Nujol, absorption bands

In order to clarify the reason why the Rap-Stoermer reaction proceeds so efficiently under solvent-free conditions, the K2C03-assisted reaction of 89a and 90a was studied by IR spectral monitoring in Nujol mulls [ 16]. Firstly, the potassium salt formation of 89a was studied (Scheme 16). One minute after mixing of 89a with twice the molar amount of K2CO3, a vC=0 absorption band (B) appeared at 1692 cm" (spectrum II in Fig. 1), although 89a itself shows vC=0 absorption (A) at 1664 cm (spectrum I in Fig. 1). After 10 min, B disappeared and a new vC=0 absorption band (C) appeared at 1670 cm (spectrum III in... 

Methylcarborane is an air-stable, white crystalline solid which is soluble in common organic solvents. The infrared spectrum (Nujol mull) contains major absorption bands at 3.90 (s), 8.83 (w), 9.12 (w), 9.69 (w), 9.83 (w), 10.03 (w), and 13.85 (s) p. The proton nuclear magnetic resonance spectrum of a carbon tetrachloride solution of methylcarborane contains a broad —CH resonance of intensity 1 at 6.52 r and a —CH3 resonance of intensity 3 at 8.02 r. 

The infrared absorption spectrum of dorzolamide was obtained in a Nujol mull using a Nicolet 51 Op spectrophotometer, and is shown in Figure 7. Assignments for the characteristic absorption bands in the spectrum are provided in Table 1. 

Genzel and Martin (1972, 1973) measured extinction by MgO smokes loosely packed on transparent substrates both in air and covered with the transparent oil Nujol. Their results showed absorption bands appreciably shifted from the bulk absorption band the peak frequencies agreed with calculations, but the widths were consistently greater than predicted by sphere theory. In addition, a narrower absorption feature always appeared at the... 

The product [(j75-C5Me5)Mo(CO)n]2 is a mixture of the compounds with n = 2 and 3.13 It is not necessary to separate the mixture, since the oxidation described below proceeds with loss of CO. The mixture is moderately air sensitive, but may be stored in an inert atmosphere. The H NMR spectrum of the mixture (200 MHz, CDC13 solution) shows singlets at 1.92 and 1.89 ppm. The infrared spectrum (Nujol mull) shows v(CO) absorption bands at 1925, 1895, 1870, and 1827 cm 1. 

The red-violet crystalline compound, which decomposes at 195°, is fairly stable to air it is soluble in benzene, toluene, and THF (tetrahydrofuran). Its solutions slowly react with air. Its infrared spectrum, determined in Nujol mull, shows a broad, weak absorption band at 1955 cm-1, assignable to the Fe—H stretch. When the complex is treated with solid iodine at 60°, about 0.5 mol of hydrogen is evolved per mole of complex. On treatment with iodine in benzene solution at room temperature, only 20-40% of the stoichiometric amount of hydrogen is evolved. 

As the VCO absorption bands due to the dicarbonyl decreased an IR band at 2340 cm due to CO. developed gradually together with a set of absorptions around 2100-2000 cm- due to new linear carbonyls and absorptions around 1800 cm- presumably due to bridged carbonyls (14). CO- appearance was interpreted as an indication of the further reduction of the monovalent rhodium either by CO or via the water gas shift reaction producing H- which is reported to occur on monoculear monovalent carbonyls (19, 20). As rhodium I was reduced to the zerovalent state, the observed VCO bands were ascribed to Rh (C0)j2 compound, in view of the excellent agreement between the observed frequencies and those reported for Rh (C0)j- in CI C or nujol or when adsorbed on fully dehydrated zeolite. 

The IR-spectra (in nujol) of 14a-c show only absorption bands at 1596 to 1612 cm-1, but not the characteristic C = 0 bands of the quinols 13ac between 1610 to 1670 cm-1. The electron spectra are at a somewhat longer wave length than those of the phenoxyls. The H—NMR spectra of the protons at C-3 and C-5 (in CDClj) are shifted to a lower field (7.2 ppm) than those of the phenols (6.95 ppm). 

The table below lists the six major absorption bands which have been selected from recorded spectra over the range 2000 to 650 cm" (5 to 15 pm). The selected peaks are the six most intense peaks, except that peaks in the region where Nujol absorbs (1490 to 1320 cm" 6.7 to 7.6 pm) have been omitted. The peaks are arranged in descending order of amplitude. Shoulders have been chosen only if they are clearly resolved and the point of maximum absorption can be easily determined. Where there is more than one peak of the same intensity at the sixth intensity level, the choice has been arbitrary. It should be noted that, because of variations in instruments and conditions, other determinations of the spectrum may not give peaks... 

The infrared spectra of Nujol mulls of these complexes all show the usual absorption bands for coordinated triphenylphosphine, and, in addition, all show bands attributed to the p (Re = 0) mode, while the ethoxy complexes also show an absorption band attributed to the 5 (OCH2—) mode of the ethoxy group. ... 

