Thermochemistry of heteroatomic compounds

The enthalpies of solvation of four geometric isomers of 2,5-dimethyl-1-phenyl-1-thioxophosphorinan-4-one in chloroform, nitrobenzene, and methanol were calculated using the enthalpies of vaporization of the isomers determined by the modified Solomonov—Konovalov method from the enthalpies of solution of the compounds in CCl₄ andp-xylene and molar refractions. The enthalpies of formation (ΔH _f ^o) of the isomers in the condensed and gas phase were assessed in the framework of Benson's group additivity scheme by summing the ΔH _f ^o values for phosphacycloketone fragments obtained from molecular mechanics calculations with the contributions of the phenyl group and S atom attached to the P atom. Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1533–1536, September, 2000.     

Thermochemical and theoretical study of some methyldiazines

The standard (p ⁰ = 0.1 MPa) molar enthalpies of formation for the liquid 2,3-dimethylpyrazine and trimethylpyrazine and the crystalline 2,3-dimethylquinoxaline and tetramethylpyrazine were derived from the standard molar enthalpies of combustion, in oxygen, atT=298.15 K, measured by static-bomb combustion calorimetry. The standard molar enthalpies of vaporization or of sublimation for the same compounds were determined by Calvet microcalorimetry. Ab initio full geometry optimization at the 3-21G and 6-31G^* levels were also performed for all the methylpyrazine isomers. MP2/RHF/3-21G//3-21G and DFT energies were also calculated for all the methylpyrazine isomers, thus allowing us to estimate their isodesmic resonance energies.     

Synthesis of cyclic sulfides

Two isomers of 2,3-dimethyl-1-thiahydrindane and two isomers of 4-methyl-1-thiadecali were obtained by the reaction of cyclohexene episulfide with crotylmagnesium bromide and subsequent cyclization of the resulting 2-(-methyl--propenyl)-1-cyclohexanethiol by the action of 75% sulfuric acid and UV irradiation.See [3] for communication IV.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 622–625, May, 1972.     

Crown-containing styryl dyes

New crown ether styryl dyes containing various heterocyclic moieties and substituents were synthesized. Thecis andtrans isomers of crown ether styryl dyes and their complexes with metal cations were characterized by their absorption and fluorescence spectra. Based on an analysis of the spectral parameters and the shifts of the absorption and fluorescence maxima upon photoisomerization and complexation, the effects of the nature and structure of the heterocyclic moiety on the photochromism of styryl ionophores were revealed.For Part 12, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 129–135, January, 1995.This study was financially supported by the Russian Foundation for Basic Research (Grants No. 94-03-08-531 and 93-03-04-089) and the International Science Foundation (Grant M8QOO).     

Thermodynamic characteristics of sorption of heterocyclic compounds m capillary gas chromatography

Dependences of sorption energies of sulfur-, oxygen-, and nitrogen-containing heterocyclic compounds on the nature of heteroatoms, structure of substituents and their position in the ring were studied. The contributions of heteroatoms, functional and alkyl groups to the energy of dispersive interaction of position isomers with nonpolar stationary phases were determined for imidazoles, piperidines, morpholines, thiomorpholines, dioxalanes, oxathiolanes, dithiolanes, thiophenes, and furans. The nonequivalence of contributions of the same substituents to the sorption energy of each of the heterocyclic compounds, depending on the nature of the heteroatom and position of the substituent, was shown. The obtained values of contributions of heteroatoms and substituents can be used for apriori calculation of retention indices of position isomers of five- and six-membered heterocycles containing one or two heteroatoms in the ring.Translated from lzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 2033–2038, August, 1996.     

Discrimination of the geometrical isomers of 2,3-, 2,5-, and 2,6-dimethylpiperazines based on 1 H?Nmr spectral data

¹ H-Nmr spectra of cis and trans isomers of 2,3-, 2,5-, and 2,6-dimethylpiperazines were taken at various temperatures. The spectra of geometrical isomers bearing the ae or ea dimethyl groups showed broadening at lower temperatures. It was clarified that the measurement of the spectra at lower temperatures is useful for the discrimination of the geometrical isomers of dimethylpiperazines.     

