bluuebunny/crossref_metadata_2025 huggingface dataset:
Validity of radiographic evaluations of bone formation in a rat calvaria osteotomy defect model
Authors: Pryor Mary E. , Susin Cristiano , Wikesjö Ulf M. E.
Published: May 2006

Objective: The objective of this study was to evaluate the validity of radiographic evaluations of bone formation in a critical‐size rat calvaria osteotomy defect model.

Methods: Bilateral, critical‐size (∅ 6 mm) calvaria osteotomy defects in 30 adult Sprague–Dawley rats treated with a rat platelet‐rich plasma preparation or control treatments were evaluated by radiographic and histometric measures following a 4‐ or 8‐week healing interval. Standardized radiographic images of the rat calvaria gross specimens were used to assess bone formation within the defect sites by visual evaluation of the grey scale by three masked examiners. The most central portion of each defect site was subject to histometric analysis using a PC‐based image analysis system. Kappa statistics and percentage agreement between the radiographic and histometric analysis were estimated.

Results: Radiographic evaluations of bone formation are associated with significant weaknesses poorly representing actual healing events; κ statistics (0.17) denoting slight agreement beyond chance. Perfect agreement between the histologic and radiographic analysis for defect sites showing complete and partial histologic bone fill was achieved 63% and 50% of the time, respectively. Agreement reached only 20% for sites with no/limited bone fill. When no/limited and partial bone fill occurred, the radiographic analysis tended to overestimate bone fill and underestimate bone fill when complete closure of the defect sites was observed in the histologic analysis.

Conclusion: Low accuracy was observed when radiographic evaluations were employed in identifying and characterizing bone fill in the rat calvaria osteotomy defects. Assessment of bone healing in animal models aiming at treatment recommendations for clinical application must not solely be based on radiographic analysis, but should be confirmed using histologic observations.
Inflammatory external root resorption following surgical treatment for intra‐bony defects: a report of two cases involving Emdogain® and a review of the literature
Authors: St. George Geoffrey , Darbar Ulpee , Thomas Gareth
Published: May 2006

Background: Enamel matrix‐derived proteins have been shown to regenerate periodontal tissues lost as a result of disease in humans. Emdogain®, a commercial preparation of porcine enamel matrix derivative (EMD), has been shown to induce new cementum, periodontal ligament and bone formation in human periodontal defects. Although a number of studies have reported successful outcomes, local adverse effects have so far not been reported in the literature. This case report describes two examples of external inflammatory resorption following surgical root surface debridement and the use of Emdogain®.

Treatment: The treatment in both cases involved raising a full‐thickness flap following completion of non‐surgical therapy. The granulation tissue from the defect was removed and the root surfaces debrided. Emdogain® was applied following the manufacturers' instructions and involved conditioning the root surfaces with Pref‐Gel and applying the Emdogain® to the defect. The flaps were sutured and the site reviewed regularly. Radiographs were taken before the treatment was undertaken and also at 6 months to assess the healing of the defect.

Results: External inflammatory root resorption was observed on the treated teeth 6–24 months after therapy.

Conclusion: External inflammatory root resorption may be an unusual adverse event following Emdogain® treatment.
EU Reform of the Sugar Beet Regime: Implications for UK Agriculture
Authors: Giha Cesar Revoredo , Renwick Alan , Lang Ben , Reader Mark
Published: May 2006

The purpose of this article is to discuss possible scenarios for UK sugar beet production after the reform of the sugar regime. The analysis is built on an evaluation undertaken by the University of Cambridge and The Royal Agricultural College of the impact that reforming the EU sugar regime may have on UK agriculture. The analysis focuses on the implications of reductions in quota and the support price and on the possible reactions by British Sugar, as the final outcome in terms of production will depend on the interaction between British Sugar and sugar beet farmers. The analysis indicates that British Sugar strategies such as reallocating the available quota to the more efficient producers or paying higher beet prices might mitigate the impacts of the reform. The key factor in limiting the overall impact on production is the extent that the industry can restructure and reduce its cost base. For example, following a 40 per cent reduction in the sugar beet price we estimate that if farmers could reduce their average costs by 20 per cent, about 52 per cent of UK beet production would still be viable, compared to less than 20 per cent if costs were not altered.
Development of the Balkan Countries: Where Does the European Responsibility Lie?
Authors: Tomić Danilo , Umićević Biljana
Published: May 2006

At this stage in its development, Europe faces special challenges. A united Europe, of the form that we might describe as an ‘open workshop’, is a challenge for 21st century management, to create a peace‐oriented and prosperous Europe. The principles of solidarity, sustainability and support applied within Europe are precious contributions to global strategies. What can the Balkan experience offer? The region is rich in natural resources and labour potential for accelerated economic and agricultural development. The European and Asian civilizations meet in this region. It offers labour and production potential as well as 60 million food consumers and important tourist destinations. The Balkan challenge is to utilize the European model of development and the forthcoming period must be used to prepare for membership of the EU. In the meantime the region must take advantage of local free trade zones, encourage team work amongst domestic and foreign experts on agricultural and rural development, reform education at all levels, launch well focused programmes of agricultural and rural development, complete the process of transition and of general privatization, create domestic brands with labels offering geographical origin and ensure that changes in agricultural policy are consistent with the direction of the EU's CAP.
Effets des cations alcalins et pseudo-alcalins sur quelques équilibres et en particulier sur l'équilibre d'extraction de l'acide thiocyanique par la méthylisobutylcétone
Authors: Schriver Louise
Published: May 2006

