bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal and molecular structure of novel 10‐membered ring compound: 10‐Chloro‐1,7‐ditosyl‐8‐phenyl‐4,1,7‐benzoxadiazecine
Authors: Bartczak Tadeusz J. , Kajkowski Tomasz , Trzebiñski Piotr , Mikiciuk‐Olasik Elżbieta , Kotełko Barbara 
Published: January 2005

Abstract10‐Chloro‐1,7‐ditosyl‐8‐phenyl‐4,1,7‐benzoxadiazecine is obtained by reacting the sodium salt of N,N′‐ditosyl‐2‐amino‐5‐chlorobenzhydrylamine with the ditosylate of bis(hydroxyethyl) ether in DMF. The structure of the title compound was established by X‐ray crystal structure analysis. The 10‐membered ring that is the core of the molecule is asymmetric and considerably folded. © 1995 John Wiley & Sons, Inc.
Crystal and molecular structure of cis‐ and trans‐2,4‐dihydroxy‐2,4‐dimethylcyclohexanetrans‐1‐acetic acid γ‐lactone
Authors: Wieczorek Michal W. , Majzner Wieslaw , Sikora Magdalena , Kula Józef 
Published: January 2005

AbstractDuring the transformation process of limonene to tetrahydrofuran derivatives, the title compounds (±)‐(4) have been obtained as crystalline products and subjected to X‐ray analysis. The crystals of trans‐(4) are orthorhombic, space group P212121, with the lattice constants a = 7.0445(5) Å, b = 10.0908(4) Å, c = 14.0309(6) Å; the absolute configuration at atoms C1, C2, and C4 is Rc1, Sc2, and Rc4, respectively. The isomeric form cis‐(4) crystallizes in the monoclinic system, space group P21, with the following unit‐cell parameters: a = 10.8275(4) Å, b = 8.6994(5) Å, c = 16.4722(6) Å, β = 106.515(3)°. The asymmetric part of the unit cell of cis‐(4) contains three independent molecules. Each of these three molecules has the identical absolute configuration at all centers of chirality: Sc1, Sc2, and Rc4. © John Wiley & Sons, Inc.
Synthesis of some new spiroindoline derivatives incorporated with pyrazoloheterocycles
Authors: Al‐Thebeiti Marzoog S. , El‐Zohry Maher F. 
Published: January 2005

AbstractIndole‐2,3‐dione (1) was treated with malonic acid (2) in a mixture of ethanol/pyridine to afford 1‐[3‐(2‐oxoindolinylidene)]acetic acid (3). Compound 3 reacted with thionyl chloride to give the corresponding acid chloride (4). The acid chloride 4 reacted with arenes in the presence of AlCl3 to yield 3‐(2‐oxoindolinylidene)acetophenones 5a–c. Compounds 5a–c reacted with 3‐methylpyrazolin‐5‐one derivatives 6a,b to give 3‐aracyl‐3‐[4′‐(3′‐methylpyrazolin‐5‐onyl)]‐indoline‐2‐one derivatives 7a–f. Compounds 7a–f were treated with phosphorus pentoxide in phosphoric acid, with ammonium acetate or methanolic methylamine and with phosphorus pentasulfide to give spiro[indoline‐3,4′‐(pyrazolo[4,5‐b]pyran)]‐2‐ones 8a–f, spiro[indoline‐3,4′‐(pyrazolo[4,5‐b]‐dihydropyridine)]‐2‐ones 9a–f, 10a–f and spiro[indoline‐3,4′‐(pyrazolo[4,5‐b]thiopyran)]‐2‐ones 10a–f, respectively. All of the synthesized spiroheterocycle derivatives were identified by conventional spectroscopic methods (IR, 1H NMR) and elemental analyses. © John Wiley & Sons, Inc.
Reductive allylation of poly(chlorotrifluoroethylene)
Authors: Taylor Richard T. , Allison Steven , Kamolratanayothin Thanaporn 
Published: January 2005