Benzopyridofulvenes

A group of benzopyridofulvenes was obtained by condensation of 3-methyl-2-azafluorene and 4-azafluorene with anisaldehyde, veratraldehyde, and p-nitrobenzaldehyde. It was established that they are produced in the form of geometrical isomers, which could be isolated in the case of the 9-(o-methoxy) and 9-(m,p-dimethoxy) derivatives of 3-methyl-2-azafluorene. One isomer of the analogous benzylidene derivative and 3-[-hydroxy--(p-nitrophenyl)ethyl]-2-azafluorenone were obtained in the condensation of this azafluorene with p-nitrobenzaldehyde. The dimethoxybenzylidene derivatives of both azafluorenes were reduced to dimethoxybenzyl derivatives. The geometrical isomers of a substituted indenoindolizine were obtained from the mixture of isomers of N-phenacyl-9-(m,p-dimethoxybenzylidene)-4-azafluorene bromide and dimethyl acetylenedicarboxylate.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1653–1659, December, 1978.     

Potentiometric Liquid Membrane Sensors That Discriminate Linear Homologs and Geometrical/Positional Isomers of Dicarboxylates

Abstract

Potentiometric discrimination of series of linear homologs (4-7), geometrical isomers (8,9), and positional isomers (10-12) of dicarboxylate guests by a liquid membrane sensor containing Iipophiiic macrocyclic polyamine 1 as a sensory element is described. the pH conditions were carefully set so that the potentiometric response to the dianionic forms of the guests could be specifically observed. Whereas only small discrimination was observed for the flexible linear homologs (4-7), marked discrimination was observed, for the geometrical isomers (8,9) and positional isomers (10-12) having rigid structures. the selectivities of the potentiometric response were found to correlate well with the reported selectivities of host-guest complexation in water displayed by macrocyclic polyamines having the structures related to 1.     

CHEMISTRY OF CIS- AND TRANS-9-PHENYLSELENOXANTHENE-N-ARYLSULFONYLSELENILIMINES1

Abstract

cis- and trans-9-Phenylselenoxanthene-N-(arylsulfonyl)selenilimines were synthesized and isolated. Their stereochemistry was ascertained from the NMR spectra. Cis isomers reacted with chloramine-T or -B by an S_N 2 type substitution to form trans isomers, but the reverse reaction did not take place. When trans isomers were refluxed in toluene they underwent intermolecular 1,4 rearrangement to give 9-arylsulfonamido-9-phenylselenoxanthene. The cis isomers neither rearranged nor isomerized. On treatment with DABCO, both isomers rearranged intermolecularly to 9-(N-arylsulfonamido)selenoxanthenes at room temperature. Hydrolysis of both isomers yielded trans-9-phenylselenoxanthene 10-oxide. Reactions with p-methoxyphenylmagnesium bromide or methylmagnesium iodide afforded 9-(p-methoxyphenyl)-9-phenylselenoxanthene or 9-phenylselenoxanthene as a main product, respectively.     

Synthesis and three-dimensional structures of substituted 4-silyl-4-piperidols

1,2 5-Trimethyl-4-(methyldiphenylsilyl)- and 4-(dimethylphenyl)silyl-4-piperidols were obtained. The isomers of these piperidols of the series, which exist in the chair conformation, have all of their substituents, except the hydroxyl group, equatorially oriented. The isomers of the series exist in solution in the form of an equilibrium mixture of chair and boat conformations, and all of the substituents, except the silyl grouping, are equatorially oriented in the chair conformation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 502–505, April, 1976.     

