Tritium isotope fractionation between ammonia,methylamine, dimethylamine and n-butane thiol

An automatic gamma-ray spectrometer equipped with a micro-robot for sample changing has been developed and constructed. The facility is comprised of a commercially available micro-robot, sample changer for up to 36 samples, personal computer programmed in BASIC language, input/output devices, detector and multichannel analyzer. This paper describes the components, software and effective uses of the above facility.     

Ruthenium-catalysed transfer hydrogenation reactions with dimethylamine borane

Dimethylamine-borane adduct has been used as the hydrogen source for the reduction of carbonyl compounds, imines, oximes, nitriles, nitroarenes and alkenes using [Ru(p-cymene)Cl₂]₂ as the catalyst.     

Determination of nitrogen content of methylamine and dimethylamine compounds by an automatic rapid nitrogen analyser

Summary It has been observed that when the Heraeus automatic nitrogen analyser is used for compounds containing anN-methyl group, values higher than theoretical are obtained, because the volume of methane arising from the methyl group is measured along with the nitrogen. This interference is found to be eliminated by increasing the temperature of the oven. When the traditional Pregl-Dumas method is used, the duration of combustion can be lengthened to eliminate this effect.

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Zusammenfassung Bei Verwendung des automatischen Gerätes von Heraeus zur N-Bestimmung in N-Methylverbindungen werden überhöhte Werte erhalten, da sich Methan bildet, das mit Stickstoff gemeinsam gemessen wird. Diese Störung läßt sich durch Erhöhung der Ofentemperatur bescitigen. Wenn die herkömmliche Methode von Dumas-Pregl verwendet wird, kann man den gleichen Erfolg durch Verlängerung der Verbrennungszeit erzielen.

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Work performed under the auspices of the U. S. Department of Energy under contract No. W-7405-Eng-48.     

Size-dependent reactions of ammonium bisulfate clusters with dimethylamine

The reaction kinetics of ammonium bisulfate clusters with dimethylamine (DMA) gas were investigated using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Clusters ranged in size from 1 to 10 bisulfate ions. Although displacement of the first several ammonium ions by DMA occurred with near unit efficiency, displacement of the final ammonium ion was cluster size dependent. For small clusters, all ammonium ions are exposed to incoming DMA molecules, allowing for facile exchange ("surface" exchange). However, with increasing cluster size, an ammonium ion can be trapped in an inaccessible region of the cluster ("core" exchange), thereby rendering exchange difficult. DMA was also observed to add onto existing dimethylaminium bisulfate clusters above a critical size, whereas ammonia did not add onto ammonium bisulfate clusters. The results suggest that as the cluster size increases, di-dimethylaminium sulfate formation becomes more favorable. The results of this study give further evidence to suggest that ambient sub-3 nm diameter particles are likely to contain aminium salts rather than ammonium salts.     

离子色谱法同时测定高纯试剂中痕量甲胺、二甲胺、三甲胺和6种阳离子

建立离子色谱法同时测定高纯试剂和有机溶剂中甲胺、二甲胺、三甲胺和6种阳离子的方法.对样品处理、色谱柱类型、淋洗液梯度等条件进行优化,实现了过氧化氢、乙醇、丙酮和异丙醇样品的直接进样分析.选用Metrosep C Supp 1阳离子交换柱进行梯度分离,采用微填充床阳离子抑制电导检测器检测.9种待测物质的质量浓度在5～20...     

A comparative theoretical study of the reactivities of the Al+ and Cu+ ions toward methylamine and dimethylamine

A very recent laser ablation‐molecular beam experiment shows that an Al⁺ ion can react with a single methylamine (MA, CH₃NH₂) or dimethylamine (DMA, (CH₃)₂NH) molecule to form a 1:1 ion–molecule complex Al⁺[CH₃NH₂] or Al⁺[(CH₃)₂NH)], whereas a dehydrogenated complex ion Cu⁺[CH₃N] or Cu⁺[C₂H₅N] is detected, respectively, in the similar reaction for a Cu⁺ ion. Here, we show a comparative density functional theory study for the reactivities of the Al⁺ and Cu⁺ ions toward MA and DMA to reveal the intrinsic mechanism. It is found that the interactions of the Al⁺ ion with MA and DMA are mostly electrostatic, leading to the direct ion–molecule complexes, Al⁺? NH₂CH₃ and Al⁺? NH( CH₃)₂, in contrast to the non‐negligible covalent character in the corresponding Cu⁺‐containing complexes, Cu⁺? NH₂CH₃ and Cu⁺? NH( CH₃)₂. The general dehydrogenation mechanism for MA and DMA promoted by the Cu⁺ ion has been shown, and the preponderant structures contributing to the mass spectra of the product ions Cu⁺[CH₃N] and Cu⁺[C₂H₅N] are rationalized as Cu⁺? NHCH₂ and Cu⁺? N( CH₂)( CH₃). The presumed dehydrogenation reactions are also discussed for the Al⁺‐containing systems. However, the involved barriers are found to be too high to be overcome at low energy conditions. These results have rationalized all the experimental observations well. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Simultaneous determination of dimethylamine,trimethylamine and trimethylamine-n-oxide in aquatic products extracts by ion chromatography with non-suppressed conductivity detection

