IR spectroscopic measurements

The FT-IR spectroscopic measurements shown that in most cases the -COO or -0 groups formed a bridge between two Sn central atom, and polymerization occurred. The pqs approximations proved the formation of complexes with Oh, Tbp, and structures. H NMR measurements performed in DMSO solution have shown that the polymeric structure of the complexes does not persist in solution, and depolymerization occurs.. ... 

IR spectroscopic measurements allow more practical, lower, catalyst concentrations than NMR spectroscopic measurements. More importantly, an... 

Tsvetanov et al. (55) found evidence for this allylic anion from IR spectroscopic measurements on living oligomers in THF. However,... 

We would like to thank Spectroscopic Laboratories of the CRIC for the assistance in the IR-spectroscopic measurements. Support for this work was provided by the Committee for Research and Development, Hungary (OMFB, Project No. 213/87) and the Nitrochemical Works, Hungary. 

Initially the properties calculated were energetic in nature and related to IR spectroscopic measurements.64 Bishop s work was the first serious attempt to calculate the rovibronic energies of the hydrogen molecule and molecular ion without using the Born-Oppenheimer approximation (i.e., three- and four-body calculations). Many years later, this work is still cited and the relativistic... 

In spite of the experimental difficulty of using infrared spectroscopy to study the surface structure of carbon, IR spectroscopic measurements (especially in the form of Fourier transform IR, FTIR) have brought to light important information on the changes in surface chemistry produced by oxidation and substitution reactions. As a result of the systematic FTIR studies of Starsinic et al. (1983), van Driel (1983) and others (see Zawadzky, 1989 Boehm, 1994), considerable progress has been made in the assignment of IR bands. 

IR and UV/Vis [65a], mass spectrometric [65b], photoelectron [65c], microwave [65d], as well as low-temperature matrix-isolation IR spectroscopic measurements [65e] reveal that 2- and 4-hydroxypyridine (as well as 2- and 4-mercaptopyridine [65f]) exist in the gas phase and in inert matrices (N2, Ar) under equilibrium conditions mainly in the lactim (hydroxy or mercapto) form, in contrast to the situation in solution. While in nonpolar solvents such as cyclohexane and chloroform both tautomers exist in comparable amounts, the tautomeric equilibrium is shifted entirely in favour of the lactam (0x0 or thioxo) form in polar solvents such as water, as well as in the crystalUne state [66, 67, 141-145, 251-255], Supercritical-fluid 1,1-difluoroethane can be used to adjust the tautomeric constant Ki = [(llb)]l[(lla)] iso thermally over a continuum from gas-phase values to those measured in polar solvents, simply by increasing the pressure [254]. The gas-phase and solution equilibrium constants of 2- and 4-hydroxypyridine are given in Table 4-4. 

One point should be noted here the importance of using a 10% D2O mixture with HjO in IR spectroscopic measurements because of the properties of HOD, which contributes a much more clearly resolved spectrum with respect to 0-D. Thus, greater clarity (hence information) results from a spectrum in the presence of HOD. However the chemical properties (e.g., dipole moment) of HOD are very similar to those of H O. 

Below 0.07 h thermodynamic and IR spectroscopic measurements have shown that water adsorbed to the protein is localized at charged... 

This evidence is based on IR-spectroscopic measurements on the copper-ylide complex prepared by two independent routes. First, sulfonium salt 417 was made by alkylation of dimethyl siflfide 416 with bromide 415. The... 

IR spectroscopic measurements were performed in the mid and far infrared regions. For mid infrared measurements a Matson Genesis FT-IR spectrometer and the KBr technique (2 mg of sample in 200 mg KBr) were utilized. Far infrared measurements were run on a Bio-Rad-Win-IR FT-IR spectrometer in the 500-100 cm range. In this case HDPE (high density polyethylene) was the matrix material and 128 scans were collected for... 

Adsorption and IR spectroscopic measurements proved that significant structural changes occured in the adsorbed cyclopropane and propene molecules upon interaction with the cations. Similarly, the results of X-ray diffraction measurements revealed that significant changes took place in the geometry of the adsorption sites, first of all in the positions of the... 

