A spectroscopic facility which is capable of obtaining DRIFT spectra of adsorbed species at high sensitivity and in situ operating conditions has been established. This technique has been used to study the adsorption of CO on titania- and alumina-supported rhodium catalysts. By using various combinations of the three parameters: reduction temperature, metal loading, and support material, several different species of surface-bonded CO on Rh have been identified. The three main species are: geminal dicarbonyl, linear CO, and bridging CO. As each of these species is associated with a specific Rh site, conclusions concerning the oxidation state and dispersion of the Rh on the surface could be made. It has been found that higher Rh loadings lead to Rh site distributions resembling those found on Rh(III) single crystals, whereas low Rh loadings produce isolated Rh sites preferentially. It was found that the AI2O3 support enables more facile reduction of the Rh precursor material to Rh metal than does the TiO2 support. This is probably due to strong metal-support interaction for Rh-TiO2.
Reaction of MM'(CO)10 (M,M' = Mn, Re) with equimolar amounts of Me3NO in CH3CN readily gives MM'(CO)9(CH3CN) in high yield (>80%). Competitive reactions reveal that the rate of reaction increases Re2(CO)10 > MnRe(CO)10 > Mn2(CO)10, with substitution of MnRe(CO)10 occurring at Re (>90%). Reaction of MM'(CO)9(CH3CN) with L gives axial: equatorial isomer mixtures of MM'(CO)9L [L = P(OMe)3, P(OiPr)3, P(O-o-tol)3, PMe2Ph, PMePh2, PPh3, P(CH2Ph)3 and the products have been characterized by i.r. and n.m.r. (31P, 1H) spectroscopy as well as cleavage reactions with Br2. Isomerization of equatorial to axial isomers was studied by n.m.r. spectroscopy and the rate and extent of isomerization was observed to be dependent on both steric and electronic properties of L. Axial and equatorial isomers of MM'(CO)9L were unambiguously identified by 31P n.m.r. spectroscopy since the axial isomer gives an absorption 10-20 p.p.m. downfield of the equatorial isomer. I.r. spectroscopy can not generally be used to establish the axial: equatorial isomer ratios for MM'(CO)9L owing to similarities between the two spectra, especially in polar solvents.
A flow-injection analysis system is descriptionbed for the indirect determination of sulphate by direct measurement of lead with a coated tubular lead ion-selective electrode. An excess of lead(II) ions as lead perchlorate is added to the sample solution-carrier stream mixture as a reagent stream in an environment of sodium perchlorate, as ionic strength adjustor, and methanol-formaldehyde, to decrease solubility of formed PbSO4 and retard oxidation of the membrane. The system is useful for the determination of sulphate in the range 50-10 000 mg dm-3 at a sampling rate of 60 h-1 with a coefficient of variation of better than 1,70%. Major interference is caused by cations (Ag+, Hg2+, Cu2+) and anions (Po43-) which form insoluble lead salts.
Excess molar volumes for (toluene + methanol, + ethanol, + propan-1-ol, and + propan-2-ol) have been determined. These results together with the excess molar enthalpies and excess molar volumes for related binary systems of (benzene, toluene, o-, m-, p-xylene, and mesitylene + methanol, + ethanol, + propan-1- ol, and + propan-2-ol) are compared and discussed in terms of the influence of the methyl groups on the benzene ring. The excess molar volume results for mesitylene mixtures do not fit the patterns generated by the other aromatic systems.
2-Nitrophenol condenses with trichloroacetaldehyde in the presence of concentrated sulphuric acid to give among other products 2,2-di(3-nitro-4-hydroxyphenyl)-1,1,1-trichloroethane and smaller amounts of 8-nitro-2,4-bis(trichloromethyl)-1,3-benzodioxin. To investigate the possible steric effect of the nitro group ortho to the phenolic oxygen atom in such condensations, the molecular structure of this benzodioxin and that of 8-nitro-6-methyl-2,4-bis(trichloromethyl)-1,3-benzodioxin were determined by single crystal X-ray diffraction analysis and compared with those of 6-nitro- and 6,8-dinitro-2,4-bis(trichloromethyl)-1,3-benzodioxin and related compounds.
Fragmentation patterns in the mass spectra of 2,3-dihydro-2- phenyl-1,4 -benzoxazepin-5 (4 H) -ones have been elucidated using a combination of low- and high-resolution mass spectrometry, Benzoxazepinones have been shown to exhibit a variety of phannacological effects, which include analgesic, antiinflammatory, anti-depressant, and anti-histaminic activity,' In the course of research on heterocyclic systems with medicinal potential, we have prepared a range of 2,3-dihydro- 2-phenyl-l,4-benzoxazepin-5(4H)-one derivatives and we now report the results of mass fragmentation studies of these compounds.
An efficient synthesis of 2,3,5-tri-O-benzoyl-4-thio-D-xylofuranosyl acetate (2) is descriptionbed. ?-Uracilation and elaboration of the 5-position furnished a 4-thio-6-amino-6-deoxy-L -glycero-L-idohepturonic acid derivative (3).