Magnetic properties of some aromatic compounds

The effect of hydrogen bonds on the anisotropy of the diamagnetic susceptibility of 2-amino-3-methyl-benzoic acid, 2-hydroxy-3-methylbenzoic acid and o-aminobenzoic acid has been studied. From measured values of the crystal susceptibilities and molecular orientations, the principal molecular susceptibilities have been calculated. The observed anisotropics are interpreted in the light of the hydrogen bonding of these molecules.     

New aromatic azo compounds: syntheses and liquid-crystalline properties

The chemical syntheses of 12 new azo dyes are reported. The optically active compounds were prepared by the Mitsunobu reaction, amide formation, and esterification with optically active alcohols or acids. Several new compounds showed liquid-crystalline properties, and their phase transition behavior was investigated.     

Influence of temperature on thermodynamic properties of substituted aromatic compounds

This work presents experimental liquid densities and ultrasonic velocities for a collection of substituted aromatic compounds (isobutylbenzene, 1,3,5-trimethylbenzene, butylbenzene, isopropylbenzene, p-xylene, m-xylene and o-xylene) at the range of temperature 278.15–323.15 K and atmospheric pressure of a collection of halogenated and aromatic hydrocarbons. Fitting equations were applied to data in order to correlate for later computer-based design. The estimation of the studied properties was made by the application of different theoretical procedures. An equation of state based on the generalised Van der Waals theory which combines the Staverman–Guggenheim combinatorial term of lattice statistics with an attractive lattice gas expression and the free length theory (FLT) showed a good response at the studied conditions.     

芳基取代咪唑衍生物的合成及其紫外、荧光性质研究

设计合成了两种新颖的三芳基咪唑类化合物5和6,研究了其反应机理,优化了环合加成反应的工艺条件,化合物经FT-IR、HMR和MS进行结构表征。研究了两个化合物在不同溶剂中的紫外与荧光光谱,发现官能苄基的引入,会使吸收峰和发射峰均有不同程度的蓝移,这些光谱性质为今后研究其双光子吸收、双光子荧光和非线性光学性质奠定了实验基础。     

Alkenylation of aromatic compounds

The review summarizes new data on the introduction of alkenyl (vinyl) groups into aromatic and heteroaromatic structures via reactions with alkenes and alkynes. The main attention is given to the characterization and estimation of synthetic potential of the alkenylation of aromatic compounds with acetylene derivatives in the presence of transition metal complexes, as well as by the action of electrophiles, Lewis acids, and Brønsted superacids.     

Fluoroalkylation of aromatic compounds

Perfluoroalkylation of benzene, halobenzenes, pyridine, furan and thiophene has been accomplished through thermolysis of perfluoroalkyl iodides (CF₃I, n-C₁₀F₂₁I and R_fOR_fI) in the presence of the appropriate aromatic compound. Yields of alkylated products vary depending on temperature, presence of an HI acceptor and reactants ratio. Isomeric mixtures are obtained with halobenzenes, pyridine and thiophene. Furan however yields only the alpha substituted product.     

Quantum chemical estimation of thermodynamic and molecular properties of acyclic and aromatic compounds

The semiempirical MNDO, AM1, and PM3 methods were used to calculate the standard entropies, heats, and Gibbs energies of substance formation as well as the first ionization potentials and dipole moments for 64 acyclic and aromatic compounds. The linear dependences P_exp =bP _theor (P denotes any of the properties listed above) are revealed. Variations from the above-mentioned correlations are considered. Translated fromZhurnal Strukturnoi Khimii, Vol. 41, No. 4, pp. 696-700, July-August, 2000. This work was supported by International Soros Foundation (Project Nos. d96-16 and d97-1381). The authors are grateful to Dr. A. E. Shchavlev for his assistance with some calculations.     

