The reaction of triphenylmethyl bromide with potassium O-ethyl dithiocarbonate (potassium xanthate) in benzene and cumene. A note of caution on the application of the radical trap dicyclohexylphosphine as a probe for electron-transfer-initiated reactions of triphenylmethyl halides

P. Huszthy, Gyöngyi Izsó, Károly Lempert, Miklós Györ, A. Rockenbauer

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

The title reaction was studied under conditions where homolysis of the triphenylmethyl-to-sulphur bond of the dithiocarbonate 1d, its main product does not take place, or is negligible. Triphenylmethane 1c, triphenylmethanol 1g and benzophenone were obtained as further products under argon in cumene and in the presence of oxygen in benzene, respectively. This, together with ESR studies, indicates that part of the dithiocarbonate 1d results from single-electron transfer from O-ethyl dithiocarbonate anion to triphenylmethyl bromide 1a and out-of-cage recombination of triphenylmethyl and xanthyl radicals 6a. The main pathways leading to dithiocarbonate 1d appear, under the conditions studied, to be either a polar pathway consisting of two successive SN2′- type steps [mechanism 2, Scheme 3] and/or an SET-type reaction [mechanism 3, Scheme 3] with rapid in-cage recombination of triphenylmethyl and xanthyl radicals 6a. The hydrogen-atom donor dicyclohexylphosphine (DCPH) may not be used for trapping of the triphenylmethyl radicals formed in the title reaction because DCPH acts as a single-electron donor towards bromide 1a, i.e. it itself generates triphenylmethyl radicals from the bromide.

Original languageEnglish
Pages (from-to)2009-2015
Number of pages7
JournalJournal of the Chemical Society, Perkin Transactions 2
Issue number11
DOIs
Publication statusPublished - 1990

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Benzene
Bromides
Potassium
Electrons
Argon
Sulfur
Anions
Paramagnetic resonance
Hydrogen
Oxygen
Atoms
cumene

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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title = "The reaction of triphenylmethyl bromide with potassium O-ethyl dithiocarbonate (potassium xanthate) in benzene and cumene. A note of caution on the application of the radical trap dicyclohexylphosphine as a probe for electron-transfer-initiated reactions of triphenylmethyl halides",
abstract = "The title reaction was studied under conditions where homolysis of the triphenylmethyl-to-sulphur bond of the dithiocarbonate 1d, its main product does not take place, or is negligible. Triphenylmethane 1c, triphenylmethanol 1g and benzophenone were obtained as further products under argon in cumene and in the presence of oxygen in benzene, respectively. This, together with ESR studies, indicates that part of the dithiocarbonate 1d results from single-electron transfer from O-ethyl dithiocarbonate anion to triphenylmethyl bromide 1a and out-of-cage recombination of triphenylmethyl and xanthyl radicals 6a. The main pathways leading to dithiocarbonate 1d appear, under the conditions studied, to be either a polar pathway consisting of two successive SN2′- type steps [mechanism 2, Scheme 3] and/or an SET-type reaction [mechanism 3, Scheme 3] with rapid in-cage recombination of triphenylmethyl and xanthyl radicals 6a. The hydrogen-atom donor dicyclohexylphosphine (DCPH) may not be used for trapping of the triphenylmethyl radicals formed in the title reaction because DCPH acts as a single-electron donor towards bromide 1a, i.e. it itself generates triphenylmethyl radicals from the bromide.",
author = "P. Huszthy and Gy{\"o}ngyi Izs{\'o} and K{\'a}roly Lempert and Mikl{\'o}s Gy{\"o}r and A. Rockenbauer",
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T1 - The reaction of triphenylmethyl bromide with potassium O-ethyl dithiocarbonate (potassium xanthate) in benzene and cumene. A note of caution on the application of the radical trap dicyclohexylphosphine as a probe for electron-transfer-initiated reactions of triphenylmethyl halides

AU - Huszthy, P.

AU - Izsó, Gyöngyi

AU - Lempert, Károly

AU - Györ, Miklós

AU - Rockenbauer, A.

PY - 1990

Y1 - 1990

N2 - The title reaction was studied under conditions where homolysis of the triphenylmethyl-to-sulphur bond of the dithiocarbonate 1d, its main product does not take place, or is negligible. Triphenylmethane 1c, triphenylmethanol 1g and benzophenone were obtained as further products under argon in cumene and in the presence of oxygen in benzene, respectively. This, together with ESR studies, indicates that part of the dithiocarbonate 1d results from single-electron transfer from O-ethyl dithiocarbonate anion to triphenylmethyl bromide 1a and out-of-cage recombination of triphenylmethyl and xanthyl radicals 6a. The main pathways leading to dithiocarbonate 1d appear, under the conditions studied, to be either a polar pathway consisting of two successive SN2′- type steps [mechanism 2, Scheme 3] and/or an SET-type reaction [mechanism 3, Scheme 3] with rapid in-cage recombination of triphenylmethyl and xanthyl radicals 6a. The hydrogen-atom donor dicyclohexylphosphine (DCPH) may not be used for trapping of the triphenylmethyl radicals formed in the title reaction because DCPH acts as a single-electron donor towards bromide 1a, i.e. it itself generates triphenylmethyl radicals from the bromide.

AB - The title reaction was studied under conditions where homolysis of the triphenylmethyl-to-sulphur bond of the dithiocarbonate 1d, its main product does not take place, or is negligible. Triphenylmethane 1c, triphenylmethanol 1g and benzophenone were obtained as further products under argon in cumene and in the presence of oxygen in benzene, respectively. This, together with ESR studies, indicates that part of the dithiocarbonate 1d results from single-electron transfer from O-ethyl dithiocarbonate anion to triphenylmethyl bromide 1a and out-of-cage recombination of triphenylmethyl and xanthyl radicals 6a. The main pathways leading to dithiocarbonate 1d appear, under the conditions studied, to be either a polar pathway consisting of two successive SN2′- type steps [mechanism 2, Scheme 3] and/or an SET-type reaction [mechanism 3, Scheme 3] with rapid in-cage recombination of triphenylmethyl and xanthyl radicals 6a. The hydrogen-atom donor dicyclohexylphosphine (DCPH) may not be used for trapping of the triphenylmethyl radicals formed in the title reaction because DCPH acts as a single-electron donor towards bromide 1a, i.e. it itself generates triphenylmethyl radicals from the bromide.

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