bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Grunwald–Winstein relationship in the solvolysis of crowded tertiary alkyl chlorides. Hindered hydration and hydrophobic effect
Authors: Takeuchi Ken'ichi , Takasuka Masaaki , Shiba Eiji , Tokunaga Hironobu , Endo Tadasuke , Ushino Takuhiro , Tokunaga Kazuhiko , Okazaki Takao , Kinoshita Tomomi , Ohga Yasushi 
Published: January 2005

AbstractVarious highly crowded tertiary alkyl chlorides having a neopentyl or a (1‐adamantyl)methyl substituent on the reaction center were subjected to solvolysis rate studies, and the Grunwald–Winstein (GW) type relationship with respect to the YCl scale was examined. Analyses of the plots showed that these bulky substituents efficiently preclude the nucleophilic solvent participation from the rear side and that the data points for non‐aqueous protic solvents give linear GW type plots. On the other hand, increased crowding causes considerable downward dispersions of the data points in aqueous mixtures of ethanol, acetone and 1‐propanol. The magnitude of the downward dispersion increases in this order, giving a curvature with a downward bulge in the GW type relationship. Aqueous mixtures of the smallest alcohol, methanol, on the other hand, give only slight downward dispersions of the data points, which constitute a linear GW type plot. These results can be explained in terms of two causes. First, structural crowding makes the transition state of ionization less susceptible to the Brønsted base‐type hydration to the β‐hydrogens than 1‐chloroadamantane as the standard of the YCl scale. Second, with highly hydrophobic substrates the first solvation shell in aqueous ethanol is expected to become more ethanol rich than the bulk phase, causing less easy ionization of the substrate. The rate data can be semiquantitatively analyzed by using Hansch's hydrophobicity parameters. The present anomalies found in solvolysis reactions are regarded as a kinetic version of Wepster's observations of the solvent effects on the magnitude of Hammett σ constants of bulky alkyl groups. Copyright © 2001 John Wiley & Sons, Ltd.
Solvent effect on the volume of activation and volume of the Diels–Alder reaction
Authors: Kiselev Vladimir D. , Konovalov Alexandr I. , Asano Tsutomu , Kashaeva Elena A. , Iskhakova Gulnara G. , Shihab Mahdi S. , Medvedeva Margarita D. 
Published: January 2005

AbstractVolumes of activation, ΔV≠, and reaction, ΔV, partial molar volumes, $\bar{V}$, and enthalpies of solution, ­ΔsolH, were determined for tetracyanoethylene, cyclopentadiene, 1,3‐butadiene, trans, trans‐1,4‐diphenyl‐1,3‐butadiene and their Diels–Alder adducts at 25 °C in some solvents of π‐ and n‐donor type. The values of the activation and reaction volumes were exceptionally small in the former type of solvents. Large solvent effects on ΔsolHTCNE (up to 26 kJ mol−1), $\bar{V}$TCNE, ΔV and ΔV≠ (up to 11 cm3mol−1) were observed in aromatic solvents and these values are linearly correlated with each other. Poor correlations were found for n‐donor solvents, but a linear dependence between ΔV and δr−nH (enthalpy of reaction) was obtained for all solvents. Copyright © 2001 John Wiley & Sons, Ltd.
A quantum‐chemical study of PBX: intermolecular interactions of TATB with CH2F2 and with linear fluorine‐containing polymers
Authors: Xiao He‐Ming , Li Jin‐Shan , Dong Hai‐Shan 
Published: January 2005

AbstractThe calculations of density functional theory at the B3LYP/3‐21G* level have been employed to optimize the 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB)CH2F2 complex. The complex binding energy is corrected for the basis set superposition error. In addition, the interactions of TATB with (CUVCXY)
n (U, V, X, Y = H. U = F; V, X, Y = H. U, V = F; X, Y = H. U, V, X = F; Y = H. U, V, X, Y = F. U, V, X = F; Y = Cl) have been studied with the MO‐PM3 method, and the complex binding energy with approximation of electron correlation correction by the dispersion energy has been given. The results computed indicate that the greatest corrected binding energy of TATB and CH2F2 is −4.62 kJ mol−1 at the B3LYP/6‐311G*//B3LYP/3‐21G* level. The interactions of ­(CF2CH2)
n with TATB and of (CF2CFH)
n with TATB are stronger than those of (CUVCXY)
n (U, V, X, Y = H. U = F; V, X, Y = H. U, V, X, Y = F. U, V, X = F; Y = Cl) with TATB (n = 5). Copyright © 2001 John Wiley & Sons, Ltd.
Linear free energy relationship analysis of the solubility of solids in supercritical CO2
Authors: Saunders Robert A. , Platts J. A. 
Published: January 2005

