Quantum-chemical study of allylic and vinylic compounds of fifth-group elements

Energies and oscillator strengths of the long-wave electronic transitions for several conformers of allyl- and vinylamine and allyl- and vinylphosphine have been calculated by the semiempirical quantum-chemical MNDO method. The electronic structure of these molecules is discussed in detail, and the spectral and conformational effects ofn, and , conjugation are analyzed. Some suggestions concerning possible conjugation effects in the allylic compounds of As, Sb, and Bi are made.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1551–1554, September, 1993.     

Scaling in the S and P states of the helium isoelectronic sequence

Mean values of r ₁ ^r and r _r ¹² for the ground and several excited states of the helium isoelectronic sequence are used to demonstrate that a simple scaling which superimposes the distribution function f(r ₁₂) as a function of the atomic number leads to a similar result for the electron density distribution D(r₁). On the basis of a screening interpretation of the scaling parameter , it is concluded that screening is greater in the singlet than the triplet state of a particular configuration, that screening is greater in the P states than the corresponding S states, and that the screening approaches the limiting value of 1 for the highly excited states. The perturbation expansions of Scherr and Knight are used to determine the limiting value of when Z and the relationship between the scaling parameter and the scale factor, chosen so that a trial wave function satisfies the virial theorem, is discussed. A brief discussion of the scaling of the Coulomb hole is presented.     

Effects of 17α-ethinylestradiol on zoo- and phytoplankton in lentic microcosms

The effects of 17-ethinylestradiol (EE), an endocrine disruptor, on zoo- and phytoplankton were studied in outdoor 230-L still-water microcosms. Cell density and biomass, diversity, and community composition were analyzed. Five microcosms were treated by controlled release for six weeks, three by direct application of EE. To investigate recovery, sampling was continued for four weeks after treatment. Most characteristics of the zooplankton were not unambiguously affected by EE. Only the relative density of copepods, especially of their larvae, decreased significantly after EE application. For phytoplankton, no unambiguous concentration- or toxodose-correlated effects on any biotic characteristics could be found. However, most properties of the phytoplankton deviated from those of controls, i.e. tended to be smaller (number of species per microcosm, biomass, cell density) or covered a wider range (diversity, evenness). PCA indicated a shift of species structure in the treated microcosms. This was supported by the species scores calculated by the principal response curve method, although the principal response curve itself showed no clear EE-correlated shifts. High variability within the biocenosis between microcosms and over time, probably because of disturbance of the ecosystem before starting of the test, might have superimposed EE-dependent effects.Abbreviations c _dt Canonical coefficient - CRD Controlled-release device - E Shannon–Wiener index for evenness - EC10 Effect concentration for 10% of maximum effect - EC50 Effect concentration for 50% of maximum effect - EE 17-Ethinylestradiol - H Shannon–Wiener index for diversity - LPDE Low density polyethylene - NOEC No observed effect concentration - PCA Principal component analysis - PRC Principal response curve - RDA Redundancy analysis - SD Standard deviation     

Preferential inclusion of food colours via formation of their inclusion complexes withβ-cyclodextrin (β-CD)

The encapsulation of commercially utilized food colours with-cyclodextrin is reported. Thus, inclusion complexes of Sunset Yellow, Amaranth, Ponceau 4R, Carmoisine, Fast Red E, Tartrazine and Erythrosine with-CD were prepared. The formation of inclusion complexes was established by, among other methods, UV, reflectance and X-ray diffraction techniques. The host-to-guest ratio was determined by a UV spectral method. The effect of inclusion with-CD on binary mixtures such as Raspberry Red, Tomato Red and Orange Red was also studied.     

9β-hydroxy-11β(H),13-dihyhdrosantamarine, a new eudesmanolide fromArtemisia leucotricha

A new sesquiterpene lactone, 9-hydroxy-11(H),13-dihydrosantamarine, and known terpenes are isolated from the underground part ofArtemisia leucotricha Krasch ex Ladyg (Asteraceae). The structure is determined by spectral and x-ray structural analysis.Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 230–232, May–June, 2000.     

