Triterpene Glycosides of Tragacantha Stipulosa and Their Genins. Structures of Askendosides G and D and Cycloglobiceposide B from One- and Two-Dimensional 1H and 13C NMR Spectroscopy

Roots of Tragacantha stipulosa Boriss yielded three triterpene glycosides of the cycloartane series: askendoside G (1), askendoside D (2), and cycloglobiceposide B (3). Glycoside 1 is 3-O--L-arabinopyranosyl-(12)--D-xylopyranoside; 16-O--D-glucopyranoside-24R-cycloartan-3,6,16,24,25-pentaol; 2 - 3-O--L-arabinopyranosyl-(12)--D-xylopyranoside; 6-O--D-xylopyranoside-20R,24S-epoxycycloartan-3,6,16,25-tetraol; 3 - 3-O--D-xylopyranoside; 16-O--D-glucopyranoside; 25-O--D-glucopyranoside-24R-cycloartan-3,6,16,24,25-pentaol.     

Synthesis of γ- dihydropyrones and β- dihydrofuranones on the basis of acetylenic γ- and δ-keto alcohols and acetals of γ- and δ-formyl alcohols

Acetylenic - and -keto alcohols and acetals of acetylenic - and -keto alcohols and acetals of acetylenic - and -formyl alcohols undergo cyclization to -dihydropyrones and -dihydrofuranones under the influence of acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1471–1473, November, 1976.     

Prediction of the non-Newtonian viscosity and shear stability of polymer solutions

The structure-property relationships derived here permit the prediction of both the zero-shear viscosity ₀, as well as the shear rate dependent viscosity . Using this molecular modeling it is now possible to predict over the whole concentration range, independently of the molecular weight, polymer concentration and imposed shear rate. However, the widely accepted concept: dilute — concentrated, is insufficient. Moreover it is necessary to take five distinct states of solution into account if the viscous behavior of polymeric liquids is to be described satisfactorily. For non-homogeneous, semi-dilute (moderately concentrated) solutions the slope in the linear region of the flow curve (= must be standardized against the overlap parameterc · []. As with the ₀-M-c-relationship, a-M -c- relationship can now be formulated for the complete range of concentration and molecular weight. Furthermore, it is possible to predict the onset of shear induced degradation of polymeric liquids subjected to a laminar velocity field on the basis of molecular modeling. These theoretically obtained results lead to the previously made ad hoc conclusion (Kulicke, Porter [32]) that, experimentally, it is not possible to detect the second Newtonian region.Roman and Italian symbols a exponent of the Mark-Houwink relationship - b exponent of the third term of the ₀-M -c relationship - c concentration /g · cm^–3 - E number of entanglements per molecule - F(r) connector tension - f function - G _i ^A shear modulus; A indicates that it /Pa has been evaluated by a transient shear flow experiment; i is the shear rate to whichG ^A refers to - G storage modulus /Pa - G _p plateau modulus /Pa - H() relaxation spectrum /Pa - h shift factor (₀/_r) - K _H Huggins constant - K _b third constant of the ₀-M -c relationship - K constant of the Mark-Houwink relationship - M molecular weight /g · mol^–1 - M _e molecular weight between two /g · mol^–1 entanglement couplings - N number of segments per molecule - n slope in the power-law region of the flow curve - p p-th mode of the relaxation time spectrum - R gas constant /8.314 J·K^–1·mol^–1 - r direction vector - T temperature /K Greek symbols ß reduced shear rate - shear rate /s^–1 - shear viscosity /Pa·s - _s solvent viscosity /Pa·s - _sp specific viscosity - ₀ zero-shear viscosity /Pa·s - apparent viscosity at shear rate - reduced viscosity - viscosity of polymeric liquid in /Pa·s the second Newtonian region - [] intrinsic viscosity/cm³·g^–1 - screening length/m - /g·cm ^–3 density - relaxation time/s - ₀ experimentally derived relaxation time/s - angular frequency of oscillation Indices conc concentrated - corr slope corrected - cr critical - deg degradation - e entanglement - exp experimental - mod moderately concentrated/semi-dilute - n number average - p polymer - R Rouse - rep reptation - s solvent - sp specific - theo theoretical - weight average - relaxation time - o experimental or steady state - * critical - ** transition moderately conc. — conc. - + transition dilute — moderately cone. Paper presented at the 2nd bilateral U.S.-West German Polymer Symposium, Yountville, the 7th–11th September 1987.     