AbstractLinear free energy relationship (LFER) methods were used to construct a model for the solubility of a species in supercritical CO2. The final model was based on 64 molecules and 782 data points, employing a modified version of the Abraham LFER equation incorporating π1, the dipolarity/polarizability of the CO2 at a given density. This allowed us to model data ranging from 308 to 435 K and 74.3 to 410 bar, with an accuracy of ±0.65 log mole fraction units. The model shows that solubility in supercritical CO2 is favoured by the presence of π and n electron pairs and hydrogen‐bond basicity. Solute size and hydrogen‐bond acidity are less important, whereas polarity/polarizability is statistically insignificant. Copyright © 2001 John Wiley & Sons, Ltd.
Bisimide–Lactamimide ring contraction in six‐membered bisimides: a theoretical study
Authors: Ponce Patricia , Fomina Lioudmila , Fomine Serguei 
Published: January 2005

AbstractThe bisimide–lactamimide ring contraction reaction of six‐membered bisimides has been modeled at the B3PW91/6‐31 + G(d,p)//HF/3‐21G level of theory using the isodensity polarized continuum model to take into account the solvent effect. Basically, the results of molecular modeling support the validity of the proposed mechanism. However, the calculations suggest that the final reaction step involves the direct oxidation of dianions by molecular oxygen, instead of oxidation of the hydroaromatic intermediate as proposed previously. The reactivity difference between N‐alkyl and N‐phenyl bisimides in the ring contraction reaction has been explained. Copyright © 2001 John Wiley & Sons, Ltd.
Correlation analysis of reactivity in the oxidation of substituted benzaldehydes by pyridinium hydrobromide perbromide
Authors: Aneja Meenakshi , Kothari Seema , Banerji Kalyan K. 
Published: January 2005

AbstractThe oxidation of benzaldehyde and 35 monosubstituted benzaldehydes by pyridinium hydrobromide perbromide (PHPB) in aqueous acetic acid leads to the formation of the corresponding benzoic acids. The reaction is first order with respect to each of the benzaldehydes and PHPB. Addition of pyridinium bromide has no effect on the rate of oxidation. The oxidation of [2H]benzaldehyde (PhCDO) indicated the presence of a substantial kinetic isotope effect. The effect of solvent composition indicated that the reaction rate increases with increase in the polarity of the solvent. The rates of oxidation of meta‐ and para‐substituted benzaldehydes were correlated in terms of Charton's triparametric LDR equation whereas those of ortho‐substituted benzaldehydes were correlated with a tetraparametric LDRS equation. The oxidations of para‐ and ortho‐substituted benzaldehydes are more susceptible to the delocalization effect while the oxidation of meta‐substituted compounds displays a greater dependence on the field effect. The positive value of η suggests the presence of an electron‐deficient reaction centre in the rate‐determining step. The reaction is subjected to steric hindrance by the ortho substituents. Copyright © 2001 John Wiley & Sons, Ltd.
Application of correlation analysis to solvolytic reactions of tertiary haloalkanes and Menschutkin reactions
Authors: Gonçalves Raquel M. C. , Albuquerque Lídia M. P. C. 
Published: January 2005

AbstractWe present a selection of our studies concerning solvent, substrate and temperature effects in solvolytic and Menschutkin reactions, by means of multiparametric equations and, more recently, by the use of factor analysis. Important steps in this development are recapitulated: (i) the application of correlation relationships relating rate constants to the properties of the solvents and of the solvents, substrates and temperature, simultaneously; (ii) the dissection of solvent effects into contributions from the initial state and the transition state; (iii) the split of intermolecular forces through the application of linear solvation energy relationships to the enthalpies of solution; and (iv) recent developments including the use of target factor analysis. The parametric descriptions reveal the dominant interaction mechanisms. Copyright © 2001 John Wiley & Sons, Ltd.
Predominance of 2‐arylhydrazones of 1,3‐diphenylpropane‐1,2,3‐trione over its proton‐transfer products
Authors: Gawinecki Ryszard , Kolehmainen Erkki , Janota Henryk , Kauppinen Reijo , Nissinen Maija , Ośmiałowski Borys 
Published: January 2005

