bluuebunny/crossref_metadata_2025_split huggingface dataset:
Solvent and structure effects on rotamerization in 3,4‐alkylenedioxy‐ and 3,4‐dialkoxy‐2,5‐bis[di(tert‐butyl) hydroxymethyl]thiophenes: an NMR, IR, molecular mechanics and single‐crystal x‐ray study
Authors: Lomas John S. , Vaissermann Jacqueline 
Published: January 2004

AbstractSolvent effects on the rotational equilibria of two‐rotor systems consisting of 3,4‐alkylenedioxy‐ and 3,4‐dialkoxy‐2,5‐bis[di(tert‐butyl)hydroxymethyl]thiophenes have been investigated. In these systems there are three rotational isomers: syn,syn (SS); anti,syn (AS or SA) and anti,anti (AA) (syn, [free] hydroxy group; anti, intramolecularly hydrogen‐bonded hydroxy group). In non‐hydrogen‐bonding solvents, such as chloroform and benzene, the AA rotamer is preferred for the larger bridges (three or four methylenes) and the dialkoxy derivatives, AS/SA being the minor component and SS hardly detectable. In contrast, the 3,4‐methylenedioxythiophene derivative is largely SS with AS/SA minor and just perceptible. The 3,4‐ethylenedioxythiophene (EDOT) derivative shows all three isomers in similar amounts. In hydrogen bond acceptor solvents, such as pyridine and DMSO, the two equilibria AA⇋AS/SA and AS/SA⇋SS shift in favour of the AS/SA and SS forms, respectively. The equilibrium constants, K1 and K2, show different sensitivities to solvent hydrogen bond basicity, the latter being about 25% (log/log) less sensitive than the former. Work on the BiEDOT derivative suggests that this is probably due to the proximity of the two OH groups, which inhibits solvation of the SS form. Comparison of rotation barriers (mainly in the range 20–22 kcal mol−1) with those for the monosubstituted compounds indicates that the SS→AS/SA barrier is unusually low in pyridine and DMSO. The structure of the AA isomer of the 3,4‐propylenedioxythiophene derivative has been determined by single‐crystal x‐ray diffraction. Copyright © 2004 John Wiley & Sons, Ltd.Additional material for this paper is available in Wiley Interscience
Intermolecular interaction and thermodynamic properties of N‐methylacetamide and hydroxyacetonitrile dimers
Authors: Ju Xue‐Hai , Xie Lun‐Jia , Hua Wen‐Ting , Xiao He‐Ming 
Published: January 2004

AbstractAb initio Hartree–Fock (HF) and second‐order Møller–Plesset correlation energy correction (MP2) theories with 6–311+G* and aug‐cc‐pVDZ basis sets in combination with a counterpoise procedure for basis set superposition error (BSSE) correction were applied to the investigation of intermolecular interactions and thermodynamic properties of N‐methylacetamide and hydroxyacetonitrile (HAN) dimers. The heterodimer of N‐methylacetamide with HAN was selected as the computational model for the complex of cyclo[(S)‐His‐(S)‐Phe] (CHP) with (R)‐mandelonitrile, a chiral catalyst for the asymmetric hydrocyanation of aldehydes. Cyclic structures were identified as the most stable conformation in N‐methylacetamide dimer (I), HAN dimer (II) and their heterodimer (III). The corrected binding energies for I, II and III are −52.89, −45.83 and −49.95 kJ mol−1 at the MP2/aug‐cc‐pVDZ//HF/aug‐cc‐pVDZ level, respectively. The Gibbs free energy change (ΔG) in the process I+II → 2III was predicted to be −6.41 kJ mol−1 at 298.15 K. Dimer III can be spontaneously produced in the mixture of N‐methylacetamide and HAN, which is in agreement with the experimental fact that most cyanohydrins are capable of interacting with CHP and form non‐covalent complexes. Copyright © 2004 John Wiley & Sons, Ltd.
Configurational isomerization of push–pull thiazolidinone derivatives controlled by intermolecular and intramolecular RAHB: 1H NMR dynamic investigation of concentration and temperature effects
Authors: Marković Rade , Shirazi Ata , Džambaski Zdravko , Baranac Marija , Minić Dragica 
Published: January 2004