The equilibrium constant for the extraction of thiocyanic acid by methylisobutyl ketone at constant ionic strength, depends on the nature of alkaline cations present in the aqueous phase. The phenomenon could be explained by the existence of ion pairs for which the association constant Kp is derivable. However the extraction of chlorpromazinium thiocyanate by the same solvent and the formation of the monothiocyanate complex of zirconium in aqueous phase are both independent of the nature of the electrolyte. The observed variations for the extraction of thiocyanic acid which exist also for the extraction of hydrochloric and perchloric acids by methylisobutyl ketone, result from the variation of species activities with a change in the identity of the cations.
Decomposition of butyl dixanthogen in the presence of cationic micelles
Authors: Sepulveda Luis , Contreras Sergio
Published: May 2006

The decomposition of butyl dixanthogen in the presence of cetyl trimethylammonium bromide (CTA) at pH 10.5 is studied. CTA micelles strongly catalyze the decomposition. A great difference is also found between freshly prepared dixanthogen and that stored pure or dissolved in dioxane for more than one month. A general mechanism is proposed to account for the results obtained.
A photoelectron investigation of acyl silanes: the photoelectron spectra of trimethylsilyl phenyl ketone and phenyl tert-butyl ketone
Authors: Brown R. S.
Published: May 2006

not available
On the interpretation of measured rotational and vibrational relaxation times. I. Sound dispersion experiments
Authors: Pritchard Huw O. , Labib Nabil I.
Published: May 2006

The simultaneous relaxation to equilibrium of both rotational and vibrational populations is considered for a diatomic molecule immersed in a heat bath of inert-gas atoms. The relaxation is analyzed in terms of normal modes of relaxation, and it is shown that each mode, having its own distinct relaxation time, in general has both rotational and vibrational components. The qualitative form of these modes is very persistent, and survives considerable variations in the assumed temperature and the assumed set of transition probabilities. Using these modes of relaxation, an approximate treatment is given of the contribution made by the diatomic gas to the sound dispersion of the mixture, and conditions under which modes of relaxation may or may not be resolved from each other, or may be characterized as either 'rotational' or 'vibrational' are examined.
Concentration fluctuations in water–methanol mixtures as studied by ultrasonic absorption
Authors: Dale William D. T. , Flavelle Peter A. , Kruus Peeter
Published: May 2006

Measurements of the ultrasonic absorption and velocity, and viscosity have been carried out in the system methanol–water at 0, 15, and 25 °C at frequencies from 10 to 50 MHz. The data show the existence of two maxima in the excess absorption as a function of composition. The existence of the two maxima are predicted by the Romanov–Solovyev theory relating the absorption to concentration fluctuations. The magnitude of the excess absorption is calculated at 25 and 0 °C from density, vapour pressure, and diffusion data. New experimental data on density and vapour pressure are presented for this system at 0 °C. The calculated excess absorption is in reasonable agreement with the measured. This indicates that any specific localized intermolecular interactions present in this system could be responsible for at best a smaller portion of the excess ultrasonic absorption, as longer range concentration fluctuations account for essentially all of the excess. Ultrasonic data on the systems methanol–octanol and n-propanol–water are also presented in the course of examining the generality of these phenomena.
Comments on "The aqueous photochemistry …", and "The radiation chemistry of aqueous solutions of sodium 9,10-anthraquinone-2-sulfonate"
Authors: Stonehill H. I. , Clark K. P.
Published: May 2006

Some of the mechanistic conclusions of the title articles are criticized because they are inconsistent with other results available to the present authors. Further, the mechanisms of the title articles would not operate in aerobic systems for which alone the present authors' mechanisms were designed.
The addition of 2,4-dinitrobenzenesulfenyl chloride to a series of phenyl substituted cis- and trans-1-phenylpropenes
Authors: Schmid George H. , Nowlan Vincent J.
Published: May 2006

The rate of addition of 2,4-dinitrobenzenesulfenyl chloride to cis and trans 3-NO2, 4-Cl, 4-CH3, 4-OCH3, 4-OC6H5, 4-OCH(CH3)2 substituted-1-phenylpropenes has been measured in 1,1,2,2-tetrachloroethane at 25 °C and the product stereochemistry has also been determined. While a plot of log k2vs. either σ or σ+ is linear a better correlation is obtained with σ. Such a linear relationship is obtained even though the product stereochemistry changes from stereospecific and nonregiospecific for electron-withdrawing substituents (3-NO2, 4-Cl) to regiospecific and nonstereospecific for electron-donating substituents (4-OCH3, 4-OC6H5, and 4-OCH(CH3)2). These results suggest that the rate determining step for all the additions is bridged and that any open ion is formed after this step.
Preparation, Mössbauer and vibrational spectra of diorganotin chromates and carbonates
Authors: Goel R. G. , Prasad H. S. , Bancroft G. M. , Sham T. K.
Published: May 2006

Dimethyltin chromate and basic dimethyltin and diphenyltin carbonates have been isolated for the first time. Structural features of these compounds, as well as of the previously known basic dimethyltin chromate, have been investigated by examining their infrared, Raman, and Mössbauer spectra. Infrared, Raman, and Mössbauer spectra of [Me2Sn(NCS)]2O have also been examined, and by comparing its spectroscopic data with those for (Me2Sn)2OCrO4, (Me2Sn)2OCO3, and (Ph2Sn)2O(CO3), possible structures have been suggested for the latter compounds. From the combined infrared and Mössbauer data, a structure is also proposed for Me2SnCrO4. All compounds are indicated to have polymeric structures with bridging CrO42− or CO32−.
X-ray analysis of the structure and correlation with the spectra of haplophytine
Authors: Cheng P.-T. , Nyburg S. C. , MacLachlan F. N. , Yates Peter
Published: May 2006