Abstract2‐Phenylhydrazones of 1,3‐diphenyl‐1,2,3‐trione are the dominant tautomeric form detected in chloroform solution by 15N NMR chemical shifts. The substituent in the phenylhydrazone moiety does not affect this tautomeric preference. The substituent effect is transmitted effectively only to the hydrazone nitrogen and hydrogen atoms. Ab initio calculations show that the ketohydrazone tautomer is really very much favoured over its proton‐transfer products in chloroform solution. The same tautomer was also detected in the crystal state by X‐ray crystallography. Copyright © 2001 John Wiley & Sons, Ltd.
Optimization of micellar catalysis of nucleophilic substitution reactions in buffered solutions of cetyltrimethylammonium halide surfactants, part 2: buffers in the pH range 7–8
Authors: Ouarti Nadia , Blagoeva Iva B. , Seoud Omar A. El , Ruasse Marie‐Françoise 
Published: January 2005

AbstractBinding of the phosphate, tris‐(hydroxymethyl)‐methylamine, aminomethylpropanediol, and glycinemethylester buffers by cetyltrimethylammonium chloride (CTACl) in aqueous solutions has been probed by investigating: (1) the dependence of the buffer pH (starting pH 7.9) on [CTACl], and (2) the micellar effect on the kinetics of dephosphorylation of p‐nitrophenyldiphenylphosphate (PNDPP) by the anion of isonitrosoacetylacetone (INAA) in CTACl solutions in the presence of the same buffers. The pH–[CTACl] profiles showed a marked dependence on the buffer employed and the coion, Y−, of its acidic component, $\hbox{RNH}_{3}^{+}\hbox{Y}^{-}$. The sizeable pH decrease observed with phosphate buffer (0.43 pH units for [Buffer] = 10−2 M at [CTACl] = 2 × 10−2 M) indicates that both buffer components, namely $\hbox{H}_{2}\hbox{PO}_{4}^{-}$ and $\hbox{HPO}_{4}^{2-}$, exchange with the surfactant counterion, Cl−. This ion exchange occurs at the expense of the nucleophile (anion of INAA)–Cl− counterpart. Indeed, the micellar acceleration of the phosphate‐buffered reaction is the smallest, kmax/kw = 410 (kmax and kw are the maximum pseudo first‐order rate constants in buffered micellar solutions and bulk water, respectively). Although CTACl micelles do not seem to incorporate the neutral component of amino buffers, the pH–[CTACl] profiles were found to depend on the nature in Y− (F−, Cl− or AcO−). The micellar accelerations (kmax/kw ≈ 600), however, were not strongly altered by a change in the buffer coion, except where Y− = F−. In the interfacial region, the partially desolvated fluoride ion behaves as a nucleophile, competing with INAA anion for the dephosphorylation of PNDPP. The rate–[surfactant] profiles were interpreted in terms of the pseudophase ion‐exchange model, as applied to a reaction scheme involving competitive exchanges of the oximate and Y− for the surfactant counterion. The second‐order rate constant of the micelle‐mediated reaction, smaller (ca one‐third) than that in bulk aqueous solution, is discussed in terms of the properties (ionic strength and microscopic polarity) of interfacial water. Copyright © 2001 John Wiley & Sons, Ltd.
The mode of transmission of electrical effects: evidence from infrared stretching frequencies
Authors: Charton Marvin , Charton Barbara I. 
Published: January 2005

AbstractThe transmission of the universal electrical effect in infrared stretching frequencies is well fit by the modified field effect model with m ≈ −1.5 ± 0.2. The considerable variation in rm/p, the ratio of transmission of the electrical effect through meta‐substituted benzene derivatives to that through para‐substituted benzene derivatives and rc/t, the ratio of the transmission of the electrical effect through the s‐cis conformer to that through the s‐trans conformer and the failure of these ratios to show a Gaussian distribution provides further evidence against the existence of the inductive effect. The values of rm/p obtained show that, in the general case, the Hammett equation is inferior to either di‐ or tri‐parametric equations, as it assumes the equality of ρm and ρp. This is also true of the Yukawa–Tsuno equation. It has been shown that the inductive effect does not fit the experimental data on the transmission of electrical effects in a range of chemical reactions and in infrared stretching frequencies. Recent quantum chemical calculations support the field effect as the mode of electrical effect transmission. The inductive effect model of electrical effect transmission should be abandoned. Copyright © 2001 John Wiley & Sons, Ltd.
Microstructure determination of methyl methacrylate and n‐butyl acrylate copolymers synthesized by atom transfer radical polymerization with two‐dimensional NMR spectroscopy
Authors: Brar A. S. , Kaur Sukhdeep 
Published: January 2005

