Ultraviolet spectrum, of benzene

FIG. 8.4 Determination of the microenvironment of a molecule (a) a portion of the ultraviolet spectrum of benzene in (1) heptane, (2) water, and (3) 0.4 M sodium dodecyl sulfate and (b) ratio of the intensity of the solvent-induced peak to that of the major peak for benzene versus the index of solvent polarity. The relative dielectric constant is also shown versus the index of polarity. (Redrawn, with permission, from P. Mukerjee, J. R. Cardinal, and N. R. Desai, In Micellization, Solubilization and Microemulsions, Vols. 1 and 2 (K. L. Mittal, Ed.), Plenum, New York, 1976.)... 

Figure 8.4a shows a portion of the ultraviolet spectrum of benzene in three media (1) heptane, (2) water, and (3) 0.4 M aqueous sodium dodecyl sulfate. It is not the prominent peaks in these spectra that interest us, but rather the small bands located 3.6 nm on the long-wavelength side of the major features. This band is absent in benzene vapor, but is present with variable intensity in solutions. Accordingly, it is described as a solvent-induced band with an intensity that depends on the polarity of the solvent. 

Fig. 17 Ultraviolet spectrum of benzene, showing the secondary band (256 nm) and the two primary bands ( Bj, 183 L, 203 nm).

Figure 7.17a shows the molecular orbitals of benzene. If you were to attempt a simple explanation for the electronic transitions in benzene, you would conclude that there are four possible transitions but each transition has the same energy. You would predict that the ultraviolet spectrum of benzene consists of one absorption peak. However, owing to electron-electron repulsions and symmetry considerations, the actual energy states from which electronic transitions occur are somewhat modified. Figure 7.17b shows the energy-state levels of benzene. Three electronic transitions take... 

FIGURE 7.18 Ultraviolet spectrum of benzene. (From Petruska, J., J. Chem. Phys., 34 [1961] 1121. Reprinted by permission.)... 

Effect of the monochromator s slit width on noise and resolution for the ultraviolet absorption spectrum of benzene. The slit width increases from spectrum (a) to spectrum (d) with effective bandpasses of 0.25 nm, 1.0 nm, 2.0 nm, and 4.0 nm. 

Figure 8.12 The He I ultraviolet photoelectron spectrum of benzene. (Reproduced from Karlsson, L., Mattsson, L., Jadmy, R., Bergmark, T. and Siegbahn, K., Physica Scripta, 14, 230, 1976)...

Weber, Th., von Bargen, A., Riedle, E., and Neusser, H. J. (1990), Rotationally Resolved Ultraviolet Spectrum of the benzen-Ar Complex by Mass-Selected Resonance-Enhanced Two-Photon Ionization, J. Chem. Phys. 92,90. 

Benzene. The ultraviolet absorption spectrum of benzene is characterized by the low intensity L band at 256 nm and the more intense La band at about 200 nm, both bands being 77 77 transitions. Changes in the absorption spec-... 

There is considerable interest in establishing the location within a micelle of the solubilized component. As we have seen, the environment changes from polar water to nonpolar hydrocarbon as we move radially toward the center of a micelle. While the detailed structure of the various zones is disputed, there is no doubt that this gradient of polarity exists. Accordingly, any experimental property that is sensitive to the molecular environment can be used to monitor the whereabouts of the solubilizate in the micelle. Spectroscopic measurements are ideally suited for determining the microenvironment of solubilizate molecules. This is the same principle used in Section 8.3, in which the ultraviolet spectrum of solubilized benzene was used to explore the solvation of micelles. Here we take the hydration for granted and use similar methods to locate the solubilizate. 

Figure 22-3 Ultraviolet absorption spectrum of benzene (in cyclohexane) showing the benzenoid" band...

Spectral characteristics are frequently affected by the local environment of the material. Increased pressure tends to broaden and shift spectral lines, as does physical state. Fig 5 shows the effect of solvent on the ultraviolet absorption spectrum of benzene... 

Fig 5 Ultraviolet Absorption Spectrum of Benzene (a) vapor (b) ethanol solution... 

The resolution of the ZEKE-PE spectrum of 1,4-difluorobenzene can be compared with, for example, that of the ultraviolet photoelectron spectrum of benzene in Figure 8.12. The greatly increased resolution in the ZEKE-PE spectrum is attributable mostly to the fact that only photoelectrons with zero kinetic energy are being detected. It is also partly attributable to the molecules being in a supersonic jet this has the effect of sharpening the bands because of the restricted rotational populations in the ground state of the molecule. 

Ultraviolet Spectroscopy The ultraviolet spectra of aromatic compounds are quite different from those of nonaromatic polyenes. For example, benzene has three absorptions in the ultraviolet region an intense band at Amax = 184 nm (e = 68,000), a moderate band at Amax = 204 nm (e = 8800), and a characteristic low-intensity band of multiple absorptions centered around 254 nm (e = 200 to 300). In the UV spectrum of benzene in Figure 16-19, the absorption at 184 nm does not appear because wavelengths shorter than 200 nm are not accessible by standard UV-visible spectrometers. 

Figure 2. Ultraviolet absorption spectrum of benzene in ethanol...

A dlatortion of the B2q state of benzene to D j has also been proposed (66) to account for inconsistencies in the interpretation of the ultraviolet spectrum of pure crystalline benzene at low temperatures. Such distortions may be the result of the solid medium or, more probably, the spectral inconsistencies may be due to state splitting by the environment. 

Fig. 3 Near-ultraviolet absorption spectrum of benzene (B), naphthalene (N), and anthracene (A).

Tris(3-bromoacetylacetonato)chromium(III) is a dark red-brown crystalline material, which dissolves in benzene to form a green solution. The infrared spectrum of this chelate exhibits a characteristic strong singlet at 1540 cm. i, whereas chromium(III) acetylacetonate exhibits two peaks in this region, at 1560 and 1520 cm. b The ultraviolet spectrum of the brominated chromium chelate in chloroform exhibits a Xmax at 358 m/i(e = 13,070). The brominated chelate is reported to form a stable clathrate complex with chloroform (m.p. 240 to 241°). ... 

Figure 7.12 Ultraviolet spectrum of the S, state of benzene with partially resolved rotational structure. Although the K levels are not resolved, the transition probability is peaked for K = /. The absorption of one additional photon produced the benzene ion. Taken with permission from Kiermeier et al. (1988).

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