Cyclohexane solutions spectra from

Figure 4.33 UV spectrum of the cyclohexane solution extracted from the oxidized DDTC solution by H2O2...

Despite the conflicting evidence, Heyes and Trahar (1984) believe there is sufficient evidence to confirm the presence of sulphur on mineral surface. They leached the surface of floated pyrrhotite from a typical test with cyclohexane and have examined the leach solution in a UV spectrophotometer. They found that sulphur could be extracted from the surface of pyrrhotite, which had been floated in the absence of collector. As can be seen from Fig. 2.26, the spectrum from the leached pyrrhotite was compared with the spectrum of sulphur dissolved in cyclohexane indicating that sulphur was present at the siuface. Kelebek and Smith (1989) used UV spectrophotometer to determine sulphur in the ethanol extract from the surface of floated galena and chalcopyrite showing that the amount of sulphur on the minerals can be correlated with their flotation rate which was found to be first order within the critical surface tension range. 

Azulene. The absorption spectrum of azulene, a nonbenzenoid aromatic hydrocarbon with odd-membered rings, can be considered as two distinct spectra, the visible absorption due to the 1Lb band (0-0 band near 700 nm) and the ultraviolet absorption of the 1L0 band.29 This latter band is very similar to the long wavelength bands of benzene and naphthalene CLb) and shows the same 130 cm-1 blue shift when adsorbed on silica gel from cyclohexane.7 As in the case of benzene and naphthalene, this blue shift is due to the fact that the red shift, relative to the vapor spectra, is smaller (305 cm"1) for the adsorbed molecule than in cyclohexane solution (435 cm"1). Thus it would appear that the red shifts of the 1La band are solely due to dispersive forces interacting with the aromatic molecule, in agreement with Weigang s prediction,29 and dipole-dipole interaction is negligible. 

It is very soluble in all organic solvents, but insoluble in water. The IR spectrum of a cyclohexane solution shows v(co) at 2076 (m), 2004 (s), 1996 (vs), and 1961 (vs)cm-1, and the HNMR spectrum (CDC13 TMS internal standard) contains several multiplets in the aromatic region d 7.2-8.1. The mass spectrum contains a parent ion at m/z 348, together with five lower-mass multiplets at 28 amu intervals, resulting from stepwise loss of N2 and four CO groups. 

The infrared spectrum of the liquid mixture shows a broad absorption band at 3000-2700 cm-1 and an intense absorption band at 1613 cm 1. In cyclohexane solution, the substance has Amax at 272 nm with emax = 12,000. (a) What can you conclude from this data as to the magnitude of K, the equilibrium constant for the interconversion of the two forms (b) What can you deduce from the fact that the absorption at 272 nm is much weaker in aqueous solution (pH 7) than it is in cyclohexane ... 

Figure 11 Time-resolved IR spectrum obtained after flash photolysis of [CpFe(CO)2]2 and MeCN in cyclohexane solution. Two intermediates, B = CpFe(CO)2 and C = CpFe(/.t-CO)3, are seen. Dis the reaction product Cp2Fe2(CO)3(MeCN). (Reproduced by permission of The Royal Society of Chemistry from Dixon et al, J. Chem. Soc., Chem-. Commun., 1986, 994)...

The H NMR spectrum consists of a singlet at 4.64 ppm shifted downfield from tetramethylsilane in cyclohexane solution. Principal features in its infrared... 

In order to increase the transparency of silicic acid powder Robin and Trueblood suspended it as a slurry in cyclohexane, possessing approximately the same refractive index and thus obtained absorption spectra of adsorbed benzene and its derivatives (46). However, the adsorption from even dilute solutions produced poorly resolved broad bands, contrasting with the sharp spectrum of the cyclohexane solution itself with the same total number of dissolved molecules. J In comparison with the cyclohexane solution, the maxima of the broad absorption bands of adsorbed benzene and its derivatives are seen to be shifted to the higher frequencies. However, relative to the gaseous state, the shift is to the red by < 130 cm . ... 

In contrast to gas phase adsorption, pyridine, adsorbed from a cyclohexane solution on silica gel, immersed as a mull into Nujol, displays remarkably sharp bands of the tt-tt transition with only a small red shift (Fig. 4). This structured spectrum is nearly identical with that of pyridine in hydroxylated solvents, and in the solid state at low temperature. 

