Conte

Chechik

2010

Chem. Commun.

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confidence: 99%

Spin trapping of radical intermediates in gas phase catalysis: cyclohexane oxidation over metal oxides

Conte

Chechik

2010

Chem. Commun.

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“…Typical examples are given by the study of irradiated 4-methyl-2,6-di-t-butylphenol [35] and irradiated 10-nonadecanone in urea [36] where wobbling of the methylene groups and rotational motion of the radical in the channel were detected. Varying temperature can be useful to follow the interconnecting of the planar and puckered conformers of the adduct pyrroline ring [39] by ENDOR measurements. Varying temperature can be useful to follow the interconnecting of the planar and puckered conformers of the adduct pyrroline ring [39] by ENDOR measurements.…”

Section: Organic Radicals In Organic Host Crystalsmentioning

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Endor Spectroscopy

Kispert

Piekara-Sady

Handbook of Applied Solid State Spectroscopy

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To understand what electron nuclear double resonance (ENDOR) transitions are, let us consider the energy levels of a system containing one unpaired electron (S = ½) and one nuclear spin (I = ½), as in a hydrogen atom. Since the electron spin and nuclear spin can each be oriented with or against the external magnetic field, there are four possible energy levels as shown in Figure 4.1. The two electron spin eigenfunctions are denoted by e and e , whereas the two nuclear spin wavefunctions are denoted n and n . In the presence of a large external applied field, the selection rule in electron paramagnetic resonance (EPR) is that the electron flips (changes directions) but the nuclear spin does not flip in an EPR transition. Thus, in Figure 4.1, an EPR transition will occur between energy levels 1 and 4 and a second EPR transitions will occur between energy levels 2 and 3. The intensity of the transition between energy levels 1 and 4 will depend on the population differences of these two energy levels. If one then applies a nuclear frequency to the system, which corresponds to either the energy difference between levels 4 and 3 or the difference between lines 2 and 1, one will induce nuclear spin flip that will change the populations in energy levels 4 and 1, respectively. This changes the intensity of the observed EPR signal. This change in intensity is referred to as the ENDOR response. Figure 4.1 Energy diagram for S = 1/2 and I = 1/2.

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Effects of temperature on the ESR and ENDOR spectra of the DMPO–OBut spin adduct; the problems of identifying the trapped radical

Cited by 2 publications

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Spin trapping of radical intermediates in gas phase catalysis: cyclohexane oxidation over metal oxides

Spin trapping of radical intermediates in gas phase catalysis: cyclohexane oxidation over metal oxides

Endor Spectroscopy

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