75. The kinetics of aromatic halogenation. Part II. The chlorination of hydrocarbons

Mare, P. B. D. de la; Robertson, P. W.

doi:10.1039/jr9430000279

Cited by 37 publications

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“…The structure of pentamethylchlorobenzenepentacarboxylate (III) was demonstrated by comparison with a sample synthesized from pentamethylchlorobenzene (4). The tetramethyl dichlorobenzenetetracarboxylate was not obtained in sufficient quantities to be characterized.…”

Section: Resultsmentioning

confidence: 99%

Investigations on the Structure of the Color Compound in Caustic

Wawzonek

Eftax

1957

J. Electrochem. Soc.

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The material isolated by Heller from stubs of graphite anodes used in chlorine-caustic soda cells and shown by him to give the color in concentrated caustic soda has been reinvestigated. An extract from the stubs after treatment with nitric acid was found to consist of mellitic acid, pentacarboxychlorobenzene, a tetracarboxychlorobenzene of unknown configuration, and material of unknown structure which is the source of the color. The acids were formed during the treatment with nitric acid. The color forming material seems to be of high molecular weight and structurally more complex than proposed by Heller.

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Section: Resultsmentioning

confidence: 99%

Investigations on the Structure of the Color Compound in Caustic

Wawzonek

Eftax

1957

J. Electrochem. Soc.

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“…49 For tert.-butylbenzene and benzene 60 tt relative rate of 115 : 1 was obtained, a result which cannot be accounted for by hyperconj ugation involving hydrogen atoms, and therofore the difference in rates was explained as being due to release of electrons from the tert.-butyl group through structures of the type (XVI) contributing to the resonance hybrid. The experimental data, however, are not sufficient to warrant such a postulate, for partial rate factors were not determined.…”

Section: Absorption Spectra and Ionisation Potentials-(a)mentioning

confidence: 97%

Hyperconjugation

Crawford¹

1949

Q. Rev., Chem. Soc.

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SINCE the review by C. L. Deasy the concept of hyperconjugation has become well established, and, furthermore, has been extended and widely applied ; consequently, the present more extensive review was undertaken.Historical Introduction and Definition of the Term.-If electron displacement in alkyl groups resulted solely from the operation of the inductive effect, then the order But > Pri > E t > Me should always be obtained for those reactions which require accession of electrons to the reaction region.Experimental evidence that this order is not universally applicable was first provided by J. W. Baker and W. S. Nathan,2 who studied the rate of reaction of various alkyl-substituted benzyl bromides with pyridine. It was found that all alkyl substituents increased the reaction rate, while with a single p-alkyl substituent the rate decreased in the orderSince the reaction studied is one facilitated by electron accession towards the side chain, it follows that the accelerating effects of alkyl groups must be related to their capacity for electron release, and, furthermore, that the relative magnitude of this electron release diminishes in the order indicated in (a), which order is exactly the reverse of that expected on the basis of the inductive effect of alkyl groups. The methyl group, it would seem, is therefore capable of permitting additional electron release, by some mechanism which is either greatly reduced or inoperative in the more highly alkylated groups. Since an anomaly of this kind is not found in every type of system containing alkyl groups, Baker and Nathan pointed out that the additional mechanism of electron release by the methyl group in p-methylbenzyl bromide is to be associated with the presence of the attached conjugated system of the aromatic nucleus. It was therefore suggested that when a methyl group is attached to a conjugated system, the pair of electrons forming the C-H bond in the methyl group, are appreciably less localised than are those in a similarly situated carbon-carbon bond. Hence a methyl group attached to the requisite system permits electron release by what is essentially a type of electromeric effect :- ( a ) This new effect acts in addition to, and in the same direction as, the inductive effect, but, since it depends on the number of C-H bonds, its magnitude clearly will diminish in the order Me > E t > Pri >

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“…At high dilution the second step may occur without the aid of the catalyst but with a higher heat of activation (70), and the solvent could serve as the proton acceptor; this would account for the second-order reaction at low concentrations. Water facilitates the reaction, probably owing to stabilization of the intermediate, ArHX®, by solvation; and HX retards reaction, owing to the formation of HX3 (58,70). It is noteworthy that if a benzene solution of iodine is treated with an anhydrous silver salt, reaction occurs to yield iodobenzene and silver iodide (13), the silver ion thereby serving in the capacity of C above.…”

Section: Hydrolysis Alcoholysismentioning

confidence: 99%

Orientation of Substitution in the Benzene Nucleus.

Ferguson¹

1952

Chem. Rev.

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75. The kinetics of aromatic halogenation. Part II. The chlorination of hydrocarbons

Cited by 37 publications

References 0 publications

Investigations on the Structure of the Color Compound in Caustic

Investigations on the Structure of the Color Compound in Caustic

Hyperconjugation

Orientation of Substitution in the Benzene Nucleus.

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