Abstract1H NMR spectroscopy was used to investigate hydrogen bonding in the structurally related (Z)‐ and (E)‐5‐substituted‐2‐alkylidene‐4‐oxothiazolidines in polar and apolar solvents. The equilibrated mixtures of these typical push–pull alkenes consist of the intramolecularly H‐bonded E‐isomer and intermolecularly H‐bonded Z‐isomer in varying proportions which depend on the solvent polarity. For a representative of the series, (E)‐(5‐ethoxycarbonylmethyl‐4‐oxothiazolidin‐2‐ylidene)‐1‐phenylethanone (1), the lack of a concentration and temperature dependence of the large chemical NH shift (δ 12.06 ppm) in CDCl3 indicates strong intramolecular resonance‐assisted hydrogen‐bond formation (RAHB). The upfield chemical shifts of the NH proton of the (Z)‐1 isomer as a function of temperature increase and the large 1H NMR Δδ/ΔT value (−11.82 ppb°C−1, Z/E=60 : 40, or −10.33 ppb°C−1, Z/E=20 : 80) in CDCl3 are explained in terms of a decrease in intermolecular H‐bonding resulting in a greater amount of free or unassociated Z‐isomer. Copyright © 2004 John Wiley & Sons, Ltd.Additional material for this paper is available in Wiley Interscience
Scope and limitation of the inductive effect :  importance of charged substituents
Authors: Exner Otto , Böhm Stanislav 
Published: January 2004

AbstractThe interaction of two relatively distant charged or dipolar groups was evaluated on 1,4‐disubstituted bicyclo[2.2.2]octane derivatives as the reaction energy of the isodesmic–homodesmotic reaction, in which this derivative is formed from two mono derivatives. Energies of the individual compounds were calculated at the B3LYP/6–311+G(d,p) level. All combinations of 12 common substituents were investigated, representing 78 reaction energies in a 12×12 data matrix. The behaviour of charged and dipolar substituents is considerably different. Interaction with a charged group is described precisely (R>0.997) by one parameter, essentially identical with the standard inductive constant σI. Interaction of two dipolar substituents depends also on σI, but requires an additional parameter, important particularly in the case of donor substituents (NH2, OH, Cl), less important to insignificant with the others. It is significantly correlated with the electronegativity of the first atom. Alternatively, it can be evaluated as a new parameter characterizing the substituent effect, say a new scale of group electronegativity different from the suggested scales. With two parameters, the interaction of polar substituents is expressed with similar high precision (R>0.99) as with charged substituents and one parameter. Copyright © 2004 John Wiley & Sons, Ltd.
Role of functional groups in linear regression analysis of molecular properties
Authors: Cortés‐Guzmán F. , Bader R. F. W. 
Published: January 2004

AbstractThis paper contrasts the use of functional groups, coupled with the quantum theory of atoms in molecules (QTAIM), in expressing the results of linear fittings of molecular properties, as opposed to expressing the linearity in terms of the total number of electrons. The use of QTAIM brings to the fore the additivity and transferability of group properties. Copyright © 2004 John Wiley & Sons, Ltd.
Contributions of anharmonics to the nuclear relaxation second hyperpolarizability of a push–pull polyene
Authors: Squitieri Emilio 
Published: January 2004

AbstractA theoretical study of the contributions of anharmonics to the nuclear relaxation second hyperpolarizability of π‐conjugated push–pull polyenes by using an analytical evaluation of electrical properties method and a valence‐bond–charge‐transfer model was carried out. A relationship between nuclear relaxation and electronic contributions to the second hyperpolarizability is derived. It was found that the anharmonicity is essential in a numerical estimation of nuclear relaxation second hyperpolarizability. Copyright © 2004 John Wiley & Sons, Ltd.
Kinetics of the reactions between 1‐fluoro‐2,6‐dinitrobenzene and pyrrolidine and piperidine in binary solvent systems: Influence of the nucleophile structure
Authors: Mancini P. M. , Fortunato G. G. , Vottero L. R. 
Published: January 2004

AbstractWe studied the kinetics of the reaction between 1‐fluoro‐2,6‐dinitrobenzene and pyrrolidine or piperidine in ethyl acetate–chloroform or acetonitrile and acetonitrile–chloroform binary solvent mixtures. The kinetic response of these reactions was compared with that of the reactions with homopiperidine. The aim of this work was to evaluate the influence of the nucleophile structure and of solvent effects on those reactive systems. The amine structure has a great influence on second‐order rate constants, especially on the rate constants related to the catalyzed step. In mixtures with chloroform the amine structure is also responsible for the change in the reaction mechanism. Theoretical quantum mechanics calculations confirm that the origin of these results lies in stereoelectronic effects due to the conformational difference between the amino moieties in the intermediate σ adducts as they release the nucleofuge. Solvation effects are dominated by non‐specific interactions. The order of incidence of the molecular–microscopic solvent properties on the second‐order rate coefficient kA is dipolarity/polarizability>hydrogen‐bond donor ability (HBD)>hydrogen‐bond acceptor ability (HBA). The (HBA+HBD) and (HBA+HBA/HBD) solvent systems have similar solvation mechanisms: the critical state is preferentially solvated by the structure formed by intersolvent hydrogen‐bonded species. Mixtures of the type (HBA/HBD+HBD) manifest a particular solvation behavior. Among the reactive systems selected there is only one example in which preferential solvation is not operative. Copyright © 2004 John Wiley & Sons, Ltd.Additional material for this paper is available in Wiley Interscience
Experimental and theoretical study of the homogeneous, unimolecular gas‐phase elimination kinetics of methyl oxalyl chloride
Authors: Cordova Tania , Rotinov Alexandra , Chuchani Gabriel 
Published: January 2004

