Photolysis of <Emphasis Type="Italic">meta</Emphasis>-azidophenol in solutions

The photolysis of meta-azidophenol in various organic solvents and aqueous solutions is studied by IR spectroscopy, electronic absorption spectroscopy, thin-layer chromatography (TLC), and analytical spot-test reactions. The polymeric derivatives of hydroxylamine are formed in organic solvents (benzene, chloroform, acetonitrile) via the interaction of nitrene with the phenol group of a neighboring m-azidophenol molecule. N-(meta-Hydroxyphenyl)hydroxylamine,—the product of the nitrene reaction with water, is formed in ethanol and aqueous solutions.     

Photolysis of <Emphasis Type="Italic">meta</Emphasis>-azidophenol in water-organic mixtures

Photolysis of m-azidophenol (m-AP) in organic solvents and water-organic mixtures of various composition was studied using the methods of electronic spectroscopy. m-Azidophenol dissolved in water-organic mixtures was shown to form associates with solvent molecules, depending on the composition of the mixture. The nature of m-AP photolysis products and the rate of their formation are determined by the character of m-AP solvation in water-organic mixtures. In acetonitrile solution, a polymeric product is formed via the interaction of the phenol group with the nitrene of an adjacent m-AP molecule. An increase in the mole fraction of water in a water-acetonitrile mixture leads to a decrease in the yield of the polymeric product and an increase in the yield of the hydroxylamine derivative. In water-ethanol mixtures, the hydroxylamine derivative is the main product of photolysis.     

Effect of <Emphasis Type="Italic">ortho</Emphasis>-methyl groups in the benzene rings of the macrocyclic frame on the chemistry of phosphacavitands

Effect of ortho-methyl groups in the benzene rings of the macrocyclic matrix on the chemistry of cavitands with phosphorous amide bridges in the upper rim is studied. The presence of ortho-methyl groups is shown to prevent formation of phosphacavitands of C _4v symmetry and favor formation of macrocyclic systems of C _2v symmetry, enhance solubility of phosphacavitands in organic solvents, hinder oxidation of phospha(III)cavitands and decrease the yield of phospha(V)cavitands, prevent formation of binuclear molybdenum complexes of phosphorous amide cavitands, and favor formation of their tetranuclear analogs.     

Intra- and intermolecular hydrogen bonding in solutions of <Emphasis Type="Italic">N</Emphasis>-(2-hydroxy-3,8-diiodocyclooctyl)trifluoroacetamide and <Emphasis Type="Italic">N</Emphasis>-(4-iodo-2,2,5,5-tetramethyltetrahydrofuran-3-yl)trifluoroacetamide

The methods of IR spectroscopy and quantum chemistry (B3LYP/DGDZVP) were applied to investigation of the types of self-associates formed in solutions of N-(2-hydroxy-3,8-diiodocyclooctyl)trifluoroacetamide and N-(4-iodo-2,2,5,5-tetramethyltetrahydrofuran-3-yl)trifluoroacetamide in CCl₄ by means of hydrogen bonding. The ОН group of N-(2-hydroxy-3,8-diiodocyclooctyl)trifluoroacetamide participates in the formation of intramolecular hydrogen bond ОH···О=С, while chain dimers are formed due to interactions between the NH and С=О groups of the neighboring molecules. Due to the formation of the intramolecular bond, the dimers of N-(2-hydroxy-3,8-diiodocyclooctyl)trifluoroacetamide are energetically less stable than the chain dimer of N-(4-iodo-2,2,5,5-tetramethyltetrahydrofuran-3-yl)trifluoroacetamide.     

Formation of solvate structures by the <Emphasis Type="Italic">ortho</Emphasis>-, <Emphasis Type="Italic">meta</Emphasis>-, and <Emphasis Type="Italic">para</Emphasis>-isomers of hydroxybenzoic acid in supercritical fluid

The solvate structures formed by the ortho-, meta-, and para-isomers of hydroxybenzoic acid (o-HBA, m-HBA, and p-HBA) with a polar co-solvent (methanol at a concentration of 0.030 and 0.035 mole fractions) in supercritical carbon dioxide at a constant density of 0.7 g/cm³ and temperatures of 318 and 328 K have been studied by the classic molecular dynamics. It has been determined that a stable hydrogen-bonded complex with the co-solvent forms via the hydrogen of the carboxyl group for all isomers. The probability of this complex existence is high at all temperatures and concentrations. In the o-HBA molecule, the other functional groups are engaged in the intramolecular hydrogen bond, but not involved in interactions with methanol. It has been found that m-HBA and p-HBA can be involved in hydrogen bonds with methanol via hydroxyl hydrogen and oxygen atoms; they are characterized by the presence of one more co-solvent molecule (rarely, two molecules) in their solvation shell and intermittent formations/breakages of hydrogen bonds via other functional groups. These bonds are far less stable, and their formation is sensitive to change of temperature and co-solvent concentration. It has been concluded that the degree of selective solvation of m-HBA and p-HBA by co-solvent molecules is approximately the same, but the rate of structural rearrangements in the nearest environment of m-HBA is higher than that of p-HBA.     

