Solutions, infrared absorption spectra

The fluctuating cage model presented in Chapter 7 is an alternative. The idea came from comparison of the different kinds of absorption spectra of HC1 found in liquid solutions (Fig. 0.5). In SFg as a solvent the rotational structure of the infrared absorption spectrum of HC1 is well resolved [15, 16], while in liquid He it is not resolved but has... 

Place about 25 mL of the stock solution, prepared as directed in the Assay, in a 50 mL beaker, and evaporate on a steam bath with the aid of a current of filtered air to dryness. Dry the residue at 105 °C for 10 min the infrared absorption spectrum of a potassium bromide dispersion of it so obtained exhibits maxima only at the same wavelengths as that of similar preparations of USP Miconazole Nitrate RS. 

Figure 4.6 Infrared absorption spectrum of phosphomolybdenum blue solution (a) reduced with ascorbic acid and antimony (giving maximum absorbance at 882 pm), (b) reduced with tin(II) chloride, (c) reduced with ascorbic acid. Reprinted from Analytica Chimica Acta 27, Murphy, J. and Riley,...

Infrared absorption spectrum of phosphomolybdenum blue solution 86... 

The infrared absorption spectrum is concordant with the spectrum of cortisone acetate EPCRS. If the spectra are not concordant, prepare new spectra using 50% w/v solutions in chloroform IR. 

From the Raman spectrum in aqueous solution the anion ring was considered to be planar (139, 268). On the other hand the infrared absorption spectrum (57) of crystals of the stable form was interpreted in favor of the more probable chair form (36). The only X-ray study of the crystalline hexahydratc (40) published up to the present has proved to be incorrect (212). 

The infrared absorption spectrum thus showB that o-chlorophenol in solution in carbon tetrachloride consists of about 91 percent cis molecules and 9 percent trans molecules. The cis molecules are more stable than the trans molecules by a standard free-energy difference of about 1.4 kcal/mole (calculated from the ratio of the areas of the peaks). This is presumably the difference in free energy of the cis molecule with its intramolecular hydrogen bond and the trans molecule with a weaker hydrogen bond with a solvent molecule. 

The solution infrared (IR) spectrum of condensed dithiazole 32 is very simple with only four absorptions above 600 cm-1 at 1488, 895, 885, and 625 cm-1, and the ultraviolet (UV) spectrum has long wavelength maxima at 322 (log e 3.35) and 492 nm (3.31), suggesting a highly symmetrical and delocalized structure <2000ARK228>. 

Identification The infrared absorption spectrum of a 1 50 solution in chloroform, determined in a 0.1-mm cell, exhibits relative maxima at the same wavelengths as those of USP Ethyl Maltol Reference Standard, similarly prepared. 

D. Obtain the infrared absorption spectrum of the sample by the following procedure Prepare a 0.2% aqueous solution, cast films 0.0005 cm thick (when dry) on a suitable nonstick-... 

Infrared analyses of the gas sample and the methylene chloride extract (differential vs. solvent) showed no significant absorptions. The aqueous solution was found to contain 7.41 meq. of free acid and 25 mg. (1.3 meq.) of fluoride ion. The infrared absorption spectrum of the bright yellow-orange solid (m.p., 79°-81° C.) was superimposable upon that of triphenylmethyldifluoramine. 

Epoxy-P-ionone had been reported previously by Viani et al.,(13), Schreler et al., (J 4) and V/obben et al., ( ). In the present study besides the mass spectrum an infrared absorption spectrum was also obtained and was found to be identical to that of an authentic sample. An odor threshold was determined in water solution to be 100 ppb. It is, therefore, a relatively weak odorant and as its concentration, in all fresh tomato samples examined, is well below this figure it seems unlikely that it can contribute to fresh tomato aroma. 

The ether layer is washed successively with 5% hydrochloric acid, 5% sodium carbonate aqueous solution and water, and then dried over sodium sulfate. Upon evaporation of ether, the residue is subjected to fractional distillation in vacuo, thereby to yield 8.9 g. of N-methyl linseed oil fatty acid amide, B.P. 178-190° C./0.03 mm. Hg, I.R. 1,650 cm.-l. (I.R. means wave number of the infrared absorption spectrum.)... 

