Hydrogen abstraction from substituted aromatic compounds

The reactivity of tert-butoxy radicals with methyl substituted aromatic compounds is almost exclusively determined by the aromatic moiety and almost independent of the methyl group position. The hydrogen abstraction from the carbon α to the aromatic ring is hardly sensitive to the produced radical stabilization. This lack of dependence can be explained in terms of the large exothermicity of the process.     

Plasma polymerization of trifluoromethyl substituted aromatic compounds

Thin film coatings were prepared by polymerizing trifluoromethyl-substituted aromatic compounds in a glow discharge with low power levels and medium pressures. Smooth, continuous films which are adherent and insoluble in conventional solvents were produced. A significant amount of the fluorine content from the monomer was retained in the polymer. The trifluoromethyl group was not removed by the plasma conditions and appeared in the film as trifluoromethyl and difluoromethylene groups. The films were slightly less wettable than those of the unfluorinated films.     

A theoretical analysis of substituted aromatic compounds

The substituents ? CH₃, ? F, ? NO₂, ? OCH₃, and ? CH₂?CH₂ were placed at the ortho, meta, and para positions on the aromatic molecules aniline, benzaldehdye, nitrobenzene, and phenol. MMFF94, AM1, B3LYP, M06, M06‐2X, ωB97X, ωB97X‐d, and RI‐MP2 using cc‐pVDZ and cc‐pVTZ and CCSD(T) with cc‐pVDZ basis sets were used to calculate the geometries and energies of all regiomers of the molecules. Relative energies of the ortho and meta regiomers relative to the para regiomers were calculated and compared to the CCSD(T) values. A good basis set correlation between cc‐pVDZ and cc‐pVTZ was observed in RI‐MP2. Overall, RI‐MP2 gave the best correlation with the CCSD(T) results. All of the hybrid functionals showed similar accuracy and could effectively describe the intramolecular hydrogen‐bonding interactions of these compounds. The methoxy group at the para position in methoxyaniline, methoxyphenol, methoxynitrobenzene, and methoxybenzaldehyde was rotated around the phenyl‐O bond. HF, along with the cc‐pVDZ basis with the other methods, generated inaccurate energy profiles for p‐methoxyphenol. For the density functional theory methods, it was necessary to use improved grids to get smooth curves. © 2013 Wiley Periodicals, Inc.     

Photoreactions of aromatic compounds—XXXV: Nucleophilic photosubstitution of methoxy substituted aromatic compounds. Monophotonic ionization of the triplet

Methoxy groups exert an activating and ortho/para directing influence in light induced nucleophilic substitution reactions (cyanation, hydroxylation, etc) of aromatic compounds in aqueous media. The first chemical step in these processes is monophotonic ionization of the aromatic compound in its lowest triplet state, followed by reaction of the radical cation with the nucleophile Quantum yields of photocyanation of 4-fluoro- and 4-chloroanisole indicate that in 99% (mole fraction) water virtually all triplets formed undergo electron ejection.This hypothesis is in agreement with the results of charge density calculations for the radical cations. It is directly supported by the similarity of the product composition of these photochemical substitutions with that of anodic substitutions, where the intermediacy of an aromatic cation is generally accepted. The presence of an oxidizing agent (oxygen, or persulphate) is required only when a hydrogen is replaced. The nucleophilic photosubstitution at electron rich aromatic systems in solvents as water can therefore be classified as an S_r⁺n¹(³Ar^*) process.     

Vibrational spectra and force field of azacyclic compounds. I. Pyrrole

For the molecules of pyrrole and its symmetric deuterated derivatives, vibrational spectra have been analyzed, and the force field has been defined in natural coordinates.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 29, No. 5, pp. 651–655, May, 1993.     

Charge stripping and the site of cationization of substituted aromatic compounds

The site of protonation, methylation and ethylation of anilines, phenols and thiophenols can be determined by tandem mass spectrometry (MS/MS). The extent to which the cation attachment products formed from these compounds undergo charge stripping is related to the site of cation attachment. The formation of doubly charged ions for phenols and anilines is favored when cation attachment occurs on the ring. For thiophenols alkylation occurs almost exclusively on the substituent, and yet an abundant stripping peak is recorded. This behavior is opposite to that seen for anilines and phenols and is accounted for in terms of orbital energies in the three systems. The site of cation attachment, as deduced by charge stripping, agrees with conclusions drawn from the fragmentation behavior of these ions upon collision-induced dissociation.     

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.     

Design and synthesis of diversely substituted azacyclic inhibitors of endothelin converting enzyme

A series of azacyclic phosphonic acids were synthesized from L-pyroglutamic acid, 6-oxo-L-pipecolic acid, and their enantiomers. The objective was to study the effect of constraining acyclic inhibitors of endothelin converting enzyme on inhibitory activity. Potential pharmacophoric tethers were introduced by stereocontrolled reactions to give highly substituted pyrrolidine- and piperidine-alpha-phosphonic acids. Weak inhibitory activity was observed for one diastereomer in each series having the same relative orientation of substituents.     

