IR investigations

Infrared (IR) investigations can be made on a sample of reactant previously heated to a known extent of reaction (a) and studied in the form of a mull or in an alkali halide disc. An alternative approach is to incorporate the reactant substance in a compact alkali halide disc [287] which is intermittently withdrawn from the reaction vessel for infrared measurements at appropriate intervals. Heated sample holders [288,289] permit repetitive scanning of the spectrum or continuous monitoring of a peak of interest during decomposition. 

Iwasita T, Nart EC. 1991. Identihcation of methanol adsorbates on platinum An in situ FT-IR investigation. J Electroanal Chem 317 291-298. 

The IR investigations described in this presentation are based on the SPAIRS variant of SNIFTIRS. 

IR investigations of methanol oxidation have been mainly devoted to demonstrate the nature of strongly adsorbed residues produced during the adsorption of methanol [21,59,67,68], Bulk oxidation products were not investigated by in situ IR spectroscopy. 

Unsaturated Silicon Compounds - Matrix IR Investigations and Quantum Chemical Calculations... 

The major fragmentation in mass spectra of 1,2,5-oxadiazoles is attributed to the loss of nitrile and nitrile oxide or expulsion of NO. The conversion of 3,4-dicyano-l,2,5-oxadiazole-2-oxide (3,4-dicyanofuroxan) 10 to cyanogen iV-oxide 11 (Equation 5) was investigated under the conditions of collisional activation (CA) and neutralization-reionization (NR) mass spectrometry. Flash vacuum thermolysis mass-spectrometry (FVT-MS) and flash vacuum thermolysis infra-red (FVT-IR) investigations of furoxans 10, 12, and 13 reveal that small amounts of cyano isocyanate accompany the formation of the main thermolysis product 11 <2000J(P2)473>. 

Infrared microscopy is well suited for in situ analysis of contaminants fount in pharmaceutical processes. Due to the nondestructive nature of the analysis further experiments such as energy dispersive x-ray analysis may be performer on the same sample once IR investigations are complete. To illustrate the potentia of IR microspectroscopy, one application from the Bristol-Myers Squibl laboratories is presented. 

Edwards and Schrader—IR investigations support common formate intermediate in water-gas shift and methanol synthesis over Cu/ZnO. Edwards and Schrader,234 using careful reduction procedures (95%N2/5%H2), were able to obtain direct evidence by infrared spectroscopy of the formation of active OH groups on Cu/ZnO, that formed surface formates on the surface of the zinc phase (1576, 1381, 1366, 2970, and 2878 cm-1, respectively for OCO asymmetric, OCO symmetric, and C-H stretching bands) upon exposure to CO. In the presence of CO and H20, the formate intensity initially increased, followed by the production of C02, indicative of water-gas shift. A carbonyl band was also observed at 2093 cm-1. The authors... 

Le Peltier, Lavalley, and coworkers—IR investigations indicate RWGS proceeds via copper formates/carbonates during methanol synthesis over Cu/ZnAl204. 

Jacobs, Davis, and coworkers—IR investigation shows Pt/thoria is an important analog to Pt/ceria for low temperature shift—formate mechanism advanced. 

Several methods are successfully applicable in this field, e.g. dielectric relaxation methods 164>, IR investigations in the near, fundamental, and far IR regions 165>, RAMAN spectroscopy 166>, NMR spectroscopy 32-34-16 ), and ultrasonic absorption i 8-i70). 

R. Lindeman and G. Zundel, Proton transfer in and polarizability of hydrogen bonds coupled with conformational changes in proteins. II. IR investigation of polyhistidine with various carboxylic acids, Biopolymers 17, 1285-1301 (1978). 

The situation is quite different for physisorbed molecules. In that case, there is no transfer of charge, the mechanical renormalization is weaker due to a much weaker metal-molecule bond and also the image interaction is smaller as the molecule probably is adsorbed further out from the surface. In a recent IRS investigation of CO physisorbed on Al(100) the measured frequency is only shifted down a few cm from the gasphase value. However, there is for this system also a short range intermolecular interaction that certainly will affect the vibrational frequency. As yet there exist no theoretical calculations for the van der Waals interaction between a CO molecule and a metal. 

That the parameter values obtained from this fit of the theory to experimental data are physicaUy relevant was confirmed by a study on CO in the ontop position on Pt(lll). In an IRS investigation of this system Schweizer using the same theory obtained ... 

This ethylidyne intermediate has recently been subject to two IRS investigations, by Chesters and McCash and in a more detailed study by Malik et alP Their spectra show three absorption peaks above 800cm which in light of the EELS work could be assigned to the C—C stretch mode at 1120cm , the symmetric CH3 bend mode at 1340cm and the symmetric CH3 stretch mode at 2885 cm In contrast to the surface methoxy discussed in the previous section, there is no peak associated with the asymmetric CH3 stretch mode at 2950cm" This shows, in line with the discussion above, that the CCHj is oriented with the C—C axis normal to the surface (as indicated in Fig. 19) and verifies at the same time the validity of the infrared surface selection rule. 

Their hypothesis was confirmed by the work of Aurbach and co-workers, who performed detailed FT-IR investigations on the graphitic anode surface that... 

Tabata, T Ohtsuka, H Kokitsu, M Okada 0 IR investigation of selective reduction of NO by ethene on Cu-ZSM-5, Bull. Chem. Soc. Japan, 1995, Volume 68, Issue 7, 1905-1914. 

Table 6 reports theoretical and experimental data relative to the red shift for the intramolecular stretching frequency of the HCl bond in the complex. This is greater than that observed for the H2O-HCI system, a further evidence of the strength of this hydrogen bond. Experimental data, however, show large differences between the Aco recorded in different matrixes. The first IR investigation was accomplished by Ault and Pimentel [30] in N2 matrix but later, in a more complete study, Barnes et al. [35]... 

Palard I, Soum A, Guillaume SM (2005) Rare earth metal tris(borohydride) complexes as initiators for e-caprolactone polymerization general features and IR investigations of the process. Macromolecules 36 54—60... 

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