AbstractTreatment of poly(chlorotrifluoroethylene) with allyltin reagents results in the clean replacement of chlorine by the allyl group under free‐radical–chain conditions (AIBN, allyltributyltin), affording about a 10% degree of functionalization. An improved method using one‐electron reduction of the polymer with cobalt(II) (generated by reduction of chloro(pyridine)bis(dimethylglyoximato)cobalt(III) with Mg) and allyltributyltin gives 50% functionalization. Further modification of the allyl group is realized through hydroboration‐oxidation to the alcohol and subsequent Cr(VI) oxidation to the acid. A mechanistic discussion is provided. © John Wiley & Sons, Inc.
Syntheses and characterization of new (2S)‐2‐hydroxy‐1,4‐oxazin‐3‐ones derived from β‐aminoalcohols
Authors: Mancilla Teresa , De Jesus Rosales Ma. , García‐Baez Efren V. , Carrillo Lourdes 
Published: January 2005

AbstractThe reactions of methyl glyoxylate hemiacetal 1 with 2‐(methylamino)ethanol 2, (1R,2S)‐(–)‐ephedrine 3 and (1S,2S)‐(+)‐pseudoephedrine 4 provide the (2S)‐2‐hydroxy‐1,4‐oxazin‐3‐ones 2a, 3a, 4a in good yield. They were characterized by 1H, 13C, NMR, and infrared and mass spectroscopy. The structures of 2a and 3a were established by X‐ray diffraction. The configuration of C2 (S) is demonstrated by 1H NMR data and confirmed for compounds 2a and 3a by single‐crystal X‐ray diffraction studies. © John Wiley & Sons, Inc.
Acid‐Induced cyclotrimerization of a phosphaalkyne with formal incorporation of water [1]
Authors: Mackewitz Thomas W. , Bergsträßr Uwe , Leininger Stefan , Regitz Manfred 
Published: January 2005

Abstracttert‐Butylphosphaacetylene 1 can be cyclotrimerized with incorporation of water to furnish the 1,2,4‐triphosphabicyclo[2.1.1]hex‐2‐ene 5 in the presence of trifluoroacetic acid. This novel bicyclic system has been fully characterized by spectral and analytical data. The constitution of 5 has been unambiguously demonstrated by X‐ray crystallography. © John Wiley & Sons, Inc.
Crystal and molecular structure of cyclic sulfoxides: 2‐cyano‐2‐ethoxycarbonyl‐3,6‐dihydro‐4,5‐dimethyl‐2H‐thiapyran 1‐oxide and 2‐phenyl‐2‐methoxycarbonyl‐3,6‐dihydro‐2H‐thiapyran 1‐oxide
Authors: Wieczorek Michał W. , Błaszczyk Jarosław , Dziuba Błażej , Kiełbasiński Piotr , Mikołajczyk Marian , Zwanenburg Binne , Rewinkel Johannes B. M. 
Published: January 2005

AbstractCrystal and molecular structures of the title compounds 1b and 1c have been determined by the X‐ray method. Crystals of 1b are monoclinic, space group P21/c, and crystals of 1c are orthorhombic, space group P212121. The sulfinyl oxygen atom and the alkoxycarbonyl group in both compounds are trans oriented, and the six‐membered rings adopt a sofa conformation. The differences between conformation, bond lengths, and angles in the compounds investigated are discussed. © John Wiley & Sons, Inc.
Characterization of molecular orbitals by counting nodal regions
Authors: Hatano Yasuyo , Yamamoto Shigeyoshi , Tatewaki Hiroshi 
Published: January 2005

AbstractThe number of nodal regions can be used as an index for characterizing molecular orbitals. A computer program has been developed to count the number of nodal regions, based on the labeling and contraction algorithms. This program is applied to the water molecule, the hydrogen sulfide molecule, the hydrogen atomic orbitals, the Rydberg excited states of ethylene, dissociation of carbon monoxide, and CASSCF calculations of formaldehyde. Because the number of nodal regions is independent of the coordinate system, the method is applicable even when the molecular structure changes drastically as in bond rotation or bond elongation. Changes of nodal regions with bond elongation are investigated for carbon monoxide. A prescription for problems arising with basis set expansion techniques is also given. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 325–333, 2005
The measure of wear in N‐vinyl pyrrolidinone (NVP) modifed glass‐ionomer cements
Authors: Yamazaki Tomoko , Brantley William , Culbertson Bill , Seghi Robert , Schricker Scott 
Published: January 2005

