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1991 (1)
1972 (1)
1Author    D. Ietm Ar Kuek, Andreas SchusterRequires cookie*
 Title    Oxidations of Alkylbenzenes with Dimethyldioxirane  
 Abstract    The oxidation o f various alkylbenzenes (1 -1 7) with excess dim ethyldioxirane (D M D O) in hom ogeneous acetone solutions has been studied. In general, the benzylic methylene and methine C -H bonds were oxidized to give the corresponding phenones and tertiary benzylic alcohols, respectively, in relatively low yields. W hereas a tert-buiy\ substituent at the reaction centre leads to very low conversion due to steric hindrance, the presence o f additional phenyl groups appears to favour the oxidation in most, but not all cases. Di-and triphenylmethane (4 and 14) were found to be considerably less reactive than cw-decalin. By contrast, the intra­ molecular competetive oxidation o f isobutylbenzene (19) and l-m ethyl-4-phenylcyclohexanes (20) reveals that the benzylic C -H bonds are slightly more reactive than the tertiary ones at remote positions. 
  Reference    Z. Naturforsch. 46b, 1223—1226 (1991); received April 4 1991 
  Published    1991 
  Keywords    D ioxiranes, Dimethyldioxirane, Alkylbenzenes, Oxidation 
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 TEI-XML for    default:Reihe_B/46/ZNB-1991-46b-1223.pdf 
 Identifier    ZNB-1991-46b-1223 
 Volume    46 
2Author    G. Sosnovsky, M. W. ShendeRequires cookie*
 Title    Friedel-Crafts Alkylation of Aromatic Compounds with Phosphorus Esters la b  
 Abstract    The alkylations of aromatic compounds with trialkyl phosphites (1), dialkyl phosphites (2), and trialkyl phosphates (3) in the presence of aluminum chloride were studied involving several raction variables, such as time, ratio of reactants, nature of catalyst and solvent, and combinations thereof. Extensive disproportionation and isomerization were observed in the reaction with mono-substituted alkylbenzenes under heterogeneous reaction conditions obtained by the use of an excess of aromatic substrates. A combination of aluminum chloride —nitromethane complex and dichloro-methane as solvent was used to eliminate these undesirable effects and to give homogeneous and practically non-isomerizing conditions. The scope of the reaction was studied with a number of aromatic substrates, and their relative reactivities were compared to that of benzene in competitive isopropylations with triisopropyl phosphite. The relative rates and isomer distributions showed low substrate and low positional selectivities and poor agreement with B r o w n's selectivity relation-ship. The substrate selectivity was somewhat higher and the positional selectivities were somewhat lower than those obtained in competitive isopropylation reactions with other isopropylating agents. The selectivity factor, SF, and partial rate factors were calculated. An electrophilic alkylation mechanism is proposed on the basis of (1) the relative rates of isopropylation, (2) the isomer distribution of dialkylated aromatics, and (3) the necessity of a strong Lewis acid in these reactions. 
  Reference    (Z. Naturforsch. 27b, 1339 [1972]; received June 26/August 22 1972) 
  Published    1972 
  Keywords    Friedel-Crafts, Electrophilic Alkylation, Phosphorus Esters, Alkylbenzenes 
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 TEI-XML for    default:Reihe_B/27/ZNB-1972-27b-1339.pdf 
 Identifier    ZNB-1972-27b-1339 
 Volume    27