Deuterium oxide, as solvent

The power of the new spectrometer to reveal configurations of difficult cyclitols or sugars was first tested with mt/o-inositol (2), using deuterium oxide as solvent. At 60 or 100 MHz. the one equatorial and five axial protons appear to have different chemical shifts as shown by Lemieux in 1956 with a 40 MHz. instrument (14,15). However, since the five-proton axial signal could not be resolved, one could probably not have assigned the configuration 2 (which was already known from laborious chemical correlations extending over many years.)... 

Apart from the preparation of radiotracers, microwave-assisted transformations have also been utilized to carry out simple hydrogen-deuterium exchange reactions. In the case of acetophenone, for example, simple treatment with deuterium oxide as solvent in the presence of molecular sieves at 180 °C for 30 min led to complete... 

An increase in solvent polarity further favours the open-chain tautomer in water there is no evidence for any cyclic form [79], This is remarkable in view of the fact that the furanose/pyranose equilibria of sugars, which are interconverted through the open-chain form, are also solvent-dependent [80, 81, 159], Arabinose, for example, in [Dsjpyridine consists of 66 cmol/mol pyranose form (a y9 = 33 33) and 34 cmol/mol furanose form (a y9 = 21 13), compared with 95.5 cmol/mol pyranose form (a y9 = 60 35.5) and 4.5 cmol/mol furanose form (a y9 = 2.5 2.0) in deuterium oxide as solvent [80, 159],... 

Replacement of carbon tetrachloride by deuterium oxide as solvent causes a greater downfield shift (approx. 0.3 ppm) in signals for H-2 and H-5 than in that for H-4 ( 0.2). Change of solvent has a relatively... 

In reeent years, tire use of elevated temperatures has been reeognised as a potential variable in method development. Witlr inereased temperature, aqueous-organie mobile phases separations ean improve, viseosity deereases and diffusion inereases so baek pressures are redueed. At higher temperatures (usually with superheated water > 100 °C under modest pressures) water alone ean be used as the mobile phase and eair provide unique separation opportunities. The absenee of an organie solvent enables the use in HPLC of alternative deteetors sueh as FID or on-line LC-NMR using deuterium oxide as the eluent. 

LC/MS of the isolated impurity indicated the presence of two peaks, corresponding to a dimer-like degradant and the parent drug. A full set of NMR experiments was performed to elucidate the structure. Despite having an adequate amount of sample, sensitivity was limited by low solubility. Deuterium oxide as the solvent eliminated the ability to detect exchangeable protons, although this was not deemed to be a significant limitation for this structural elucidation. The NMR analysis confirmed that there were two primary components present in a ratio of approximately 2.5 to 1,... 

The version of the selective-deuteration experiment most widely practiced involves the use of deuterium oxide as the solvent for n.m.r. measurements, instead of water without this procedure, the interpretation of n.m.r. spectra of sugars in aqueous media is generally diflBcult. Even so, prior deuteration of labile protons (such as those of hydroxyl and amino groups) by a series of exchange experiments is necessary before the residual-water peak can be lessened to an acceptable intensity. Other, potentially acidic protons can be similarly exchanged by deuterium through repeated lyophilization from deuterium oxide. 

For similar reasons, the dialdehydes 48 and 49, obtained from methyl aldopen-topyranosides or aldotetrofuranosides, can be formulated as hemialdals according to NMR-spectral data, however, they exist in deuterium oxide as an almost 1 1 mixture of the acyclic hydrated dialdehyde (58 or as the p anomer) and the hemialdal (60 or 61) form. They occur almost exclusively as the latter form in such solvents as dimethyl sulfoxide or pyridine. ... 

Absorption of butadiene by a hydrogenated solution of pentycyano-cobaltate(II) is rapid, one mole equivalent being taken up for each atom equivalent of hydrogen preabsorbed. The solution so formed gradually evolves an approximately equimolar mixture of butadiene and isomeric butenes when places in an inert atmosphere. Reversibility of 2 is further demonstrated by adding deuterium to butadiene and employing deuterium oxide as the solvent. The predominant product, butene-1, was 66% di-... 

D-glucose or D-fructose into 5-(hydroxymethyl)-2-furaldehyde in solution in acidified deuterium oxide.17 The 2-furaldehyde was isolated as 5-(hydroxymethyl)-2-furoic acid, and thus this experiment did not permit an evaluation of reversible equilibration of 1,2-enediols with the parent sugars. However, the 2-furoic acid was devoid of measurable carbon-bound deuterium, which indicated the absence of 3-deoxyglycosulose intermediates. It is also noteworthy that 3-deoxy-D-en/fhro-hexosulose is converted, in acidified deuterium oxide, into 5-(hydroxymethyl)-2-furaldehyde with no solvent exchange84 this result lends further support to the conclusion that 45 does not participate in the reaction as an intermediate. 

Horton and coworkers104 have likewise shown that l,2 3,4-di-0-isopropylidene-a-D-gaZaeto-hexodialdo-l,5-pyranose exists exclusively as the hydrate in deuterium oxide, and that this compound remains partially hydrated in moist chloroform. As early as 1931, Wolfrom105 had shown that the formation of hemiacetals from aide-hydo sugars in hydroxylic solvents is a common occurrence. 

The zinc-copper couple technique [61a-e] is generally used to give good yields of terminal allenes and also of allenes with neighboring double or triple bonds. Ethanol or butanol is used as the solvent, and deuterium oxide is used if deuterioallenes are desired (see Table III). 

All of the H-n.m.r. spectra, and most of the 13C-n.m.r. spectra, were recorded for solutions in deuterium oxide, on the tacit assumption that the composition in that solvent would be the same as that in natural-abundance water. It is by no means certain that this assumption is valid,... 

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