Condensation of aldehydes and ketones

The alkaline condensation of -aceto-and -propionaphthalenes with furfural has given, respectively, 2-(-furfuryl)-1, 3-di(-naphthoyl)-propane and 3-(-furyl)-2,4-di(-naphthoyl)pentane; both -diketones have also been obtained by the Michael condensation. Under more severe conditions, two molecules of furfural condense with three molecules of -acetonaphthalene to form 2, 4-di(-furyl)-1, 3, 5-tri(-naphthoyl)pentane. Under similar conditions, benzaldehyde exhibits only a feeble capacity for triketone condensation with -acetonaphthalene. The condensation of -propionaphthalene with furfural has given the new compound furylidenepropionaphthalene. It has been shown that both under the conditions of the improved Chichibabin pyridine synthesis and under the conditions of the Leuckhardt reaction, 3-(-furyl)-1, 3-di(-naphthoyl)propane gives 4-(-furyl)-2, 6-di(-naphthyl)pyridine.     

Kinetics and mechanism of the hydrolysis of sodium carboxymethylcellulose (Na-CMC) by a cellulase complex

TheSomogyi-Nelson colorimetric method is applied in a new manner more suitable for evaluating the kinetics of the enzyme hydrolysis of sodium carboxymethylcellulose (Na-CMC) catalyzed by the cellulase complex. By means of selective inhibition of a chosen enzyme from the cellulase complex it became possible to trace the effect of the other enzymes included in its composition.

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Kinetik und Mechanismus der Hydrolyse von Natriumcarboxymethylcellulose (Na-CMC) durch einen Cellulase-Komplex

Zusammenfassung Die kolorimetrische Methode nachSomogyi undNelson wird nach einem neuen Verfahren zur Verfolgung der Kinetik der hydrolytischen Spaltung von Natriumcarboxymethylcellulose (Na-CMC), katalysiert durch den Cellulase-Komplex, angewandt. Durch selektive Inhibierung eines bestimmten Enzyms des Cellulase-Komplexes kann man die Wirkung der anderen zu seiner gesamten Zusammensetzung gehörenden Enzyme verfolgen.

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Symbols Used E enzyme (E—cellulase;E—exo-cellobiohydrolase;E—-glucosidase) - [E] _w weight concentration of enzymeE - S substrate (Na-CMC—sodium carboxymethylcellulose) - [S]₀ weight concentration of substrateS - I inhibitor (I—lactose;I—calcium chloride;I—condurrite-B-epoxide) - P product (P—oligosaccharides;P—cellobiose;P—D-glucose) - P end product (K , K , K ) - DP degree of polymerization - DS degree of substitution - ES enzyme-substrate complex (E S, E S, E S) - EP enzyme-product complex (E P, E P) - EI enzyme-inhibitor complex (E I, E I, E I) - M _s molecular mass of substrateS - K _s substrate constant (K _s , K _s , K _s ) - K _I inhibitor constant (K _I , K _I , K _I ) - K _m Michaelis-Menten constant - k ₊₁,k ₊₂ (k ₊₂ ,k ₊₂ ,k ₊₂ ) forward rate constants - k _–1 reverse rate constant - ₀ initial rate of reaction - V maximal reaction rate - A change in absorbance - molar absorption coefficient - wavelength Herrn Prof. Dr.Hans Tuppy zum 60. Geburtstag herzlichst gewidmet.     