Adsorption of xylene isomers on ordered hexagonal mesoporous FDU-15 polymer and carbon materials

The oil industry has been facing the challenges of separation of xylene isomers, o-xylene, m-xylene and p-xylene or removing them from the environment. In our present work, we investigated the adsorption of the three isomers on two mesoporous materials, FDU-15-350 polymer and FDU-15-900 carbon materials. The isomer adsorption capacities are well correlated with their physical pore properties. It is found that the micropores are very crucial for the adsorption of these three isomers. The more micropore volume the adsorbent has, the better the adsorption capacity is. Henry’s constants were also calculated for the three isomers on the two adsorbents. Both on FDU-15-350 polymer and FDU-15-900, the Henry’s constants for the three isomers show the same trend o>m>p xylene which is coincidently in accordance with their polarity trend, indicating more polar adsorbate is preferred for adsorption on the two adsorbents. The isosteric heats of adsorption are correlated with the microporosity and the size of the adsorbate molecule. More microporosity and smaller molecules give higher heats of adsorption. Extracted information on pore properties of adsorbents by using the three isomers has very similar results as that resolved from nitrogen adsorption, indicating the feasibility of using the three isomers as adsorbates to extract pore information. This work is devoted to commemorating the 60th birthday of Professor Mieczyslaw (Mietek) Jaroniec.     

Separation of m- and p-Ethylphenols,and of 2,4- and 2,5-Dimethylphenols by Inclusion Complexation with 1,1-Bis(p-hydroxyphenyl)cyclohexane as Host Compound

Separation of isomers with the same or similar boiling points is very difficult, since fractional distillation cannot be used. For example, separation of m-?(bp 214°C) and p-ethylphenol (bp 219°C) and of 2,4- (bp 212°C) and 2,5-dimethylphenol (bp 212°C) by fractional distillation is almost impossible. However, when an inclusion complexation process with 1,1-bis(?p-hydroxyphenyl)cyclohexane is applied, these isomers were easily separated. m- and p-Ethylphenols were separated on a ton scale by the inclusion complexation technique.     

Separation of (3R, 3′ R)-, (3R, 3′ S; meso)-, (3S, 3′ S)- Zeaxanthin, (3R, 3′ R, 6′ R)-, (3R, 3′ S, 6′ S)- and (3S, 3′ S, 6′ S)-Lutein via the dicarbamates of (S)-(+)-α-(1-naphthyl) ethyl isocyanate

A method is described for the qualitative and quantitative determination of configurational isomers of zeaxanthin (=3,3′ -dihydroxy-β, β -carotene) and lutein (=3,3′ -dihydroxy-α -cartotene). It is based on the reaction of these zeaxathin and lutein isomers with (S)-(+)-α-(1-naphthyl) ethyl isocyanate to afford diastereomeric dicarbamates, which are analyzed by HPLC.     

Übergangsmetallkomplexe mit Nitronylnitroxylradikalliganden

The stable free radicals, the isomers of 4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide with the 2-substituentR (R=para-,meta-,ortho-pyridyl), have been prepared and used as ligands in copper(II), palladium(II) and platinum(II) complexes. The magnetic moments and the EPR spectra of the complexes and the free radicals have been investigated. Most of the complexes show a considerable intramolecular interaction between the radicalic groups of the ligands. No intramolecular interaction was found, however, between the transition metal ions and the unpaired electrons of the ligands. But by analysis of the EPR spectra in the solid state there was found in some cases an intermolecular interaction between the metal ion [copper(II)] and the unpaired electrons of the ligands.

     

Acylation of phosphoryl- and thiophosphorylacetonitriles under phase transfer catalysis conditions and the keto-enol tautomerism of phosphorus-substituted acylacetonitriles

A procedure was developed for acylation of phosphoryl- and thiophosphorylacetonitriles under phase transfer catalysis conditions. The reaction in the solid KOH/MeCN system affordedC-acylation products in high yields. In the individual state and in aprotic solvents, these products exist in the enol form (Z isomers) stabilizedvia a strong intramolecular hydrogen bond. In hydroxyl-containing media and in aprotic bipolar solvents, these compounds exist as a mixture of two geometric isomers (E andZ) of the corresponding enols. In this case, theZ isomer exists in two forms, namely, in the cyclic form with an intramolecular hydrogen bond and in the open form stabilized by intermolecular hydrogen bonds with the solvent. The results of X-ray diffraction analysis of both forms ofZ isomers of the compounds containing the phosphoryl and thiophosphoryl groups are discussed. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1687–1694, September, 1998.     