Haplophytine crystallizes as the methanolate in the orthorhombic space group P212121 with a = 13.874(4), b = 10.628(4), c = 22.890(9) Å, Z = 4. X-Ray structure analysis confirms that the previously assigned structure 3 is correct and that haplophytine undergoes reversible rearrangement on conversion to its dihydrobromide 1. The dimensions of 3 provide evidence supporting previous interpretations of unusual features of the infrared and proton magnetic resonance spectra of haplophytine.
The crystal and molecular structure of 1,1-bis(diphenylphosphino)-2,2-dimethylhydrazine
Authors: Faught J. Brian
Published: May 2006

The structure of 1,1-bis(diphenylphosphino)-2,2-dimethylhydrazine, [(C6H5)2P]2NN(CH3)2 has been determined crystallographically. The compound crystallizes from n-heptane in the space group P21/c with a = 8.910(1), b = 9.686(1), c = 27.489(4) Å, and β = 102.94(2)° with four molecules per unit cell. The structure was solved from 2669 independent reflections with I > 3σ(I) and refined by block diagonal least squares methods to R = 0.032 and Rω = 0.048. Each diphenylphosphino group is bonded to the same hydrazine nitrogen and the geometry about this nitrogen is nearly planar. The average dimensions of the structure are P—C = 1.828 ± 0.005, P—N = 1.715 ± 0.014, N—N = 1.451, and N—C = 1.457 ± 0.003 Å, [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text].
A stereodynamic investigation of antivitamins K in the dicoumarol series. II. Differentiation between the two hydroxyl groups by the nuclear Overhauser effect
Authors: Laruelle Claude , Godfroid Jean-Jacques
Published: May 2006

Dicoumarol derivatives, substituted at the bridgehead, show a double restricted rotation. This hindered rotation is manifest through the appearance of two signals, the hydroxyl protons being diastereotopic at low temperatures.In this work we assign the two respective signals by the nuclear Overhauser effect. The high-field signal corresponds to a hydroxyl site close to the bridgehead tertiary proton, while the other corresponds to a site in proximity to the substituent R. The case of structurally analogous dimethones has been investigated by the same technique with identical conclusions. This disproves the interpretation made previously on the basis of steric and anisotropic effects.The interatomic distances concerned have been calculated, and these have yielded an estimate of deformations induced by the bridgehead substituents.Evidence is supplied for the different behavior of the two sites and this study gives evidence for a very facile intermolecular chemical exchange of the hydroxyl site close to the tertiary bridgehead proton in the presence of traces of protonated compounds.The overall behavior is the result of the asymmetry of the molecules of this series in their chelated form.
The vibrational spectrum and normal coordinate analysis of tellurium chloride pentafluoride
Authors: Brooks W. V. F. , Eshaque M. , Lau Clement , Passmore Jack
Published: May 2006

The infrared and Raman spectra of TeClF5 have been recorded. Assignments have been made on the basis of C4v symmetry. A normal coordinate analysis was carried out on SClF5, SeClF5, TeClF5, SF6, SeF6, and TeF6 and the derived force constants compared.
15N–13C spin–spin coupling constants in some aniline derivatives
Authors: Wasylishen Roderick E.
Published: May 2006

Nitrogen–carbon spin–spin coupling constants in aniline-15N and some of its derivatives have been measured using 13C Fourier transform nmr spectroscopy. Observed values of 1J(15N,13C) in these aniline derivatives are dependent on the nature of the substituent as well as the solvent. Observed values of 1J(15N,13C) in the amino fragment of a number of amine derivatives are linearly related to the corresponding 1J(15N,H) values in these compounds. The 1J(15N,13C) values in these compounds also appear to be related to the N(s)—C(s) bond order. Comparison of observed 1J(15N,13C) values in a number of compounds with those calculated using INDO–MO theory indicate that 1J(15N,13C) in aniline and its derivatives is negative, that is, 1K(N,C) is positive. Observed and calculated 15N–13C spin–spin coupling constants over two and three bonds are also presented.
Infrared spectra of the ammonium ion in crystals. III. The ammonium ion in crystal sites of symmetry S4
Authors: Oxton Ian A. , Knop Osvald , Falk Michael
Published: May 2006

The infrared spectra of the isotopically isolated NH3D+ ion in polycrystalline ammonium perrhenate, NH4ReO4, and ammonium tetrachlorocuprate(II) dihydrate, (NH4)2.CuCl4.2H2O, have been recorded at room and liquid-nitrogen temperatures. In the crystals of both compounds the ammonium ions are located at sites of S4 symmetry. The N—D stretching mode of NH3D+ in NH4ReO4 is a singlet, as expected for this site symmetry. In (NH4)2.CuCl4.2H2O, however, a doublet is observed which reveals the occurrence of two non-equivalent orientations of the ammonium ion. The spectra of the undeuterated compounds contain bands due to combination modes involving the librations of the ammonium ion. This shows that the ions are non-rotating.
Sphere tensiometry: an evaluation and critique
Authors: Huh C. , Mason S. G.
Published: May 2006

An absolute gravimetric method of measuring surface and interfacial tensions of liquids by pulling a sphere through the interface is examined. The method also permits simultaneous measurement of the contact angle of the liquid on the sphere surface; this enables corrections to be made for incomplete wetting of the solid by liquids in measuring the interfacial tension, a feature which the conventional ring and plate methods lack. Simultaneous measurements of the interfacial tension and the difference in phase densities across the interface are in principle also possible. Preliminary experimental results are presented, and the advantages and disadvantages of the method are critically discussed.
The synthesis of chasmanine: aromatic intermediate
Authors: Lee Shy-Fuh , Sathe Ganesh M. , Sy Wing Wah , Ho Pak-Tsun , Wiesner Karel
Published: May 2006

