bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular and electronic structure of benzeneselenenyl molecules and cations
Authors: BelBruno Joseph J. 
Published: January 2005

AbstractMolecular and electronic structures of a select group of molecules and cations, including benzeneselenenyl chloride, benzeneselenenyl bromide, and benzeneselenol have been studied using ab initio calculations at the Hartree–Fock and MP2 levels of theory. Very few experimental data are available for this class of compounds. The properties and structures of these molecules are compared. © John Wiley & Sons, Inc.
Synthesis of diphosphine dioxides for extraction of actinides using supported liquid membranes technology
Authors: Cristau Henri‐Jean , Mouchet Patrick , Dozol Jean‐François , Rouquette Hélène 
Published: January 2005

AbstractA recurrent method for synthesis of diphosphine dioxides to be used for extraction of actinides from acidic aqueous solution is described. Selective phosphonium salt formation and cleavage permits the stepwise introduction of different bridges between the phosphorus atoms as well as various chains on them. The influence of the structural parameters on liquid‐liquid extraction properties of plutonium, neptunium, and americium is studied. Plutonium and neptunium can be efficiently removed from radioactive contaminated liquid wastes, using the supported liquid membranes technology with the more lipophilic organophosphorus extractants. © John Wiley & Sons, Inc.
X‐Ray spectral determination of the effective charges on phosphorus, sulfur, and chlorine atoms in chemical compounds with a nonempirical charge scale
Authors: Dolenko G. N. , Latajka Z. , Ratajczak H. 
Published: January 2005

AbstractLinear dependence between the experimental Ka line shifts and Mulliken atomic charges obtained by SCF ab initio calculations with 4‐31G, 4‐31G*, and 4‐31G** basis sets for the P, S, and Cl atoms have been found. The electron density redistribution of PCl3 and SPCl3 free ligands on their complexation with AlBr3 has been investigated. It has been shown that a significant transfer of the total ligand electron density to the acceptor is absent, but there is an essential growth of the ionicity of all bonds on complexation. The P = S and PS bond ionicities are found to increase linearly with the growth of the positive charge on the central phosphorus atom. © John Wiley & Sons, Inc.
Pyrazoline derivatives: A convenient synthetic route to new pyrazolo‐benzothia‐(oxa) or diazepinone derivatives
Authors: El Latif Fawi M. Abd 
Published: January 2005

AbstractNew pyrazolo‐[3,4‐b]‐[1,5]‐benzoazepinone derivatives are reported. One pot reactions of 5‐chloro‐4‐carboxy‐1‐phenyl (3‐substituted) pyrazole derivatives with o‐thioaminophenol, o‐phenylenediamine, and o‐aminophenol derivatives were realized. The influences of the polarizability of the heteroatoms on the reaction rates and chemical yields are discussed. © John Wiley & Sons, Inc.
3‐Silanyl‐propenylphosphonates: Properties and alkylation potential
Authors: Probst Michael F. , Modro Tomasz A. 
Published: January 2005

AbstractTwo 3‐silanyl‐propenylphosphonate esters (1a, 1b) were synthesized, and their deprotonation was attempted using RONa/ROH, RLi/THF, and LDA/THF systems. In the first two cases, the nucleophilic addition was the predominant (or exclusive) reaction observed; deprotonation was achieved with LDA, as confirmed by the reaction of the lithiated species with alkylating agents and with benzaldehyde. Chemical behavior of substrates 1 does not parallel closely that of the parent silanyl or phosphoryl‐substituted allylic systems. © John Wiley & Sons, Inc.
Studies with polyfunctionally substituted heteroaromatics: 2‐Phenyl‐4‐p‐tolylhydrazono‐2‐oxazoline‐5‐one as a precursor for the synthesis of substituted 1,2,4‐triazoles and pyridines
Authors: Elnagdi Mohamed Hilmy , Negm Abdalla Mohamed , Erian Ayman Wahba , El‐Kousy Salah 
Published: January 2005

