Benzene, absorption systems

The charge-tranter concept of Mulliken was introduced to account for a type of molecular complex formation in which a new electronic absorption band, attributable to neither of the isolated interactants, is observed. The iodine (solute)— benzene (solvent) system studied by Benesi and Hildebrand shows such behavior. Let D represent an interactant capable of functioning as an electron donor and A an interactant that can serve as an electron acceptor. The ground state of the 1 1 complex of D and A is described by the wave function i [Pg.394]

Several in vivo and in vitro studies conclusively demonstrate that benzene can be absorbed through human skin (Blank and McAuliffe 1985 Franz 1984 Susten et al. 1985 Tsuruta 1989). In general, skin absorption is considered a minor source of concern in the occupational environment as it occurs at a much lower rate and extent compared with benzene absorption through the respiratory system (OSHA 1989). However, benzene absorption through the skin as a result of benzene contamination in rubber solvents is a major route of exposure in tire building operations (Susten et al. 1985). Benzene is an irritant to the skin and, by defatting the keratin layer, may cause erythema, vesiculation, and dry and scaly dermatitis... 

Direct excitation of electron-transfer states may yield surprising results. This is the case with the bimolecular benzene iodine charge-transfer complex. In solutions this system is the prototypical case of charge transfer as reported by Mulliken [262]. The characteristic 280 nm absorption band of the benzene-iodine system is distinct from any absorption features of neat iodine or benzene. It has been identified as being due to a promotion of the HOMO benzene n electron to a a LUMO orbital on iodine resulting in benzene iodine electron transfer. 

Our first use of crystal polarization was in hexamethylbenzene. It had all molecular planes parallel to one another and perpendicular to the main faces of a sublimed crystal. It was known that the lowest absorption system was polarized in the molecular plane, conforming with its assignment to a n-n transition. However in the next system of benzene at 200 nm, corresponding to the hexamethylbenzene system at 230 nm, the vapour phase spectrum had been assigned to a Rydberg transition polarized perpendicular to the molecular plane [210]. 

For both I-hexene-Mg and I-hexene-benzene-Mg systems, the infrared absorptions attributed to Mg—H bonds disappear after samples formed at... 

Much work, both experimental and theoretical, has been carried out on the radiationless transitions of collision-free Si benzene. At vibrational energies greater than about 3000cm"1, both the quantum yield [58] and lifetime [59] of fluorescence and the quantum yield of S, - TISC [60-62] decrease dramatically relative to those at lower excess energies. Concomitantly, the Al9(S0) absorption system exhibits a sudden... 

T <- Tj spectrum shows a single peak at 235 nm F 0.35) and a shoulder around 310nm (F 0.12). Vibronic mechanisms in the two-photon spectrum of benzene and also toluene, halobenzenes, and aniline have been studied by Goodman and co-workers. Two-photon excitation of benzene crystals at 4.2 K has been recorded in the 200 nm second absorption system. The data suggest that the transition is in which the vibronic intensity is derived from the state in the one photon and E g in the case of two-photon excitation. Spectral solvent effects on toluene have been reported by Macovei. Traverso and Brunet have examined the 5j Sq transition in biphenyl and confirmed the earlier conclusion that this is a forbidden process. 

Nordheim G, Sponer H, TeUer E (1940) Note on the ultraviolet absorption systems of benzene vapor. J Chem Phys 8 455-458... 

Norman Wright of the Dow Chemical Company was the first to report that a series of weak absorption bands in the 2000-1650 cm region could dependably be used to assign substitution patterns in benzene ring systems. The approach is as follows ... 

Poly(l,4-naphthylenevinylene) (106) is accessible via the Wessling polymerization procedure. Lenz, Karasz, Wegner et al. have published the synthesis of PNV 106, starting from l,4-bis(chloromethyl)naphthalene [127, 128]. The poly(l,4-naphthylenevinylene) (106) displays an optical absorption energy of 2.05 eV, slightly red-shifted by about 0,3 eV relative to the parent PPV 60-system, due to the electronic effect of the annelated benzene ring. 

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