Symmetry and other properties of second-order phenomenological coefficients and thier significance in a chemical system

Using a second-order phenomenological equationJ _i = _j L _ij X_j + _{j, k} L _ijk X_j X_kand assuming that the system is at a state near equilibrium, it has been shown that the symmetry ofL _ijk is retained with respect to the permutations of suffices i j and k Furthermore, using the second-order flux equations, the thermodynamic stability criterion is expressed. The symmetry is shown to be retained in a reaction scheme representing the emplate model. The significance of the stability criterion as expressed by the higher-order phenomenological coefficients is discussed.     

Kinetics of photoreduction of 9,10-phenanthrenequinone in the presence of amines and polymethylbenzenes

A study of the kinetics of photoreduction of 9,10-phenanthrenequinone in the presence of hydrogen donors (para-substituted N,N-dimethylanilines and polymethylbenzenes) showed that plots of the quantum yield of photoreduction (_H) and apparent reaction rate constant (k _H) vs. oxidation potential of hydrogen donors are extreme. In the presence of amines, k _H and _H increase, as a whole, whereas they decrease in the presence of polymethylbenzenes. In coordinates _H-G _e (G _e is the change in the free energy of electron transfer) for pairs quinone-H donor, _H increases with G _e approaching to zero. For the amine series, this effect is mainly in the exothermic region of G _e (G _e < 0). For the series of polymethylbenzenes, this increase is observed in the endothermic region (G _e > 0).__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2381–2385, November, 2004.     

Thermodynamics of Proton Association of Polyacrylates and Polymethacrylates in NaCl(aq)

Enthalpies of protonation of polyacrylates and polymethacrylates with different molecular weights in aqueous NaCl solutions, 0 I 2 mol-L^–1 were determined by titration calorimetry at 25°C. H values are dependent on both the neutralization degree, , and the molecular weight of polyacids. T S of protonation was obtained using pK values already reported and the present H results. Empirical equations for the dependence on I, , and molecular weight are reported for both H and T S.     

GC-FTIR and GC-MS in odour analysis of essential oils

The analysis of odour components in East Indian Sandalwood Oil (Santalum album L.) and in Patchouli Oil (Pogostemon cablin Benth.) based on GC-, GC-FTIR- and GC-MS-data resulted in the identification of-santalene,-santalal,-santalal, epi--santalal,-santalol,-santalol, (E)--santalol,-bergamotol and spirosantalol in Sandalwood Oil and of (–)-patchoulol,-guaiene,-patchoulene, seychellene,-bulnesene, norpatchoulenol and pogostol in Patchouli Oil as the most intense aroma compounds of these oils.     

Cohesion of crystals and the temperature coefficient of their equilibrium surface pressure

Summary Surface tension _e of mercury in equilibrium with crystals (floating on its surface) of octacosane, 1-hexadecanol, 1-octadecanol, ethyl palmitate, benzophenone and azoxybenzene at 7° is almost equal to that at 23° (measured earlier); also the difference between the surface tension ( ₀) of uncontaminated mercury and _e (i. e., equilibrium surface pressure) is independent of temperature within the limits of the experimental error. This shows that the hypothesis making ₀- _e an analog of the vapor pressure of the solid is incorrect. The relation _e= (=cohesion of the crystal,=thickness of the surface layer of mercury) is in agreement with the negligible temperature coefficient of _e . The calculated is approximately 9 angstroems.