AbstractThe products of the gas‐phase elimination of methyl oxalyl chloride are methyl chloroformate and carbon monoxide. The kinetics were determined in a static system over the temperature range 280.3–320.7 °C and pressure range 56–140.4 Torr. The reaction, in vessels seasoned with allyl bromide and in the presence of the free‐radical inhibitor cyclohexene, is homogeneous, unimolecular and follows a first‐order rate law. The rate coefficients are given by the Arrhenius equation: log[k1 (s−1)]=(12.73 ± 0.58)−(174.3 ± 6.3) kJ mol−1 (2.303 RT)−1. Theoretical studies of the mechanism at the semi‐empirical PM3 and MP2/6–31G* levels imply a concerted non‐synchronous process. Analysis of the three‐membered ring transition state suggests that polarization of the ClC(O) bond is rate limiting in the elimination process. The kinetics and thermodynamic parameters are in good agreement with the experimental values. Copyright © 2004 John Wiley & Sons, Ltd.
Density functional theory study of the Diels–Alder reactivities of [b]‐annelated cyclic five‐membered dienes
Authors: Punnagai M. , Dinadayalane T. C. , Narahari Sastry G. 
Published: January 2004

AbstractB3LYP/6–31G* calculcations were performed to model the Diels–Alder reaction of cyclobutano‐, cyclobuteno‐ and benzo[b]‐ fused cyclic five‐membered ring dienes with two prototypical dienophiles, ethylene and acetylene. The cyclobuteno[b]‐fused dienes, which loose the unfavorable antiaromaticity upon cycloaddition, are the most reactive; in contrast, the benzo[b]‐fused dienes, which encounter disruption of aromaticity in the course of the reaction, are the least reactive. Synchronicity calculations based on bond order analysis indicate that the reactions of benzo[b]‐annelated dienes show significant deviations from synchronicity, indicating highly unsymmetrical transition states. Deformation energies were employed to corroborate the computed activation energies. Although there are some deviations in the quantitative results between ethylene and acetylene reactions, the trends are essentially the same with all the dienes considered, with acetylene showing a slightly higher reactivity. The comparison with the corresponding [c]‐fused dienes further strengthens the argument that product stability controls the reactivity in these reactions, as exemplified by excellent linear fits between the activation and reaction energies. Copyright © 2004 John Wiley & Sons, Ltd.Additional material for this paper is available in Wiley Interscience
Deconstruction of Taft's σ* parameter: QSAR meets QALE
Authors: Babij Claudia , Poë Anthony J. 
Published: January 2004

AbstractTaft's σ* parameter has been mostly disregarded in QSAR (quantitative structure–activity relationships) analyses because it appears to reveal only simple field‐inductive substituent effects. However, it can be shown that, when a reference reaction different from that adopted by Taft is used, the σ* values reveal considerably more subtle features. This occurs when a reference reaction parameter, pKa′, is used that is closely related to the Brønsted basicity of P‐donor molecules and that is regarded in QALE (quantitative analyses of ligand effects) analyses as measuring the purely σ‐donor properties of the phosphines. Values of Taft's σ* parameter for alkyl groups show an excellent linear correlation with pKa′ but significant deviations from the correlation increase in the order CH2Ph (0.19)<Ph (0.46)<p‐O‐i‐Pr (1.38)<OEt (1.44)<OMe (1.51)<OPh (1.82)<Cl (1.88), and the deviations for the p‐YC6H4 groups increase linearly with decreasing pKa′ as Y changes in the order Me2N (0.29)<MeO (0.32)<Me (0.39)<F (0.41)<H (0.46)<Cl (0.50)<F3C (0.60). The new substituent effects for these ‘deviant’ groups that can be derived from the linear correlations of σ* with pKa′ are different (even in sign for the p‐Me2NC6H4 group) from the original values of the Taft parameter, and they are much smaller than the additional effects detected here. These results show that σ* values contain within themselves a variety of new features that should be compared with those shown by parameters used in more recent QSAR analyses, and that might be useful in such analyses. Copyright © 2004 John Wiley & Sons, Ltd.
CC chemokine concentrations increase in respiratory distress syndrome and correlate with development of bronchopulmonary dysplasia
Authors: Baier R. John , Majid Abdul , Parupia Haroon , Loggins John , Kruger Thomas E. 
Published: January 2004

