[en] The approximation methods for the zero-point energy (ZPE) previously developed using the Lanczo's tau method have been applied to the shifts in ZPE due to hydrogen isotope substitutions. Six types of approximation methods have been compared and analyzed on the basis of a weighing function Ω(lambda) varies as lambda/sup k/ and the actual eigenvalue shift spectra. The method generated by the most general optimzation treatment yields a predictable and generally satisfactory precision of the order of 1% or better. A linear frequency sum rule has been derived, which approximately holds for the sets of isotopic molecules which satisfy the second-order frequency sum rule. 19 references, 3 figures, 3 tables

[en] Some selected bibliographical references about deuterium process are presented, as follow: diffusion, chromatography, destillation, isotope exchange, centrifugation and eletrolysis. (E.G.)

[en] The thermoreorganizations of methylene-3-vinylcyclobutane to 4-methylenecyclohexene and 1,1-divinyl-3-methylenecyclobutane to 4-methylene-2-vinylcyclohexene were investigated. Two mechanistic options were available for these rearrangements; one which involved the intervention of diradical intermediates, the other involved a concerted [3,3]-sigmatropic or Cope rearrangement. Activation parameters were determined for both of these pyrolyses. The heats of formation of their transition states were approximated by the group equivalent method, and these were consistent with the lower heats of formation, calculated for the speculated diradical intermediates. The indication from the kinetic data that diradical intermediates intervene in these thermoreorganizations was corroborated by an intermolecular secondary deuterium isotope effect study where the rates of reaction of 1,1-divinyl-3-methylenecyclobutane were compared with 1,1-di(vinyl-2,2-d₂)-3-methylenecyclobutane. The preponderant weight of analogy indicates that transformation of an isotopically substituted carbon from a trigonal to a tetrahedral orientation in the product should be associated with an inverse secondary deuterium isotope effect. However, a normal intermolecular isotope effect (k/sub H//k/sub D = 1.05 +- 0.03) was observed at 99.9⁰ which can be accounted for by a diradical process. From examination in the nmr of the product ratio, resulting from the thermolysis of 3- methylene-1-vinyl-1-(vinyl-2,2-d₂)-cyclobutane, an intramolecular isotope effect (k/sub H//k/sub D/ = 1.14 +- 0.07) was determined. The discrimination process which gives rise to this kind of secondary deuterium isotope effect is thought to involve a twisting motion of an isotopically substituted, terminal methylene group, resulting in a nonplanar pentadienyl radical with concomitant destruction of π-bonding at its terminus

No abstract available

[en] The secondary kinetic isotope effect associated with the competitive protonolysis of (di-n-octyl-l-l-d₀)Hg(di-n-octyl-l,1-d₂)Hg, respectively, and di(n-octyl-2,2-d₀)HG(di-n-octyl-2,2-d₂)Hg, respectively, by anhydrous HCl in dioxane has been evaluated. Also listed are corresponding data of the competitive Br cleavage of 1-d₀ and 1,1-d₂, together with equiv data for trineopentyl (n-octyl)-l,l-d₀)SN and trineopentyl(n-octyl-l,l-d₂)Sn. The data reveal that a normal alpha-deuterium kinetic isotope effect prevails, corresponding to 1.10 per D at 25⁰C. Neither the solvent nor the size or polarizability of the entering or leaving groups appear to influence the magnitude of this effect. The corresponding beta-deuterium isotope effect is negligible. 10 references, 1 figure, 1 table

[en] Short communication

[en] The synthesis of cholesterol with specific substitution of deuterium for hydrogen in positions 20 and 22 to 27 inclusive is reported. (U.S.)

[en] Dynamics of deuterium recycling, including retention and sputtering behaviors was studied for C⁺ implanted tungsten. The amount of deuterium trapped by irradiation damages was clearly increased in the C⁺ implantation sample because the irradiation damages in the C⁺ implanted sample were formed more than those in the only D₂⁺ implanted one. In addition, the deuterium diffusion toward the bulk would be refrained by the formation of W–C mixed layer, which would work as the deuterium diffusion barrier. The in situ sputtered particle measurement system has been established and revealed that the formation of hydrocarbons such as CD₄ was directly observed during D₂⁺ implantation into the C⁺ implanted tungsten. In the lower deuterium fluence, the CD₄ sputtering rate was enhanced with increasing the deuterium fluence. It was considered that the sputtering rate of CD₄ would be controlled by the concentration of deuterium on the top surface of the W–C mixed layer

[en] Gaseous isotopes may be separated by enhanced in oscillatory flow. This paper evaluates the application of this method to the enrichment of deuterium. The oscillations of the carrier raise the diffusional flux without changing the diffusional character of the transport. The process has been well studied and is derived from primary principles. It follows Fick's law. Experimental work shows excellent agreement with the theory. The maximal increase of diffusional flux of H²₂ in water vapor as the carrier by the oscillations reaches 1200 times. The process is tuned for optimal separation from H¹₂. Some modifications of the standard diffusion setup were introduced: The separation ratio was raised 50 times by having the diffusion take place against a low velocity, constant, upstream current of the carrier; the yield was raised 60-fold by concentrating the feed within the reservoir at the high concentration end of the diffusing path. These combined modifications improve the cost effectiveness of the system by several orders. The method may be further improved. It is versatile in that the yield and the separation ratio can be freely chosen over a large range by adjusting the operating conditions

[en] Analogous to the triple point of a pure substance are a binary mixture's triple line and a ternary mixture's three-phase surface, where pressure, temperature, and composition must all be considered. The first three-phase study on a ternary hydrogen system, D₂-DT-T₂, is reported