Catalysis of the oxidative chlorination of aromatic compounds with substituted iron phthalocyanines

Iron phthalocyanine-catalyzed oxidative chlorination of aromatic hydrocarbons using the H₂O₂-HCl system led to the formation of the corresponding chlorine derivatives.     

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。     

Electron impact mass spectra of some substituted aromatic boronate derivatives of bifunctional compounds

The electron impact mass spectra of the 3,5-bis(trifluoromethyl)benzeneboronate, 2,4-dichlorobenzene-boronate and 4-bromobenzeneboronate derivatives of some bifunctional diols and aminoalcohols are characterized by prominent molecular ions with diagnostically useful modes of fragmentation. Many of the principal ions in the mass spectra retain boron in their structure.     

Sterically hindered aromatic compounds. X—molecular distortions and asymmetry in a symmetrically substituted azobenzene

No significant steric effects are observed in the proton and carbon resonance spectra of 2,2′,4,4′,6,6′-hexa-t-butylazobenzene, a very distorted molecule in the solid state.     

Formation of charge-transfer complexes in systems containing substituted aromatic hydrocarbons and electron-donating organic compounds

Binary systems of monosubstituted benzene derivatives of type C₆H₅X (X=CN, NO₂, COMe, F, Cl, Br, I) and furan, pyrrole, thiophene, pyridine, tetrahydrofuran, and piperidine are analyzed physicochemically by a refractometric method.From deviations from additivity of n (V) isotherms for systems containing furan plus C₆H₅CN, C₆H₅NO₂, or C₆H₅COMe, conclusions can be drawn about interactions of components leading to formation of charge-transfer complexes (CTC) of 21 composition.With pyrrole possible intermolecular interaction must be confirmed by other methods of physicochemical analysis.Almost all of the systems containing tetrahydrofuran investigated, differ by showing more marked interaction between the components, giving CTC of 11 composition.n (V) isotherms for systems containing pyridine and C₆H₅NO₂ are slightly concave to the composition axis. At the same time piperidine clearly reacts with C₆H₅CN and C₆H₅NO₂, giving a 21 complex with the former, and a colored mixture with the latter, (formation of a complex in this case requires confirmation by other methods).All the thiophene binary systems investigated are characterized by linear refractive index isotherms, i.e., they are refractometrically ideal.The electron-donor properties of the heterocyclic compounds investigated vis a vis the aromatic ring with a lowered-electron density lie in the order tetrahydrofuran > furan > piperidine > pyrrole > thiophene.For Part III see [6].     

Theoretical and experimental analysis of the antioxidant features of substituted phenol and aniline model compounds

Structural Chemistry - Although natural polyphenols have attracted extended attention as antioxidants, there is only limited information available on their structure-activity relationship (SAR). In...     

The photochemical characteristics of aromatic enediyne compounds substituted with electron donating and electron withdrawing groups

trans- and cis-1-(4-Dimethylaminophenyl)-6-(4-nitrophenyl)hex-3-ene-1,5-diynes (trans- and cis-DANE) were synthesized and their photochemical properties were studied. The absorption spectra of trans-DANE red-shifted compared with the parent compound bisphenylethynylethene (BEE) due to intramolecular charge transfer. The fluorescence spectra, Stokes shift, fluorescence lifetime, fluorescence quantum yield, and quantum yield of trans-to-cis photoisomerization of trans-DANE showed strong dependence upon the solvent polarity in the less-polar region. No fluorescence emission from trans-DANE was observed in medium-polar and polar solvents. The quantum yield of cis-to-trans isomerization was almost solvent independent. The donor-acceptor substituents shifted the equilibrium between the trans perpendicular triplet state and the trans planar triplet state to the trans triplet state, and resulted in an increase in the triplet lifetime. Comparison of the photochemical properties of trans-DANE with trans-4-dimethylamino-4'-nitrostilbene (DANS) suggests that trans-DANE is a possible fluorescent probe in the non-polar region.     

Characteristic vibrations of 2-monosubstituted pyrimidines

The frequency intervals of the localization of the bands of the characteristic and noncharacteristic vibrations of 2-substituted pyrimidines have been determined on the basis of calculated and analysis of experimental results. A theoretical interpretation of the bands according to the form of the vibrations has been given and the groups of characteristic and noncharacteristic vibrations of the aromatic skeleton of the 2-monosubstituted pyrimidines has been established. For the noncharacteristic vibrations, groups of substituents with different regions of localization of the frequencies of the aromatic skeleton have been isolated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 121–125, January, 1984.