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Zusammenfassung Die Oberflächenspannung _e von Quecksilber im Gleichgewicht mit Kristallen (schwimmend auf der Oberfläche) von Octosane, 1-hexadecanol, 1-octodecanol, Äthylpalmitat, Benzophenon und Azoxylbenzol bei 7 °C ist nahezu gleich der bei23 °C gemessenen. Auch die Differenz der Oberflächenspannung von reinstem Quecksilber ( ₀) und ( _e), d. h. dem Gleichgewichtsobderflächendruck ist unabhängig von der Temperatur innerhalb der experimentellen Fehlergrenze. Dies zeigt, daß die Hypothese, nach der man ₀- _e in Analogie zum Dampfdruck des Festen betrachtet, unkorrekt ist. Die Beziehung _e= (=Kohäsion des Kristalls,=Dicke des Oberflächenfilms auf Quecksilber) ist in Übereinstimmung mit dem vernachlässigbaren Temperaturkoefifzienten von _e. Das berechnete beträgt ungefähr 9 Å.

     

Vibrational isotope effect of linear and planar molecules: Deuterated bromoethenes

Linear (planar) molecules A and B which are identical except for isotopic substitutions at the atomic sites are considered. Stretching (bending, out-of-plane) frequencies _k and normal modes _k of the isotopically perturbed molecule B are expressed in terms of stretching (bending, out-of-plane) frequencies _i and the corresponding normal modes _i of the unperturbed molecule A. Complete specification of the unperturbed normal modes is not required. All that is needed are stretching (bending, out-of-plane) amplitudes | _i of the normal modes _i at those sites that are affected by isotopic substitution. The rule which interlaces frequencies _k of molecule A with frequencies _i of molecule B is derived. Given two isotopic molecules A and B that differ by a single isotopic substitution at site , the inversion relation is derived. This relation expresses unperturbed stretching (bending, out-of-plane) amplitudes at the site in terms of stretching (bending, out-of-plane) frequencies of molecules A and B . As an example, out-of-plane vibrations of deuterated bromoethene were considered. In the simplest method 12 out-of-plane frequencies of four polydeuterated bromoethenes were calculated from 12 out-of-plane frequencies of bromoethene and three monodeuterated bromoethenes. Standard deviation of thus calculated frequencies from experimental frequencies is =2.74 cm^–1. In another method, 15 out-of-plane frequencies of four polydeuterated bromoethenes and selected monodeuterated bromoethene are calculated from 9 out-of-plane frequencies of bromoethene and the remaining two monodeuterated bromoethenes. Depending on which monodeuterated bromoethene is selected (1-, cis- or trans-), standard deviation of thus obtained frequencies from experimental frequencies is 1=2.84 cm^–1, c=2.96 cm^–1 and t=2.72 cm^–1.     

Triterpene Glycosides of Scheffleropsis angkae. IV. Structure of Glycosides L-C2 and L-I2

Two new triterpene glycosides of the -amyrin series, L-C ₂ and L-I ₂ , 27-hydroxyursolic acid 3-O--L-arabinopyranoside and its 28-O--L-rhamnopyranosyl-(14)-O--D-glucopyranosyl-(16)-O--D-glucopyranosyl ester, are isolated from leaves ofScheffleropsis angkae(Araliaceae). The structures of the glycosides are established using chemical methods and NMR techniques ( ¹ H, ¹³ C, ¹³ C-APT, COSY, TOCSY, HSQC, HMBC, and ROESY).     

Isothermic spherulitic growth and the shape of grain boundaries and growth fronts

We investigate experimentally and theoretically the isothermic growth of two spherulites of different modification into a supercooled isotactic polypropylene film. The faster growing-spherulite grows around the-spherulite, and finally the-spherulite is symmetrically and completely included in. In contrast to literature but in agreement with experimental evidence we find that the grain boundary between the teardropshaped-spherulite and the surrounding-spherulite consists of two parts, where one is always an arc of a logarithmic spiral. This-spherulite ends always in a vertex. Its angle depends on the ratio of the two growth rates only. Behind the vertex an intrinsic--grain boundary exists, degenerating to a channel in bulk material. The growth fron of the-spherulite, which ends on the logarithmic spiral or on the intrinsic grain boundary during growth, consists of an arc of a circle continued by an arc of a logarithmic spirial, too.     