Shake for 1 minute, allow the layers to separate, and filter the chloroform extracts through separate filters of about 2 g of anhydrous granular sodium sulfate supported on pledgets of glass wool. Extract each aqueous layer with two additional 10 mL portions of chloroform, filtering and combining with the respective main extracts. Evaporate the chloroform solutions under reduced pressure to dryness, and dissolve each residue in 10 mL of carbon disulfide. The infrared absorption spectrum, determined in a 1-mm cell, of the solution obtained from the test specimen exhibits maxima only at the same wavelengths as that of the solution obtained from the Reference Standard (RS). 

Figure 2. Crystal structure of N-propargyloxy-phthalimide (top, drawn based on a published X-ray structure [30]) and the infrared absorption spectrum of a polycrystalline sample in a KBr pellet (bottom, unpublished spectrum recorded in the course of preparing ref. 30) v h in a dilute CCI4 solution, 3312 cm , is shown by a dashed line. Distances are given in A.

Dissolve 0.1 g of amodiaquine hydrochloride in 10 ml of water and add 2 ml of 2 M sodium hydroxide. Extract with two 20 ml quantities of chloroform, wash the combined chloroform extracts with 5 ml of water, dry with anhydrous sodium sulphate and evaporate to dryness. Dissolve the residue in 2 ml of chloroform. The infrared absorption spectrum of the resulting solution is concordant with the reference spectrum of amodiaquine. 

A. Acidiiy 10 mL of a 10% w/v solution of thiopoital sodium in carbon dioxide free water with 2 M hythochloiic acid. The solution effervesces. Shake the solution with 20 mL of ether, separate the ether layer, wash with 10 mL of water and dry over anhydrous sodium sulphate. Filter, evaporate the fHtrate to dryness and dry the residue at 100 to 105 °C. The infrared absorption spectrum of the residue is concordant with the spectrum of thiopental HPCRS. 

To measure an infrared absorption spectrum from a liquid or solution sample, it is necessary to use windows (polished plates of certain crystals) or a cell for containing the sample. The material used for the windows must be transparent to the infrared radiation and appropriate for the purpose of the measurement to be performed. Some characteristics of representative infrared transparent materials are given in Table 2.1. More information is available elsewhere [1 -3]. The windows are commercially available usually in the form of polished plates varying in size and thickness. 

In 1951, Witkop et al. interpreted the infrared spectra of quinol-2-and -4-ones to favor the oxo formulation. Since then, many investigators, especially Mason, have reported that potential a- and y-hydroxy compounds show infrared absorption bands in the vN—H (3500-3360 cm ) and vC—O (1780-1550 cm ) regions of the spectrum and, hence, exist predominantly in the oxo form references to this work appear in Table I. A study of the bands which occur in the NH-stretching region of the infrared spectra of a series of substituted pyrid-2-ones and quinol-2-ones also supported an oxo formulation for these compounds. Detailed band assignments have been published for pyrid-2- and -4-one. Mason has reported that solutions of j8-hydroxy compounds in chloroform or carbon tetrachloride show... 

Ionic polysulfides dissolve in DMF, DMSO, and HMPA to give air-sensitive colored solutions. Chivers and Drummond [88] were the first to identify the blue 83 radical anion as the species responsible for the characteristic absorption at 620 nm of solutions of alkali polysulfides in HMPA and similar systems while numerous previous authors had proposed other anions or even neutral sulfur molecules (for a survey of these publications, see [88]). The blue radical anion is evidently formed by reactions according to Eqs. (5)-(8) since the composition of the dissolved sodium polysulfide could be varied between Na2S3 and NaaS with little impact on the visible absorption spectrum. On cooling the color of these solutions changes via green to yellow due to dimerization of the radicals which have been detected by magnetic measurements, ESR, UV-Vis, infrared and resonance Raman spectra [84, 86, 88, 89] see later. 

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