Abstract2‐Phenyl‐4‐p‐tolylhydrazono‐2‐oxazoline‐5‐one (3) was rearranged by the action of phenols and naphthols into 1,2,4‐triazole‐5‐carboxylic esters (5) that were rearranged further on reflux in AcOH‐ZnCl2 into triazolyl ketones (7). Rearrangement of 3 into 1,2,4‐triazole derivatives could also be effected by the action of heterocyclic amines and 1‐naphthylamine. © John Wiley & Sons, Inc.
Stereostructure of 8‐chloro‐5,6‐di(methoxycarbonyl)‐4,7‐dimethyl‐2‐ethoxy‐2‐phosphabicyclo[2.2.2]octa‐5,7‐diene 2‐oxide
Authors: Keglevich György , Tőke László , Böcskei Zsolt , Menyhárd Dóra , Quin Louis D. 
Published: January 2005

AbstractThe first X‐ray structure of a phosphabicyclooctadiene, together with the NMR and mass spectral characterization of its isomers, is reported. © John Wiley & Sons, Inc.
Fluorsulfonylmethylidene sulfur difluoride oxide, FSO2CH  SF2  O
Authors: Henkel Thomas , Seppelt Konrad 
Published: January 2005

AbstractSO3 adds across the CS double bond of H2C  SF4 with formation of 2‐tetrafluoro‐4‐dioxo‐1,2,4‐oxadithietane, which rearranges to fluorsulfonylmethylidene sulfur difluoride oxide, FSO2CH  SF2  O in the presence of CsF. © John Wiley & Sons, Inc.
Geminal conjugation in disulfides
Authors: Dolenko G. N. , Deryagina E. N. , Turchaninova L. P. , Elin V. P. , Basina E. I. , Pavlova T. O. , Voronov V. K. 
Published: January 2005

AbstractSome aspects of the spatial and electronic structure of disulfides XSSX (X = H, Alk, Ph, Hal) are considered. It is shown that the growth of the geminal ns‐σSX* conjugation efficiency leads to a shortening of the SS bond that is more than three times as large as the simultaneous SX bond lengthening. The positive effective charge on the sulfur atom also increases as a result of this conjugation. These effects increase with the growth of ‐ I and + M abilities of the substituents X. The SKa line shifts and the HOMO bonding degree (Delta;nS) have been measured by the X‐ray fluorescence spectroscopy method for dialkyl disulfides (Alk = Me, Et, Pr, i‐Pr, Bu, i‐Bu, t‐Bu, C5H11, C8H17, H2NCH2CH2, CH2CH  CH2, CH2Ph) and S8. With the help of ΔnS values that are proportional to the nS–σSC* conjugation efficiency, the sequence of the enhancement of the geminal conjugation efficiency has been established for the disulfides investigated. In the framework of the nS–σSS* geminal conjugations, the shortening of the SS bonds in S8 is explained. © John Wiley & Sons, Inc.
Protein–protein interactions of a Kvβ subunit in the cochlea
Authors: Sokolowski Bernd , Harvey Margaret , Venkataramu Chinnambally , Duzhyy Dmytro 
Published: January 2005

AbstractAccessory subunits associated with voltage‐gated potassium (Kv) channels can influence the biophysical properties and promote the surface expression of channel‐forming α‐subunits. Previously, we cloned several α‐subunits and a β‐subunit from a cDNA library of the chicken cochlea. In the present study, we raised an antibody against the N‐terminus of chicken Kvβ1.1 (cKvβ1.1) and characterized the Kvβ‐related polypeptide in cochlear tissues and heterologous cells. The anti‐cKvβ1.1 antibody recognizes a 45‐kDa polypeptide in chick cochlear extracts as well as in Chinese hamster ovary (CHO) cells transfected with cKvβ1.1. The accessory subunit was localized to the ganglion cells of the chick cochlea using immunohistochemistry and in situ hybridization. Coimmunoprecipitation studies show that Kvβ1.1 interacts with Shaker channel members Kvα1.2 and 1.3, both of which colocalize with β to the cochlear ganglion cells. Additionally, coimmunoprecipitation studies show that Kvα1.2 and 1.3 interact with each other, suggesting that these ion channels are formed by heteromultimers. In comparison, Kvβ did not coprecipitate with a member of the Shal subfamily. The presence of Kvβ in the cochlea suggests that this subunit contributes to the modulation of auditory signals in the ganglion cells, presumably by regulating properties of inactivation as well as surface expression of Kvα channels. © 2005 Wiley‐Liss, Inc.
Relaxation of drawn Nafion films studied with birefringence experiments
Authors: Heijden P. C. van der , Rosa A. de la , Gebel G. , Diat O. 
Published: January 2005