Charge monotonicity of atomic systems and radial expectation values

A functionf(r) is monotone of orderp if itspth-derivativef ^(p)(r) fulfils that (–1) ^p f ^(p)(r)0. So, e.g. the monotonicity properties of orderp=0, 1, 2 describe the non-negativity (p=0), the monotonic decreasing from the origin (p=1) and the convexity (p=2) of the function, respectively. Here, the monotonicity properties of the electron functiong _n (r; )=(–1) ^{n (n)} (r)r ^– , 0, of the ground state of atomic systems are analysed both analytically and numerically. The symbol (r) denotes the spherically averaged electron density. First of all, the condition which specifies, if exists, a value _np such thatg _n (r; _np ) be monotone of orderp is obtained. In particular, it is found that ₀₁=max {r(r)/(r)}, ₀₂=max {q ₀(r)}, ₁₁=max {r(r)/(r)} and ₁₂=max {q ₁(r)}, whereq ₀(r) andq ₁(r) are simple combinations of the first few derivatives of (r). Secondly, numerical calculations of the first few values _np in a Hartree-Fock framework for all ground-state atoms with nuclear chargeZ54 are performed. In doing so, the pioneering work of Weinstein, Politzer and Srebrenik about the monotonically decreasing behavior of (r) is considerably extended. Also, it is found that Hydrogen and Helium are the only two atoms having the functions (r), –(r) and (r) with the property of convexity. Thirdly, it is analytically shown that the charge functionr ^– (r) with [(1+4Z ²/I)^1/2–1]/2, I being the first ionization potential, is convex everywhere. Finally, the above mentioned monotonicity properties are used to obtain rigorous, simple and universal inequalities involving three radial expectation values which generalize all the similar ones known up to now. These inequalities allow to correlate various statical and dynamical quantities of the atomic system under study, due to the physical meaning of the radial expectation values. It is worth to remember that some of these expectation values may be experimentally measured in experiments of (e, 2e)-type.     

Effects of pressure and solvent on the diffusion of aromatic compounds through polymers

The diffusion of six azo and five anthraquinone derivatives through nylon 6, poly(ethylene terephthalate) and secondary cellulose acetate films were studied under high hydrostatic pressures of up to 3000 bar and at temperatures 80–130 °C, by analyzing the diffusion profiles yielded in a stacked multiple film, placed in the solution of the diffusant. It was found that the diffusion coefficient,D, of the diffusant decreased with increasing pressure, giving a linear relationship between InD and the pressure, the slope of which gave the activation volume for the diffusion,V . It was revealedV increased linearly with increasing intrinsic molecular volume of the diffusant,V _w , the slopes being different between the azo and the anthraquinone derivatives. The ratio ofV toV _w (V /V _w ) ranged from 0.13 to 0.93, depending in a sensitive manner on the degree of swelling of the polymer matrix which in turn was varied by the solvent. The overall results could be explained in accordance with the formulation,V _{f, local} +V =V _w , whereV _{f, local} represents the free volume contribution. It was proposed thatV _w is increased by solvation when the solvent is good for the diffusant.     

All-valence-electron and transition density matrix calculations of the electronic spectra of [2.2]paracyclophanequinones

The combined CNDO/S and transition density matrix methods reproduced well the UV-VIS spectra of the intramolecular charge-transfer complexes of double- and triple-layered [2.2]paracyclophanequinones in which benzene and p-benzoquinone represent the donor and acceptor layers: DA, DDA and DAD. Calculations pointed to the already known experimental bathochromic shifts of the longest wavelength absorption band for the DADDADAD transformations. The electronic transitions corresponding to this band are for DA and DDA the CT transitions of the ^* type; however, for DAD the band represents the n ^* transition localized on the acceptor ring.     

