Aqueous solution infrared spectroscopy

Carbonyl Frequencies and Reactivity toward Nucleophilic Reagents 

The maximal carbonyl frequencies of the compounds investigated by Jencks et al. (1960) are given in Tables 19.1 through 19.6, grouped by chemical class. Other absorption frequencies are also listed, but are not necessarily repeated for compounds that are listed in more than one table. Carbonyl absorption bands have strong intensity other bands are strong unless indicated otherwise (see footnote d ofTable 19.1). 

Ethyl acetate 1710 1275b 2970m, 1470w, 1448w, I397sh, 1380  

Acetylcholine chloride 1735 1255b 2960w, 1483, 1460sh, I425w, 1383  

Alanine ethyl ester hydrochloride 1743 2950w, 1462, 1445, 1393w, I359w, 1320m 

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More recent reviews have appeared on the subject of aqueous solution infrared spectroscopy, each giving emphasis to different applications (Nachod and Martini, 1959 Goulden, 1959 Jencks, 1963 Parker, 1962,1967). Table 3.1 shows some infrared frequency assignments in D2O solution (see Jencks, 1963, for details). 

Among various spectroscopic techniques, IR and RS are commonly utilized in experimental science. IR-active modes and RS-active modes are known to be mutually exclusive in centrosymmetric molecules because these optical processes are realized as one-photon and two-photon transitions, respectively (Fig. 5.1). It is important to obtain full vibrational information when characterizing materials. Therefore, a combined use of both methods should be helpful for understanding their chemical structures. However, this is practically difficult due to relatively low energies of infrared photons, IR spectroscopy sometimes faces problems, e.g., in situ observation in IR-opaque aqueous solution. RS spectroscopy often suffers with... 

Hazen, K. H., Arnold, M. A. and Small, G. W. (1994) Temperature-insensitive near-infrared spectroscopic measurement of glucose in aqueous solutions. Applied Spectroscopy, 48,477-83. Hecht-Nielsen, R. (1989) Neurocomputing, Addison-Wesley, Reading, MA. 

Into a mixture of 1.6 g of 2-amino-4-methylpyrlmidine with 10 ml of glacial acetic acid is slowly added 2.13 g of concentrated sulfuric acid. A mixture of 2.4 g of 2-formyl-1-methyl-5-nitroimidazole in 20 ml of glacial acetic acid is slowly added to the mixture of the pyrimidine under stirring. The reaction mixture is maintained at a temperature of about 55°C for 4 hours. The resultant mixture is then diluted with 200 ml of distilled water and neutralized with a saturated aqueous solution of sodium bicarbonate. A brownish-yellow precipitate (MP 232° to 235°C) is formed and recovered. The product is analyzed by infrared spectroscopy and is found to conform to 2-amino-4-[2-(1-methyl-5-nitro-2-imidazolyI)vinyl] pyrimidine. 

Verell, R. E. Infrared Spectroscopy of Aqueous Electrolyte Solutions, in Water — a Comprehensive Treatise (ed. Franks, F.), Vol. 3, chapter 5, New York, Plenum Press 1973... 

Zou S, Gomes R, Weaver MJ. 1999. Infrared spectroscopy of carbon monoxide and nitric oxide on palladium(lll) in aqueous solution unexpected adlayer structural differences between electrochemical and ultrahigh-vacuum interfaces. J Electroanal Chem 474 155-166. 

Between pH values of ca. 6 and 12 aqueous solutions hold very little dissolved beryllium because of the low solubility of Be(OH)2. When the pH is raised above 12, the hydroxide begins to dissolve with the formation of, first, Be(OH)3 and then, at even higher pH values, Be(OH) (52). The presence of these species in strongly alkaline solutions was confirmed by means of solvent extraction experiments (90) and infrared spectroscopy (31). A speciation diagram is shown in Fig. 7, which was constructed using the values of log /33 = 18.8 and log /34 = 18.6 critically selected from Table III. The diagram illustrates clearly the precipitation and dissolution of Be(OH)2. 

The fact that soil always contains water, or more precisely an aqueous solution, is extremely important to keep in mind when carrying out an analytical procedure because water can adversely affect analytical procedures and instrumentation. This can result in an over- or under-determination of the concentrations of components of interest. Deactivation of chromatographic adsorbents and columns and the destruction of sampling tools such as salt windows used in infrared spectroscopy are examples of the potential deleterious effects of water. This can also result in absorbance or overlap of essential analytical bands in various regions of the spectrum. 

Persson et al. (1991) used diffuse reflection infrared Fourier transform (DRIFT) spectroscopy to study the interactions between galena, pyrite sphalerite and ethyl xanthate. They provided the evidence that the DRIFT spectrum of oxidized galena treated with an aqueous solution of potassium ethyl xanthate is practically identical with that of solid lead (II) ethyl xanthate, which can be formed as the only detectable siuface species on oxidized galena. Dialkyl dixanthogen is formed as the only siuface species in the reaction between oxidized pyrite and aqueous solution of potassium alkyl xanthate. 

R. Cinier and J. Guihnent, Quantitative analysis of resorcinol in aqueous solution by near-infrared spectroscopy, Vib. Spectrosc., 11, 51-59 (1996). 

For the pressure studies, two phase" compact ion behavior is observed with an inflection point between 7 and 11 atms. For the aqueous solution studies, the hydraulic permeability K and the g-ratio are hardly effected by solute type (within experimental error). The solute diffusive permeability however, varies with solute type in good qualitative agreement with free energy parameters, infrared overtone shifts, and spin echo and continuous wave nuclear magnetic resonance spectroscopy results from the literature. 

Tejedor-Tejedor, M.L Yost, E.C. Anderson, M.C. (1990a) Characterization of benzoic acid and phenolic complexes at the goethite/ aqueous solution interface using cylindrical internal reflectance Fourier transform infrared spectroscopy. Part 5 Methodology. Langmuir 6 979-987... 

Applying in situ infrared spectroscopy and STM, Cai et al. [253] have studied adsorption of pyridine on Au(lll) electrodes from aqueous NaCl04 solutions. It has been found that pyridine molecule is flatly adsorbed on the surface at negative potentials. Its molecular plane rises up as the applied potential and surface concentration increase. Moreover, orientation of pyridine molecule changed with the applied STM potential. Ikezawa et al. [243] have used in situ FTIR spectroscopy to investigate adsorption of pyridine on Au(lll), Au(lOO),... 

The infrared (IR) spectra of 1,10-phenanthroline, its hydrate and perchlorate in the region 600-2000 cm-1 have been obtained, and the principal features of the spectra interpreted.66 Further studies on the IR spectra of 1,10-phenanthroline,67-69 substituted 1,10-phenanthrolines,70,71 and 1,7-phenanthroline67 have also been reported. The IR spectrum of 4,7-phenanthroline in the region 650-900 cm-1 has been analyzed, and the C—H out-of-plane deformation frequencies were compared with those of phenanthrene and benzo[/]quinoline.72 The IR spectra of salts of 1,10-phenanthroline have been taken, and the NH vibrations determined.28,73 Infrared spectroscopy has been used to detect water associated with 1,10-phenanthroline and some of its derivatives on extraction into nitromethane from aqueous solution.74 The Raman spectrum of 1,10-phenanthroline has been compared with its IR spectrum.75 Recently, the Raman and IR spectra of all ten isomeric phenanthrolines were measured in solution and solid states, and the spectra were fully discussed.76... 

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