AbstractCopolymers of methyl methacrylate (MMA) and n‐butyl acrylate (n‐BA) were synthesized under atom transfer radical polymerization (ATRP) conditions. The molar infeed ratio was varied to obtain copolymers with different compositions. Methyl 2‐bromo propionate was used as the initiator with CuBr/Cu(0)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as the catalyst at 60 °C. Molecular weight distribution was determined by gel permeation chromatography (GPC). Copolymer compositions (FM) were calculated from 1H NMR spectra. Reactivity ratios calculated with the Mao–Huglin terminal model at a high conversion were found to be rM = 2.17 and rB = 0.47. The polymerization mechanism was studied with the α‐methyl region of MMA. The backbone methylene and carbonyl carbons of both MMA and n‐BA units were found to be compositionally as well as configurationally sensitive. Complete spectral assignments were performed with the help of heteronuclear single quantum coherence (HSQC) spectroscopy along with total correlated spectroscopy (TOCSY). Further, the assignments of the carbonyl region were made with the help of heteronuclear multiple quantum coherence (HMBC) spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1100–1118, 2005
Preparation of densely grafted poly(aniline‐2‐sulfonic acid‐co‐aniline)s as novel water‐soluble conducting copolymers
Authors: Hua Fengjun , Ruckenstein Eli 
Published: January 2005

AbstractVarious densely grafted polymers containing poly(aniline‐2‐sulfonic acid‐co‐aniline)s as side chains and polystyrene as the backbone were prepared. A styryl‐substituted aniline macromonomer, 4‐(4‐vinylbenzoxyl)(N‐tert‐butoxycarbonyl)phenylamine (4‐VBPA‐tBOC), was first prepared by the reaction of 4‐aminophenol with the amino‐protecting moiety di‐tert‐butoxyldicarbonate, and this was followed by substitution with 4‐vinylbenzyl chloride. 4‐VBPA‐tBOC thus obtained was homopolymerized with azobisisobutyronitrile as an initiator, and this was followed by deprotection with trifluoroacetic acid to generate poly[4‐(4‐vinylbenzoxyl)phenylamine] (PVBPA) with pendent amine moieties. Second, the copolymerization of aniline‐2‐sulfonic acid and aniline was carried out in the presence of PVBPA to generate densely grafted poly(aniline‐2‐sulfonic acid‐co‐aniline). Through the variation of the molar feed ratio of aniline‐2‐sulfonic acid to aniline, various densely grafted copolymers were generated with different aniline‐2‐sulfonic acid/aniline composition ratios along the side chains. The copolymers prepared with molar feed ratios greater than 1/2 were water‐soluble and had conductivities comparable to those of the linear copolymers. Furthermore, these copolymers could self‐dope in water through intermolecular or intramolecular interactions between the sulfonic acid moieties and imine nitrogens, and this generated large aggregates. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1090–1099, 2005
Impact fracture toughness of polyamide‐6/montmorillonite nanocomposites toughened with a maleated styrene/ethylene butylene/styrene elastomer
Authors: Tjong S. C. , Bao S. P. 
Published: January 2005

AbstractPolyamide‐6 (PA6)/montmorillonite (MMT) nanocomposites toughened with maleated styrene/ethylene butylene/styrene (SEBS‐g‐MA) were prepared via melt compounding. Before melt intercalation, MMT was treated with an organic surfactant agent. Tensile and impact tests revealed that the PA6/4% MMT nanocomposite fractured in a brittle mode. The effects of SEBS‐g‐MA addition on the static tensile and impact properties of PA6/4% MMT were investigated. The results showed that the SEBS‐g‐MA addition improved the tensile ductility and impact strength of the PA6/4% MMT nanocomposite at the expenses of its tensile strength and stiffness. Accordingly, elastomer toughening represents an attractive route to novel characteristics for brittle clay‐reinforced polymer nanocomposites. The essential work of fracture (EWF) approach under impact drop‐weight conditions was used to evaluate the impact fracture toughness of nanocomposites toughened with an elastomer. Impact EWF measurements indicated that the SEBS‐g‐MA addition increased the fracture toughness of the PA6/4% MMT nanocomposite. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 585–595, 2005
Enhanced rockfall activity during the Little Ice Age: further lichenometric evidence from a Norwegian talus
Authors: McCarroll Danny , Shakesby Richard A. , Matthews John A. 
Published: January 2005

