Catalytic conversion of polycyclic aromatic hydrocarbons: Mechanistic investigations of hydrogen transfer from an iron-based catalyst to alkylarenes

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Results of our model compound studies suggest that free radical hydrogen transfer pathways from the catalyst to the alkylarene are responsible for the scission of strong carbon-carbon bonds. There are two requisites for the observed selective bond scission. First is the stability of the ipso adduct precursor leading to displacement, the more stable the adduct the more probable bond scission. This explains why benzyl radical displacement > phenoxy radical displacement in benzyldiphenyl ether and explains why PhCH{sub 2}CH{sub 2}PhCH{sub 2} radical > naphthylmethyl radical from NMBB. Second, given equal ipso adduct precursor stabilities, e.g. methyldiphenylmethane, the stability of the departing ... continued below

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7 p.

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Autrey, T.; Linehan, J.C.; Camaioni, D.M.; Powers, T.R.; McMillan, E.F. & Franz, J.A. August 1, 1995.

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  • Pacific Northwest Laboratory
    Publisher Info: Pacific Northwest Lab., Richland, WA (United States)
    Place of Publication: Richland, Washington

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Results of our model compound studies suggest that free radical hydrogen transfer pathways from the catalyst to the alkylarene are responsible for the scission of strong carbon-carbon bonds. There are two requisites for the observed selective bond scission. First is the stability of the ipso adduct precursor leading to displacement, the more stable the adduct the more probable bond scission. This explains why benzyl radical displacement > phenoxy radical displacement in benzyldiphenyl ether and explains why PhCH{sub 2}CH{sub 2}PhCH{sub 2} radical > naphthylmethyl radical from NMBB. Second, given equal ipso adduct precursor stabilities, e.g. methyldiphenylmethane, the stability of the departing radical determines the selectivity. this explains benzyl radical > methyl radical in the methylated diphenylmethanes and explains why {alpha}-hydroxyphenethyl radical > methyl radical in 1,2-ditolylethanol. We have assumed little physical interaction between the molecules and the catalytic surface and have been able to satisfactorily explain most of the observed selectivity. However, for NMBB we expect a higher selectivity for -A- bond scission relative to -B- bond scission, given the ca. 6 kcal/mol difference between the radical adduct formed by the hydrogen atom addition to 1-methylnaphthalene and p-xylene. It is possible that physical properties play a role in lowering the selectivity in -B- bond scission. Also, catalysts prepared by other methods may contain different activity sites and operate by different mechanisms.

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7 p.

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OSTI as DE96002614

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  • 210. national meeting of the American Chemical Society (ACS), Chicago, IL (United States), 20-25 Aug 1995

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  • Other: DE96002614
  • Report No.: PNL-SA--26378
  • Report No.: CONF-950801--17
  • Grant Number: AC06-76RL01830;FG06-89ER75522
  • Office of Scientific & Technical Information Report Number: 159223
  • Archival Resource Key: ark:/67531/metadc626810

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  • August 1, 1995

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  • June 16, 2015, 7:43 a.m.

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  • April 7, 2016, 2:29 p.m.

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Autrey, T.; Linehan, J.C.; Camaioni, D.M.; Powers, T.R.; McMillan, E.F. & Franz, J.A. Catalytic conversion of polycyclic aromatic hydrocarbons: Mechanistic investigations of hydrogen transfer from an iron-based catalyst to alkylarenes, article, August 1, 1995; Richland, Washington. (digital.library.unt.edu/ark:/67531/metadc626810/: accessed December 14, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.