A novel method to study the reversibility of aromatic substitution reactions.
Item
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Title
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A novel method to study the reversibility of aromatic substitution reactions.
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Identifier
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AAI9119609
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identifier
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9119609
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Creator
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Aria, Porus Soli.
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Contributor
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Adviser: Leonard H. Schwartz
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Date
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1991
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Organic
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Abstract
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Optically active 2,2{dollar}\sp\prime{dollar}-dicarbomethoxy-9,9{dollar}\sp\prime{dollar}-bianthryl (1) has been observed to racemize in the presence of phenyl and benzyl radicals. This racemization process is suggested as a means of studying the reversibility of radical addition to an anthracene ring. It is suggested that addition of the radical forms of {dollar}\sigma{dollar}-complex that has a lower rotational energy barrier between the central C-9, C-9{dollar}\sp\prime{dollar} carbon atoms than the starting bianthryl 1. Reversal of the addition step would result in recovery of racemized 1 if the bond rotation in the {dollar}\sigma{dollar}-complex were competitive with the reversal step. No racemization was observed in the absence of the radical source. The racemization was reduced or completely prevented by the presence of radical inhibitors. These results are interpreted to mean that the radical adds reversibly to the anthracene ring of 1.;The phenyl radical was generated by the thermal decomposition of (1) phenylazotriphenylmethane (PAT) at 50{dollar}\sp\circ{dollar}C, (2) benzoyl peroxide at 80{dollar}\sp\circ{dollar}C and (3) diphenylmercury at 180{dollar}\sp\circ{dollar} and 200{dollar}\sp\circ{dollar}C in bromobenzene. The benzyl radical was generated by the thermal decomposition of dibenzylmercury at 160{dollar}\sp\circ{dollar}, 130{dollar}\sp\circ{dollar}, 100{dollar}\sp\circ{dollar} and 50{dollar}\sp\circ{dollar}C in bromobenzene and the m-fluorobenzyl radical was generated by the thermal decomposition of bis(m-fluorobenzyl)mercury at 160{dollar}\sp\circ{dollar} and 130{dollar}\sp\circ{dollar}C.;Initial rates of racemization and the order with respect to each reagent was determined. Arrhenius parameters for the racemization of bianthryl 1 in the presence of dibenzylmercury were determined.;Methyl-2-{dollar}\alpha{dollar}-naphthyl-3-nitrobenzoate (51a) was observed to racemize in the presence of KF in 18-crown-6 solution of acetonitrile at 83{dollar}\sp\circ{dollar} and 100{dollar}\sp\circ{dollar}C. These results suggests that the fluoride ion adds reversibly to biaryl 51a.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