AbstractA recent study of lichen sizes on a talus in western Norway suggested that rockfall frequency was enhanced considerably during the cold conditions of the Little Ice Age. That conclusion is tested here using another talus in western Norway, in an area where lichen (genus Rhizocarpon) growth rates are higher. That part of the talus retaining a late Holocene record yields a lichen size–frequency distribution quite different to that reported in the previous study. However, when the appropriate lichenometric dating curve is used within a model that simulates the influence of late Holocene rockfall activity on lichen size–frequency distributions, a similar temporal pattern of rockfall supply is obtained. The results suggest that, at this site, rockfall frequency during the eighteenth century, the coldest phase of the Little Ice Age, may have been up to seven times higher than the normal late Holocene rate. Copyright © 2001 John Wiley & Sons, Ltd.RÉSUMÉUne étude récente de la taille des lichens sur un talus de l'ouest de la Norvège suggérait que la fréquence des chutes de roches a été beaucoup plus élevée que maintenant pendant le ‘petit âge glaciaire.’ Cette conclusion est testée ici sur un autre talus de la même région où la vitesse de croissance des lichens est plus élevée. La partie du talus qui contient l' information portant sur la fin de l'Holocène montre une distribution de la taille des lichens tout à fait différente de celle mentionnée dans l'étude antérieure. Toutefois quand la courbe de datation lichenométrique est utilisée dans le cadre d'un modèle qui simule l'influence de l'activité des chutes de blocs holocènes sur la distribution des lichens, les auteurs obtiennent une figure de l'alimentation par chute de blocs comparable à celle de l'étude précédente. Le résultat suggère qu'en cet endroit la fréquence des chutes de blocs pendant le 18e siècle, qui a été la phase la plus froide du ‘petit âge glaciaire’ pourrait avoir été jusqu'à sept fois plus grande que la vitesse normale de la fin Holocène. Copyright © 2001 John Wiley & Sons, Ltd.
Reducing value chain vulnerability to terrorist attacks
Authors: Downes A.M. (Tony) 
Published: January 2005

AbstractLike most U.S. chemical companies, you probably know where your security‐sensitive inventories are located within your sites and have assured yourself that you have taken reasonable precautions to reduce the risk of their being used in a terrorist attack. What about when you ship them? How secure are the various parts of your value chain—offsite storage and transportation of your products, raw materials, intermediates, and wastes, and processing of ordering and invoicing transactions? Value chain security focuses on tampering and misuse of materials handled outside the plant boundaries.At FMC, we took a three‐stage approach to identifying and dealing with potential security issues posed by materials in transit. Stage 1 was a quick review to determine which of our products, intermediates, or raw materials might be potentially useful to terrorists. In Stage 2 we looked for specific security‐emergency scenarios that might involve those chemicals, estimated the risk of those scenarios, and made recommendations to reduce the vulnerability to terrorist attack. In Stage 3 we are implementing the plans we developed.FMC's approach has successfully focused our efforts and used familiar techniques to break down complex Value Chains into manageable sections and then to identify the possible scenarios and (relative) risks at each section. We were able to do this with minimal travel costs.This paper describes the general organization of FMC's value chain security efforts and our analysis technique, and discusses lessons (including a few surprises) that we have learned from the analyses. © 2005 American Institute of Chemical Engineers Process Saf Prog, 2005
Herbicide‐resistant crops and weed resistance to herbicides
Authors: Owen Micheal DK , Zelaya Ian A 
Published: January 2005

AbstractThe adoption of genetically modified (GM) crops has increased dramatically during the last 3 years, and currently over 52 million hectares of GM crops are planted world‐wide. Approximately 41 million hectares of GM crops planted are herbicide‐resistant crops, which includes an estimated 33.3 million hectares of herbicide‐resistant soybean. Herbicide‐resistant maize, canola, cotton and soybean accounted for 77% of the GM crop hectares in 2001. However, sugarbeet, wheat, and as many as 14 other crops have transgenic herbicide‐resistant cultivars that may be commercially available in the near future. There are many risks associated with the production of GM and herbicide‐resistant crops, including problems with grain contamination, segregation and introgression of herbicide‐resistant traits, marketplace acceptance and an increased reliance on herbicides for weed control. The latter issue is represented in the occurrence of weed population shifts, the evolution of herbicide‐resistant weed populations and herbicide‐resistant crops becoming volunteer weeds. Another issue is the ecological impact that simple weed management programs based on herbicide‐resistant crops have on weed communities. Asiatic dayflower (Commelina cumminus L) common lambsquarters (Chenopodium album L) and wild buckwheat (Polygonum convolvulus L) are reported to be increasing in prominence in some agroecosystems due to the simple and significant selection pressure brought to bear by herbicide‐resistant crops and the concomitant use of the herbicide. Finally, evolution of herbicide‐resistant weed populations attributable to the herbicide‐resistant crop/herbicide program has been observed. Examples of herbicide‐resistant weeds include populations of horseweed (Conyza canadensis (L) Cronq) resistant to N‐(phosphonomethyl)glycine (glyphosate). An important question is whether or not these problems represent significant economic issues for future agriculture. Copyright © 2005 Society of Chemical Industry