Effect of the structure of the <Emphasis Type="Italic">ortho</Emphasis>, <Emphasis Type="Italic">meta</Emphasis>, and <Emphasis Type="Italic">para</Emphasis> isomers of perhydroterphenyl on their reactivity in heterogeneous catalytic dehydrogenation

The kinetics of the dehydrogenation of the individual ortho, meta, and para isomers of perhydroterphenyl and their mixtures over a (3 wt % Pt)/C catalyst has been investigated in a flow reactor at 280–340°C. The rate of the isomerization of the stereoisomers of the initial substrate (perhydroterphenyl) and terphenyl dehydrogenation products has an effect on the hydrogen release kinetics. The highest reactivity in isomerization is shown by the ortho isomer. The largest amount of hydrogen (7.0 wt %) is released in the dehy-drogenation of perhydro-meta-terphenyl and perhydro-para-terphenyl, whose conversion at 320°C is 96%.     

Surface properties and hydrogen bonds of mono-functional polybenzoxazines with different <Emphasis Type="Italic">N</Emphasis>-substituents

A series of mono-functional benzoxazine monomers with different N-substituents were synthesized from phenol, formaldehyde, and various amines (ammonia, methylamine, n-butylamine, dodecylamine), named P-am, P-m, P-b, and P-da, respectively. The surface properties of these polybenzoxazine films were proven by contact angle measurements. The hydrogen bond network of the polybenzoxazine systems was studied using the FTIR spectra. And the results showed that the surface free energy increased with increasing the fraction of intermolecular hydrogen bonding when the N-substituent was an alkyl chain. However, the rule was not suitable when the N-substituent was H. That was because there was one more kind of intramolecular hydrogen bond in the poly(P-am). Based on these findings, we proposed that both the N-substituent alkyl group and the fraction of intermolecular hydrogen bonding had effects on the surface free energy.     

Hydrogenation of biphenyl and isomeric terphenyls over a Pt-containing catalyst

Catalytic hydrogenation of benzene, biphenyl, and ortho-, metha-, and para-isomers of terphenyl over a 3 wt.% Pt/C at 180 °C and 70 atm was studied. The directions of hydrogenation of each substrate were revealed. Relationships between structures of the substrate and hydrogen consumption rates were found. It was shown that hydrogenation rate decreases on going from benzene to terphenyl and with increasing degree of the substrate hydrogenation. Hydrogenation rate of terphenyl isomers decreases in the following order: p-terphenyl > > m-terphenyl > o-terphenyl.     

Dipole moments and structure of <Emphasis Type="Italic">ortho</Emphasis>-diphenyl(diethyl)phosphinoyl-substituted benzyl alcohols,phenols, and their derivatives

The method of dipole moments and DFT B3LYP/6-31G* quantum-chemical calculations were used to study the structures of ortho-substituted aryl-and arylmethyldiphenyl(diethyl)phosphine oxides. It was established that methyl ethers of phosphorus-containing benzyl alcohols and phenols exist as equilibrium mixtures of several conformers with prevalence of forms with the weakest steric interactions. Preferred conformers of o-[(diethylphosphinoyl)methyl]benzyl alcohol and i-[(diphenylphosphinoyl)methyl]phenol contain an intramolecular hydrogen bond between the hydroxyl hydrogen atom and phosphinoyl oxygen atom.     

Photochemistry of <Emphasis Type="Italic">N</Emphasis>-substituted salicylic acid amides

The products of photolysis of N-substituted salicylic acid amides, viz., 2-hydroxy-3-tert-butyl-5-ethylbenzoic acid N-(4-hydroxy-3,5-di-tert-butylphenyl)amide (1) and 2-hydroxybenzoic acid N-[3-(4-hydroxy-3,5-di-tert-butylphenyl)prop-1-yl]amide (2), in heptane were studied by optical spectroscopy and stationary and nanosecond laser photolysis (Nd: YAG laser, 355 nm). It was shown by the method of partial deuteration of amides 1 and 2 that they exist in both the unbound state and as complexes with intraand intermolecular hydrogen bond. Amides 1 and 2 are subjected to photolysis, which results in the formation of a triplet state and phenoxyl radicals RO? presumably due to the absorption of the second photon by the excited singlet state. The formation of radical products due to N–H bond ionization was not observed. The main channel of decay of the triplet state and radicals RO? is triplet–triplet annihilation and recombination (k _r ≈ 2.3?10⁸ L mol^–1 s^–1), respectively. The UV irradiation of compounds 1 and 2 leads to the excitation of the amide groups, and no formation of radical products due to N–H bond ionization was observed.     

