Electronic spectra acetic acid

Vanadium(n) Complexes.—Dehydration of VSO. THjO has been shown to proceed via the formation of VS04,mH20 (where n = 6, 4, or 1) and V(OH)-(SO4), which were characterized by X-ray studies. The polarographic behaviour and the oxidation potential of the V -l,2-cyclohexanediamine-tetra-acetic acid complex, at pH 6—12, have been determined.Formation constants and electronic spectra have been reported for the [Vlphen),] " and [V20(phen)] complexes. The absorption spectrum of V ions doped in cadmium telluride has been presented and interpreted on a crystal-field model. The unpaired spin density in fluorine 2pit-orbitals of [VF ] , arising from covalent transfer and overlap with vanadium orbitals, has been determined by ENDOR spectroscopy and interpreted using a covalent model. " ... 

The Ni(tpp) prepared by this method is of analytical purity. It is slightly soluble in CHC13, CH2 Cl2, and ligating solvents, such as pyridine. It is insoluble in acetic acid, water, and alcohols. The material is indefinitely stable in the solid state and is stable in solution when protected from the light. The electronic absorption spectrum in dichloromethane shows maxima at 413 and 527 nm with molar absorptivities of 275,750 and 18,450, respectively. 

Mesohemin IX prepared by this method shows a single band on polyamide tic (benzene/methanol/formic acid, 110 15 1 and methanol/acetic acid 100 2)10 and on silica gel tic14 (benzene/methanol/formic add, 110 30 1). The electronic spectrum of the pyridine hemochrome, prepared by reducing the mesohemin (in pyridine) with an aqueous solution of sodium dithionite, contains the bands (4 N pyridine, 0.2 N KOH) Xmax 407.5, 516, 546.2 nm. e 139.5,20.9,35.8 (mAT1). 

Finally, the combined voltammetric and on-line differential electrochemical mass spectrometry measnrements allow a quantitative approach of the ethanol oxidation reaction, giving the partial current efficiency for each product, the total number of exchanged electrons and the global product yields of the reaction. But, it is first necessary to elucidate the reaction mechanism in order to propose a coherent analysis of the DBMS results. In the example exposed previously, it is necessary to state on the reaction products in order to evaluate the data relative to acetic acid production which cannot be directly detected by DBMS measurements. However, experiments carried out at high ethanol concentration (0.5 mol L" ) confirmed the presence of the ethyl acetate ester characterized by the presence of fragments at m/z = 61, 73 and 88 at ratios typical of the ethyl acetate mass spectrum. " This ethyl acetate ester is formed by the following chemical reaction between the electrochemically formed acetic acid and ethanol (Bq. 29) and confirms the formation of acetic acid. 

The experimental quantity of electricity, Qex, increases with the initial concentration, while the mean number of electrons, n, decreases and reaches a constant value (n 2) for concentrations greater than 0.1 M. This is in agreement with SNIFTIRS results (see Section IV.2./), which showed that the amount of acetic acid is greater at low ethanol concentrations, while at higher ethanol concentrations, the IR spectrum indicates an higher amount of acetaldehyde (AAL). In the latter case, the main reaction would be ... 

Lutski directed attention to the H bond in simpler molecules by proposing that the influence of ethanol solvent on the UV spectrum of an orthoh.y6.voxy keto- or nitro aromatic provides a criterion for an j n/ramolecular H bond (1287, 1285). Brieglieb and Strohmeier were able to detect the influence of H bonded dimer formation on the spectra of acetic acid vapor at different temperatures (near 2100 A) (279). There have followed many valuable studies directed at the effect of H bonding on the electronic transitions of acids such as phenols, aniline (1483, 1481, 2056), benzoic acid and derivatives (2076, 1998, 671, 190), acetanilides (2075, 2074), HF (1771, 1770), naphthols (1479, 1484), sulfinic acids (521), and amides (1436). The most extensive work, that of Nagakura, Baba, and co-workers, is of particular importance because it led to theoretical consideration of the nature of the H bond (see Section 8.3.2). (See adso 2056,. 1418, 1850.)... 

Sodium nonatungstosilicate is a white solid, which is slightly soluble in water. The solution is metastable at all pH values, but it changes slowly. The best characterization is polarography in 1 M sodium acetate-1 M acetic acid buffer The polarogram shows only one four-electron wave with 1/2 = — 0.80 V versus SCE. The polyanion can be characterized in the solid state by its IR spectrum (KBr pellet, cm ) 985, 940(sh), 930, 865, 848(sh), 808, 712, 552, 530, 490(sh), 435, 373, and 335. 

The potassium salt of [y-SiWj oOse] is soluble in water and stable below pH 8 (in strongly acidic solution, pH < 1, it converts very slowly into [) -SiWi204o] "). A polarogram of the solution exhibits two reversible two-electron waves, with half-wave potentials —0.75 and —0.84 V versus SCE in 1 M acetic acid — 1 M sodium acetate buffer, pH 4.7. The NMR spectrum of the solution in H2O-D2O (90/10) mixtures shows three lines with relative intensities 2 2 1, in agreement with the X-ray diffraction determination of the structure of the polyanion in the rubidium salt. The chemical shifts are, respectively, - 96.4, - 137.2, and - 158.2 ppm (external reference 2 M Na2WO4 in alkaline D2O). 

Potassium /Jj Undecatungstosilicate is a white solid, which is soluble in water. In solution it slowly converts into the isomer (Compound G). It is characterized by polarography in 1 M sodium acetate-1 M acetic acid buflen The polarogram shows two two-electron waves at — 0.63 and — 0.77 V versus SCE. The visible spectrum of the [ 2-SiWi,039V0] complex in aqueous solution (see properties of Compound D) shows — E o = 420, E" s,o = 780, - 290. 

The acid and its potassium salt are white solids, which are soluble in water. The polyanion is stable below pH 4.5. It is characterized by polarography of the fresh solution in M sodium acetate-IM acetic acid buffer The polarogram shows two one-electron and one two-electron waves at — 0.24, — 0.48, and — 0.95 V versus SCE, respectively. The UV spectrum in aqueous solution shows e" 2 58 = 47, 000, and e "232 = 19, 200. 

Ph M (M = As or P) salts of the CrOCl anion have been isolated by reduction of CrOjClj with HCl in acetic acid and precipitation with Ph MCl. Magnetic moments measured were 1.76 and 1.72 BM for M = As and P respectively. The single crystal electronic spectrum of (Ph As)CrOCl4 has been recorded and the bands assigned with the aid of ab initio MO calculations. ... 

An intervalence electron-transfer band, not present in the Fe analogue, was observed in the room temperature electronic spectrum at 13 800cm . Mossbauer spectra indicated distinct Fe" and Fe " sites at 17K while at 300 K a single absorption was observed. The thermal barrier to electron transfer in the trimer was estimated as about 470 cm. Triiron clusters of this type, in the presence of zinc powder, acetic acid, aqueous pyridine and oxygen, are reported " to effect the oxidation of saturated hydrocarbons. The exchange interactions in the series of complexes [Fe2 M 0(02 CMe)spyj] py (M = Mg, Mn, Co, Ni or Zn) which, M = Ni excepted, are isomorphous with the mixed valence complex referred to above have been measured. 

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