Elektronenspinresonanz freier Radikale bei photochemischen Reaktionen von Ketonen in Lösung

Paul, H.; Fischer, Hanns

doi:10.1002/hlca.19730560514

Cited by 186 publications

(50 citation statements)

References 61 publications

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“…15 for numbering system). If, as expected for freely diffusing radical pairs, the l C enrichment increases monotonically,' with ac (15), it is apparent from Table 2 that the ordering of ' C enrichment should be C, > C10 > C1H > Caromatic According to the mechanism in Fig. 12, 1-phenyl-4-methylacetophenone is a combination product which both results after 3RP -* 'RP ISC and which preserves the memory ofeach distinct carbon atom of3RP in its final structure.…”

Section: Photolysis Of Dbk In Micellar Aggregatesmentioning

confidence: 75%

“…For instance, ionic detergents commonly have a straight chain hydrocarbon "tail" consisting of [10][11][12][13][14][15][16][17][18] carbon atoms terminating in an ionic "head." Hexadecyltrimethylammonium chloride (C16NMe3Cl), CH3(CH2)15N(CH3)3C 1, is an example of a cationic detergent and sodium dodecylsulfate, CH3(CH2)11OSO-Na', is an example of a anionic detergent.…”

Section: Micellar Aggregates From Aqueous Solution Of Detergentsmentioning

confidence: 99%

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Influence of nuclear spin on chemical reactions: Magnetic isotope and magnetic field effects (A Review)

Turro

1983

Proc. Natl. Acad. Sci. U.S.A.

183

143

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The course of chemical reactions involving radical pairs may depend on occurrence and orientation of nuclear spins in the pairs. The influence of nuclear spins is maximized when the radical pairs are confined to a space that serves as a cage that allows a certain degree of independent diffusional and rotational motion of the partners of the pair but that also encourages reencounters of the partners within a period which allows the nuclear spins to operate on the odd electron spins of the pair. Under the proper conditions, the nuclear spins can induce intersystem crossing between triplet and singlet states of radical pairs. It is shown that this dependence ofintersystem crossing on nuclear spin leads to a magnetic isotope effect on the chemistry of radical pairs which provides a means of separating isotopes. on the basis of nuclear spins rather than nuclear masses and also leads to a magnetic field effect on the chemistry of radical pairs which provides a means of influencing the course of polymerization by the application of weak magnetic fields. PHYSICAL MODEL OF NUCLEAR SPIN "Spin" is the term used to describe an intrinsic and characteristic property associated with the angular momentum of a particle. A physical model ofspin is conveniently generated by the supposition that this property is the angular momentum that arises from a body rotating about its own axis. This classical model allows recognition of most of the important characteristics of quantum mechanical spin. For example, it provides an understanding of why charged particles with spin.possess an intrinsic magnetic moment and why charged particles without spin do not possess an intrinsic magnetic moment (1, 2) ( Fig. .1).The magnitude of the spin angular momentum of a particle is uniquely determined by the spin quantum number which may be a positive integral or half-integral number that is characteristic of the particle. For example, the value of the electronic spin quantum number(s) for an electron is +1/2. This value pertains whatever the state of the electron. On the other ,hand, the value of the nuclear spin quantum number (f) depends on the nucleus. Indeed, some nuclei (e.g., 12C, 160, 180) do not possess spin (f = 0), whereas others possess half-integral values (e.g.,. for 170 f = 5/2, for 1H f = 1/2, and for`3C e = 1/2) or integral values (e.g., for 2H e = 1). For simplicity, I shall consider some of the consequences of a simple model of spin for.a particle with spin quantum number of + 1/2.According to the rules of quantum mechanics, the spin angular momentum of a rotating body is quantized and may take up only a discrete set of orientations with respect to any arbitrarily selected axis (Fig. 2). With the z axis as a frame of reference, the allowed-orientations for a spin of +1/2 are "up" (a spin) and "down" (A spin). Quantum mechanics allows that only one axial component ofthe spin angular momentum vector can be specified. We shall arbitrarily select this component to be projected on the z axis. The specific orientation (termed the...

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Section: Photolysis Of Dbk In Micellar Aggregatesmentioning

confidence: 75%

Section: Micellar Aggregates From Aqueous Solution Of Detergentsmentioning

confidence: 99%

Influence of nuclear spin on chemical reactions: Magnetic isotope and magnetic field effects (A Review)

Turro

1983

Proc. Natl. Acad. Sci. U.S.A.

183

143

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“…CH2OH (18) As Table I reveals the same reaction occurs for formic acid and derivatives, for esters of acetic acid, for malonic acid and esters, for succinic acid and for propionic acid in hydrogen donor solvents. In aqueous solulion most of these compounds undergo a-cleavage, however.…”

Section: -Spectrum Of Radicals During Photolysis Of Methylchloro Acetmentioning

confidence: 54%

“…which should be easily observable in the system. The acyl radical (CH,),CHCO should exhibit a very broad line (dH,,=0.23 mT at -95") at g=2.0007 [18] and may easily escape detection. Thus, for isobutyric acid the a-cleavage (1 a) is the major photolytic pathway in methanol, other reactions as (2a), (3a) or (5a) are only of minor importance.…”

Section: Ch2cooch2ch3')mentioning

confidence: 99%

“…P-Elimination of chlorine, bromine and iodine atoms is a well known photochemical process also of carbonyl compounds for which, however, fluorine elimination has not been reported [2] [18]. Our observation of fluorine elimination from monofluoroacetic acid (Table 1) seems surprising, however, the process is energetically feasible since the bond energy of the C-F bond (-485 kJ/mol) is lower than the excitation energy under our conditions (498 kJ/mol for /z = 240 nm).…”

Section: -Spectrum Of Radicals During Photolysis Of Methylchloro Acetmentioning

confidence: 99%

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Free Radical Formation from Excited States of Aliphatic Carboxylic Acids and esters in solution as studied by electron spin resonance

Kaiser

Grossi

Fischer

1978

Helvetica Chimica Acta

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SummaryDuring UV.-irradiation of aliphatic carboxylic acids and esters in aqueous and nonaqueous solutions various alkyl and acyl type radicals derived from parent compounds and solvents have been observed by ESR.-spectroscopy. The structures of the radicals point to a-cleavage, P-dehalogenation and photoreduction as major photolytic processes of carboxylic acids and esters. The relative contributions of these processes to the overall photodecompositions depend on the carboxyl substituents, on solvent and temperature. Similarities of carboxyl and carbonyl group photochemistry are discussed.

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Spin‐Statistical Factors in Diffusion‐Controlled Reactions

Saltiel

Atwater

1988

Advances in Photochemistry

137

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Elektronenspinresonanz freier Radikale bei photochemischen Reaktionen von Ketonen in Lösung

Cited by 186 publications

References 61 publications

Influence of nuclear spin on chemical reactions: Magnetic isotope and magnetic field effects (A Review)

Influence of nuclear spin on chemical reactions: Magnetic isotope and magnetic field effects (A Review)

Free Radical Formation from Excited States of Aliphatic Carboxylic Acids and esters in solution as studied by electron spin resonance

Spin‐Statistical Factors in Diffusion‐Controlled Reactions

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