Ethane spectroscopy

The photo-Kolbe reaction is the decarboxylation of carboxylic acids at tow voltage under irradiation at semiconductor anodes (TiO ), that are partially doped with metals, e.g. platinum [343, 344]. On semiconductor powders the dominant product is a hydrocarbon by substitution of the carboxylate group for hydrogen (Eq. 41), whereas on an n-TiOj single crystal in the oxidation of acetic acid the formation of ethane besides methane could be observed [345, 346]. Dependent on the kind of semiconductor, the adsorbed metal, and the pH of the solution the extent of alkyl coupling versus reduction to the hydrocarbon can be controlled to some extent [346]. The intermediacy of alkyl radicals has been demonstrated by ESR-spectroscopy [347], that of the alkyl anion by deuterium incorporation [344]. With vicinal diacids the mono- or bisdecarboxylation can be controlled by the light flux [348]. Adipic acid yielded butane [349] with levulinic acid the products of decarboxylation, methyl ethyl-... 

A preparation of the third nitrogenase from A. vinelandii, isolated from a molybdenum-tolerant strain but lacking the structural genes for the molybdenum and vanadium nitrogenases, was discovered to contain FeMoco 194). The 8 subunit encoded by anfG was identified in this preparation, which contained 24 Fe atoms and 1 Mo atom per mol. EPR spectroscopy and extraction of the cofactor identified it as FeMoco. The hybrid enzyme could reduce N2 to ammonia and reduced acetylene to ethylene and ethane. The rate of formation of ethane was nonlinear and the ethane ethylene ratio was strongly dependent on the ratio of nitrogenase components. 

In a typical run, bis(l,2-diphenylphosphino)ethane (DPPE) (0.022 g, 0.05 mmol) and 1,3 diene (32.5 mmol) are added to a portion of the co-condensate, containing 5.2 mg of rhodium (0.05 mg. atom) in 10 ml of mesitylene. The solution is introduced by suction into an evacuated, 80 ml stainless steel autoclave. Carbon monoxide is introduced to the desired pressure and the autoclave is rocked and heated at 80 °C. Hydrogen is rapidly charged to give 1 1 gas composition. When the pressure reaches the theoretical value corresponding to the desired conversion, the autoclave is cooled, depressurised, and the reaction mixture analyzed by GLC. The crude product is distilled. The aldehydes are obtained as pure samples by preparative GLC and characterized by H NMR spectroscopy and GC-MS analysis. 

The l,2-bis(dicyclohexylphosphino)ethane (dcpe) bidentate ligand forms the mononuclear, square-planar Ir1 complexes [Ir(cod)(dcpe)lBPh4, [Ir(dcpe)2]BPh4, and JTIrCl(CO)(dcpe)], which have been characterized by IR, ll, and 31 P 1II) NMR spectroscopy. 1 Products of reaction with CO are discussed. 

The compounds 93 (R = Me, Et) are extremely sensitive toward oxidation and moisture and were not isolated in a pure state. Their structures were supported by NMR spectroscopy. Treatment of 93 with pyridine also gives rise to pyridine-l-boraadamantane complex 111 and starting acetylene derivative, via 1,1-deorganoboration. Accordingly, the 1-boraadamantane-TMEDA adduct (TMEDA - bis(dimethylamino)ethane) (along with Me3SnC CSnMc() is formed when the tricyclic borane 93a (R=Me) reacts with TMEDA <2003JOM(687)108>. 

One of the few studies that have been performed is the work of Cheng and Schiffrin [6] at the interface between water and 1,2-dichloro-ethane. The reactant in the aqueous phase was the [Fe(CN)g]3-,/4 couple, and a few different couples (e.g., lutetium diphthalocyanine) were employed in the organic phase. While the reaction rates could be measured by impedance spectroscopy (see Chapter 13), and were clearly... 

Three different isomers are formed consecutively on reacting [RuCl2(PPh3)3] with 4,6 -bis(pyrazol-l-yl)pyrimidine, bpzpm the final product is cis,trons-[RuCl2(PPh3)2(bpzpm)] (160). Nuclear magnetic resonance spectroscopy (NMR) shows facile cis < - trans interconversion for [H(dtbp)Ru(p-Cl)2Ru(dtbp)H], where dtbp = bis[di(t-butyl)phosphano-methane or -ethane. Crossover experiments implicate mononuclear intermediates in these isomerizations (161). 

From a structural point of view the OPLS results for liquids have also shown to be in accord with available experimental data, including vibrational spectroscopy and diffraction data on, for Instance, formamide, dimethylformamide, methanol, ethanol, 1-propanol, 2-methyl-2-propanol, methane, ethane and neopentane. The hydrogen bonding in alcohols, thiols and amides is well represented by the OPLS potential functions. The average root-mean-square deviation from the X-ray structures of the crystals for four cyclic hexapeptides and a cyclic pentapeptide optimized with the OPLS/AMBER model, was only 0.17 A for the atomic positions and 3% for the unit cell volumes. 

Since the maximum concentration of 07 is about an order of magnitude greater than that of 0 , one can easily follow the formation of stable intermediates using IR spectroscopy. As shown in Figure 3, after the reaction of 07 with ethane, a band appeared at 1095 cm 1, which is attributed to a surface ethoxide ion. 

The concept of atropisomerism developed to a considerable extent following other developments in chemistry, especially those in spectroscopy. Early work by Kohlrausch (4) and Mizushima (3), based on Raman spectra and dipole moment studies, established that rotational isomers—rotamers—must exist in 1,2-dichloroethane. Pitzer established that there are three energy minima when ethane is rotated about its C—C axis (6). Rotamers about single bonds have been found in a wide variety of organic compounds since then, mainly as a result of the application of vibrational spectroscopy to organic molecules (7). 

Azido complexes of Ru include [RuH(N3)(dmpe)2], formed by reacting NaN3 with [RuH2(dmpe)2] (dmpe= l,2-bis(dimethylphosphino)ethane). The reaction of NaN3 with [RUCI2 (depe)2] yields tra 5-[Ru(N3)2(depe)2] (depe= l,2-bis(diethylphosphino)ethane). A related complex is tra 5-[Ru(N3)2(PMe3)4] conversion to the cix-isomer occurs and has been followed by P NMR spectroscopy and cyclic voltammetry. ... 

Principal Component Regression (PCR) was used by Tuchbreiter and MueUiaupt to determine the composition of a number of random ethane/propene, ethane/1-hexene, and ethane/l-octene copolymers [120]. After polymerization, the polymers were characterized by both Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FT-IR) and C NMR and multivariate calibration models using PCR were subsequently developed to estimate the co-monomer content. 

In this paper selectivity in partial oxidation reactions is related to the manner in which hydrocarbon intermediates (R) are bound to surface metal centers on oxides. When the bonding is through oxygen atoms (M-O-R) selective oxidation products are favored, and when the bonding is directly between metal and hydrocarbon (M-R), total oxidation is preferred. Results are presented for two redox systems ethane oxidation on supported vanadium oxide and propylene oxidation on supported molybdenum oxide. The catalysts and adsorbates are stuped by laser Raman spectroscopy, reaction kinetics, and temperature-programmed reaction. Thermochemical calculations confirm that the M-R intermediates are more stable than the M-O-R intermediates. The longer surface residence time of the M-R complexes, coupled to their lack of ready decomposition pathways, is responsible for their total oxidation. 

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