The absorption spectrum of nitrobenzene molecules adsorbed on silica gel from the vapor phase has been recorded by Okuda (55) (Fig. 7), and that from a cyclohexane solution in a slurry of silicic acid by Robin and Trueblood (46). The first author has found a shift from 240 in the gas to 260, and the second authors from 253 in cyclohexane to 270 mp, which is equivalent to about about 3000 cm-. Such a large displacement does not necessarily indicate a chemisorption, since the position of the 260 mju. band of adsorbed nitrobenzene is between those of its aqueous and ethanol solutions. However, Fig. 7 shows that after desorption the most firmly held molecules display a broad absorption band with a maximum at 300 m/a, which might indicate a kind of chemisorption. 

The spectrum of aniline, adsorbed on silica gel either from the gas phase (27), or from a cyclohexane solution (46) is situated at higher frequencies with respect to that of the vapor, owing to the expected H-bond formation with the acidic silanol groups of the surface. The shift is larger than that observed in an aqueous solution but smaller than that characteristic of the anilinium ion. For aniline vapor, adsorbed on silica gel in vacuo at low coverages (6 = 0.05-0.1) the first band is situated at 280 mp, whereas on the silica-alumina gels of different compositions, it is shifted to 260 mjal Fig. 11 (27). Within the precision limits the latter corresponds to the spectrum of the C H5NH2-H+ ion in an acidified aqueous solution. A similar behavior was shown by a-and 8-napthylamine vapor adsorption on silica-alumina gel and bentonite (27). 

Solutes that Produce no New Intermediates. Methanol, ethyl alcohol, cyclohexene, cyclohexane, n-hexane, 3-methylpentane, and biacetyl also remove the absorption spectrum attributed to (CCV), but no additional new spectra are observed from 3500 to 6000 A. Millimolar concentrations of these solutes remove the long-lived portion of (CC14+) while 0.1 M of all solutes apart from cyclohexane completely removes the short and long-lived (CC14+) cyclohexane O.lAf increases the decay rate of the positive ion. Adding 10 mAf methanol and 20 mAf n-hexane decreases the ti/2... 

Fig. 16. Time-resolved infrared spectrum obtained after UV flash photolysis of f(r)r>-C5H5)Fe(CO)2]2, VIII (A), and MeCN in cyclohexane solution at 25°C. The bands are labeled thus B, (r)5-C6H5)Fe(CO)2, X C, (p -Cr,Hs)2Fe2(p-CO).i, IX and D (7f-C5Hs),Fe,-(CO)s(MeCN). The first three spectra correspond to the duration of the firing of the UV flash lamp, and subsequent spectra are shown at intervals of 10 /us. The negative peaks in the first spectrum are due to material destroyed by the flash these have been omitted from the subsequent traces to avoid undue confusion [reproduced with permission from Dixon, A. J. Healy, M. A. Poliakoff, M. Turner, J. J. J. Chem. Soc., Chern. Com-mun. 1986, 994],...

The starting material for the present synthesis was the already described alcohol (171), prepared from the Wieland-Miescher ketone (1). It was converted to the ketone (182) by oxidation. Reduction of the ketone (182) yielded the alcohol (183) in 56% yield. Irradiation of a cyclohexane solution of the alcohol with lead tetra-acetate and iodine afforded the expected cyclic ether (184) in 45% yield, which on oxidation yielded the keto-ether (185). The formyl derivative prepared from the keto-ether on subjection to Robinson annelation with 4-diethylaminobutan-2-one methiodide following the procedure of Howell and Taylor [74] afforded the adduct (186). The adduct, when heated with sodium methoxide in methanol produced the tricyclic keto ether (187) whose H N.M.R. spectrum showed it to be a mixture of C-lOa epimers. The completion of the synthesis of pisiferic acid (196) did not require the separation of a and P-epimers and thus the keto ether (187) was used for the next step. 

The limonene content was estimated by FT-Raman spectroscopy. FT-Raman spectra of limonene and cyclohexane are presented in Fig. 2. The FT-Raman spectrum of R(+)limonene showed characteristic peaks at 1678 cm (vc=c of cyclohexene) and 1645 cm (vcc of vinyl) [10,11]. In FT-IR Raman spectrum of cyclohexane there is no absorption in 1600-1700 cm region. Thus, the limonene amount from cyclohexane solutions can be determined by monitoring the intensities of the 1678 or 1645 cm peaks. For calibration, FT-Raman spectra of different ccmcentrations of limonene in cyclohexane were recorded (see Fig.3). In our study, the intensity of 1645 cm was correlated to limonene content in cyclohexane. There was a linear relationship. The calibration curve had the following equation y = 12.2577x+<).00955, R=0.98 (Fig. 4). Content (%) of R(+)Iimonene in EC microcapsules was measured using the above equation. According to the proposed method, the EC microcapsules contained 9.8 5.5% limonene. 

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