The stereospecific total synthesis of the pentacyclic tetrasubstituted intermediate 39 is described. The conversion of this material to the delphinine type alkaloid chasmanine IV by the method worked out recently by the same group (1) is envisaged.
Synthesis and vibrational spectra of lead(II) thiocyanate complexes
Authors: Baranyi Anthony D. , Makhija Ramesh , Onyszchuk Mario
Published: May 2006

The preparation, properties, and vibrational spectra are reported for the following complexes of lead(II) thiocyanate with mono- and bidentate ligands: Pb(NCS)2•2py, Pb(NCS)2•phen, Pb(NCS)2•2phen, Pb(NCS)2•tmen, Pb(NCS)2•en, Pb(NCS)2•2en, Pb(NCS)2•2dmso, and Pb(NCS)2•2dma. Assignments are made for the ν(CN), ν(CS), and δ(NCS) vibrational bands of the thiocyanate group and the results are discussed in terms of the type of coordination of NCS with lead(II). Values are consistent with bridge-bonded and/or N-bonded thiocyanate. Infrared and Raman spectra of the complexes Pb(NCS)2•bipy and Pb(NCS)2•4tu are reexamined and new assignments are made which support bridge-bonded and/or N-bonded NCS contrary to previous reports of S-bonded NCS.
Nuclear magnetic resonance and molecular orbital studies of the conformational preferences of the fluoromethyl group in some benzylfluoride derivatives
Authors: Schaefer Ted , Rowbotham J. Brian , Parr William J. E. , Marat Kirk , Janzen Alexander F.
Published: May 2006

The proton magnetic resonance spectra of some benzylfluoride derivatives yield long-range spin–spin coupling constants between ring protons and protons or fluorine nuclei in the fluoromethyl group. In conjunction with the eigenfunctions for a hindered twofold rotor, the couplings over six bonds are used to show that in 3,5-dichlorobenzylfluoride in solution the C—F bond prefers the benzene plane by 260 ± 50 cal/mol; in close agreement with ab initia and MINDO/3 molecular orbital calculations. The latter method suggests that in a conformation in which the C—F bond lies in a plane perpendicular to the benzene ring, the C – C – F angle reduces to 107.2° and the C – C – H angles become 116.1°, perhaps due to increased conjugation of the C—F bond or fluorine atom with the π electrons of the ring. The observed barrier is presumably a delicate balance between steric interactions, hyperconjugation or p–p conjugation effects, and dipole–dipole interactions between polarized bonds.
Spectre de l'indazole en résonance magnétique nucléaire du 13C
Authors: Elguero José , Fruchier Alain , Pardo Maria Del Carmen
Published: May 2006

Synthesis of all monodeuterio indazole derivatives has allowed the assignment of the seven carbons in the 13C nmr spectrum of indazole. Some 1J, 2J, and 3J coupling constants have been measured from the coupled spectrum.
Alkylation of the dimethylglyoximato ligands in reduced cobaloxime
Authors: Silverman Richard B. , Dolphin D.
Published: May 2006

Cobalt(II) cobaloximes can undergo atom transfer reactions with certain alkyl halides to give the corresponding alkyl cobalt(III) cobaloximes. However, in the presence of powerfully electrophilic alkyl halides, such as chloromethyl methyl ether, reaction at the periphery, and not at the cobalt, occurs to give dimethylglyoxime-O-methoxymethyl ether.
Tautomeric equilibrium study of thiazolidine-2-thione. Transition metal complexes of the deprotonated ligand
Authors: Preti Carlo , Tosi Giuseppe
Published: May 2006

The complexes of deprotonated thiazolidine-2-thione (ttz) with many transition metals have been prepared. Probable structures have been proposed for the complexes on the basis of chemical analysis, spectral data (infrared and visible), and magnetic susceptibility measurements. The ligand field parameters have been evaluated and are in keeping with the proposed structures.
Pouvoirs donneur et accepteur des ligands dans les dérivés de Mo(CO)6
Authors: Barbeau Claude , Turcotte Jacques
Published: May 2006

A model of electron distributions in some Mo(CO)6 derivatives has been constructed from certain correlations among the CO stretching frequencies. The use of spectroscopic data for the compounds Mo(CO)6−nLn permitted establishing a scale of the relative donor and acceptor powers of more than 50 ligands. [Journal translation]
Spectres de résonance paramagnétique électronique de quelques radicaux de type diarylméthyle
Authors: Devolder P.
Published: May 2006

Electron paramagnetic resonance spectra of some anthronyl, xanthyl, or thioxanthyl type radicals are obtained and compared to their simulated spectra. Spin density calculations according to the method of McLachlan give the assignments of most experimental splittings. A few unexpected high splittings are interpreted with Pople's INDO calculations on the twisted benzyl radical.
Nitration of the tetramethylbenzenes in acetic anhydride. Formation and rearomatization of adducts
Authors: Fischer Alfred , Leonard David R. A.
Published: May 2006

Nitration of the tetramethylbenzenes in acetic anhydride at temperatures below –50 °C gives the l-acetoxy-4-nitro and 5-acetoxy-2-nitro adducts from the 1,2,3,4 isomer, the 5-acetoxy-2-nitro adduct from the 1,2,3,5 isomer, and the l-acetoxy-4-nitro adduct from the 1,2,4,5 isomer as well as the expected nitro derivatives. Corresponding nitritonitro adducts are also formed as well as side-chain (benzylic) derivatives: nitrates and phenylnitromethanes. Rearomatization of the tertiary acetate adducts leads to aryl acetates, benzylic derivatives, or nitroarenes, depending upon the acidity of the solvent. In the benzylic derivatives the methyl group substituted is that ipso to the acetate in the precursor adduct, that para to the most activated ipso position of the arene.
Chaleurs de dilution de solutions aqueuses d'acide polyméthacrylique et de ses sels de sodium et de rubidium
Authors: Daoust Hubert , Lajoie Alain
Published: May 2006