Molecular Recognition of Aromatic Nitro Compounds at Cyclodextrin Dithiocarbamate-modified Electrodes

Silver electrodes were modified by the adsorption of α-, β-, and γ-cyclodextrin dithiocarbamates (2α–γ) and characterized by reductive desorption experiments. Their molecular recognition properties were studied by cyclic voltammetry using three families of positional isomers of aromatic nitro compounds. Electrodes modified with 2α and 2β were selective for meta and para isomers while 2γ showed little selectivity. These observations are explained in terms of cavity sizes and guest structure. Computational studies suggest that the main reason for the observed selectivity is the different position of the NO² group in ortho and para isomers with respect to the CD cavity.     

Condensed isoquinolines. 34.* Transformations of 4H-thieno-[3',2':5,6]- and 4H-thieno[2',3':5,6]pyrimido-[1,2-<Emphasis Type="Italic">b</Emphasis>]isoquinolines

Syntheses are given for previously unreported 4-chloro derivatives of 4H-thieno[3′,2′:5,6]- and 4H-thieno[2′,3′:5,6]pyrimido[1,2-b]isoquinolines and the reactions of these compounds with N- and S-nucleophiles were studied. The spectral characteristics and biological activity of the positional isomers were compared. The electron spectra most clearly reflect the differences related to the position of the sulfur atom in these quasiaromatic systems. *For Communication 33, see [1]. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 619–630, April, 2009.     

Synthesis of Heterocycles from Arylation Products of Unsaturated Compounds: XIII. 5-R<Superscript>1</Superscript>-Benzyl-2-(R<Superscript>2</Superscript>-2-pyridylimino)thiazolidin-4-ones

Meerwein reactions of arenediazonium bromides with methyl and ethyl acrylates gave 3-aryl-2-bromopropionic acid esters which were subjected to cyclocondensation with N-(2-pyridyl)- and N-(6-methyl-2-pyridyl) thioureas to obtain 5-R¹-benzyl-2-(R²-2-pyridylimino)thiazolidin-4-ones. The latter were shown to exist in solution as E isomers of the imino form.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 7, 2005, pp. 1071–1075.Original Russian Text Copyright © 2005 by Matiichuk, Obushak, Tsyalkovskii.     

A new stereoselective synthesis of 2-amino-4,5-dihydrothiophene-3-carbonitrile derivatives

A new stereoselective method for the synthesis of trans-isomers of 2-amino-4-aryl-5-benzoyl-4,5-dihydrothiophene-3-carbonitriles was proposed. The method involves base-catalyzed reactions of phenacyl thiocyanate with 3-(het)aryl-2-cyanoprop-2-enethioamides. (4R,5S/4S,5R)-2-Amino-5-benzoyl-4-(2-chlorophenyl)-4,5-ihydrothiophene-3-carbonitrile was structurally characterized by X-ray diffraction analysis. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1379–1383, July, 2007.     

Mechanisms and kinetics of the elementotropic rearrangements of tetrahydro-4,4,8,8-tetramethyl-4,8-disila-sym-indacene

The dynamic stereochemistry of silatropic rearrangements of tetrahydro-4,4,8,8-tetra-methyl-4,8-disila-sym-indacene (dimer of 6,6-dimethyl-6-silafulvene), which exists in solution as an equilibrium mixture of two interconverting isomers, was studied. The mechanisms and complete kinetic scheme of rearrangements were established using¹H,¹³C, and²⁹Si 2D quantitative EXSY NMR spectroscopy. It was found that the interconversion and degenerate rearrangements of the observed isomers proceedvia two concurrent pathways due to the formation of different intermediates. The activation parameters of the rearrangements were determined by means of total lineshape analysis of dynamic NMR (DNMR) spectra. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1285–1295, July, 1997.