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.     

The photo-chlorination of polystyrene

Polystyrene and poly-β,β-dideuterostyrene have been photo-chlorinated in solution in carbon tetrachloride. The products have been examined by i.r., 220 MHz NMR and laser Raman spectroscopy. For chlorination at 13°, approximately equal numbers of chlorine atoms are introduced at α- and β-sites along the chain; in the later stages of reaction, there is appreciable addition of chlorine to the rings. The photo-chlorination is accompanied by degradation of the polymer; the average number of scissions per polymer molecule is better correlated with the amount of chlorine introduced into the main chain than with the total chlorine content of the polymer.     

Reactions ofN-pentafluorophenylcarbonimidoyl dichloride with aromatic hydrocarbons in the presence of aluminum chloride

N-Pentafluorophenylcarbonimidoyl dichloride reacts with aromatic hydrocarbons (benzene, toluene, xylenes, and mesitylene) in the presence of AlCl₃ to give stableN-pentafluorophenylbenzimidoyl chlorides, which can further react with aromatic hydrocarbons to give azomethine derivatives. An increase in the number of methyl groups in the molecule of a hydrocarbon favors the reaction.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1605–1611, September, 1993.     

The iodination of aromatic substrates on alumina

The iodination of a wide variety of aromatic substrates has been attained on dehydrated alumina. The procedure is particularly well suited for arenes.     

Biphasic photochemistry: time-resolved spectra of adsorbed hydrocarbons

Time-resolved fluorescence spectra were measured for pyrene and naphthalene adsorbed on a silica gel surface using the time-correlated photon-counting technique Excimer-Iike emission was observed within an excitation lamp duration of a few nanoseconds with both pyrene and naphthalene. It is suggested, from the excitation spectra, that ground state complexes of the adsorbates are responsible for the formation of the excimer-like emission.     

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).     

The effect of HCl on the polymerization of aniline with ferric chloride

The chemical oxidation of aniline with ferric chloride, FeCl₃ · 6H₂O in the HCl aqueous solutions to form polyaniline (PANI) powder and films has been investigated. The effect of acid concentration on the deposition of PANI film in situ was studied. The presence of an acid affects both the yield of the polymer and the growth rate of the film. This effect was corroborated by the UV-visible absorption studies of the films deposited on glass supports during the polymerization. The influence of the acid on the yield of the PANI powder formed in the bulk solution was also examined. We have found that the yield of the polymer formed either on the surface or in the bulk solution decreased with the increasing concentration of HCl. The effect of HCl concentration on the in situ UV-visible absorption at the early stages of aniline polymerization is also discussed. The text was submitted by the authors in English.     

Surface photochemistry : The cds photoinduced dimerization of n-vinylcarbazole

The CdS dispersion mediated photoinduccd dimerization of N-vinylcarbazole (NVC) has been investigated and found to be efficient. The rate of reaction is not affected over quite a wide range of CdS masses at constant NVC concentration in solution. The reaction requires the presence of oxygen. At low light intensities the rate is linearly related thereto. A cation radical mechanism is proposed since the reaction can be efficiently quenched by electron donors. The dimerization appears to follow the Langmuir-Hinshelwood and modified Eley-Rideal mechanisms, as does the quenching. CdS of different origins with different surface areas, purities and structures were used and the rates varied by a factor of four. None of these functions appears to play a dominant role in the rate of dimerization. The variation in rates and in activation energies suggested the importance of traps located close to the conduction band.     

Infrared photochemistry of cyclobutyl chloride

The decomposition of cyclobutyl chloride following multiple infraredphoton excitation has been investigated. The primary photolysis products are butadiene, from elimination of HCl, and ethylene and vinyl chloride, fromring scission. The vinyl chloride undergoes secondary decomposition to acetylene and HCl. In addition to these products, known from thermal VLPP experiments, we also find 1-butene, which may arise from a higher energy C? Cl homolysis channel. Collisions with either reactant molecules oradded buffer gas lead to cooling of the laser-produced vibrational energy distributions. The average amount of energy removed per collision is 15–20 kcal/mol for self-collisions and 2–4 kcal/mol with argon.     

Polymerization of aromatic hydrocarbons with sulfur

The polymerization reactions of elemental sulfur with the polynuclear aromatic hydrocarbons pyrene and chrysene were studied. Heating the hydrocarbons with sulfur produces a series of sulfur-containing oligomers in which the aromatic ring systems remain intact. Polymerization is effected through the dehydrogenative action of sulfur and leads to thermally stable five- or six-membered heterocyclic ring systems. The major loss of sulfur during subsequent heat treatment occurs only at carbonization temperatures above 1000°C.     

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.     

The extraction of ferric chloride with methyl isobutyl ketone and amyl acetate

Summary The extraction of iron as ferric chloride in 7 M hydrochloric acid by a mixture of (1+1) or (2+1) methyl isobutyl ketone and amyl acetate is quantitative for macro as well as for micro amounts of iron. The distribution ratio is very high ( 4000). With these mixtures no emulsification difficulties are encountered as they are with methyl isobutyl ketone alone. The behaviour of 44 elements in this extraction has been investigated.     

The spectrophotometric determination of polycyclic aromatic hydrocarbons

The determination of polycyclic aromatic hydrocarbons by elution chromatography from alumina columns followed by ultra-violet spectrophotometry has been elaborated for a more extended range of substances than has been published previously. The methods have been standardised and tables of absorption peaks are provided for easy identification of a number of compounds commonly found as traces in combustion products. Recommendations are given for the preparation of samples for determinations by this method, which has been successfully employed for the analysis of carbon blacks, soots, urban air solids, condensible smokes such as tobacco smoke, wood smoke and coal tar. thermal decomposition or pyrolysis products and other substances, such as urban vegetation, soil, tobacco, snuff, smoked food, and surface drainage water, which have been subjected to the action of smokes or other combustion products.     

Reaction of undecyl radicals with aromatic hydrocarbons

A competition method (R^.+O₂RO ₂ ^. , R^.+XHRH+X^.) is proposed to measure the relative rate constants for the interaction of alkyl radicals with different organic compounds. Partial (per C–H bond) rate constants have been determined for the reaction of undecyl radicals with cumene, ethylbenzene and toluene.

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(R^.+O₂RO ₂ ^. , R^.+XHRH+X^.), . ( C–H ) , .