Heats of dilution of aqueous solutions of two polymethacrylic acid samples having a viscosity average molecular weight of 5000 (PMA-I) and 140 000 (PMA-II) respectively and of isobutyric acid (BA) have been measured at 25 °C using a Tian–Calvet microcalorimeter. The same measurements have been repeated in presence of HCl (0.2 N). Aqueous solutions of sodium and rubidium salts of PMA-I and II have also been investigated. Dilution of BA solutions is endothermic at high solute concentration and then becomes exothermic as concentration decreases and the presence of HCl does not affect the results. Dilution of PMA solutions is exothermic over the investigated concentration range in agreement with the results of Eliassaf and co-workers. PMA-I gives a more exothermic heat of dilution than PMA-II in the lower concentration range. The presence of HCl does not affect appreciably the results for PMA-II but it makes the dilution of PMA-I solutions less exothermic. The results are discussed in the light of Liquori et al.'s model for PMA chain which may adopt a globular or an extended solvated coil depending on solvent properties. Heats of dilution of aqueous solutions of sodium salts of both samples I and II are endothermic over the entire concentration range investigated whereas the heats of dilution of rubidium salts are exothermic.
Solubilities in the system indium tribromide – sodium bromide – water at 25 °C
Authors: Kartzmark Elinor M.
Published: May 2006

The system InBr3–NaBr–H2O shows the existence of the following solid phases at 25 °C: InBr3(anhyd.), NaBr(anhyd.), and NaBr.2H2O. A hydrated form of indium tribromide does not exist at 25 °C
Reactions of oxygen and sulphur anions with oxazolidine and thiazolidine derivatives of 2-mesyloxymethylglyceraldehyde acetonide
Authors: Just George , Chung Bong Young , Kim Sunggak , Rosebery Gerald , Rossy Phillip
Published: May 2006

Reactions of the oxazolidine (2) and thiazolidine (3) derivatives of 2-mesyloxymethylglyceraldehyde acetonide with oxygen and sulphur anions are described. Whereas oxazolidine formation does not protect the aldehyde function against nucleophilic attack, the thiazolidine group is completely inert to these nucleophiles.
Reaction of organic compounds under high temperature – dilute acid (HTDA) conditions. III. The perdeuteration of bicyclo[2.2.1]heptanes
Authors: Werstiuk Nick Henry , Kadai Tonu
Published: May 2006

The hydration of norbornene (1) and nortricyclane (2) under the high temperature and dilute acid (HTDA) conditions of aqueous acetic acid at 250 °C gives as products exo-2-norborneol, endo-2-norborneol, exo-2- and endo-2-norbornyl acetate, and a mixture of stereoisomeric dinorbornyl ethers 4. When the reactions are carried out in deuterated medium perdeuteration (>90% in one cycle) of the [2.2.1]-products is accomplished. Respectable overall yields (50–70%) of the products are obtained. Solvolysis of the products exo-norborneol, and endo-norbornyl acetate under HTDA(D) conditions also leads to perdeuterated 3a, 3b, 3c, 3d, and 4.
The infrared and Raman spectra of 1,2-dibromotetrafluoroethane
Authors: Shurvell H. F. , Cahill F. , Devarajan V. , James D. W.
Published: May 2006

Infrared and Raman spectra of 1,2-dibromotetrafluoroethane have been recorded in vapour, liquid, and polycrystalline solid states. Assignments have been made to trans and gauche isomers. A force field has been obtained for the trans isomer and used to predict the frequencies of the gauche form.
Isothermal compressibility of water–glycerol mixtures at 60.0 °C measured relative to water
Authors: Whalley E. , Heath J. B. R.
Published: May 2006

The compression of aqueous glycerol relative to pure water has been measured up to ∼250 bar at 60 °C, and the measurements analyzed to yield the compressibilities at zero pressure to an accuracy of ∼0.02–0.1 Mbar−1 depending on the concentration. The method used is a simplified version of a more elaborate method (by Kell and Whalley) and is particularly suitable for measuring accurately and quickly the compression of one liquid relative to another.
Nuclear quadrupole resonance and intermolecular interactions: temperature and pressure effects in Group V trichlorides
Authors: Gillies Grant Callum , Brown Richard Julian Challis
Published: May 2006

Nuclear quadrupole resonance frequencies for the metal and chlorine atoms in AsCl3 and SbCl3 have been measured as functions of temperature and pressure. These data are analysed to obtain the isothermal volume dependences and the isochoric temperature dependences of the field gradient parameters. Existing knowledge of the Group V trichlorides shows that the strength of intermolecular bonding increases in the order AsCl3 < SbCl3 < BiCl3, and this trend is reflected in the relative importance of volume effects in determining the nqr frequencies in these solids. A simple theory of the pressure dependences of nqr frequencies in molecular crystals is proposed, which accounts for all data presently available. The pressure coefficient contains static and dynamic contributions which are of opposite signs; the static contribution is negative and becomes numerically larger as the strength of intermolecular bonding increases.
A synthesis of homosafranic acid and related compounds
Authors: Schmidt Cirill
Published: May 2006

