The stark effect in condensed aromatic hydrocarbons

The changes in the static electric polarizability upon transition to excited singlet states are measured by perturbing the absorption spectrum with an intense (10⁶ V/cm) electric field. Observations of the Stark effect in a polystyrene matrix are reported for a series of substituted anthracenes, a group of condensed aromatic hydrocarbons and a substituted hexatriene.     

Mass spectra of negative ions of condensed aromatic hydrocarbons and biphenyl

Conclusions The positions of the maxima of the effective yield of the (M-H)^– ions on the energy scale of the electrons for condensed hydrocarbons and biphenyl coincide with the maximum yield of the (M-H)^– ions for benzene. The existence of a molecular ion M^–, with a life span with respect to autoionization of 21sec, was observed for anthracene.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1885–1886, August, 1973.     

Theoretical study of the in-plane components of the 13C shielding tensors in condensed aromatic hydrocarbons

The Pople model for chemical shielding is applied to calculate the in-plane components of the ¹³C shielding tensors of condensed aromatic hydrocarbons. The wave functions are evaluated using the MNDO method and the calculated results are supported by the very good agreement with the experimental results in the few cases in which experimental information is available.The relationship found between the calculated bond orders and the in-plane components of the ¹³C shielding tensors suggest that the experimental study of the ¹³C shielding tensors in these compounds may provide a powerful technique for studying aromaticity. The in-plane components are found to be directly affected by the degree of delocalization of the -electrons in the adjacent bonds. Rules are given for estimating the orientation of the two in-plane components of the shielding tensor.     

Retention prediction of large and condensed polycyclic aromatic hydrocarbons in reversed-phase microcolumn liquid chromatography with diphenylsilica stationary phase

The retention behavior of condensed large polycyclic aromatic hydrocarbons has been investigated with diphenylsilica stationary phases in reversed-phase microcolumn liquid chromatography. The results were correlated with two parameters which indicate size and shape of the molecules. Since the resulting equation can be used for retention prediction of large polycyclic aromatic hydrocarbons, computer-assisted “standardless” identification is accomplished for “unknown” compounds contained in the standard.     

Vibronic calculations in aromatic hydrocarbons

On the basis of a simple composite approach involving semi-empirical MO and valence force field methods, it is demonstrated that vibronic band intensities can be calculated in good quantitative accuracy not only for benzene in contrast to some earlier work but also for larger systems.     

Ring currents in aromatic hydrocarbons

Coupled Hartree-Fock theory is used to compute and map the current density induced in planar hydrocarbons by an external magnetic field. Results of useful accuracy can be obtained with modest (6-31G**) basis sets by employing a continuous gauge transformation. Maps are presented and discussed for benzene, naphthalene, anthracene, tetracene, pentacene, heptacene, and biphenylene. © 1996 John Wiley & Sons, Inc.     

Sonochemiluminescence of aromatic hydrocarbons

Multibubble sonoluminescence of water and a series of aromatic hydrocarbons, viz., benzene, toluene, ethylbenzene, and m-xylene (at 25 °C), and a naphthalene melt (at 110–120 °C) was studied. An analysis of the influence of oxygen and argon on the sonoluminescence intensity and the luminescence spectra of these liquid compounds, as well as the effect of additives of ionol, ethanol, and 9,10-dibromoanthracene on m-xylene sonoluminescence, showed that a considerable contribution to the sonoluminescence of aromatic hydrocarbons is made by chemiluminescence reactions associated with their oxidation. This sonochemiluminescence is observed in both the gas phase of cavitation bubbles and the bulk solution where luminescence is retained for a long time after ultrasonication switching-off (the initial intensity of the residual chemiluminescence is up to 10% of the luminescence intensity during sonolysis). As for thermoinitiated oxidation, the afterglow of m-xylene contains the radical and molecular components.     

Hydroxyaminomethylation of aromatic hydrocarbons

Conclusions The electrophilic hydroxyaminomethylation of aromatic hydrocarbons was accomplished for the first time, with toluene and m-xylene as examples.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1135–1136, May, 1967.     

The amidoalkylation of aromatic hydrocarbons

The Nyberg procedure (the use of trifluoroacetic acid in chloroform) for the efficient amidoalkylation of aromatic hydrocarbons is limited to substrates more nucleophilic than benzene. The reaction involves protonation of the electrophile, cleavage to a carbonium ion and alkylation of the nucleophile by the carbonium ion. Either the cleavage step or the alkylation step may be rate-determining. The present work identifies some cases where a carbonium ion is formed but fails to alkylate the nucleophile (with benzene and nitro-substituted benzenes as nucleophiles) and other cases where the reaction conditions are not sufficient to permit cleavage of the protonated electrophile (the reactions of N-phthalimidomethylamides).     

Surface ionization of aromatic hydrocarbons

The surface ionization of 14 aromatic hydrocarbons on oxidized tungsten strips was investigated. The principal relationships governing the ionization of aromatic compounds with alkyl substituents were established on the basis of the obtained mass spectra of the ions and the temperature dependence of the ion currents.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 6, pp. 733–738, November–December, 1988.     

X-ray results on aromatic hydrocarbons

Recent X-ray results for the bond lengths in naphthalene and anthracene agree to about 0·01 Å with the simple MO and Pauling theories. Chrysene and quaterrylene are also discussed. The bearing of these results on the controversy about the effects of environment and -bonding in CC bonds is considered.     

Molecular ordering in some liquid aromatic hydrocarbons

This study presents a comparison of the structures and molecular correlations for the linear aromatic hydrocarbons: benzene, naphthalene, and anthracene in the liquid phase, performed for the first time by the method of X-ray diffraction. Also for the first time the X-ray diffraction results obtained for anthracene at 513?K have been reported. Monochromatic radiation CuK_α was used to determine the scattered radiation intensity between S _min?=?4π?sin?Θ_min/λ?=?0.417?Å^?1 and S _max?=?4π?sin?Θ_max/λ?=?7.06?Å^?1. The mean angular distributions of X-ray scattered intensity were measured and the differential radial distribution functions of electron density (DRDFs) were calculated. The mean distances between the neighbouring molecules and the mean coordination numbers were found. The most probable models of local ordering of these molecules were suggested. Correlations have been found between the number of benzene rings in the molecules studied and their physical properties.