Antioxidant Study and Assignments of NMR Spectral Data for 3′,4′,7-Trihydroxyflavanone 3′,7-Di-O-β-D-glucopyranoside (Butrin) and Its Hydrolyzed Product

The NMR spectral data including high resolution ¹H, ¹³C and 2D NMR for butrin, 3,4,7-trihydroxyflavanone 3,7-di-O--D-glucopyranoside, isolated from flowers of Butea monosperma, are reported here for the first time. Butrin was hydrolyzed using b-glucosidase to butin in high yield. They were subjected to free radical scavenging test using 2,2-diphenyl-1-picrylhydrazyl (DPPH) spectrophotometric assay. At a dose of 4 × 10^-8 mol of tested compounds, the percentage of reduced DPPH for butin was 14.5% while no reduction was observed for butrin (0%).     

Synthesis and properties ofN′-(phosphorylalkyl)diazeneN-oxides

A method has been developed for the synthesis ofN-(phosphorylalkyl)diazeneN-oxides based on the reaction of nitroso compounds with dialkyl (-aminoalkyl)phosphonates in the presence of dibromoisocyanurate. Some chemical properties of the synthesized compounds have been studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1290–1293, July, 1994.     

Intercalation ofn-alkylamines into α-titanium phosphate from aqueous solutions

The intercalation reactions betweenn-alkylamines and -titanium phosphate in aqueous media have been investigated. The compounds with the maximum intercalation have the formula -Ti(HOPO₃)₂ · 2 C _n H _2n+1 NH₂ · H₂O (n=1–10). Defined crystalline phases with lower amine content are described, the general formula being -Ti(HOPO₃)₂ · _m C _n H _2n+1 NH₂ ·pH₂O (m=1.0 1.3, 1.5, 1.7). Whenm=1.0 then-alkylamines form a monomolecular layer. Whenm>1.0 the layer is bimolecular. The inclination angle and the packing density of then-alkylamines in the interlayer space is determined.     

The crystal structure of the inclusion complex of cyclomaltoheptaose (β-cyclodextrin) with 3,5-dimethylbenzoic acid

The crystal of theCD-3,5-dimethylbenzoic acid inclusion complex is triclinicP1 witha=15.707(3),b=15.694(3),c=15.999(3) Å, =101.502(5),=101.557(5), =103.805(4)°,V=3624 ų, andZ=1. Two crystallographically independentCD molecules form a dimer by means of hydrogen bonds between secondary hydroxyl groups in which disordered guest molecules in six orientations are accommodated. In two of them the guest molecules are situated at the dimer interface, their carboxyl groups interacting with the carboxyl groups of two other guest orientations that are found on either side of the monomer cavity. In the two last orientations the guest molecules enter the monomer cavities in an opposite sense with the carboxyl groups protruding from the primary side and are stabilized by cyclodextrin hydroxyl groups. A dense water network is formed in the interdimer space consisted of 18.2 water molecules distributed over 24 sites. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82175 (61 pages).Dedicated to Professor József Szejtli.     

1α-Acetoxy-11β(H),13-dihydrodouglanin, a New Eudesmanolide from Artemisia lehmanniana

A new sesquiterpene lactone, 1-acetoxy-11(H),13-dihydrodouglanin, was isolated fromArtemisia lehmanniana.The structure was established by spectral data and an x-ray analysis.     

Inclusion complexes of proteins: Interaction of cyclodextrins with peptides containing aromatic amino acids studied by competitive spectrophotometry