A four step sequence was found to convert 2,2,6-trimethylcyclohexanone, 1, to 1-(2-hydroxyethyl)-2,6,6-trimethyl-1,3-cyclohexadiene, 2a (overall yield 76%). An efficient route to homosafranic acid 3 is also described (overall yield 80% from ketone 1).
Studies on inorganic ion exchangers. II. Synthesis, ion exchange properties, and applications of ferric arsenate
Authors: Rawat J. P. , Singh J. P.
Published: May 2006

A new inorganic ion exchanger, ferric arsenate, has been prepared under varied conditions. The product formed by the homogeneous precipitation method is most stable. Ion exchange selectivity with different metal ions (alkali metal and alkaline earth metal ions) is different and depends upon the hydrated radii of the exchanging cation. A straight line is obtained for the plot of capacity against hydrated radii of the cation in the same group. Some important separations are achieved quantitatively on the columns of ferric arsenate.
Seven-coordinate metal carbonyl derivatives of cis-(CH3)2AsC(CF3)=C(CF3)As(CH3)2
Authors: Cullen William R. , Mihichuk Lynn M.
Published: May 2006

The seven-coordinate complexes (L—L)M(CO)3X2 (M = Mo, W; X = Br, I; (L—L) = cis-(CH3)2AsC(CF3)=C(CF3)As(CH3)2) were prepared and characterized. 1H and 13C nmr studies at 25 and −70 °C suggest that the complexes are nonrigid. Similarly 1H nmr studies indicate the seven-coordinate (L—L)LMo(CO)2Br2 complexes are also nonrigid. The (L—L)L2Mo(CO)Br2 complexes (L is a monodentate phosphite or phosphine) are rigid at 25 °C and nonrigid at higher temperatures. Activation parameters are calculated for the motion of two of the complexes and possible mechanisms are discussed.
On the constitutions of silver iodine dibenzoates (Simonini complexes)
Authors: Bunce Nigel J. , Hadley Mary
Published: May 2006

Infrared and conductance measurements on three Simonini complexes (silver iodine dibenzoates) indicate a symmetrical structure. Ag+ (ArCO2)2I−is considered a limiting constitution, but the substance is an extremely weak electrolyte. The constitution is discussed in terms of the observed chemistry and the stabilizing role of the silver cation.
Réaction oscillante de Belousov. 1. Cinétique de la réaction bromate–céreux
Authors: Herbo Claude , Schmitz Guy , Glabbeke Martine Van
Published: May 2006

During the oxidation of malonic acid by potassium bromate catalyzed by the Ce(III)–Ce(IV) couple in a sulfuric acid solution, concentration oscillations of ceric and bromide ions are observed. This reaction, discovered by Belousov, can be resolved into two parts: reduction of bromate by cerous ions and oxidation of malonic acid by ceric ions. The former shows very unusual kinetic features and its mechanism is the basis of the explanation of the oscillations. It is autocatalytic but inhibited by bromide ions. We have thus reinvestigated this reaction varying not only the initial concentrations of bromate and of cerium but also that of bromide. The mechanism suggested involves, besides the classic steps of the bromate–bromide reaction, the oxidation of cerous ions by BrO2• radicals produced by the step[Formula: see text]
Thermodynamics of ester and orthoester formation from trifluoroacetic acid
Authors: Guthrie J. Peter
Published: May 2006

not available
The effect of monolayers on the rate of evaporation of H2O and solution of O2 in H2O
Authors: O'Brien R. N. , Feher A. I. , Li K. L. , Tan W. C.
Published: May 2006

The well-known effect of the retardation of evaporation by monolayers of surfactants has been investigated by laser interferometry and the appropriate conventional apparatus. The temperature drop caused by evaporation has been calibrated for several surfactants in general use for conserving reservoir waters and for lecithins considered to be part of living membranes. Rate of ingress of oxygen has been treated in the same way. The best performance was about 60% retardation of evaporation for the molecules that pack well. The behaviour for O2 ingress retardation was very similar. The lecithins were suitably permeable to be able to act as a bilamellar layer cell membrane.
Charge distributions and Chemical effects. XII. A unifying concept
Authors: Fliszár Sándor
Published: May 2006

Major inconsistencies which are currently acknowledged in discussions involving atomic charges, inductive effects, 13C nmr shifts, and stability of carbonium ions are removed (i) by the use of an appropriate definition of charges and (ii) by the recognition that in alkanes and alkyl carbonium ions any decrease in positive charge at carbon atoms results in a downfield 13C shift. Methyl appears to be less electron withdrawing than hydrogen, and stability of carbonium ions is associated with dispersion of positive charge at the carbonium center, in line with the more traditional views which are repeatedly challenged in recent literature.
13C nuclear magnetic resonance spectra of alkyl indoles including derivatives of hexahydroechinulin
Authors: Fraser Robert R. , Passannanti Salvatore , Piozzi Franco
Published: May 2006

Revised structures for 4-bromohexahydroechinulin and 6-nitrohexahydroechinulin have been established using 13C nmr spectroscopy. For this purpose the substituent parameter for the nitro group at a site flanked by two methyl groups has been measured. Inconsistencies in previous data on alkyl indoles in comparison with hexahydroechinulin suggested a reassignment of the C4 and C6 signals in 5-methylindole, which we have proven by single frequency spin-decoupling experiments. The original data on methyl indoles has been retabulated to include the above reassignments and others recently reported by Gribble et al. A more consistent and reliable set of methyl substituent parameters is thereby obtained.
Etude des mobilités ioniques dans les mélanges eau–hexaméthylphosphotriamide. I. Cas du HMPT pur à 25 °C
Authors: Bollinger Jean-Claude , Yvernault Théophile , Gal Jean-Yves , Persin Françoise
Published: May 2006