An ion chromatography method with non-suppressed conductivity detection was developed for the simultaneous determination of dimethylamine (DMA), trimethylamine (TMA) and trimethylamine-n-oxide (TMAO) in aquatic products. They were separated by means of cation-exchange chromatography using a 3.0 mmol/L methanesulfonic acid solution as eluent and an IonPac CS17 column (250 mm × 4 mm i.d.) as the separation column. Detection limits of dimethylamine, trimethylamine and trimethylamine-n-oxide were 0.06, 0.08 and 0.10 mg/L, respectively. The relative standard deviations (RSDs) of peak area were less than 3.53%. The recoveries were between 93.7% and 104.1%. Unlike traditional methods, this validated method is inexpensive and stable.     

Solid-gas reactions of diphenyl-F-phenyl phosphine oxide with methylamine and ammonia [1]

The reactions of gaseous MeNH₂ and NH₃ with solid Ph₂P(O)C₆F₅ have been examined. The principal products of the reaction are $\text{para}$-Ph₂P(O)C₆F₄ NHMe and $\text{para}$-Ph₂P(O)C₆F₄NH₂ and not the $\text{ortho}$ isomers. This is due to the low reactivity of Ph₂P(O)C₆F₅ and the nature of the solid-gas reaction. This reactivity is contrasted with the prediction based on the X-ray crystal structure of Ph₂P(O)C₆F₅, which has been determined. The solution reactivity of Ph₂P(O)C₆F₅ is compared to C₆F₅NO₂.     

Ion-Molecule Reaction Products Found in the Mass Spectra of Trimethylsilyl Derivatives

Abstract

Mass spectrometric studies of trimethylsilyl derivatives of glycerophosphates revealed the presence of several ions of mass greater than M⁺. It is suggested that these ions are formed by the reaction of abundant fragment ions containing positively charged silicon with neutral molecular species.     

Oscillatory reactions in polymer systems

Modified Belousov–Zhabotinskii (BZ) oscillation reactions were studied in the systems of ferroin or tris(2,2′-bipyridyl)ruthenium(II) dichloride or the polymerized ruthenium complex as electron transfer agents and sulfuric acid or polyethylenesulfonic acid (HPES) as acidic media. HPES was a good acidic medium for the chemical oscillation in spite of a long induction period. Moreover, chemical oscillation was observed at low concentration of HPES, where no oscillation was observed in the solution of sulfuric acid. On the other hand, no oscillation was observed in the solution of polystyrenesulfonic acid (HPSS). These results were discussed from the standpoint of the nature of polyelectrolytes.     

The formation of iron carbonyl radical anions in the reactions of iron carbonyls with trimethylamine N-oxide

The interaction of iron carbonyls, Fe(CO)₅, Fe₂(CO)₉ and Fe₃(CO)₁₂ with Me₃NO occurs according to a one-electron redox-disproportionation scheme giving rise to iron carbonyl radical anions: Fe₂(CO)₈^·− (1), Fe₃(CO)₁₂^·− (2), Fe₃(CO)₁₁^·− (3) and Fe₄(CO)₁₃^·− (4). The role of Me₃NO, inducing CO-substitution, consists of the generation of reactive 17-electron species with a labile coordination sphere in which the substitution for other ligands occurs, resulting from fast ligand and electron exchange in the confines of the ETC-reaction.     

Studies on organophosphorus compounds—IV: HMPA as precursor for dimethylamine in nucleophilic aromatic substitution reactions

The potential leaving groups (NO₂, Cl, Br, OH, OMe) in nucleophilic aromatic substitution reactions are replaced by a dimethylamino group simply by heating the aromatic compounds (activated by cyano- or nitro-groups) in HMPA at elevated temperature.     

The di-(2-alkyl-2-nitroethyl)-methylamines from reactions of nitroalkanes with formaldehyde and methylamine

Di-(2-alkyl-2-nitroethyl)-methylamines obtained from reactions of nitroalkanes with formaldehyde and methylamine were separated in diastereoisomers. NMR assignments of meso and racemic forms, and conformations are discussed. Partial separation of racemates into enantiomers was carried out by liquid-solid chromatography, on an optically-active adsorbent.