Deuterium

Ohne Zusammenfassung     

Deuterium

Ohne Zusammenfassung     

Deuterium

Ohne Zusammenfassung     

Deuterium labelled liquid crystalline compounds

Abstract

The synthesis of 4-(2′-methylbutyl)phenyl4′n-heptylbiphenyl-4-carboxylate-d ₁₈(7BEF5-d ₁₈) is presented. The compound is intended to be used as a means of studying the collective modes of liquid crystals by the coherent inelastic neutron scattering technique. The 4′-n-heptylbiphenyl-4-carboxylic acid-d ₁₂, a liquid crystalline intermediate was prepared as well; its acid chloride was coupled with 4-(2′-methylbutyl)phenol-d ₆ to obtain the final product. The intermediates and final products were investigated by spectroscopic methods.     

Mechanism of Deuterium Distribution in Ethanols

Deuterium distribution in ethanols produced by sulfuric acid hydration of ethylene was studied by quantitative NMR spectroscopy.     

Reactivity of Cobalt-Fullerene Complexes towards Deuterium

The adsorption of molecular deuterium (D₂) onto charged cobalt-fullerene-complexes Co_nC₆₀⁺ (n=1–8) is measured experimentally in a few-collision reaction cell. The reactivity is strongly size-dependent, hinting at clustering of the transition metal atoms on the fullerenes. Formation and desorption rate constants are obtained from the pressure-dependent deuterogenation curves. DFT calculations indeed find that this transition metal clustering is energetically more favorable than decorating the fullerene. For n=1, D₂ is predicted to bind molecularly and for n=2 dissociative and molecular configurations are quasi-isoenergetic. For n=3–8, dissociation of D₂ is thermodynamically preferred. However, reaching the ground state configuration with dissociated deuterium on the timescale of the experiment may be hindered by dissociation barriers.     

Glass Electrode Measurements in Deuterium Oxide

Abstract

When hydrogen selective glass electrodes are transferred between acid solutions in ordinary water and deuterium oxide their potentials drift systematically by 1–2 mV over several hours, and hence electrodes standardised in H₂O cannot be readily used for the precise measurement of deuterium ion activity a_D+ in D₂O.     

Synthesis of Deuterium Labeled Tryptamine Derivatives

The synthesis of deuterium labeled tryptamine derivatives, [2‐(1H‐indol‐3‐yl)‐[²H₄]‐ethyl]‐dimethylamine (DMT), [²H₁₀]‐diethyl‐[2‐(1H‐indol‐3‐yl)‐ethyl]‐amine (DET), [2‐(1H‐indol‐3‐yl)‐ethyl]‐[²H₆]‐dipropyl‐amine (DPT) and [²H₂]‐alpha‐methyltryptamine (AMT) is described. The isotopically labeled compounds are used as internal standards in gas chromatography‐mass spectrometry (GC‐MS) assays.     

Deuterium isotope effect on charge-transfer fluorescence

Quantum yields and decay times of fluorescence of charge-transfer complexes of tetracyanoethylene (an electron acceptor) with protonated and deuterated aromatic hydrocarbon donors were measured. The deuterium isotope effect on radiationless transition (identified as the

internal conversion) was observed. This observation is taken as evidence of the dominant role of intramolecular within the donor and/or the acceptor molecule) vibrations in radiationless transitions from excited charge-transfer states of molecular complexes.     

Partial Deuterium Labeling of Dimethacrylate Monomers

Summary. Methacrylic acid-d₅ was prepared in a yield of 30% with 98.6% deuterium incorporation using a two step synthesis. A solution of acetone-d₆ and KCN in D₂O was treated with glacial acetic acid to give the cyanohydrin of acetone-d₆. The latter compound was then dehydrated in anhydrous sulfuric acid at 120°C and subsequently hydrolysed in water at 90°C to form methacrylic acid-d₅. Hydrolysis of commercial nonaethyleneglycol dimethacrylate gave a mixture of ethylene glycols. These glycols were combined with methacrylic acid-d₅ in the presence of p-TsOH in benzene to form nonaethyleneglycol dimethacrylate-d₁₀ with ∼21% deuterium incorporation. Deuterated bisGMA was also prepared from methacrylic acid-d₅ and diglycidyl ether of bisphenol-A. Present address: Boron Molecular Pty Ltd, PO Box 756, Noble Park, VIC 3174, Australia     