AbstractInflammation is one of the primary processes underlying respiratory distress syndrome (RDS) and its evolution into bronchopulmonary dysplasia (BPD). Recruitment and subsequent activation of macrophages in the lung are mediated by CC chemokines. The role of CC chemokines has not been extensively studied in the course of RDS. Serial tracheal aspirates (TA) were obtained from 56 mechanically ventilated infants with birth weights less than 1,500 g during intervals in the first 21 days of life. Tracheal aspirate concentrations of monocyte chemoattractant proteins‐1,2,3 (MCP‐1,2,3) and macrophage inflammatory proteins‐1α and ‐1β (MIP‐1α, MIP‐1β) were determined by enzyme‐linked immunosorbent assay (ELISA). Tracheal aspirate concentrations of MCP‐1, MCP‐2, MCP‐3, and MIP‐1β increased during the first week of life in infants with RDS, whereas MIP‐1α concentrations did not increase appreciably. Increased TA cytokine concentrations were associated with the development of BPD. Maximal TA concentrations of MCP‐1, MCP‐2, MCP‐3, MIP‐1α, and MIP‐1β were significantly higher in infants who were oxygen‐dependent at 28 postnatal days compared to infant who were not. Similarly, maximal TA MCP‐1, MCP‐2, and MCP‐3 but not MIP‐1α and MIP‐1β concentrations were significantly higher in infants who were oxygen‐dependent at 36 weeks of postconceptional age (PCA) than those who were not oxygen‐dependent at 36 weeks PCA. Histologic chorioamnionitis and isolation of Ureaplasma urealyticum from the airways were associated with higher maximal TA concentrations of MIP‐1α and MIP‐1β. Pulmonary hemorrhage was associated with increased maximal concentrations of MCP‐1, MCP‐2, and MCP‐3. These data suggest a role for CC chemokines in the development of BPD in the newborn infant. Pediatr Pulmonol. 2004; 37:137–148. © 2004 Wiley‐Liss, Inc.
Redesigned face mask improves “real life” aerosol delivery for nebuchamber
Authors: Amirav Israel , Mansour Yasser , Mandelberg Avigdor , Bar‐Ilan Igal , Newhouse Michael T. 
Published: January 2004

AbstractThe currently available facemask interface for the Nebuchamber (N) valved‐holding chamber (VHC) provides a very poor seal to the face, which, on average, decreases the aerosol dose and was previousely shown to increase the variability of aerosol delivery. The efficiency of a redesigned mask (RD) for the Nebuchamber with a potentially better seal was compared to the standard mask (SM) supplied with the N in a randomized real‐life crossover clinical trial. Twenty children (mean age, 26 ± 10 months) were randomized to use the Nebuchamber for 1 week with the old mask and then for another week with the newer mask, and vice versa. Filters, changed daily, inserted between the mask and the VHC, trapped the delivered drug (budesonide). The dose of budesonide was quantified by high‐performance liquid chromatography (HPLC). Use of the redesigned mask improved aerosol delivery to the filter by 30%, compared to the SM (mean 28.1 ± 7.7% of nominal dose with RD vs. 21.6 ± 9.6% with SM, P = 0.017). The relatively high within‐subject variability in aerosol delivery (36–38%) did not change, however. Facemasks are arguably the most important determinants of aerosol delivery. The newly developed RD for the Nebuchamber proved to be considereably more efficient than the SM for aerosol delivery to young children. Patient‐related factors may be more important with respect to the variability observed. Pediatr Pulmonol. 2004; 37:172–177. © 2004 Wiley‐Liss, Inc.
Design of exponential observers for nonlinear systems by embedding
Authors: Rapaport A. , Maloum A. 
Published: January 2004

AbstractFor nonlinear systems in ℝn which are observable but not uniformly, we study how to design explicitly exponential observers, after having the system immersed in ℝm with m>n. The central issue concerns the determination of a lipschitzian extension in ℝm of the dynamics, which is defined exclusively on a subset of empty interior. We propose some constructive tools and illustrate their utility on a biological example. Copyright © 2004 John Wiley & Sons, Ltd.
Selling system dynamics to (other) social scientists
Authors: Repenning Nelson P. 
Published: January 2004

