Deuteration studies

So far this remains the only microwave-enhanced borohydride deuteration study. Corresponding tritiation studies can be anticipated in due course, especially with the wider range of tritiated reducing agents, referred to previously, becoming available. Significant reductions in radioactive waste can be anticipated. 

Deuteration studies with acetic acid-d4 (99.5% atom D) as the carboxylic acid building block, ruthenium(IV) oxide plus methyl iodide-d3 as catalyst couple and 1/1 (C0/H2) syngas, were less definitive (see Table III). Typical samples of propionic and butyric acid products, isolated by distillation in vacuo and glc trapping, and analyzed by NMR, indicated considerable scrambling had occurred within the time frame of the acid homologation reaction. 

The addition of 1-alkynes to a,/3-unsaturated ketones in water is catalyzed by a palladium(n)/phosphine combination. Deuteration studies suggest that this reaction proceeds via carbometallation of the olefinic moiety by an alkynylpalladium intermediate (Equation (193)).1... 

The structurally related JM-Phos catalyst 11 (Fig. 30.10) gave generally lower selectivity for substrates 36-40 [15]. Deuteration studies using D2 with these catalysts showed substantial deuterium incorporation into the allylic positions of substrates 39 and 2. Deuterium incorporation has also been observed with Ir-PHOX catalysts [35], which implies that reversible H abstraction at the allylic position occurs during the hydrogenation reaction. 

Deuteration studies with a silylbutatriene with KOtBu in tBuOD provided evidence for a selective a-deprotonation [340]. 

Many of the older bis-indenyl catalysts are less selective at higher temperatures, which was ascribed initially to a lower selectivity of the insertion reaction itself. More recent work by Busico, based on deuteration studies and again based on very detailed and elegant analysis of 13C NMR spectra of the polymers, has shown that in fact epimerisation of the growing alkyl chain occurs via a series of (3-hydride eliminations and re-insertion reactions [36] involving even tertiary alkyl zirconium species. 

Replacement of the proton by deuterium represents the simplest electrophilic substitution the process is effected by concentrated deuteriosulfuric acid. Deuteration studied over the ranges 45-96% acid and 150-250 °C showed that for both quinoline and quinoline AT-oxide reaction occurs in the positions 8>5,6>7>3 and rates increased both with increasing acid concentration and with temperature. The mechanism proceeds via the conjugate acid (Scheme 4) (75TL1395, 72IZV2092, 71JCS(B)4, 67CPB826). 

Anomalous behavior is exhibited by the tricarbonylruthenium complex of 1-methoxycar-bonyl-1//-azepine in that at room temperature with TCNE, perfluoropropanone or l,l-dicyano-2,2-bis(trifluoromethyl)ethylene, exo-2,5-adducts, e.g. (143), are obtained. Deuteration studies reveal that the addition is non-concerted and involves an initial electrophilic attack by the 2u--system at the uncoordinated double bond of the azepine-metal carbonyl complex <77JCS(D)204). 

Isoxazolines have been converted into unsaturated oximes, and thence into enones (76AG(E)50). Treatment of the isoxazoline (523), for example, with lithium diisopropylamide gave the ring cleavage product (524) which reacted with titanium(III) chloride to furnish enone (525 Scheme 115). Oxime formation has been shown to proceed via the anion (526) as revealed by deuteration studies. 

Deuteration studies showed that the distribution of deuterium in the glycol aldehyde was consistent with this mechanism.336 It has been shown that, in presence of small amounts of an amine, the reaction can be carried out in solvents other than dialkylamides.337 The amines also ... 

In arriving at a satisfactory analysis of the spectrum we must make use not only of the polarization data, but also of the results of deuteration studies, full [Narita, Ichinohe, and Enomoto (145)] and partial [Folt, Shipman, and Berens (55)], and studies of C—Cl frequencies in small molecules. [Mizushima, Shimanouchi, Nakamura, Hayashi, and Tsuchiya (139) Shimanouchi, Tsuchiya, and Mizushima (196)]. The lack of the Raman spectrum is a definite handicap, but is in part mitigated by the expectation that many of the Raman active fundamentals should be close to the frequencies of infrared active fundamentals. 

In the hydrogen bending region, deuteration studies [Peraldo (167) Natta (150) ] indicate that the 1437 cm-1 a band is associated with the CHg group, thus suggesting its assignment to 8 (CH2) (E). This would then require that the 1453 n and 1461 a bands be assigned to 8a (CH3) ( 4) and... 

Several changes in assignments of the CH and CH2 modes are suggested by the recent polarization and deuteration studies. The assignments for vs (CH2) and va (CH2) are unchanged. Their polarization, especially in - CD2CD)s, where vs (CD2) is n... 

The black solid (VIII) is converted into the green fulvalene titanocene (V) at 110°C, and also reacts with H2, N, and alkenes 42), as do the active metastable forms of titanocene (30). With hydrogen, (VIII) yields a green-gray precipitate, formulated as [(CsHsMCsH TU] H2, from toluene solution. The infrared spectrum and deuteration studies show this solid to contain a Ti-H bond, probably with the hydrogen in a bridging position, as either... 

The secondary alcohols investigated were (XLVII) and (XLVIII). The former loses water more easily than the corresponding primary alcohol (XLIII), and deuteration studies show that the water is eliminated by a 1,2-mechanism. Fragment ions for loss of C5H5 and C5H5 + H20 are also observed. However, the second most abundant peak (the base peak being the molecular ion) is C5HsFeOH+. 

The most cited silica deuteration study was performed by Davydov and co-workers.15,24,25,49 A known amount of D20 vapour was contacted with silica in a vacuum unit with circulation of vapours.50 The silica used for deuteration was pretreated at temperatures ranging from 298 to 473 K. Reaction was performed at room temperature with subsequent evacuation at 473 K. From a mass spectrometrical analysis of the produced vapours, a quantitative measure of the number of surface hydroxyl groups (a0n) was obtained, this quantity will be discussed in chapter 6. 

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