In the confirmation of this conclusion, 2- and 4-mercaptopyridine were shown to be the major tautomers in the gas phase by UV and IR spectroscopic measurements (.Kt — <0.1 (NH/SH) in both cases) (76JA171) and by estimation of their gas phase basicities (77TL1777). Later, the presence of the minor thione tautomer was detected for 2-mercaptopyridine in the vapor (01SA(A)2659) and in argon and nitrogen matrices (thiolrthione = 30 1) (90JPC7406). 

J. F. Ogilvie and S. Cradock Chem. Commun., 364 (1966)] derived the structural data (dNSi = 154 pm, dHN = 100pm and HNSi = 180°) from IR spectroscopic measurements. J. N. Murrell, H. W. Kroto and M. F. Guest [J. Chem. Soc., Chem. Commun., 619 (1977) and Astrophys. J., 219, 886 (1978)] calculated HNSi to be 372 kJmol-1 more stable than the isomeric HSiN and R. Preuss, R. J. Buenker and S. D. Peyer-ImhofT [J. Mol. Struct., 49, 171 (1978)] predicted a barrier of 55kJmol-1 for the rearrangement HSiN- HNSi from Cl calculations. 

The cell design has already been reported [3], It is installed in a continuous flow system built directly on the FT-IR spectrometer (Nicolet Magna 750) to minimize the dead volume. Tlie cell can be considered as a gas flow reactor with a dead volume less than 0.2 cm. Those capabilities permit reactivity experiments, combined with rapid IR spectroscopic measurements of surface species to be made in a mamier which has not been possible in standard IR cell. The GC collection was perfonned with a Delsi cliromatograph on line. Gases were also analysed by FT-IR in a short spacial cell, also directly comiected to tlie IR cell-reactor, with a Nicolet 5SX spectrometer. NOx reduction was measured as the ratio C% = (NO°- (NO + NO )) 100/NO°... 

This work gives results about the characterisation of Sn02 materials, pure and W -added, prepared via a sol-gel route. The materials were characterised as powders or thick films using a variety of techniques. The powder and thick film morphology was analysed by TEM, HRTEM and SEM, the powder texture by volumetric measurements. Powders and films made by regularly shaped and nano-sized particles, even after thermal treatments at 850 °C were obtained. Electrical and FT-IR spectroscopic measurements were employed on films and powders, respectively. Electrical and FT-IR measurements show that W lowers the response of the tin oxide towards CO, but enhances its ability to sense NO2. The surface species formed by CO and NO2 interaction were carefiilly investigated by FT-IR spectroscopy. 

For this analysis a set of consistent spectroscopic data and molecular constants for these species is presented based on recent results of IR spectroscopic measurements for UChlg), UF4(g) and ThF4(g). For the thorium tetrahalides, these estimates of molecular parameters have been somewhat overtaken by theoretical calculations using density functional theory. These confirm the tetrahedral stracture of the species, and on the whole, the current review has preferred these calculated values to the correlative estimates presented in this paper. 

Bases like pyridine are more strongly bound to such Lewis acid centers than to Bronsted acid centers, as can be shown by IR spectroscopy and temperature-controlled desorption. Figure 7-6 shows the transformation of Bronsted into Lewis acid centers on calcination of an HY zeolite, monitored by IR spectroscopic measurements on the adsorption of pyridine. 

Azidoiodanes 448 and 449 were proposed as reactive intermediates in synthetically useful azidation reactions involving the combination of PhIO, PhI(OAc)2, or PhICl2 with trimethylsilyl azide or NaNs [595-610]. Attempts to isolate these intermediates always resulted in rapid decomposition at -25 to 0 °C with the formation of iodobenzene and dinitrogen however, low-temperature spectroscopy and the subsequent chemical reactions in situ provided some experimental evidence for the existence of these species. A systematic study of structure and reactivity of these unstable azidoiodanes was attempted by Zbiral and coworkers in the early 1970s [595-598]. In particular, the IR spectroscopic measurements at-60 to 0 °C indicated the existence of PhI(Ns)2 and PhI(N3)OAc species in the mixture of PhI(OAc)2 with trimethylsilyl azide [595]. Interestingly, the absorption band of 2040 cm for the azido group in PhI(N3)OAc is very close to the absorption stretch of 2046-2048 cm in the stable, heterocyclic azidoiodanes 122-124 (Section 2.1.8.1.5). 

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