AbstractThe time dependency of the birefringence and stress of a drawn Nafion film is measured. From shrink and free relaxation experiments, the existence of a reversible regime at small draw ratios and an irreversible regime at large draw ratios is shown. In the frame of a structural model of Nafion as a fibrillar system that has been recently proposed, the existence of bundles of fibrils is used to explain both regimes. Copyright © 2005 John Wiley & Sons, Ltd.
Induced surface migration of biodegradable phosphoryl choline functional poly(trimethylene carbonate)
Authors: Nederberg Fredrik , Bowden Tim , Hilborn Jöns 
Published: January 2005

AbstractIn this article the synthesis, characterization, and surface orientation property of a biodegradable and biomimetic polymer are introduced. This phospholipid mimetic biodegradable polymer is synthesized by combining poly(trimethylene carbonate) (PTMC) with zwitterionic phosphoryl choline (PC) in a three‐step synthesis. Since the glass transition of the polymer is around −20°C this material holds elastic properties at ambient temperature. This characteristic was used to induce surface enrichment as the polar PC end‐group was enriched at the surface while treating films in an aqueous media. Film properties of the PTMC‐PC amphiphile product revealed surface enrichment behavior, as the polar PC head group is oriented towards the surface. In addition, surface depletion of polar PC groups was the result when treating films under vacuum. This was observed by both contact angle measurements and electron spectroscopy for chemical analysis (ESCA) analysis. Copyright © 2005 John Wiley & Sons, Ltd.
Radiation polymerization and concentration separation of P(NIPA‐co‐AMPS) hydrogels
Authors: Zhuang Yinfeng , Wang Guowei , Yang Hua , Zhu Zhongqi , Fu Jianwei , Song Weiqiang , Zhao Huidong 
Published: January 2005

AbstractExtraction or concentration with temperature‐sensitive hydrogels is a novel separation technology. In this study, N‐isopropylacrylamide (NIPA) was synthesized by acrylonitrile and isopropanol. Poly(N‐isopropylacrylamide) (PNIPA) and copolymer of NIPA and 2‐acrylamide‐2‐methylpropane sulfonate [P(NIPA‐co‐AMPS)] hydrogels were prepared by radiation polymerization. Dependence of their swelling behavior on temperature was studied. Effects of radiation dose on polymerization, feed composition on thermoresponse, electrolyte on relative swelling ratio, and swelling and deswelling kinetics were investigated. The experimental results showed that P(NIPA‐co‐AMPS) hydrogels with low content of AMPS/NIPA (1–5 %), prepared at a radiation dose‐rate of 1 kGy/h and total dose of 30–40 kGy, could enhance the swelling ratio of PNIPA hydrogels significantly and raise the phase‐transition temperatures. P(NIPA‐co‐AMPS) hydrogels produced under optimum conditions were used to concentrate aqueous bovine serum albumin (BSA, M = 69 000 g mol−1) solution. When aqueous BSA concentration was below 5 %, the separation efficiency was more than 80 % with low cost and low energy consumption. Copyright © 2005 Society of Chemical Industry
Synthesis and characterization of novel multifunctional poly(methyl methacrylate)s as potential fluorescent labels for electron‐beam lithography
Authors: Liao Shaowen , Soo Choi Pheng , Ye Huanwen , Valiyaveettil Suresh 
Published: January 2005