AbstractIn the last decade I have tried to use system dynamics to do research that is acceptable to scholars from other social science communities. In this paper I reﬂect upon this experience and outline several errors that reduced the accessibility of my work to those outside the system dynamics community. While some of these mistakes are likely unique to me, others are more common to research that uses system dynamics. Acknowledging these errors has several implications for the future organization of the ﬁeld. Copyright © 2003 John Wiley & Sons, Ltd.
Facilitating critical systemic praxis (CSP) by means of experiential learning and conceptual tools
Authors: McIntyre Janet 
Published: January 2004

AbstractThe article discusses and summarizes a learning resource to facilitate praxis tools for systemic governance and creative problem solving. The conceptual tools are provided as a basis for addressing challenging and complex problems through participatory design, planning and decision‐making processes that strive to be socially and environmentally just. The paper draws on earlier work on tools for ethical thinking and caring. The participatory learning process aims to promote better transdiciplinary and cultural understanding and thus to promote sustainable praxis outcomes. The learning outcomes are to develop problem‐solving ability and better governance (in the broad sense used by Vickers and White) through appreciation of the whole system and the value positions through which it is perceived. Copyright © 2004 John Wiley & Sons, Ltd.
The last days of a systems research centre: an empirical case study
Authors: Ponce Héctor R. 
Published: January 2004

AbstractThis paper presents an empirical case study in which the object of research was constituted by a small systems research centre within an English university. This research coincides with the [last days] of this centre and it may help to understand why other systems centres have also declined. A series of observations were collected through participant observation and later analysed through examining the underlying linguistic structures that characterized the conversational interactions among members of the centre. As a result of such analysis, some research strategies are proposed on how the researcher could have supported the development of the centre by making precise interventions on its communication structure. It is also indicated how individual and collective emergence was prevented. Copyright © 2004 John Wiley & Sons, Ltd.
The role of stressful life events in the development of depressive symptoms in adolescence—a longitudinal community study
Authors: Waaktaar Trine , Borge Anne Inger Helmen , Fundingsrud Hans Petter , Christie Helen Johnsen , Torgersen Svenn 
Published: January 2004

AbstractDepressive symptoms were measured in a cohort of community‐based adolescents (n=163) at two time‐points, with 1 year intervening. At Time 2, participants also answered a scale about past‐year stressful life events. Depressive symptoms increased from Time 1 to Time 2, the effect being stronger for girls than for boys. Depressive symptoms were significantly correlated with concurrent measures of recent stressful life events, but this relationship disappeared after controlling for previous depressive symptoms. Rather, previous level of depressive symptoms predicted stressful life events. This demonstrates that a unidirectional model of stressful life events as the cause of depressive symptoms in adolescents is too simplistic.
Carbon Dioxide Laser Salvage Surgery after Radiotherapy Failure in T1 and T2 Glottic Carcinoma
Authors: Puxeddu Roberto , Piazza Cesare , Mensi Maria C. , Ledda Gian Peppino , Argiolas Federico , Peretti Giorgio 
Published: January 2004

OBJECTIVESRecurrent glottic carcinoma after radiotherapy (RT) may be managed by open neck or endoscopic surgery. The impact of endoscopic treatment with CO2 laser for recurrent glottic carcinoma after RT is reported.METHODSWe present the oncologic and vocal outcomes of a retrospective study based on a series of 16 patients with rT1 and rT2 glottic carcinoma who were endoscopically managed between February 1995 and December 1999 after RT failure. All patients were males with a mean age of 68.7 years (range, 50 to 87 years). Before RT, the lesions had been staged as T1 N0 in 11 patients and T2 N0 in 5, and after RT as rT1 N0 in 12 and rT2 N0 in 4. According to the European Laryngological Society classification, a total of 9 transmuscular, 3 total, and 4 extended cordectomies were performed. Mean follow‐up was 45 months (range, 9 to 79 months).RESULTSEndoscopic salvage surgery was successful in 14 patients. One of them developed a second recurrence and was definitively cured with an additional endoscopic procedure. Two of the 16 patients had recurrent disease after salvage laser surgery and died due to progression of disease. Ultimate local control with laser alone at 3 years was 87.1%, according to the Kaplan‐Meier method. Laryngeal preservation was obtained in all survivors after endoscopic rescue surgery. Voice analysis showed a clear correlation between the amount of vocal cord tissue resected and decrease of the vocal outcome.CONCLUSIONSThe present series indicates that selected recurrences after primary RT for T1 and T2 glottic carcinoma are eligible for endoscopic salvage surgery with oncologic results comparable to those with open neck procedures but with a lower complication rate and a favorable functional outcome.