<Superscript>1</Superscript>H NMR study on intramolecular hydrogen bonding in 2,3-<Emphasis Type="Italic">O</Emphasis>-isopropylidene-D-ribofuranosides and their 5(4)-hydroxy derivatives

¹H NMR study showed the possibility for intramolecular hydrogen bonding in 5(4)-hydroxy derivatives of 2,3-O-isopropylidene-β-D-ribofuranose in CDCl₃. The obtained data were used to interpret differences in the ¹H NMR spectra of structurally related 5-halo-2,3-O-isopropylidene-D-ribofuranosides and four newly synthesized diastereoisomeric 5-bromo-5-deoxy-4-hydroxy-2,3-O-isopropylidene-D-ribofuranosides.     

Structure effects of the protonated lincomycin molecule on the mechanism of its complexation with organic compounds

The mechanism of complexation of the protonated lincomycin molecule with para-substituted nitrobenzenes in the gas phase is analyzed by quantum chemical methods. The regioselectivity of lincomycin protonation is treated in a B3LYP/6-31G(d′, p) approximation; the geometrical structure and conformation of the molecule are analyzed. The lincomycin molecule is protonated at the nitrogen atom of the pyrrolidine cycle. In stable conformers, a pseudovoid is formed and stabilized by intramolecular hydrogen bonding. The cross section of the pseudovoid (1.77–2.62 Å) is too small for the protonated lincomycin molecule to participate in host guest complexation with organic compounds. According to B3LYP/6-31G(d′, p) calculations, complexation of the protonated lincomycin molecule with nitrobenzenes occurs through hydrogen bonding.     

Preparation of a Polymer via Condensation of <Emphasis Type="Italic">o</Emphasis>-Phenylenediamine with <Emphasis Type="Italic">p</Emphasis>-Xylylene Dibromide and Its Properties

Condensation of para-dibromoxylene and ortho-phenylenediamine in glass ampule at 150°С in an alkaline aqueous solution has yielded polymer with completely substituted N–H hydrogen atoms, capable of formation of polymeric cation-radicals. Complexes of this polymer and N,N,N',N'-tetrabenzyl-o-phenylenediamine with Co(II), Ni(II), Cu(II), and Ag(I) have been obtained, and their structure has been studied.     

Reaction of nitroanilines with aldehydes. Refinement of the Doebner–Miller reaction mechanism

Due to intramolecular hydrogen bonding between the amino and nitro groups, o-nitroaniline is incapable of forming Schiff bases in the reactions with acetaldehyde and crotonaldehyde but is converted to quinoline derivative under Doebner–Miller reaction conditions via addition to the C=C double bond of the α,β-unsaturated aldehyde. Under analogous conditions, p-nitroaniline possessing a free amino group gives rise to the product of Doebner–Miller quinoline synthesis through intermediate formation of Schiff base dimer. The reaction of p-nitroaniline with benzaldehyde also yields the corresponding Schiff base, whereas o-nitroaniline is converted to N-benzyl derivative.     

Thermal Rearrangements of 3<Emphasis Type="Italic">H</Emphasis>- and 4<Emphasis Type="Italic">H</Emphasis>-Pyrazoles Prepared by Reactions of 9-Diazofluoren with Methyl Tetrolate and Methyl 3-Phenylpropiolate

9-Diazofluoren adds in Et₂O at 20°C to methyltetrolate in keeping with Auwers rule and nonregioselectively adds to methyl-3-phenylpropiolate with the formation of spirocyclic 3H-pyrazoles. The methyltetrolate adduct at boiling in toluene converts into methyl 3a-methyl-3aH-dibenzo[e,g]indazole-3-carboxylate, at 190°C in benzene, into methyl 3-methyl-2H-dibenzo[e,g]indazole-2-carboxylate, and at 160°C in methanol, into 3-methyl-2H-dibenzo[e,g]indazole. Auwers adduct of methyl 3-phenylpropiolate at boiling in benzene gives cyclopropene derivative and at boiling in methanol isomerizes into methyl 3a-phenyl-3aHdibenzo[e,g]indazole-3-carboxylate. Anti-Auwers adduct at boiling in benzene isomerizes into methyl 2-phenylpyrazolo[1,5-f]phenanthridine-3-carboxylate.     