AbstractA series of novel fluorophore‐rich polymers has been synthesized with the aim of developing radiation‐sensitive materials as electron‐beam resists. The polymers were characterized using FTIR and NMR spectroscopy, and gel permeation chromatography, differential scanning calorimetry and thermogravimetric analysis measurements. These polymers showed strong absorbance in the region of 330–380 nm, and can be patterned by an electron‐beam in their pure form or mixed with other components. All polymers also generated intense emission in the range 510–565 nm when irradiated by a laser source operating at a wavelength of 488 nm. The sensitivity of the polymeric fluorescence label as an electron‐beam resist was also discussed. Moreover, through immobilization of the fluorophores onto a polymer backbone, we managed to avoid the crystallization of fluorophores inside the polymer film. Copyright © 2005 Society of Chemical Industry
Fatigue resistance of silica‐filled natural rubber vulcanizates: comparative study of the effect of phosphorylated cardanol prepolymer and a silane coupling agent
Authors: Menon ARR , Pillai CKS , Jin WS , Nah C 
Published: January 2005

AbstractThe fatigue resistance of silica‐filled natural rubber (NR) mixes modified with phosphorylated cardanol prepolymer (PCP) was studied in comparison with similar compositions without PCP and with those containing the same dosage of a silane coupling agent (Si‐69). Considerable improvement in the fatigue resistance was observed for the PCP‐modified NR vulcanizate containing 20 phr of silica compared with the unmodified and Si‐69 modified vulcanizates. In addition, the tear strength of the PCP‐modified NR vulcanizate was higher than that of the others. Atomic force microscopy and the scanning electron microscopy of the vulcanizates showed better dispersion of silica particles in the NR matrix in the presence of PCP than in the unmodified and Si‐69‐modified NR vulcanizates. It is assumed that, at a dosage of 5 phr, PCP functions as a coupling agent between NR and the silica particles thereby improving the filler dispersion and consequently the mechanical properties of the vulcanizate. Copyright © 2005 Society of Chemical Industry
X‐ray diffraction studies and phase volume determinations in poly(ethylene glycol)–montmorillonite nanocomposites
Authors: Chen Biqiong , Evans Julian RG 
Published: January 2005

AbstractPoly(ethylene glycol)–montmorillonite nanocomposites were prepared by both solution and melt intercalation methods with a range of polymer molecular weights and at a range of polymer loadings. Particular attention was given to the reliability of low‐angle X‐ray diffraction results for basal plane spacing and a sound correlation between three diffractometers was obtained (±0.005 nm). Expansion of the basal plane spacing from 1.23 nm to 1.82 nm by solution intercalation was independent of polymer molecular weight in the range 300–20 000. Furthermore, the clay expansion was independent of the method of intercalation; melt intercalation also gave d001 = 1.82 nm irrespective of polymer molecular weight. The maximum amount of polymer intercalated by clay and the maximum loading of clay that polymer can sustain were also studied for the determination of nanocomposite formulations. The confined polymer exerts a reduced effective density (670 kg m−3) in the galleries. Copyright © 2005 Society of Chemical Industry
Circular dichroism of In‐Situ trinuclear organotransition metal complexes with optically active ligands
Authors: Barton Derek H. R. , Frelek Jadwiga , Snatzke Günther 
Published: January 2005

AbstractSeveral Cotton effects are developed within absorption bands of trinuclear organotransitionmetal complexes in the presence of acids, diols, amines and aminoalcohols even in the case of bulky substituents on nitrogen; with monohydroxy compounds no circular dichroism could be detected.
Study on 5, 15‐dialkylporphyrins interconversion between two conformers in solution
Authors: Maruyama Kazuhiro , Nagata Toshi , Osuka Atsuhiro 
Published: January 2005