Ionic mobilities have been measured in hexamethylphosphotriamide (HMPT) and in water–HMPT mixtures in order to investigate the solvation of ions. In view of the large number of studies of conductivities in pure HMPT, we felt it would be interesting to give a general analysis of these data. Our results in pure HMPT will be presented in the course of this analysis.
Activation entropy as a dominant factor in the oxidative addition of some group IV hydrides to an iridium(I) complex
Authors: Fawcett J. P. , Harrod J. F.
Published: May 2006

The kinetics of the reactions[Formula: see text]have been studied (M = Si, Ge, Sn). All three reactions proceed by predissociation of the iridium complex and concerted cis addition of Ph3MH to the square-planar intermediate. The relative rate of addition of Ph3MH increases in the order Si (1) < Ge (18) < Sn (70) and the difference in rate within experimental error is due entirely to change in ΔS0. It is concluded that, for this particular series of oxidative addition reactions, solvation effects related to a change in polarity on passage to the transition state are more important than bond energies, or acid–base properties, in determining relative reaction energetics. The relevance of entropy barriers to the problem of paraffin activation is discussed.
Crystal structure of CaK2As2O7 and CdK2P2O7
Authors: Faggiani Romolo , Calvo Crispin
Published: May 2006

Crystals of CaK2As2O7 and CdK2P2O7, both grown from the melt, are monoclinic with Z = 4. The lattice parameters are a = 9.222(6), b = 5.835(3), c = 14.698(10) Å, β = 105.84(5)° with space group P21/c for the diarsenate and a = 9.737(2), b = 5.548(1), c = 12.766(2) Å, β = 106.50(2)° with space group C2/c for the diphosphate. The structures were refined by full-matrix least-squares methods utilizing 2070 reflections (R = 0.056) for the diarsenate and 1145 reflections (R = 0.067) for the diphosphate. Both structures contain pseudo-hexagonally packed anions, in staggered configurations, forming layers with the divalent cations in six coordinate sites between the layers. The average M—O bond lengths are 2.342 and 2.290 Å for M = Ca and Cd respectively. The K ion has nine oxygen atoms with mean K—O bond lengths of 2.943 and 3.020 Å in the diarsenate in the coordination sphere. The mean of the ten shortest K—O is 2.939 Å in the diphosphate.
The polymerization of oxetane with hexafluorophosphate salts
Authors: Black P. E. , Worsfold D. J.
Published: May 2006

Oxetane has been polymerized using both triethyloxonium hexafluorophosphate and triphenylmethyl hexafluorophosphate as initiators at −30 °C. The former gives a slow polymerization with a slow initiation process. The latter gives a rapid initiation and rapid initial polymerization which may slow down to rates similar to those found for the former initiator. The results are interpreted in terms of the formation of two types of tertiary oxonium ions. One type incorporates the oxetane molecule and is suggested to have a very rapid reaction with more oxetane. The second type does not involve the oxetane molecule but an ether linkage, such as in the polymer chain, and reacts only slowly with oxetane.
Synthesis of some 4-pyranones and 4-pyridones structurally related to isoproterenol
Authors: Williams Haydn W. R.
Published: May 2006

The syntheses of 2-isopropylamino-1-(5-hydroxy-4H-pyran-4-on-2-yl)ethanol and the corresponding 4-pyridone and 1-methyl-4-pyridone analogues are described. The selective reduction of an aliphatic nitro group in the presence of a benzyl ether linkage was a key step in the reaction sequence.
A kinetic study of the reaction of adamantanethione with 2-adamantanethiol
Authors: Scaiano J. C. , Tremblay J. P.-A. , Ingold K. U.
Published: May 2006

The title reaction is a free radical chain process which yields di(2-adamantyl)disulfide(2). The kinetics of this reaction have been studied in benzene solution at 50 °C using both thermal and photochemical initiation. Thermal initiators which yield resonance stabilized carbon-centered radicals were surprisingly inefficient at starting the reaction. The kinetics indicate that the rate controlling propagation step is hydrogen abstraction from the thiol, AdHSH, by the carbon-centered radical, AdHSSAd•. Rotating sector studies gave a rate constant for this step, k2 = 4 × 104 M−1 s−1. There is some kinetically first order chain termination, but the predominant termination process involves the diffusion-controlled bimolecular self-reactions of AdHSSAd• radicals, 2kt = 1.8 × 1010 M−1 s−1.
Vapour phase catalytic transformations of terpene hydrocarbons in the C10H16 series. III. Dehydrogenation of Δ3-carene over modified chromia and chromia–alumina catalysts
Authors: Krishnasamy V. , Yeddanapalli L. M.
Published: May 2006

The vapour phase dehydrogenation of 3-carene has been studied over chromia, chromia–alumina, chromia doped with potassium, and chromia–alumina doped with potassium and fluoride ions. Addition of potassium to chromia and chromia–alumina up to 1% by weight does not significantly affect the overall conversion of 3-carene whereas it increases its dehydrogenation to p- and m-cymenes. Potassium ions above 1% lower both the total conversion and dehydrogenation of 3-carene to cymenes. The ratio of p- to m-cymene over chromia–alumina is enhanced by added potassium ions up to 2%, but over chromia it remains unaffected. Addition of potassium to chromia decreases the formation of menthanes and menthadienes but its addition to chromia–alumina reduces the formation of menthanes and increases that of menthadienes. Impregnation of chromia–alumina with hydrofluoric acid suppresses the formation of menthadienes and increases that of menthanes. All these are explained in terms of the effect of added potassium and fluoride ions on the acidity of the catalysts.
Pulse radiolytic formation of Na− from alkali metal–sodium ion solutions in ethylamine
Authors: Seddon William Arthur , Fletcher John Wallace , Sopchyshyn Fred Charles
Published: May 2006