Properties of Potassium Hexafluoroplatinately).—This salt is mustard yellow. A sample containing some iodine, possibly as iodyl fluoride, was paramagnetic. The low value of the magnetic moment, p = 0-87 B.M. (at 23°), may, in part at least, be due to this impurity. An infrared spectrum, of a Nujol mull, recorded with sodium chloride and cmsium bromide optics, showed two broad, overlapping, absorption bands, with peaks at 590 and 640 cm.. X-Ray powder photographs of the salt have been indexed on the basis of a rhombohedral unit-cell, a = 4-96 A, a = 97-4°, U = 119 9 A. The observed and calculated values for 1/df are given in Table 5. The solid can be stored indefinitely in well-dried, sealed tubes but decomposes... 

C -(Dimethylpropylamine)carbaundecaborane(12) is a white crystalline solid, m.p. 191-192°. It is very soluble in acetone and tetrahydrofuran, slightly soluble in chloroform and methanol, and insoluble in benzene and water. The infrared spectrum (Nujol and hexachlorobutadiene mulls) contains major absorption bands at 2988(m), 2561(vs), 1481(m), 1472(m), 1414(m), 1130(m), 1035(m), and 934(m) cm. h The proton nuclear magnetic resonance spectrum (acetone-de solution) exhibits... 

The cesium and tetramethylammonium salts are white crystalline compounds, air-stable and nonhygroscopic. The cesium salt is soluble in acetone and hot water, insoluble in tetrahydrofuran. The tetramethylammonium salt has partial solubility in acetone or dimethylformamide, but is insoluble in water or methanol. The infrared spectra of the salts (Nujol and hexa-chlorobutadiene mulls) contain major absorption bands at the indicated frequencies ... 

The properties of S7NH are well documented, and complete infrared and Raman spectral assignments have been published. Tetrabutylammonium tetrathio-nitrate is moisture sensitive and is hydrolyzed by acids to give S, S7NH, and Se(NH)2 isomers. It can be stored for long periods of time in a dry oxygen-free atmosphere at room temperature. The salt is very soluble in THF but almost insoluble in diethyl ether. A 10 4/ solution in either THF or HMPA shows a characteristic visible absorption band at 595 nm (e = 19,000). The infrared spectrum (Nujol mull) shows bands at 1243, 1220, 1102, 1021, 922, 885,737, 710, 608 (sh), 594,560, 530 (sh), 510 (sh), 410 cm. ... 

The infrared absorption spectrum of lomefloxacin obtained as a Nujol mull on a Bio-Rad FTS-7 spectrophotometer is given in Figure 4. Proposed assignments for the major absorption bands are given inTablel. 

The mull technique involves thoroughly mixing the sample with a low. apor pressure, medium-molecular-weight hydrocarbon, generally known as N jiol. The mull or dispersion is then held between two infrared windows and its spectrum recorded. Since the Nujol itself absorbs radiation (absorption bands at —2900, —1460, and —1375 cm )> the observed spectrum consists of the superposition of the spectrum of the compound of interest on that... 

When measnring transmission for thin samples, for example films, there is a need to ensnre absorption of IR energy is not too strong in any part of the spectrum. For a colorant in a powdered form the traditional way to obtain an infrared spectrum is to dilute the colorant whilst creating a homogenous dispersion either in Nujol (a hquid paraffin) or an alkali-metal hahde (normally potassium bromide). Clearly, it is important that the diluent (e.g. Nujol or KBr) does not have absorption bands in the same region of the spectrum as the sample being analysed. 

A series of complex salts of [Ta(CO)6] and [Nb(CO)6] are synthesized by similar procedures described above. For the details, see [45]. The Nujol mull IR spectra in the v(CO) region exhibit a very broad asymmetric absorption band, while the spectra in polar solvents show one relatively sharp intense band. All the complexes are very oxygen sensitive in solution, while the solid samples can be handled in air for brief periods of time. 

Nujol presents three major absorption bands beyond which the spectrum of the sample is exploitable. This spectrum can be supplemented by another carried out in hexachlorobutadiene, transparent in the regions where paraffin absorbs. For the KBr technique, the sample is crushed with KBr in an agate mortar. The mixture is then pressed using an hydraulic press (pressure of 5 to 8t/cm ) or manually into a transparent disc. 

Tetramethyldiphosphane disulfide is stable in air. The crystals are soluble in chloroform and acetone, moderately soluble in benzene and toluene, slightly soluble in alcohols, and insoluble in ether and pentane. In the solid state the preferred conformation is trans, as indicated by one strong P—S stretching absorption in the infrared spectrum (Nujol mull) at 567 cm.-1, and the absence of a P—P band, which is found only in the Raman spectrum at 445 cm.-1.9 Other principal absorption bands are at 733, 745, 860, 882, 939, and 1281 cm."1. 

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