AbstractNovel structural features of 5, 15‐dialkylporphyrins in solution are described. The 1H‐NMR spectra of these compounds showed broad signals at room temperature, which split into two sets of signals at lower temperatures. This unusual phenomenon was ascribed to a dynamic interconversion between tow distorted structures. The 5, 15‐dialkylporphyrin has a distorted ring due to the steric hindrance between the 5(or 15)‐alkyl group and the 3, 7(or 13, 17)‐alkyl groups and, depending on the position of the 5, 15‐alkyl groups relative to the average ring plane, can exist in two conformations; syn (where the two alkyl groups are on the same side of the ring plane) and anti (on the opposite sides). Preliminary kinetic study of this interconversion using the NMR line shape analyses is also reported.
Photocyclization of N‐Alkyl‐N‐(3‐aryl‐3‐butenyl) ureas. Hydrogen transfer via charge transfer exciplexes in alkene photochemistry
Authors: Aoyama Hiromu , Tomohiro Takenori , Arata Yoshiaki , Omote Yoshimori 
Published: January 2005

AbstractPhotolysis of N‐alkyl‐N‐(3‐aryl‐3‐butenyl) ureas (1) in acetonitrile gave cyclization products, 3‐aryl‐3‐methyl‐pyrrolidines, in good yields, whereas irradiation of 1 in methanol afforded methanol adducts as well as the cyclization products. Both the reactions are singlet reactions, and the cyclization is presumed to proceed via 1,6‐hydrogen transfer from exciplexes with charge transfer character.
Concerning the weakness of intramolecular general acid catalysis in the hydrolysis of vinyl ethers. o‐carboxy‐α‐methoxy‐β,β‐dimethylstyrene
Authors: Kresge A. J. , Yin Y. 
Published: January 2005

AbstractThe rate of hydrolysis of the aromatic vinyl ether o‐carboxy‐α‐methoxy‐β,β‐dimethylstyrene was found to be accelerated 25‐fold by ionization of its carboxylic acid group, but the effective molarity which may be calculated if all of this rate acceleration is ascribed to intramolecular general acid catalysis is only EM = 1 · 1 m. This is similar to the small effective molarities found before for intramolecular catalysis by carboxylic acid groups of aliphatic vinyl ethers, which shows that, unlike the situation in other intramolecular reactions, e.g. ketone enolization, the extra rigidity of aromatic over aliphatic systems does not improve the efficiency of intramolecular catalysis in vinyl ether hydrolysis.It is suggested that this behaviour is the result of reduced conjugation between the vinyl ether group and the aromatic ring in the transition state of the vinyl ether hydrolysis reaction, which retards the rate and offsets any improvement effected by increased rigidity of the aromatic system.
The lone‐pair orbitals of triaziridine
Authors: Kaupp Gerd , Döhle Jens A. , Burger Klaus , Rademacher Paul , Poppek Rainer 
Published: January 2005

AbstractThe PE spectra of four stable bicyclic triaziridines with trifluoromethyl, methyl, phenyl, spirocyclopentane and spirocyclohexane substituents are measured. From a comparison of these experimental data with MNDO calculations the energies and the interactions of the nitrogen lone‐pair orbitals were obtained. The trifluoromethyl group may be reliably simulated by a fluorine atom. The ionization potentials are unexpectedly high and so are the cyclovoltammetric anodic potentials. The MNDO valence electron densities are in agreement with the comparatively small differences in the chemical shifts of the differently substituted nitrogens of the triaziridine rings.
Syntheses, spectroscopic characterization and electronic structure of cyclopropenylidene ligated platinum complexes
Authors: Miki Sadao , Ogno Toshinobu , Iwasaki Hideaki , Yoshida Zen‐Ichi 
Published: January 2005

AbstractNew series of platinum complexes of cyclopropenylidenes of the types of PtX2(CP)2 and trans‐PtX(PBu3)2(CP) have been synthesized, where CP is di‐t‐butylcyclopropenylidene (BCP) or bis(diisopropylamino)cyclopropenylidene (ACP). The 13C‐NMR chemical shifts, and 13C−195Pt coupling constants (1JPtC) for the complexes are discussed in comparison with those values derived from closely related series of compounds, trans‐PtCl(PR3)2L; L  CH3, C6H5 and CCBu‐t. An excellent linear relationship through the origin was obtained between 1JPtC and the formal ‘s’ % character of the carbon directly bonded to Pt for the series trans‐PtCl(PR3)2L in which the PtC bond is regarded as a pure σ‐linkage, whereas 1JPtC deviates largely from this relationship when pπdπ bonding interaction possibly exists in the PtC bond. The NMR data suggest the strong nmr trans‐influence of the cyclopropenylidenes and that in the PtCP bond the σ‐interaction is appreciable but the π‐interaction is negligible.
The solvatochromic equation and insight into chemical reactivity
Authors: Harris J. Milton , Sedaghat‐Herati M. R. , McManus Samuel P. , Abraham M. H. 
Published: January 2005