The formation of Na− from K, Rb, Cs, or Li ethylamide solutions containing small amounts of Na+ has been observed by pulse radiolysis. In K, Rb, or Cs solutions evidence is presented which shows that the production of Na− occurs via the corresponding alkali anions K−, Rb−, or Cs−. However solutions containing Li behave much differently and indicate that Na+ is 'complexed' or associated with Li+ ions. Probable reaction mechanisms are discussed.
Proton and deuteron nuclear magnetic resonance study of host and guest motions in ethylene oxide-d4 clathrate hydrate
Authors: Ripmeester John A.
Published: May 2006

The motions of water molecules in ethylene oxide-d4 clathrate hydrate have been studied between 200 and 280 K using continuous wave and pulsed 1H nmr methods. The 1H second moment and rotating frame relaxation time variation with temperature show that reorientation and diffusion of water molecules occur as two distinct processes. From the relaxation time data, activation energies of 8.15 and 12.0 kcal/mol are found for reorientation and diffusion, respectively.From the non-zero guest molecule D quadrupole coupling constant observed between ∼100 and 280 K, it is evident that there is some net orientation of the guest molecules in the hydrate cages at all temperatures. Also, there is a slow motional averaging superimposed on the rapid guest molecule reorientation which can be described approximately by the same parameters as the water molecule reorientation.
Electronic and Raman spectroscopic studies of copper adrenalin complexes and copper induced compounds
Authors: Rahaman Mohammed S. , Korenkiewicz Stephen M.
Published: May 2006

Electronic and Raman spectra of adrenalin–copper(II) complexes and copper catalyzed compounds have been studied. Adrenalin reacts with copper(II) ion at pH 9.2 and higher to produce a very short lived violet free radical, a brown adrenochrome, a yellow conjugated salt, indolyl-indoquinone, and melanin. Results indicate that copper does not form complexes with adrenalin in basic solution. Between pH 6.5 and 8.5 adrenalin transforms into adrenochrome in presence of copper. The adrenochrome in 1.5 N hydrochloric acid produces the conjugate salt that is produced in the solution of high pH. At low pH values, between pH 4.0 to 5.5, adrenalin forms a brown complex with copper(II). Copper is entirely chelated to the phenolic groups of the amines. The complex in 1.5 N hydrochloric acid produces a black polymeric pigment.
Situselective α′-acetoxylation of some α,β-enones by manganic acetate oxidation
Authors: Williams Gaynor J. , Hunter Norman R.
Published: May 2006

Heating 5,5-dimethylcyclohex-2-en-1-one, 1, with manganic acetate in acetic acid yields 6-acetoxy-5,5-dimethylcyclohex-2-en-1-one, 2, as the only isolated product. Reaction of 3-methylcyclohex-2-en-1-one (3) or (+)-pulegone (5) under similar conditions yields the analogous 6-acetoxy-3-methylcyclohex-2-en-1-one (4) and cis- (6) and trans-2-acetoxypulegone (7) respectively.
Enthalpies of transfer of aliphatic compounds from vapor to solvents. Steric hindrance to functional group solvation
Authors: Fuchs Richard , Saluja Preetpal S.
Published: May 2006

Enthalpies of transfer from the vapor to solution (ΔH(v → S)) in cyclohexane are similar for alkenes and the corresponding alkanes. The transfer from vapor to dimethylformamide is about 0.6 kcal/mol more exothermic for 1-alkenes, which results from the dipole-induced dipole interaction of the solvent dipole with the π system. When the ethylenic bond is hindered by large adjacent groups (trans-1,2-di-tert-butylethylene) to the approach of solvent dipoles, ΔH(v → DMF) becomes similar to that of the corresponding alkane (1,2-di-tert-butylethane). Similarly the interaction of di-tert-butyl ketone with DMF is 0.7 kcal/mol weaker than that of the less hindered isomer, 2-nonanone.
The metal complex catalyzed reactions of anils. I. The reaction of acetone with anilines
Authors: Boate A. R. , Eaton D. R.
Published: May 2006

It has been shown that the formation of anils from anilines and aliphatic ketones is homogeneously catalyzed by a variety of metal complexes. The products of the reactions have been unambiguously identified by preparing the anils using other synthetic routes. The catalysis is quite general and the system is therefore suitable for a systematic catalytic study varying both the catalysts and the substrates. The related reactions of anil hydrolysis and transimination may also be studied. The catalysts used, thiourea complexes of Co(II), Ni(II), and Zn(II), vary in their effectiveness by more than two orders of magnitude. In the present paper experiments defining the catalytic system are described. The equilibrium constants for the complexation of all the substrate molecules have been determined. Qualitative rate data on various ligand exchange and proton transfer steps is presented to demonstrate that such reactions cannot be rate determining in the overall catalytic reactions.
Structure of the type XXVII Streptococcus pneumoniae (pneumococcal) capsular polysaccharide
Authors: Bennett Larry G. , Bishop Claude T.
Published: May 2006

The type XXVII Streptococcus pneumoniae (pneumococcus) capsular polysaccharide contains equimolar amounts of D-glucose, D-galactose, L-rhamnose, 2-amino-2-deoxy-D-glucose, acetyl, pyruvic acid, phosphate, and choline. Structural investigations involving methylation studies and characterization of oligosaccharides obtained by three different degradations indicate the structure of the complete repeating unit to be[Formula: see text]