Deuterium tracer

The solid base catalysed aldol condensation of acetone was performed over a CsOH/Si02 catalyst using a H2 carrier gas. The products observed were diacetone alcohol, mesityl oxide, phorone, iso-phorone and the hydrogenated product, methyl isobutyl ketone. Deuterium tracer experiments were performed to gain an insight into the reaction mechanism. A mechanism is proposed. 

In an earlier presentation, we reported on a deuterium tracer method for investigating the mechanisms of coal liquefaction Q). 

Two significant results of that investigation were that deuterium incorporation was found to vary with product fraction and that preferential incorporation of deuterium was found in benzylic structural positions. The purpose of this research is to extend the use of the deuterium tracer method to donor solvent reactions. 

The use of a deuterium tracer in this research makes it possible to obtain new information regarding the reactions involved in the formation of these compounds. Since reactions of this type result in a loss of hydrogen donor capability of the solvent, research in this area is important to improve the efficiency of coal hydroliquefaction and the recycleability of the solvent. 

R. P. Skowronski, J. J. Ratto and L. A. Heredy, "Deuterium Tracer Method for Investigating the Chemistry of Coal Liquefaction", Annual Report, 1977, Rockwell International,... 

Hurd, C. D., and J.Azorlosa Deuterium Tracers in the Elbs Reaction. 

The deuterium tracer experiments of Broida and Gaydon indicated that CH does not come from acetylene itself, a peroxide, or a polymer, so they suggested... 

Catalytic activity measurements and correlations with surface acidity have been obtained by numerous investigators. The reactions studied most frequently are cracking of cumene or normal paraffins and isomerization reactions both types of reactions proceed by carbonium ion mechanisms. Venuto et al. (219) investigated alkylation reactions over rare earth ion-exchanged X zeolite catalysts (REX). On the basis of product distributions, patterns of substrate reactivity, and deuterium tracer experiments, they concluded that zeolite-catalyzed alkylation proceeded via carbonium ion mechanisms. The reactions that occurred over REX catalysts such as alkylation of benzene/phenol with ethylene, isomerization of o-xylene, and isomerization of paraffins, resulted in product distribu-... 

Deuterium tracer and isotope effect study of Mn(lll)-based oxidative free-radical cyclizations... 

The unsaturated /i-keto ester 443 is converted to methylenecyclo[3.2.1]octane, 449, with 2 equiv. of Mn(OAC)3 and 1 equiv. of Cu(OAc)2510 (equation 265). Oxidation of 443 with 2 equiv. of Mn(OAc)3 in AcOH without Cu(OAc)2 provides alkene 449 in 14% only and alkanes 450a and 450b in 7% and 17% yields, respectively510. Oxidation of 443 with 2 equiv. of Mn(pic)3 and 1 equiv. of Cu(OAc)2 in AcOH provides none of alkene 449, 15% of alkane 450 and 69% of oligomeric material. To understand the above observations deuterium tracer and KIE studies have been undertaken511. 

More recently, Finlayson et al. (66) performed deuterium tracer studies using 2,2,4,4-tetramethylpentane as a model reactant, and proved that the bond-shift isomerization to 2,2,5-trimethylhexane may go via a monoad-sorbed intermediate on Pd (as well as on Pt, Ir, and Rh). The authors show that in the mechanisms of nondestructive reactions such as cyclization and bond-shift isomerization of alkanes, only one metal atom is required as the catalytic center. 

The mechanism for the reaction over alumina supported Co and Ni catalysts based on the deuterium tracer studies is believed to be one in which the adsorbed diene and adsorbed hydrogen are in dynamic equilibrium with a- and a- -bonded half hydrogenated species, resulting in the wide distribution of deuterium in the observed butanes (Fig. 9.2). 

Reaction with epoxides [1, 611, after line 2]. The reaction of epoxides of medium-size rings with lithium diethylamide is complicated. Thus m-cyclooctene oxide (I) gives mainly the bicyclic alcohol (2), and tra/i.s-cyclooctene oxide (5) gives mainly the epimeric bicyclic alcohol (6).38 Using deuterium tracer studies, Cope showed that the bicyclic alcohols (2) and (6) arise by loss of a hydrogen atom from an a-... 

In the following text, we will present the data on catalytic hypophosphite oxidation on nickel using deuterium tracer and online electrochemical mass spectrometry studies of partial reactions and their mutual interaction as a function of electrode potential, the modeling of the catalyst surface state upon the oxidation of hypophosphite, isotopic gas composition during electroless Ni-P alloy... 

Presuming the electrochemical mechanism electroless copper plating [19], namely, the catalytic reduction of Cu(II) ions by formaldehyde, the partial reactions occurring at equal rates under open-circuit conditions could be written (using the deuterium tracer to specify the origin of hydrogen) in a simplified form as follows ... 

In support of the 6-membered transition state mechanism (28) for MPV reductions depicted in Scheme III, deuterium tracer studies by von Doering and Ash-ner (33,34), and by Williams and coworkers (35) show that the source of hydride transferred to the carbonyl substrate is indeed the carbinol carbon. Later data from Moulton, et al. (34), in 1961 did not preclude the existence of a non-... 

Kaneko and Oki made studies with a deuterium tracer and found v to be between 1 and 2. Kaneko and Oki and Kaneko et al. also conducted experiments with a 0 tracer, finding an apparent v of approximately 2, for measurements both near and far removed from equilibrium. Oki et al. found that the exchange of 0 between CO2 and H2O was very fast (v approaching infinity) but that exchange between CO and CO2 was not as fast (v approximately 2). Mezaki summarized these and other data (Table 9). 

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