1963
DOI: 10.1139/v63-184
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A Kinetic Investigation of the Reaction of Methylmagnesium Bromide With Benzophenone

Abstract: The reaction of methylnlagnesiunl bromide with benzophenone in tetrahydrofuran was found to be homogeneous and essentially quantitative. The rates of this reaction were measured b y following the decrease in absorbance of benzophenone in the ultraviolet as a function of time. Variables examined were concentrations of reactants, magnesium bromide, and temperature. Values were derived for the rate constants, dnd the energy and entropy of activation. The reaction was found to be initially first order in each reac… Show more

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Cited by 29 publications
(14 citation statements)
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“…Addition of magnesium bromide decreases the rate of reaction of diphenylmagnesium with benzonitrile in THF.9 A similar decrease has been reported numerous times in the reaction of Grignard reagents with ketones or esters. [23][24][25][26][27][28][29] Although it may have other effects on the reaction system, the addition of magnesium bromide to methylmagnesium bromide must cause a shift in the Schlenk equilibrium producing more of the CH3MgBr species and decreasing the amount of (CH3)2Mg. The reaction rate should decrease markedly on addition of magnesium bromide if the reaction of methyl bromide Grignard reagent proceeds to a significant extent through the (CH3)2Mg species.…”
Section: Resultsmentioning
confidence: 99%
“…Addition of magnesium bromide decreases the rate of reaction of diphenylmagnesium with benzonitrile in THF.9 A similar decrease has been reported numerous times in the reaction of Grignard reagents with ketones or esters. [23][24][25][26][27][28][29] Although it may have other effects on the reaction system, the addition of magnesium bromide to methylmagnesium bromide must cause a shift in the Schlenk equilibrium producing more of the CH3MgBr species and decreasing the amount of (CH3)2Mg. The reaction rate should decrease markedly on addition of magnesium bromide if the reaction of methyl bromide Grignard reagent proceeds to a significant extent through the (CH3)2Mg species.…”
Section: Resultsmentioning
confidence: 99%
“…The molar concentration of ethyl groups = total base and benzonitrile at t = 0. 6 The ratio of bromide ion to ethyl groups at t = 0. c The extent to which the reaction was followed. The results of studying the effect of temperature upon the rates in the different solvents employed are presented in Tables II-VII.…”
Section: Resultsmentioning
confidence: 99%
“…I1 est utile de relever que les di-n-butylmagnksiens (essais 10-15), complexks soit avec l'kther soit avec la pyridine, rkagissent avec la benzophknone pour former des produits solubles dans l'kther, qui, B l'hydrolyse, donnent notamment du benzhydrol; ce m&me produit de rkduction obtenu avec la solution de Grignard (essais 7-9) n'est pas soluble dans l'bther avant l'hydrolyse ; en revanche, le produit d'addition avant hydrolyse est soluble. Cette constatation nous suggkre que si la rkaction prockde par deux Ctapes conskcutives [8]- [lo], les produits d'addition et de rkduction ne peuvent pas &re formks sur la m&me molkculel). groupes R disponibles pour la rCaction d'addition n'est que de 50% ; c'est-&dire que pour chaque mole de l'alcool tertiaire form6, on trouve aprhs hydrolyse une mole de cktone et un kquivalent de diorganomagnCsien qui n'ont pas ICagi.…”
Section: Discussionunclassified
“…Les rCsultats que nous avons enregistrCs avec les r6actifs diorganomagnCsiens confirment que le m6canisme d'addition ne diffkrerait de celui de la solution de Grignard, que par la nCcessitC de l'incorporation d'une seconde molCcule de diorganomagnksien au lieu de l'halogdnure de magnesium; selon notre hypothhse, cette molCcule de di-organomagnCsien devieht complexCe au produit d'addition et non rCactive A l'attaque cktonique. Ce mCcanisme pourrait ptockder par deux Ctats cycliques de transition B. six membres [3] [8] [11]- [14] (voir schCma I). Lors de l'addition du n-Bu,Mg B la benzophbnone (essai 12), on peut s'attendre h trouver davantage de produit de rCduction que dans le cas de I'addition normale (essai l l ) , car l'association du rCactif est favorisCe en raison de sa concentration initiale BlevCe.…”
Section: Discussionunclassified