Deuterium oxide, reaction with benzene

B. Reactions of Benzene with Deuterium Oxide and with Deuterium-... 

The fact that an isotope effect of 1.7 0.1 is observed 38) in the benzene/deuterium oxide reaction at 30°C indicates that this reaction is the rate-determining step of the dissociative n complex substitution mechanism. In this respect the result agrees with the direct observations made by other investigators 41, 42), namely that unsaturated hydrocarbons chemisorb at a faster rate than their subsequent interactions with chemisorbed hydrogen. 

Unsaturated Steroids.—Irradiation of cholesterol or cholest-4-en-3/ -ol (719) in benzene-ether, or in aqueous-organic solvent mixtures containing xylene as sensitiser, affords the oxetan (722 ca. 20%) in the aqueous system, 5j -cholestane-3, 5-diol (723 54%) is also formed. With deuterium oxide instead of water, cholesterol gave the 6< -monodeuterio-3, 5i9-diol, showing the reaction to... 

In accordance with the constitution LV, the mild (70°) treatment of macralstonidine with deuterium chloride in deuterium oxide gives a mixture of the nonadeutero ketone (XXXIc), 9,11,12-trideutero-ilIa-methylsarpagine, and 9,10,11,12,18,18,18,20,11, 12 -decadeutero-macralstonidine (LV-dio)- The first of these products was unequivocally identified with the fission product obtained from macralstonine under similar reaction conditions (see above). The deuterium substitution pattern in the trideutero-V,j-methylsarpagine becomes clear from its mass spectrum since all fragment ions which contain the intact benzene ring (e.g., LVIII) are observed three mass units higher than in the un-deuterated compound. 

A trispyrazolylborate platinum complex was found to activate C-H bonds via a Pt(ii)/Pt(iv) sequence. Removal of a methyl anion from [(77 -Tp )RhMe2] leads to an unsaturated species that then adds to the hydrocarbon C-H bond (Equation (12)). The related protonatcd species Tp PtMc2H loses methane at 110°G and then oxidatively adds benzene- 6. The new methyl-phenyl-deuteride derivative then reversibly exchanges deuterium into the methyl group, indicating reversible methane activation. In addition, the Pt-H bond can undergo reaction with oxygen to... 

Four nucleophilic aromatic substitution reactions with amines have been studied for deuterium isotope effects. Hawthorne (81) found that the rates of reaction of o- and p- nitrochlorobenzene with piperidine in xylene are not altered by substitution of deuterium for hydrogen on the amino group of the nucleophile. Similarly, 2,4-dinitrochlorobenzene reacts at identical rates with -butylamine and with iV,iV-dideuterio-n-butylamine containing 0.75% ethanol (76). Under the conditions of the rate measurements the deuterated amine does not undergo exchange with either the chloroform or the ethanol present. Finally, the reaction of trichloro-s-triazene with aniline shows no isotope effect with AT,JV-dideuterioaniline in benzene as well as in benzene saturated with deuterium oxide (82). 

Aromatic hydrocarbons are mainly hydroxylated to phenolic products. Complex (12) hydroxylated benzene in MeCN at 20 °C into phenol in ca. 55% yield, and no isotope effect was found for this reaction. Hydroxylation of toluene mainly occurs at the ring positions, with minor amounts of benzylic oxidation products. Hydroxylation of 4-deuterotoluene by (12) occurred with 70% retention and migration of deuterium in the formation of p-cresol. This high NIH shift value is in the same range as that found for liver microsome cytochrome P-450 hydroxylase, and suggests the transient formation of arene oxide intermediates. 

Alkali metal benzhydrolate oxidizes in toluene [111] and benzene [112] as well as in f-butanol [113] with autocatalysis that is produced by the K02 formed in the oxidation [113]. The induction period disappears when K02 is added to a solution of potassium benzhydrolate. The kinetics of oxidation of sodium benzhydrolate was studied by Pereshein et al. [111]. The maximum oxidation rate appears to be approximately proportional to [RONa] [02]/[ROH],the activation energy being 12 kcal mole-1. The inhibiting action of alcohol (benzhydrol and t-butanol) on the oxidation of metal benzhydrolates was noted by Russell et al. [110], No deuterium exchange was observed during the oxidation of potassium benzhydrolate in t-butanol. Thus no dianions are produced from benzhydrolate ion by the equilibrium reaction... 

Reactions ofThietan 1-Oxides, Tkietan 1,1-Dioxides, and Thiet 1,1-Dioxides involving Sulphur-stabilized Carbanions. Current interest in the stereochemistry of sulphur-stabilized carbanions has extended to thietan derivatives. Determination of the relative rate of base-catalysed racemiza-tion and of deuterium exchange for the thiet 1,1-dioxide derivative (89) in t-butyl alcohol-benzene indicated exchange with complete racemization, in accord with the enforced planar configuration (Figure 1)... 

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