Epoxidation and Heterocyclization of Arenesulfonamides of the Norbornene Series

Reactions of previously known and newly synthesized N-(bicyclo[2.2.1]hept-5-en-endo-2-ylmethyl)arenesulfonamides with monoperoxyphthalic acid generated in situ from phthalic anhydride and 30% hydrogen peroxide lead mostly to the corresponding N-arylsulfonyl-exo-2-hydroxy-4-azatricyclo[4.2.1.0^3,7]nonanes (azabrendanes). In some cases, N-(exo-5,6-epoxybicyclo[2.2.1]hept-5-en-exo-2-ylmethyl)arenesulfonamides were isolated as the only products or mixtures of alternative oxidation products were obtained. The presence of electron-acceptor nitro groups in the benzene ring and bulky substituents, primarily in the ortho position, is considered to be a structural factor preventing the primary oxidation products (epoxy derivatives) from undergoing heterocyclization.     

Inter- and intramolecular interactions in 2,3-dihydroquinazolin-4(1<Emphasis Type="Italic">H</Emphasis>)-ones: molecular structure and conformational analysis

X-ray crystal structure analysis and quantum chemical calculations based on the density functional theory (DFT) were used for structural and electronic characterizations of three 2,3-dihydroquinazolin-4(1H)-ones (DHQZs). The occurrence of the C₂-stereocenter in the heterocyclic ring causes the formations of both R- and S-enantiomers. X-ray diffraction technique indicates that these compounds exist as a racemic mixture in the crystal structure, and the enantiomers are orientated to each other via hydrogen bonding between the potential hydrogen donor (N₃–H) and acceptor species (C₄ = O group) in each layer under the formation of an enantio-syndio packing. Additional intermolecular and intramolecular interactions affect the orientations of the molecules adopted in the crystal packing, especially the orientation of the ring substitution. Most computational data, including the bond lengths and angles, are well in agreement with the experimental data. Dihedral angle scanning elucidates the effect of the nature and the location of the additional substituent on the aryl group at C₂-position on the total energy content of the molecule.     

Modeling of the electronic,optoelectronics, photonic and thermodynamics properties of 1,4-bis(3-carboxyl-3-oxo-prop-1-enyl) benzene molecule

The modeling of the molecule 1,4-bis(3-carboxyl-3-oxo-prop-1-enyl) benzene has been carried out to study the electronic, optoelectronics, photonic and thermodynamics properties using Hartree–Fock, density functional theory (B3LYP) and MP2 (Möller–Plesset perturbation theory second-order) with the 6-31G and 6-31+G** basis sets. The dipole moment (µ), polarizability (〈α〉), first hyperpolarizability (β _mol), dielectric constant (ε), electric susceptibility (χ), refractive index (η) and thermodynamics properties of this molecule have been calculated using the same level of theory. The small values of ε, and LUMO–HOMO energy gap, and the high values of χ, η, MR, 〈α〉 and (β _mol) show that the molecule has very good electronic, optoelectronic and photonic applications. The results of this study show that this molecule is an interesting pi-conjugated molecule whose electronic structure and properties can be regulated over a wide range by variation in backbone structure, by side group substitution, and through intramolecular hydrogen bonding.     

Tandem molecular rearrangement in the alkylation of phenol with camphene

The alkylation of phenol with camphene in the presence of boron trifluoride in glacial acetic acid was accompanied by tandem molecular rearrangement with formation of a mixture of ortho- and para-substituted phenols having 1,7,7-trimethylbicyclo[2.2.1]hept-exo-2-yl and 5,5,6-trimethylbicyclo[2.2.1]hept-exo-2-yl substituents. The same products were obtained by rearrangement of 1,7,7-trimethylbicyclo[2.2.1]hept-exo-2-yloxybenzene under analogous conditions. Similar reactions performed in the presence of aluminum phenoxide as catalyst resulted in predominant formation of the corresponding ortho-substituted phenols.     

Homoallylic <Emphasis Type="Italic">o</Emphasis>-halobenzylamines: asymmetric diversity-oriented synthesis of benzo-fused cyclic amines

The presence of a halogen atom in the proximity of a homoallylic amine, obtained by asymmetric addition of allylzinc bromide to the corresponding tert-butyl sulfinimine, makes them versatile building blocks suitable to participate in several palladium-catalyzed processes, such as the intramolecular Heck reaction or the Sonogashira cross-coupling. The thus obtained ortho-alkynyl derivatives display two unsaturated functional groups which may be further modified by means of the intramolecular Pauson–Khand reaction or the ring-closing enyne metathesis. In this way, a variety of benzo-fused amines can be obtained in 2–3 steps from readily available starting materials.