Semiempirical calculations of singlet-triplet and triplet-triplet transitions

Semiempirical calculations of the PPP-type with optimum values of parameters ( =8.2 eV, ^c=–2.5 eV) reproduce fairly well the singlet-triplet (S-T) and triplet-triplet (T-T) excitation energies and oscillator strengths with conjugated hydrocarbons of various structural types. The usefulness of this parametrization is shown with anthracene. Moreover, the applicability of the Hückel's NV ₁ energies for estimates of the S-T transitions is mentioned.     

Quadrupole polarizability and hyperpolarizability of carbon monoxide

Summary We report a study of the electric dipole-quadrupole (A _,,), quadrupole-quadrupole (C _,,), dipole-octopole (E _,) polarizability and the dipole-dipole-quadrupole (B _,,) hyperpolarizability of carbon monoxide. All values are obtained from finite-field self-consistent field (SCF) and fourth-order manybody perturbation theory (MP4) calculations. Our best values for the dipole-octopole polarizability areE _z,zzz=60.19 andE _x,xxx=–38.06e ² a ₀ ⁴ E _h ^–1 . For the dipole-dipole-quadrupole hyperpolarizability we reportB _zz,zz=–296,B _xz,xz=–170,B _xx,zz=88 andB _xx,xx=–178e ³ a ₀ ⁴ E _h ^–2 .     

Kinetics and mechanism of oxidation of allyl alcohol byN-bromosuccinimide

The kinetics of oxidation of allyl alcohol byN-bromosuccinimide (NBS) has been studied at 35 °C in aqueous medium. The reaction shows first order dependence on bothNBS and allyl alcohol. In fairly high acid concentration, there is no change in the rate of the reaction but at low acid concentration, the rate is considerably enhanced. There is no primary salt effect. At varying mercuric acetate concentrations, the rate constant remains the same. But in the absence of mercuric acetate, the rate is enhanced. The kinetic parameters,E _a,Arrhenius factorA, H, G and S have been calculated. A rate law in agreement with experimental results has been derived. A mechanism is proposed.

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Kinetik und Mechanismus der Oxidation von Allylalkohol mixN-Bromsuccinimid

Zusammenfassung Die Kinetik der Oxidation von Allylalkohol mitN-Bromsuccinimid (NBS) wurde bei 35 °C in wäßrigem Medium untersucht. Die Reaktion zeigt erste Ordnung gegenüberNBS und Allylalkohol. Bei relativ hoher Säurekonzentration zeigt sich keine Änderung der Reaktionsgeschwindigkeit, bei niedriger Säurekonzentration wird die Reaktionsgeschwindigkeit beträchtlich erhöht. Es wurde kein primärer Salzeffekt festgestellt. Bei varriierender Quecksilberacetatkonzentration bleibt die Reaktionsgeschwindigkeit gleich, bei Abwesenheit von Quecksilberacetat wird jedoch die Geschwindigkeitskonstante erhöht. Die kinetischen Parameter,E _a, derArrheniusfaktorA, H , G und S wurden bestimmt. Ein Geschwindigkeitsgesetz in Übereinstimmung mit den experimentellen Befunden wurde abgeleitet und ein Mechanismus vorgeschlagen.

     

Topology of density difference and force analysis

The density difference (r) of a molecule A-B is defined as the difference of the density (r) of the molecule A-B and the density _A(r) + _B(r) put at the position of the atoms A and B. We investigate here the topological features of the density difference and define electron density flow (EDF) as representing the direction and the amount of the electron density flow in the course of the nuclear displacement processes. As such examples, we study H₂ molecule formation reaction and the interaction of two He atoms. By the topological analysis of (r), and by using the Hellmann-Feynman force and its partition into the AD, EC, and EGC forces, the characteristic behaviors of the (r) map are clarified. In particular, the electron cloud preceding and incomplete following are represented by using the concept of the EDF. The natures of the covalent bond are clarified based on the topological properties of the difference density (r) rather than that of the total density (r).On leave from the Department of Chemistry, Hebei Teachers' College, Shijiazhuang, Hebei, 050091, China