The Deuterium Isotope Effect in the Side Chain Halogenation of Toluene<sup>1</sup>

Wiberg, Kenneth B.; Slaugh, Lynn H.

doi:10.1021/ja01545a034

Cited by 59 publications

(27 citation statements)

References 2 publications

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“…The mechanism of reaction of the POM with 1 and 2 was further probed by isotope-labeling studies (Wiberg 1954(Wiberg , 1955Wiberg and Slaugh 1958;Zollinger 1964). Accordingly, models identical to 1 and 2 but deuterated at the benzylic-carbon atoms, 1-(3,4-Dimethoxy-phenyl)-(1-2 H)ethanol (4) and 1-(3,4,5-Trimethoxy-phenyl)-(1-2 H)ethanol (5), were reacted with the POM solution.…”

Section: Mechanism Of Pom Oxidation Of 1-(345-trimethoxyphenyl)-ethmentioning

confidence: 99%

Polyoxometalate oxidation of non-phenolic lignin subunits in water: Effect of substrate structure on reaction kinetics

Yokoyama¹,

Chang²,

Reiner³

et al. 2004

Holzforschung

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The effect of lignin-biopolymer structure on the mechanism of its oxidative depolymerization by polyoxometalates (POMs) was investigated by reacting an equilibrated POM ensemble with a series of ring-substituted benzyl alcohols. Under anaerobic conditions in mixed water/ methanol, observed pseudo-first order reaction rates (1508C) of 8.96=10 y3 and 4.89=10 y3 sec y1 were obtained for oxidations of 1-(3,4-dimethoxyphenyl)ethanol (1) and 1-(3,4,5-trimethoxyphenyl)ethanol (2), respectively. Organic products from the oxidation of 2 (95% recovery) indicate the reaction proceeds via successive oxidations of the benzylic carbon atom; aromatic-ring cleavage was not observed. A primary kinetic-isotope effect of 1.6 and 1.7 was observed for the reactions of 1 and 2 deuterated at the benzylic-carbon atoms. This combined with the relatively large activation energies, indicate that C-H bond breaking (either H-atom or proton-coupled electron transfer) occurs late along the reaction coordinate of the rate-determining step. Replacing the 4-CH 3 O-group in 2 by CH 3 CH 2 O-to give 1-(4ethoxy-3,5-dimethoxyphenyl)ethanol (3), had a substantial effect on the temperature dependence of the observed reaction rate, suggestive of a possible change in mechanism.

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Section: Mechanism Of Pom Oxidation Of 1-(345-trimethoxyphenyl)-ethmentioning

confidence: 99%

Polyoxometalate oxidation of non-phenolic lignin subunits in water: Effect of substrate structure on reaction kinetics

Yokoyama¹,

Chang²,

Reiner³

et al. 2004

Holzforschung

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“…In every case, it was shown that the relative reactivities of bromination in some aralkyl compounds by bromine, NBS and other N-bromoimides [11,14] are nearly identical, as are the ~ett 0 values for the bremination of toluene derivatives by bromine and by NBS (-1.39 at 80 °) [11,12,14]. Secondly, the bromination of toluene by bromine or NBS exhibited the same deuterit~n isotope effects [17]. Finally, the product patterns derived from NBS bromination of certain olefins were essentially the same as those obtained under a low concentration of bromine introduced under controlled conditions [18][19][20].…”

Section: The Recognition Of the Succinimidyl Radicalmentioning

confidence: 99%

“…Thirdly, HBr is scavenged instantaneously by NBS to maintain a low steady-state concentration of bromine under these conditions [11,21]; thus the reverse reaction of Eq. (5) under these conditions is unimportant in spite of the fact that the HBr reversal can operate in certain cases [12,17,20]. Finally, NBS can react rapidly with adventitious protic substrates (water, alcohol, etc.)…”