The stability constants were measured of inclusion complexes formed from aromatic amino acids and their oligopeptides with - and-cyclodextrin, hydroxypropyl-cyclodextrin, and partially methylated-cyclodextrin. The method of competitive spectrophotometry withp-nitrophenol as a competing reagent was used, and measurements were made at pH 7.4-Cyclodextrin formed complexes of higher stability than the other hosts. The stability of complexes of oligopeptides containing L-phenylalanine was invariably higher than that of L-phenylalanine itself. A model for interaction of proteins with cyclodextrins is proposed, in which the most stable complexes are formed when the native functional form of proteins is unfolded and the nonpolar residues that are buried inside the structure are exposed to water. The complexation of the unfolded structure favors its formation; thus thermal denaturation of proteins is easier in the presence of cyclodextrins. On the other hand, this complexation prevents the intermolecular association of unfolded structures by noncovalent hydrophobic bonding between the exposed nonpolar residues; furthermore, the unfolded complexed forms may revert to the native functional form. This prevention of intermolecular association may explain the stabilizing effect of cyclodextrins on solutions of proteins: a return to the native form is achieved more easily from the complexed, unfolded form than from the unfolded, aggregated forms.Dedicated to Professor József Szejtli.     

Synthesis, Spectral and Structural Study of N-[1-(N,N,N′,N′-Tetramethylphosphoramidoyl)- 1H-Benzimidazol-2-yl]-Propionimidic Ethyl Ether

The preparation of N-[1-(N,N,N,N-tetramethylphosphoramidoyl)-1H-benzimidazol-2-yl]-proponimidic ethyl ester 2 has been achieved by the reaction of N-(1H-benzimidazol-2-yl)-proponimidic acid ethyl ester 1 with N,N,N,N-tetramethylchlorophosphoramide. The structure of compound 2 has been determined by X-ray diffraction. The results of (¹H, ¹³C, ³¹P) NMR, IR, EI-MS spectral data are consistent with those obtained from the X-ray diffraction. The compound crystallizes in the triclinic system, following the EsZ conformation. In the crystal, there are two weak C3–H3s1 and C15–H15sO1 intermolecular hydrogen bonds.     

Synthesis of phosphorus (silicon,tin)-containing derivatives of mercaptoketenes and some of their properties

Some newS-phosphorylated,S-silylated, andS-stannylated derivatives of -mercaptoketones were obtained. The reactions of some of these compounds induced by the temperature and by molecular oxygen as well as the phosphorylation of the Si- and Sn-containing derivatives were studied.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 353–357, February, 1995.     

A thermodynamic and structural study of the interactions of pyridino- and diketopyridino-18-crown-6 ligands with some primary organic ammonium cations

Equilibrium constant (K), enthalpy change (H), and entropy change (S) values have been determined calorimetrically at 25°C in 90%MeOH 10%H₂O (v/v) for the interactions of pyridino-18-crown-6 (P18C6) and diketopyridino-18-crown-6 (K₂P18C6) with perchlorate salts of ammonium, benzylammonium,-phenylethylammonium,-phenylethylammonium, and-(1-naphthyl)ethyl-ammonium cations. The crystal structure of the complex of P18C6 with benzylammonium perchlorate was determined by X-ray crystallography. The¹H 1D and 2D NMR spectra of some of these complexes were used to elucidate their structural features in solution. The logK values for the interaction of the ammonium cations with P18C6 are larger than those with K₂P18C6, probably due to the higher degree of structural flexibility of P18C6. Ligand K₂P18C6 displays appreciable - interaction with the-(1-naphthyl)ethylammonium cation, but not with the-phenylethylammonium cation.- interaction between ligand and cationSupplementary Data relating to this article are deposited with the British Library as Supplementary Publication No SUP 00000 (22 pages)     

Synthesis of thermostable aliphatic alkylene-bis(N-phenyl aldonitrones)

A general method for the synthesis of alkylene-bis(N-phenyl aldonitrones) (bisnitrones) by reaction of dianions ofN,N-bisnitroacetyldiamines with nitrobenzene in DMF was proposed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2588–2590, October, 1996.     