AbstractGlass‐ionomer cements (GICs) are very useful and important as a dental restorative material because of their unique properties, such as adhesion to moist tooth structure and base metals, long‐term fluoride release that inhibits recurrent caries, thermal expansion coefficient that closely matches tooth structure, biocompatibility and low cytotoxicity. Poor mechanical properties, however, have prevented wider clinical use of these materials. Recent advances have shown that the use of NVP as a co‐monomer in the glass‐ionomer polyacid can improve mechanical properties. This work will focus on the synthesis of four NVP modified polyacids and the evaluation of their mechanical properties and wear properties. There is no significant difference between the wear of a commercial glass‐ionomer (Fuji IX) and the four experimental materials. However, the attrition component of wear appears to correlate well with the measured mechanical properties. Copyright © 2005 John Wiley & Sons, Ltd.
Electrical characterization of organic based transistors: stability issues
Authors: Gomes Henrique L. , Stallinga Peter , Dinelli Franco , Murgia Mauro , Biscarini Fabio , de Leeuw Dago M. , Muccini M. , Müllen K. 
Published: January 2005

AbstractAn investigation into the stability of metal insulator semiconductor (MIS) transistors based on α‐sexithiophene is reported. In particular the kinetics of the threshold voltage shift upon application of a gate bias has been determined. The kinetics follow a stretched‐hyperbola type behavior, in agreement with the formalism developed to explain metastability in amorphous–silicon thin film transistors. Using this model, quantification of device stability is possible. Temperature‐dependent measurements show that there are two processes involved in the threshold voltage shift, one occurring at T≈220 K and the other at T≈300 K. The latter process is found to be sample dependent. This suggests a relation between device stability and α‐sexithiophene deposition parameters. Copyright © 2005 John Wiley & Sons, Ltd.
Nanocomposite systems based on unsaturated polyester and organo‐clay
Authors: Mironi‐Harpaz I. , Narkis M. , Siegmann A. 
Published: January 2005

AbstractUnsaturated polyester (UP) systems give rise to numerous possible approaches in synthesizing nanocomposites. A simultaneous mixing method was used to synthesize UP‐resin/organo‐clay nanocomposites. The effects of various mixing processes, using several organically‐modified clay types, were investigated. The incorporation of these organo‐clays resulted in an intercalated structure, the extent of which depended mainly on the type of the clay organic treatment. Organo‐clays that exhibited the highest intercalation levels were further studied using a sequential mixing method. The UP‐alkyd (without styrene) was mixed with different organo‐clays. Processing parameters such as mixing modes, applied shearing levels, clay contents, and mixing‐temperatures were investigated. Prolonged high shear levels promoted the intercalation and exfoliation of the silicate layers, resulting in a better dispersion of clay particles. The high shear levels effects were achieved by vigorous mechanical mixing and were intensified by using large amounts of clay and optimized matrix viscosity. Rheological studies of the nanocomposites were found complementary and in correlation with morphological and thermal characterization. This methodological approach provides a basis for understanding the structuring processes involving the formation of the UP/clay nanocomposites and establishing materials‐processing‐structure interrelations. Polym. Eng. Sci. 45:174–186, 2005. © 2005 Society of Plastics Engineers.
Diamine coupling of maleic‐anhydride‐ modified polyethylene
Authors: Colbeaux Aimeline , Fenouillot Françoise , Gerard Jean‐François , Taha Mohamed , Wautier Henri 
Published: January 2005

