D2O Exchange Research Articles

Heavy water intake in tissues. II.H2O-D2O exchange in the myelinated nerve of the frog.

The kinetic parameters of D2O intake in the frog sciatic nerve are obtained by means of infrared spectroscopy. 3 aqueous compartments: a non-exchangeable one (≈29%) and 2 compartments of quasi-free exchangeable water: ≈50% intracellular and ≈21% extracellular, are revealed.

ChemInform Abstract: ISOTOPIC EXCHANGE STUDIES AND SELECTIVE OXIDATION OF PROPENE ON MIXED TIN‐ANTIMONY OXIDES

AbstractEs werden der H‐D‐Austausch in Propen/DzO‐ und Isobuten/D2O‐ Gemischen sowie der Anteil an 1°C O‐markiertem Acrolein als Produkt der Oxidation von Propen mit I′ O2 oder 1°C O2 an markiertem Metalloxid untersucht.

Isotopic exchange studies and selective oxidation of propene on mixed tin-antimony oxides

The propene–D2O and isobutene–D2O exchange reactions have been investigated to clarify the initial hydrogen-abstraction stage of the catalytic oxidation of propene to acrolein on a range of mixed tin–antimony oxides. The propene–D2O exchange at 473 K was stepwise, and i.r. and microwave analysis of the exchange products indicated the formation on propene pretreated catalysts of a symmetrical allyl intermediate similar to that reported to occur in the oxidation process. A carbonium ion species occurred in the absence of pretreatment. The formation of either intermediate is consistent with the observation that the exchange was limited to five of the propene hydrogen atoms. Stepwise exchange of all eight of the isobutene hydrogen atoms was found at 323 K, and probably involved a carbonium ion species.The oxygen-addition stage of the oxidation has been examined by use of isotopic oxygen of mass 18 either in the gas or catalyst phase. The percentage of C3H164O in the total acrolein formed at 573 K in the propene–18O2 reaction was very high initially and decreased as the reaction proceeded, indicating that the oxygen atom in the acrolein is provided by the catalyst lattice which is subsequently re-oxidised by gas phase oxygen. The 16O content of the carbon dioxide formed also decreased as the reaction proceeded. Catalysts pre-exchanged with 18O2 before use with propene–16O2 mixtures gave much less C3H418O than corresponded to the calculated 18O occupancy of the catalyst surface anion sites. This may have been due either to diffusion of 18O into the interior of the lattice at the high temperatures necessary to effect the exchange or to the low catalytic activity of exchanged anions.The near equality found for the rate of disappearance of [2H0]propene in the propene–D2O exchange and in the oxidation reaction at the same temperature suggests that the formation of the allyl intermediate may be the rate determining step in both processes. The rate of the oxygen exchange at the oxidation temperatures used was extremely low, and hence the dissociative chemisorption of oxygen necessary for the exchange does not directly provide oxygen atoms for the oxidation.

A comparison of homogeneous and heterogeneous platinum as catalysts for the deuteration of condensed polycyclic aromatic hydrocarbons

A comparison has been made of homogeneous sodium chloroplatinate(II) with heterogeneous platinum metal as catalysts for the exchange in D2O of naphthalene, anthracene and pyrene, three representative condensed polycyclic aromatic hydrocarbons. For this purpose, very careful detailed experiments have been designed so that the progressive deuteration of the aromatics could be followed with time especially in both catalytic systems. Initial isotope orientation is similar for both catalysts although specificity is better with homogeneous platinum. Naphthalene during the initial stages of exchange yields ,&orientation with an M value of 1, ultimately giving naphthalene[β-D4]. Only with heterogeneous platinum does prolonged exchange yield naphthalene[D8]. A unique scrambling reaction of naphthalene[β-D4] has been observed only with heterogeneous platinum. The reactivities of anthracene and pyrene are similar to naphthalene. Present data have been interpreted in terms of bond localization concepts, in particular the role of π-olefin type complexes in both catalytic systems. The results also indicate that π- dissociative, as compared with π-associative, mechanisms predominate both homogeneously and heterogeneously.

Helical concept of the fine structure of cellulose

AbstractThe helical concept of the fine structure of cellulose as proposed by Manley is discussed. The deuterium exchange experiments with cotton, cotton crystallites, and regenerated cellulose I, in which accessibility was determined by comparing the ratio of the infrared absorbance of the OD peak to the OH peak, revealed that the accessibility of cotton linters decreased on acid hydrolysis, whereas it increased on treatment with ethylamine followed by washing with water. This is in contrast to the finding of Manley, who had evaluated the accessibility by a gravimetric D2O exchange method and had come to the conclusion that acid hydrolysis did not change the accessibility of cellulose and hence cellulose did not contain crystalline and amorphous phases but was all crystalline. On the basis of Manley's protofibril and the accessibility data obtained in this investigation, a concept of the fine structure of cellulose is proposed, in which the role of Manley's protofibril is analogous to the role of individual molecule in the fringe micellar model. This concept explains the properties of cellulose that are otherwise explainable on the currently accepted fringe micellar theory. In addition, it explains the marked shrinkage in the length of cotton and rayon fibers when placed in 16% sodium hydroxide solution.