Complex formation of some nonionic surfactants with hydroxypropyl-β-cyclodextrin and with heptakis (2,6-di-O-methyl)-β-cyclodextrin

The interaction of six nonionic surfactants -[4-(1,1,3,3-tetra-methylbutyl)phenyl]--hydroxypoly(oxy-1,2-ethanediyl) with hydroxypropyl--cyclodextrin (HPCD) and dimethyl--cyclodextrin (DIMEB) was studied by reversed-phase thin-layer chromatography in the presence and absence of sodium chloride. Each surfactant formed complexes with both cyclodextrin derivatives; however, the strength of interaction varied considerably. DIMEB formed more stable inclusion complexes with the surfactants than did HPCD. A longer ethyleneoxide chain decreased the strength of interaction, whereas sodium chloride exerted a negligible impact. Principal component analysis indicated that both the hydrophobicity and the specific hydrophobic surface are of the surfactant influenced the complex formation indicating the hydrophobic character of the interaction.Dedicated to Professor József Szejtli.     

Topological effect on MO energies,IV. The total π-electron energy ofS- andT-isomers

A novel general property of theS- andT-isomers (a concept which has been introduced and elaborated elsewhere^{1, 2}) of alternant hydrocarbons is demonstrated, namely that due to the HMO total -electron energy theS-isomer should always be more stable than theT-isomer. Some other classes of conjugated isomers are also constructed, for which similar inequalities are derived.

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Topologischer Effekt bei MO-Energien, 4. Mitt.: Die -Elektronen-Gesamtenergie vonS- undT-Isomeren

Zusammenfassung Es wird allgemein gezeigt, daß bei einemS-T-Isomerenpaar (beschrieben in^{1, 2}) eines alternierenden Kohlenwasserstoffes infolge der HMO -Elektronen-Gesamtenergie dasS-Isomere stets stabiler sein sollte als dasT-Isomere. Weitere Klassen konjugierter Isomere werden konstruiert und ähnliche Ungleichungen angegeben.

     

Wavefunction comparisons for the valence-bond model for conjugated π-networks

Approximate ground-state wavefunctions for valence-bond (or Heisenberg) models are obtained both within Néel-state-based and within Kekulé-state-based resonance-theoretic approaches. Comparisons are made between these and other general approaches, with particular emphasis on organic -network systems. Attention is drawn to the manner in which the quality of the different approximation schemes changes with variations in structural characteristics of the system. It is suggested that resonance-theoretic ideas are most appropriate for (aromatic benzenoid) systems with low coordination number, whereas Néel-state based ideas are most appropriate for (3-dimensional) structures with higher coordination number (and little frustration).Work supported by The Robert A. Welch Foundation of Houston, Texas     

An infrared and raman spectroscopic investigation of copper(II) tetracyanonickelate complexes ofα-,β- andγ-picoline

Copper(II) dipicoline tetracyanonickelate complexes, CuL₂Ni(CN)₄ (L=,- or-picoline), have been prepared for the first time and their infrared and Raman spectra are reported. Their structure consists of polymeric layers of {Cu-Ni(CN)₄} with picoline molecules bound directly to the copper. It is proposed that the Cu-NC bonds are in two nonequivalent pairs in trans positions. Low temperature (83K) IR spectra have also been recorded and it is noted that the Ni(CN)₄ group frequencies increase with decreasing temperature while the picoline frequencies are insensitive to temperature.     

Studies on the γ-effects. Part 3. Variations in the γ-effects ofN-substituted benzylamines,o-aminomethylphenols and 3,4-dihydro-2H-1,3-benzoxazines against theE s ′ substituent constants

The magnitude of the -effects on¹³C chemical shifts was studied as function of theN-substitution [Me, Et, Bu, CH₂C₆H₅, CH₂CH₂C₆H₅, Prⁱ, Bu^t, Bu^s, c-C₆H₁₁, CH(CH₃)C₆H₅, Bu^t, or Ph] for several benzylamines,o-aminomethylphenols and 3,4-dihydro-2H-1,3-benzoxazines. A correlation between the _c-values and the steric substituent constants (E _s ) of theN-substituents proved useful in characterizing the variation of the -effects along with the conformational factors. The diastereospecificity of the -effects is discussed for purposes of configurational assignments.For part 2, see Ref. 1. This paper is also Part 5 in the series Studies on the Benzoxazine Series.