AbstractReaction rates for solvolysis of a mustard analogue are accurately correlated by the solvatochromic equation without inclusion of a nucleophilicity term, and thus the equation is shown to reveal mechanistically significant information.
Studies on organophosphorus compounds XXXII. A molecular mechanics study of the hydrolytic reaction of alkylphosphonates and alkylphosphonyl chlorides
Authors: Li Shusen , Liao Xiugao , Yuan Chengye 
Published: January 2005

AbstractThe alkaline hydrolysis of several alkylphosphonates and alkylphosphonyl chlorides has been investigated by molecular mechanics calculations (MM2, 1985 version). The difference of the steric energies (ΔE) between tetracoordinate substrate and pentacoordinate transition state of phosphorus compounds represents the activation energy (ΔE≠) in hydrolysis. The change of ΔE for various alkyl groups relative to methyl group (ΔΔER) is suggested as a measure of the steric effect of substituents. Thus the correlation analysis involving log k and ΔΔER of the branched alkyl group gives good results and it is reasonable to anticipate that analogous treatment using ΔΔER for the straight chain alkyl group is not satisfactory owing to the minor contribution of steric effect of the latter. However, the multiple regression analysis of log k with ΔΔER and Taft's σ* provides very good results. As shown by us, for the hydrolytic reactions studied, the proposed ΔΔER is much better than Taft's Es and Charton's ν, the commonly used well‐known steric parameters in the chemistry of carbon compounds.
General base catalysis of photo‐smiles rearrangement of 1‐(4‐nitrophenoxy)‐2‐anilinoethane in aqueous solution. Identity of the proton‐donating intermediate
Authors: Wubbels Gene G. , Sevetson Bradley R. 
Published: January 2005

Abstract4‐O2NC6H4OCH2CH2NHPh undergoes clean base‐catalyzed Smiles photorearrangement to 4‐O2NC6H4N(Ph)CH2CH2OH in dimethyl sulfoxide–water (25:75). A linear plot of ϕ−1 vs [OH−]−1 indicated that the limiting quantum yield at high [OH−] is 0·12 and that uncatalyzed photorearrangement does not occur. Rate constants for the deprotonation step were determined for a variety of bases having conjugate acid pKa values in the range 5–10. When plotted according to the Brønsted Catalysis Law, these data gave a non‐linear plot approaching slopes of zero and unity above and below a pKa of 6–7. This indicates that the proton‐donating intermediate in this photo‐Smiles rearrangement is the zwitterion diradical (pKa ≈ 7) rather than the Meisenheimer complex (pKa ≈ 2).
Long range electrical field effects in solvolysis and 13C‐NMR shielding of androstanes with halogen, hydroxy and oxo substituents
Authors: Schneider Hans‐Jörg , Becker Norman 
Published: January 2005

AbstractThe solvolysis of 21 different 3‐ or 17‐androstanyl tosylates or chlorides with halogen, hydroxy or oxo substituents in 17‐ or 3‐position shows rate constant variations in hexafluoro isopropanol of up to 6·3 with regular differences for epimeric substituents. Similar variations ae seen over a distance of ∼10 Å in 13C‐NMR shifts at C‐17‐ones of androstan‐17‐ones with varied halogen substituents in C‐3, whereas the shielding observed at other distant carbon atoms excludes significant through bond effects. It is shown how, on the basis of suitable Coulomb‐type equations and of force field minimized geometries, both the stability variation of carbocationic transition states and the carbonyl group polarization are predictable by linear electric field effects, using the same parametrization.