The vibrational spectrum of hydroxyl groups in hydroxyapatites

Abstract The infrared spectra of four samples of hydroxyapatites were measured using thin wafers. One sample had nearly the stoichiometric composition and one had a deficiency of Ca2+; the other samples contained small amounts of substitutional F− and Cu2+, respectively. Spectra were taken following different pretreatment procedures and at several temperatures. Particular attention was given to absorptions attributable to hydroxyl groups. A weak band at 3660 cm−1 in all samples was characterized as a surface OH group by its exchange behavior with D2O and back exchange with NH3. Internal POH groups in the non-stoichiometric sample ( Ca P = 1.58) gave rise to a band at 880 cm−1, which was unchanged following deuterium exchange, but which disappeared when heated above 400° due to condensation reactions leading to the formation of P4O74- groups which absorbed at 715 cm−1. The spectral characteristics of the stretching vibrations of lattice OH groups (and their OD analogues) were determined at temperatures from 25 to 600°C. At room temperature the absorptions at 3572 cm−1 (and 2634 cm−1) were symmetrical, approximately Lorentzian in shape and narrower in the non-stoichiometric than the stoichiometric ( Ca P = 1.67) material. At 600°C these frequencies were decreased to 3565 cm−1 (and 2628 cm−1) and new absorptions, not apparent in room temperature spectra, were observed at 3537 cm−1 for the OH form (and 2610 cm−1 for the OD form). In both instances the new absorptions comprised 30 % of the respective total band areas. The changes, brought about by temperature increase, were fully and instantaneously reversible on cooling, the new bands being of intermediate intensity at intermediate temperature. It is suggested that they result from an orders-disorder transition (of enthalpy 2.7 kcal mol−1) in the hydroxyl (and deuteroxyl) columns of the lattice.

Hydroxyl Stretching Frequencies of Synthetic Ni-, Al-, and Mg-Hydroxy Interlayers in Expanding Clays

AbstractInterlayers were produced in montmorillonite, vermiculite and hectorite in aqueous suspensions by precipitation from metal chloride salt, by hydrolysis of metal amalgams, and by slow hydrolysis of metal acetate during refluxing. In several systems an external phase of bayerite, gibbsite, or brucite was also formed. A prominent high frequency OH stretching vibration is associated with the interlayer in montmorillonites with approximate frequencies of 3660 cm−1 with nickel interlayers, 3690 cm−1 with aluminium interlayers and 3710 cm−1 with magnesium interlayers. Pleochroism studies indicate transition moment of interlayer OH to be at a relatively high angle to the planar surface of the clay crystals. Aluminium interlayers show some evidence of an additional weak absorption in the lower frequency region of 3570–3600 cm−1. In differential studies the lower frequency absorption is more evident and is shown to be unaffected by orientation. Techniques involving balancing of water deformation bands in differential spectra and D2O exchange suggest that it is not a water band. D2O flushing to remove water leaves the low frequency interlayer OH band more prominent in hectorite where the clay crystal OH is at 3680 cm−1. Deuteration studies show that flushing with D2O at room temperature removes water, and heating at 100°C in D2O vapor exchanges interlayer OH but not the clay crystal OH. Study of the OD stretching of the systems with deuterated interlayers supports observations made in the OH stretching bands.

Part VIII: N.M.R. Absorption by Water in Wool During Changes of Water Content

The change with time of the nuclear magnetic resonance absorption by water in wool was observed during uptake and loss of water following relative humidity changes between near zero and 70%, 80%, and 93%. Exchange of D2O by H2O was also observed at 93% RH. During both uptake and loss of water the results indicate that line broadening is taking place because of reduced mobility of some protons. It is suggested that this low mobility follows, at least in part, from a low level of H-bond network formation during the transient state. In desorption most of the more mobile water is quickly removed and thereafter its concentration is small. The constant- regain diffusion coefficient for water in wool at 21° C and 93% RH calculated from the D2O-H2O exchange experiment was approximately 1.5 X 10-8 cm2/sec. It appears that the corresponding intrinsic diffusion coefficient lies between conflicting values found by other workers. The exchange curve, which should be a good approximation to a self-diffusion curve, deviated grossly from a Fickian shape after the first minute. It was found that the n.m.r. signal depended on previous sorption history if the wool was not thoroughly wetted-out before a test.

Kinetics of distribution of D2O and antipyrine in isolated perfused rat liver.

Isolated rat livers were perfused via the portal vein with a blood-Ringer mixture containing a constant inflow concentration of D2O and, in some cases, antipyrine. The rate of increase of outflow concentration was studied, comparisons being made between D2O, antipyrine and a theoretical outflow curve based on completely flow-limited distribution. The effect of flow rate on the deviation of D2O from theoretical was also studied. The results indicate that exchange of D2O and antipyrine between blood and tissue in the perfused rat liver is extremely rapid relative to the rate of blood supply of these substances to the organ, even at flows several times that occurring in vivo. In the average experiment the average D2O concentration in the liver during the early period of the perfusion was about 90% of the mixed venous concentration. The factors responsible for the failure of D2O to distribute maximally, particularly tissue perfusion heterogeneity and diffusion limitation, are discussed. Although quantitation of the difference is difficult, antipyrine appears to distribute somewhat more rapidly than D2O due to its greater solubility in cell membranes.

Deuteration of Acrylonitrile

During preparation of acrylonitrile-1-d, CH2=CHD—CN, by D2O exchange, as described by Leitch (1), it was found that a linear relationship obtained between absorbance values for the 1165 cm−1 band and the degree of exchange indicated by mass spectrometer data. This note contains a brief description of the exchange experiment, spectra of acrylonitrile before and after deuteration, and a table of IR and mass spectral data recorded at intervals during the exchange.