Concentration Effects on Infrared Spectra

The infrared spectra of alcohols change markedly with increasing concentration. For example, at very low concentration, the infrared spectrum of te/t-butyl alcohol in carbon tetrachloride contains a single sharp band at approximately 3600 cm corresponding to the OH stretching motion. As the alcohol s concentration increases (by adding more alcohol to the sample), a second broad OH stretch band grows in at approximately 3400 cm and eventually replaces the other band. 

Would you expect the OH stretching frequencies in 2,3-dimethyl-2,3-butanediol to be shifted from the value in tert-butyl alcohol, even in dilute solution. Identify the OH stretching frequencies in the diol and compare them to tert-butyl alcohol. Rationalize your observations by comparing the geometry of the diol with those of tert-butyl alcohol and tert-butyl alcohol dimer. 

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The reactions with ruthenium carbonyl catalysts were carried out in pressurized stainless steel reactors glass liners had little effect on the activity. When trimethylamine is used as base, Ru3(CO) 2> H Ru4(CO) 2 an< H2Ru4(CO)i3 lead to nearly identical activities if the rate is normalized to the solution concentration of ruthenium. These results suggest that the same active species is formed under operating conditions from each of these catalyst precursors. The ambient pressure infrared spectrum of a typical catalyst solution (prepared from Ru3(CO)i2> trimethylamine, water, and tetrahydrofuran and sampled from the reactor) is relatively simple (vq q 2080(w), 2020(s), 1997(s), 1965(sh) and 1958(m) cm ). However, the spectrum depends on the concentration of ruthenium in solution. The use of Na2C(>3 as base leads to comparable spectra. 

Infrared spectra suggested that a sulfate ion coordinates to two titanium atoms as a bidentate in particles. The maximum particle size was found at Aerosol OT mole fraction of 0.35 in the mixtures. The particle size increased linearly with increasing the concentration of sulfuric acid at any Wo, but with increasing Wo the effect was the opposite at any sulfuric acid concentration. These effects on the particle size can be explained qualitatively in relation with the extent of number of sulfate ions per micelle droplet. These precursor particles yield amorphous and nanosized TiO particles, reduced by 15% in volume by washing of ammonia water. The Ti02 particles transformed from amorphous to anatase form at 400°C and from anatase form to rutile form about at 800°C. In Triton X-100-n-hexanol-cyclohexane systems, however, spherical and amorphous titanium hydroxide precursor were precipitated by hydrolysis of TiCl4 (30). When the precursor particles were calcinated,... 

The variation of CL intensity and its relation to the growth of forsterites in meteorites requires a detailed study of the chemical variation and the observed CL. Numerous line scans were described (Steele, I.M. Geochim. Cosmochim. Acta, accepted for publication) where spectra and composition were obtained at the same point for forsterites in the Ornans (C3) carbonaceous chondrite. Interpretation is complicated by the fact that some elements are strongly correlated and the effect on CL can not be attributed to any one element. The most important influence is found to be Fe which had different quenching effects on the blue and infrared CL emissions. The blue emission is effectively quenched for Fe concentrations above 0.75 wt.% FeO while the infrared emission is... 

In the final paper of this important series (Machi et al., 1979d) the effect of tbe reaction conditions on the stability of the tetraBuoroethylene latices was studied. The stabilization was believed to be due to either carboxyl and groups or to the adsorbed hydrofluoric acid formed hy radiolysis of the monomer or to both. The surface charge densities, electrophoretic mobilities, and infrared spectra were all measured. The storage stability of tbe latices, measured by the appearance of coagulum, was found to be proportional to the total dose and the polymer concentration and not to depend on the dose rate. Since the stabilization results from the radiolysis of the monomer and wat this is quite reasonable as is the effect of concentration. The presence of monomer was necessary in the sense that irradiation of the latex in the absence of monomer did not improve the storage stability. 

An interface between gel permeation chromatography (GPC) and Fourier transform infrared (FTIR) spectrometry has been developed. With this system it is possible to collect solvent free polymer deposition and to measure their infrared spectra as a function of molecular weight. The mobile phase from the GPC effluent is converted into an aerosol and removed using a pneumatic nozzle. The sample is collected on a Ge disc that rotates below the nozzle. After the sample is collected, the disc is transferred to an FTIR spectrometer where the infrared spectrum of the sample is collected. Normal GPC sample concentrations (0.1-0.25 wtJvol%) give sufficient sample for useable FTIR signals. All normal GPC solvents can be effectively removed, and the interface works with both low temperature and high temperature GPC applications. 

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