AbstractThe efficiency of the diamines 1,12‐diaminododecane (C12N2) and (4,4′‐methylene)bis(2,6‐diethylaniline) (MDEA) used as coupling agents for maleic‐anhydride‐grafted polyethylene (PEgMA) was compared. The effect of the miscibility of the diamines on the course of the reaction with PEgMA was investigated. The reaction in the molten state with the functional PE was run at 150 °C in an internal mixer and the resulting modified PE was characterized. The coupling agents reacted very fast, especially the aliphatic diamine. The MDEA was slower. Moreover, the reaction of the latter with the anhydride functions was not total owing to its immiscibility with PEgMA. With C12N2, the NH2‐to‐anhydride‐function stoichiometry leading to the higher degree of coupling was 2, indicating that the imide ring was not formed at this temperature. In this case, the coupling of the PEgMA chains resulted in a highly branched structure characterized by a high viscosity of the molten polymer and a substantial insoluble PE‐rich fraction. Copyright © 2005 Society of Chemical Industry
Structure of radical intermediates appearing in the grignard reaction of monoketones
Authors: Maruyama Kazuhiro , Katagiri Toshimasa 
Published: January 2005

AbstractThe structure of radical intermediates appearing in the reactions of MeMgBr with aromatic monoketones was investigated by using ESR and visible spectroscopy. Stable radical intermediates in the reacting solutions were assigned to the dimeric radical ion pairs.
Effect of cosolvent additives on relative rates of photooxidation on semiconductor surfaces
Authors: Sackett Debra D. , Fox Marye Anne 
Published: January 2005

AbstractThe effect of solvent additives on the course of TiO2 photocatalyzed oxygenation of α‐methylstyrene has been studied. While the addition of small amounts of nonhalogenated alcohols to TiO2 powders suspended in acetonitrile was found to decrease the rate of photooxygenation, added halogenated alcohols increase the rate of reaction. In addition, the solvent additives affect the observed product distribution.
The effect of hydrophobic‐lipophilic interactions on chemical reactivity. 11. The dependence of the wrapping‐up capability of sodium carboxymethylamylose on its degree of substitution
Authors: Jiang Xi‐Kui , Li Xing‐Ya , Huang Bang‐Zhou 
Published: January 2005

AbstractThe dependency of the wrapping‐up capability of sodium carboxymethylamylose (NaCMA) on its degree of substitution (D. S. = 0·00, 0·12, 0·18, 0·24, 0·29, 0·35 and 0·41) have been studied, using two guest species, iodine and cetyl‐trimethylammonium bromide (CTAB). The λmax values of NaCMA‐iodine helical inclusion complexes decrease with increasing D. S. values and the amounts of encapsulated iodine by NaCMA as measured by amperometric titrations also decrease with increasing D. S. values. With CTAB as the substrate, the largest number of binding sites, n, and the dissociation constants Kd have been determined by the method of surface tension versus the CTAB concentration plots. The results show that n decreases while Kd increases with increasing D. S. values. All these observations point to the fact that the wrapping‐up capability of NaCMA decreases with increasing degrees of substitution. The results are discussed in terms of host‐guest and host‐solvent hydrophobic‐lipophilic interactions as well as intramolecular hydrogen‐bonding.
The Effect of hydrophobic‐lipophilic interactions on chemical reactivity. 12. Mechanistic investigations of NaCMA‐catalyzed hydrolysis of esters
Authors: Jiang Xi‐Kui , Li Xing‐Ya , Huang Bang‐Zhou 
Published: January 2005

AbstractThe dependence of the catalytic efficiencies of sodium carboxymethylamylose (NaCMA) for the hydrolysis of N‐lauryl‐3‐acetoxypyridinium iodide (1) and p‐nitrophenyl dodecanoate (3) on its degree of substitution (D. S. = 0·00, 0·12, 0·18, 0·24, 0·29 and 0·35) and on the pH values of the solutions (pH = 7·32, 7·80, 8·10 and 9·30) have been studied. At fixed D. S. values, the observed hydrolysis rates of 1 and 3 increase with increasing concentrations of NaCMA and follow saturation kinetics. At fixed concentration of NaCMA, the rates increase with decreasing D. S. values until they reach maxima at D. S. = 0·00. Furthermore, at any D. S. value the catalytic efficiency increases with increasing pH values of the solutions. All these results indicate that the hydroxyl groups are actually the principal catalyzing groups.
Reaction branching as a mechanistic alternative to tunneling in explaining anomalous temperature‐dependencies of kinetic isotope effects
Authors: Thibblin Alf 
Published: January 2005