Section: The Recognition Of the Succinimidyl Radicalmentioning

confidence: 99%

Recent controversy on imidyl radical chemistry

Chow

Naguib

1984

Reviews of Chemical Intermediates

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“…Bei der Umsetzung von 2-Phenylpropen (13) rnit N-Bromsuccinimid (NBS) 14) in siedendem Tetrachlormethan entstanden 3-Brom-2-phenyl-I -propen (14), sowie (15)-und (Z)-l-Brom-2-phenyl-I-propen (15,16) Wir versuchten, diese Reaktion moglichst einheitlich zum gewunschten (Z)-Dien 6 zu lenken. Bei Alkylidenphosphoranen lassen sich nach Schlosser") und Bestmann durch Verwendung salzfreier Losungen (Z)-Selektivitaten bis zu 98 : 2 erzielen.…”

Section: Nbs-bromierung Von 2-phenylpropenunclassified

Synthese von isomerenreinen (E)‐ und (Z)‐1,3‐disubstituierten 1,3‐Dienen

et al. 1982

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Die (E)-I ,3-Diene 1 ap wurden durch dehydratisierende Decarboxylierung der entsprechenden 4,5-ungesattigten 3-Hydroxycarbonsauren 3 rnit Dimethylformamid-dimethylacetal (11) zu >98 Vo sterisch rein dargestellt. Die (Z)-Isomeren 6a -m erhielt man durch stereounkontrollierte Wittig-Reaktion des Phosphorans 18 mit den Aldehyden 7 und nachfolgende Thermolyse des entstandenen (E)-/(Z)-Diengemisches. 1 ging dabei quantitativ ins Dimere 5 iiber, wahrend 6 unverandert blieb und sich durch Vakuumdestillation oder Saulenchromatographie leicht von 5 abtrennen lien. Synthesis of Isomerically Pure (E)-and (2)-1,3-Disubstituted 1,3-DienesThe (E)-dienes l a -p were prepared in >98% purity by dehydrative decarboxylation of the corresponding 4,5-unsaturated 3-hydroxycarboxylic acids 3 with dirnethylforrnarnide dimethylacetal (11). The (Z)-isomers 6am were obtained by stereouncontrolled Wittig reaction of the phosphorane 18 with the aldehydes 7 and subsequent therrnolysis of the resulting (E)-/(Z)-diene mixture. Under these conditions 1 was quantitatively converted into its dimer 5, whereas 6 remained unchanged and was readily separated from 5 by vacuum distillation or column chromatography.Trotz der Vielzahl an Synthesemethoden fur 1,3-Diene1) sind Isomere des Typs 1/6 bislang nur in Einzelfallen rein dargestellt worden. Wir beschreiben hier ein neues Verfahren, 1 und 6 einfach und aus wohlfeilen Startmaterialien zu gewinnen. Uber die thermischen Reaktionen von 1 und 6 werden wir getrennt berichten2).

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The Deuterium Isotope Effect in the Side Chain Halogenation of Toluene¹

Cited by 59 publications

References 2 publications

Polyoxometalate oxidation of non-phenolic lignin subunits in water: Effect of substrate structure on reaction kinetics

Polyoxometalate oxidation of non-phenolic lignin subunits in water: Effect of substrate structure on reaction kinetics

Recent controversy on imidyl radical chemistry

Synthese von isomerenreinen (E)‐ und (Z)‐1,3‐disubstituierten 1,3‐Dienen

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The Deuterium Isotope Effect in the Side Chain Halogenation of Toluene1

Cited by 59 publications

References 2 publications

Polyoxometalate oxidation of non-phenolic lignin subunits in water: Effect of substrate structure on reaction kinetics

Polyoxometalate oxidation of non-phenolic lignin subunits in water: Effect of substrate structure on reaction kinetics

Recent controversy on imidyl radical chemistry

Synthese von isomerenreinen (E)‐ und (Z)‐1,3‐disubstituierten 1,3‐Dienen

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The Deuterium Isotope Effect in the Side Chain Halogenation of Toluene¹