Die Bestimmung von Deuterium in organischenVerbindungen

Ohne Zusammenfassung     

Fraktometrische Analyse von Deuterium im Wasserstoffstrom

Summary A universally usable, quantitative assay for deuterium-labeling work demands a stoichiometrical transformation of all samples into elementary hydrogen. For the detector, it is the best to connect directly a fractometer, that works with a catharometer cell. Tests with several carrier gases and an attempt with a palladium-black column failed; a molecular sieve with ordinary hydrogen as carrier was appropriate. The fractogram, written by a compensograph, shows a well gaugeable peak which is linearly proportional to the deuterium content of the sample. The error at full deflection amounts to ±0,5%. Protium deuteride, HD, is acting as if it were 1/2 D₂, a fact that was confirmed by mass-spectrometric measurements.

---

---

Für Ratschläge danken wir Herrn Dr. Kienitz, Leiter der physikalisch-analytischen Gruppe im Ammoniaklaboratorium der BASF. Herr Dr. Kraus machte die massenspektrometrischen Aufnahmen.     

Deuterium Isotope Effect on Excess Enthalpies of Methanol or Ethanol and Their Deuterium Derivatives at 298.15 K

Excess enthalpies of six binary mixtures of CH₃ OD+CH₃ OH, CH₃ OD+CD₃ OD, CD₃ OD+CH₃ OH, C₂ D₅ OD+C₂ H₅ OH, C₂ D₅ OD+C₂ H₅ OD, C₂ H₅ OD+C₂ H₅ OH have been determined over the whole range of mole fractions at 298.15 K in order to know the isotopic effect on hydrogen-bonding accurately, although there are many reports on the differences in the strength of hydrogen-bonding between OH and OD. All excess enthalpies measured are very small and endothermic. The mixtures of CH₃ OD+ CH₃ OH, and C₂ D₅ OD+C₂ H₅ OH showed the largest excess enthalpies among each methanol and ethanol mixtures. The difference of intermolecular interaction between OH and OD in methanol and ethanol was almost same value of (1.82±0.04) J mol^-1 Excess enthalpies of 1,4-dimethylbenzene+1,3-dimethylbenzene and 1,4-dimethylbenzene+1,2-methylbenzene were measured by three different principle calorimeters at 298.15 K in order to know the precision of calorimetry for a small enthalpy change. This revised version was published online in July 2006 with corrections to the Cover Date.     

天然氘核磁共振法测定环酮的烯胺化反应的一级动力学氘同位素效应

长期以来,测定动力学氘同位素效应都是利用在分子中特定位置富集氘的化合物。最近章本礼等提出了利用普通化合物的氘核磁谱测定动力学氘同位素效应的方法,由于此法不用特别氘代化合物,因而使氘同位素效应的测定工作大大简化。自从六十年代以来,烯胺作为烯醇负离子的替代物在有机合成中得到了广泛的应用。     

Die massenspektrometrische Bestimmung von Deuterium in Helium

Ohne Zusammenfassung     

Chemical-Reductant-Free Electrochemical Deuteration Reaction using Deuterium Oxide

We report a method for the electrochemical deuteration of α,β-unsaturated carbonyl compounds under catalyst- and external-reductant-free conditions, with deuteration rates as high as 99 % and yields up to 91 % in 2 h. The use of graphite felt for both the cathode and the anode was key to ensuring chemoselectivity and high deuterium incorporation under neutral conditions without the need for an external reductant. This method has a number of advantages over previously reported deuteration reactions that use stoichiometric metallic reductants. Mechanistic experiments showed that O₂ evolution at the anode not only eliminates the need for an external reductant but also regulates the pH of the reaction mixture, keeping it approximately neutral.