Quantum chemical estimation of thermodynamic and molecular properties of acyclic and aromatic compounds

The semiempirical MNDO, AM1, and PM3 methods were used to calculate the standard entropies, heats, and Gibbs energies of substance formation as well as the first ionization potentials and dipole moments for 64 acyclic and aromatic compounds. The linear dependences P_exp =bP _theor (P denotes any of the properties listed above) are revealed. Variations from the above-mentioned correlations are considered. Translated fromZhurnal Strukturnoi Khimii, Vol. 41, No. 4, pp. 696-700, July-August, 2000. This work was supported by International Soros Foundation (Project Nos. d96-16 and d97-1381). The authors are grateful to Dr. A. E. Shchavlev for his assistance with some calculations.     

Analysis of the relationship between the structure and aromatic properties of chemical compounds

This paper presents the results of research on the relationship between the structure and odour properties of a selection of chemical compounds. The research concerns five groups of esters, each with a different smell: almond, apricot, apple, pineapple and rose. The supposed relationship between the smell and certain selected attributes of each molecule was examined by various pattern recognition techniques using programs developed in the Department of Computer Chemistry at Rzeszów University of Technology.     

Oxidative phosphonylation of aromatic compounds

Aryl phosphonates can be prepared in good yield from the respective arenes and tri- or dialkyphosphites by either chemical or anodic oxidation. The anodic oxidation proceeds either via phosphinium radical cations, which then attack the arenes electrophilically, or via arene radical cations, which add the trialkylphosphite as nucleophile. Aryl phosphonates are also obtained in good yield by chemical oxidation with peroxodisulfate/AgNO₃ in acetonitrile/water or glacial acetic acid. The diethylphosphinium radical cation, formed from diethylphosphite by oxidation with Ag(II), is supposed to be the reactive species in this process. Raising the silver salt concentration leads to an increase in polyphosphonylation. Selectivity ratios were determined for the oxidative phosphonylation process.     

Electrochemical trifluoromethylation of aromatic compounds

It was shown that the current yield of the products of anodic trifluoromethylation of arenes correlates with the adsorptivity and the rate of electrooxidation of arenes on the surface of a platinum electrode. Translated fromIzvestiya Akademi Nauk, Seriya Khimicheskaya, No. 6, pp. 1180–1184, June, 1997.     

Microdetermination of aromatic nitro compounds

Conclusion A method was proposed for the microdetermination of nitro compounds, which is based on their reduction to amines by heating with potassium iodide and orthophosphoric acid.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 658–659, March, 1971.     

Asymmetric hydrogenation of aromatic compounds

The asymmetric hydrogenation of aromatic and heteroaromatic compounds arguably presents one of the most attractive methods for the synthesis of six-membered cyclic compounds. In recent years, a number of promising stereoselective methods for the asymmetric hydrogenation of pyridines and related heterocycles have been reported.     

Electrochemical perfluoroalkoxylation of aromatic compounds

New approaches to the electrochemical synthesis of aryl perfluoroalkyl ethers based on a) the electrooxidation of perfluorocarboxylic acid on a consumable PbO₂ anode and b) the simultaneous anodic oxidation of the “aromatic compound-alkaline perfluoroalkoholate” system on a platinum electrode were proposed.     

The influence of the Tbeta level upon fluorescence and laser properties of aromatic compounds

The fluorescence and laser properties of seven specially chosen aromatic compounds are studied at 293 degrees C. The quantum yield of fluorescence, gamma, decay times, tauf, of the deaerated and non-deaerated solutions are measured. The oscillator strength, fe, fluorescence rate constants, kf, natural lifetimes, tauT0, and intersystem crossing rate constants, kST, are calculated. Some laser parameters are calculated or measured experimentally. It is found that the position of the Tbeta level plays an important role in the fluorescence and laser properties of aromatic compounds. If the Tbeta level is situated below the Sp level, it decreases the quantum yield of fluorescence and the decay time and increases the threshold of laser action. If, due to some structural changes of a molecule, the Tbeta level is situated higher than the Sp level, then the quantum yield of fluorescence and the decay times are increasing and the threshold of laser action is decreasing. Such influence of the position of the Tbeta level upon fluorescence and laser properties of aromatic compound is explained by the fact that the Sp level mixes with the Tbeta level more readily than with other taupipi* levels.