AbstractThe temperature‐dependence of the kinetic isotope effects for branched reactions proceeding via a common intermediate has been simulated by calculations. It is shown that, under certain conditions, anomalously small isotope effects on the Arrhenius preexponential factors, as well as unusually large observed isotope effects, may originate from the branching.
Participation of beta carbon‐silicon bonds in the development of positive charge in five‐membered rings
Authors: Lambert Joseph B. , Wang Gen‐Tai 
Published: January 2005

AbstractThe development of positive charge β to silicon in a saturated five‐membered ring has been studied in the cis‐ and trans‐2‐(trimethylsilyl)cyclopentyl trifluoroacetates. The cis substrate solvolyzes in 97% trifluoroethanol at 25° C about 5 times faster than the analogous six‐membered ring, after correction for differences in ring strain. The trans substrate solvolyzes about 360 times more slowly than the analogous six‐membered ring. These changes are in agreement with a hyperconjugative mechanism for interaction between the silyl group and the developing positive charge. The expected cosine‐squared dependence of hyperconjugation on the SiCCX dihedral angle suggests that the cis dihedral angle is reduced somewhat from the 60° in the six‐membered ring, and the trans dihedral angle is reduced substantially from the 180° in the six‐membered ring.
Ab initio Mo calculations on the rearrangements of 7‐oxa‐2‐bicyclo[2.2.1]heptyl cations. The facile migration of acyl group in wagner‐meerwein rearrangements
Authors: Carrupt Pierre‐Alain , Vogel Pierre 
Published: January 2005

AbstractAb initio STO‐3G and 6‐31G minimized geometries of 5‐oxo‐ (9), 6‐oxo‐7‐oxabicyclo[2.2.1]hept‐2‐yl cation (12) and 7‐oxabicyclo[2.2.1]hept‐2‐yl cation (15) were obtained. The energy barriers for their Wagner‐Meerwein rearrangements to the more stable 5‐oxo‐ (11), 6‐oxo‐3‐oxabicyclo[2.2.1]hept‐2‐yl (13) and 3‐oxabicyclo[2.2.1]hept‐2‐yl (17) cations, respectively, have been evaluated and compared with those calculated for the rearrangement of the 5‐oxo (18) and 6‐oxobicyclo[2.2.1]hept‐2‐yl cations (20). In agreement with experimental data, the ‘true migratory aptitude’ of an acyl group is higher than that of β‐oxoalkyl group in competitive Wagner‐Meerwein rearrangments that are ‘energetically unbiased’. The ease of the acyl group 1,2‐shift toward an electron‐deficient center is related to the electron‐donating ability of the carbonyl group due to favorable n(CO) ⟷ σ σ ⟷ p(C+) hyperconjugative interaction.
Ion pairs in solvolysis reactions. Kinetic deuterium isotope effects for deprotonation of carbocation intermediates in aqueous solvent
Authors: Thibblin Alf 
Published: January 2005

AbstractSolvolysis of 2‐X‐2‐phenylpropane (1‐X) in 25 vol% acetonitrile in water at 25°C produces 2‐hydroxy‐2‐phenylpropane (1‐OH) and 2‐phenylpropene (3). The carbocationic intermediate discriminates between different nucleophiles; azide anion, acetate anion, and methanol are more efficient nucleophiles than water, k/k = 42 kOAc/k = 3, and kMeOH/k = 2·9 (ratio of second‐order rate constants). The fraction of the elimination product 3 increases with increasing basicity of the leaving group X as well as by addition of general bases. The Brønsted parameter for this catalysis is small, β = 0·13, with substituted acetate anions. The kinetic deuterium isotope effect for the dehydronation of the intermediate has been measured (assuming the reaction from intermediate to alcohol is insensitive to isotopic substitution) employing the hexadeuterated substrate d6‐1‐X as k/k = 3·5 ± 0·2 for the chloride 1‐Cl with acetate anion, and, without added base, 3·1 ± 0·2 for the acetate 1‐OAc, and 3·1 ± 0·2 for the p‐nitrobnzoate 1‐PNB, respectively, and ∼5 for the protonated methyl ether 1‐OMeH+. The variation in isotope effect with change in leaving group is discussed in terms of elimination from contact ion pairs and ‘free’ carbocation. The overall kinetic isotope effect for the solvolysis was found to be k/k = 1·31 (1‐OMeH+), 1·38 (1‐OAc), 1·40 (1‐PNB), and 5·7 (1‐OH). These isotope effects consist of the isotope effect k/k for the formation of the substitution product 1‐OH and k/k for production of the olefin 3. It is concluded that the latter isotope effect is enlarged owing to a branched mechanism in which the deprotonation of the carbocationic intermediate competes with formation of the substitution product. As large an isotope effect as k/k ∼6·5 has been measured for 1‐OMeH+.
The use of IR spectroscopy to monitor the conversion of matrix isolated phenylacetyl chloride to phenylacetyl cation, without decarbonylation to benzyl cation
Authors: Jarret Ronald M. , Sin Ny , Ramsey Timothy , Saunders Martin 
Published: January 2005

AbstractIR spectroscopy is presented as a convenient means to monitor the formation of acyl (and alkyl) cations from corresponding acid chlorides, with Lewis acids at low temperature in the solid state. Phenylacetyl chloride is co‐deposited (under vacuum at −173°C with antimony pentafluoride on a KBr window), as in the ‘molecular beam’ method of cation generation. The initial IR spectrum of the deposition shows (in addition to starting materials) that a small amount of phenylacetyl cation (2274 cm−1) has been formed. Warming the solid matrix to −123°C Promotes the smooth conversion of acid chloride to acyl cation. Ultraviolet irradiation (through quartz windows) at −123°C to −73°C facilitates this conversion but does not result in the loss of carbon monoxide from the acyl cation to form benzyl cation. When benzyl chloride is used in place of phenylacetyl chloride, there is no noticeable difference between IR spectra taken before and after warming and/or photolysis of the solid deposition.
Twisted internal charge transfer emission in B,B‐bis(mesityl) pyrroloboranes
Authors: Brittelli David R. , Eaton David F. 
Published: January 2005

AbstractSpectral characteristics of several simple substituted B,B‐bis(mesityl)pyrroloboranes are reported which support a theoretical treatment by Bonacic‐Koutecky and Michl (J. Am. Chem. Soc. 107, 1765 (1985)) describing the excited states of simple aminoboranes as an example of twisted internal charge transfer. In the aminoboranes the pyrrolo moiety functions as the electron donor group and the empty p‐orbital of the boron atom as the acceptor.
Gas phase reactivities of isomeric ions: Methylenediphenylcyclopropane and diphenylmethylenecyclopropane
Authors: Pineda C.‐J. , Roth H. D. , Mujsce A. M. , Schilling M. L. , Reents W. D. 
Published: January 2005

AbstractGas phase ion/molecule reactions have been used to probe the structure of ions obtained by electron impact upon 1‐(diphenylmethylene)cyclopropane and 2,2‐diphenyl‐1‐methylenecyclopropane. The resulting ions of molecular composition C16H14 (m/z 206+) were reacted with charge transfer reagents (6·9 < IP < 8·8eV), giving evidence for the presence of isomeric ions with different reactivities. The less reactive ion is identified as a trimethylenemethane species (TMM+) in which one cyclopropane bond is broken; the more reactive ions are assigned as vertical ions in which the cyclopropane ring is unaffected. The vertical ions have recombination energies of 8·44 ± 0·05eV, whereas TMM+ has one of 7·41±0·05eV. The TMM+ fraction is not constant; it increases with increasing IP of the reagent. This is attributed to a reagent‐catalyzed isomerization of the vertical ion to TMM+. In addition, the reagent ions are observed to undergo a unique reaction with the neutral methylenecyclopropane derivatives: electron transfer and ring opening to yield TMM+. These findings limit the application of the customary equilibrium measurements as a method to determine the substrate IP.