bluuebunny/crossref_metadata_2025 huggingface dataset:
Etude des oxydes mixtes de lanthanides et de vanadium(V)
Authors: Brusset H. , Madaule-Aubry F. , Blanck B. , Glaziou J. P. , Laude J. P.
Published: May 2006

This work presents a study of the mixed oxides of vanadium(V) and lanthanides by dry methods. The study includes all elements of the rare earth group except cerium and promethium.All orthovanadates of the formula TVO4 were prepared and their lattice parameters redetermined for all lanthanides. New materials were synthesized: lanthanides 4T2O3•V2O5, for elements from samarium to ytterbium the compounds 5T2O3•V2O5• and for praseodymium and neodymium the compounds 6T2O3•V2O5. Identification of these materials was carried out by X-ray diffraction.
The Catalytic Decomposition of Isopropyl Alcohol Vapor on Manganese (II) Oxide
Authors: Klissurski D. G. , McCaffrey E. F. , Ross R. A.
Published: May 2006

The vapor phase decomposition of isopropyl alcohol has been studied from 210 to 365 °C on manganese(II) oxide. Rates of conversion to acetone and propylene were measured with partial pressures of isopropyl alcohol from 0.3 to 22 mm. The catalyst selectivity towards dehydrogenation was around 0.80 between 320 and 365 °C while at 306 °C it was somewhat less and depended on the alcohol partial pressure. Propylene and hydrogen additions had no effect on the reaction rate while the reaction order with respect to isopropyl alcohol partial pressure was 0.4 to 0.6 except at 306 °C when it decreased with increase in the alcohol partial pressure. The effects of acetone and water additions were shown respectively to be exerted mainly on the dehydrogenation and dehydration reactions while at acetone pressures above 4 mm, considerable amounts of by-products including mesityl oxide and heavier ketones were clearly detected. The apparent activation energy of the overall decomposition as calculated from the experimental rates was 26 ± 0.5 kcal mol−1. The results have been interpreted to be in general agreement with the concept that the rate-limiting step is linked to the direct interactions on the catalyst surface and it has been established that the reaction is significantly more complex than previously recognized. The physical properties of the manganese(II) oxide were determined by X-ray and nitrogen adsorption techniques while infrared, n.m.r., and gas chromatographic methods were used to analyze the products of catalysis.
Diphenylphosphinato- and Hydroxydiphenylphosphine Complexes of Platinum(II) and Palladium(II)
Authors: Dixon K. R. , Rattray A. D.
Published: May 2006

Preparations and various interconversion reactions are described for the complexes: [M2X2(PPh2O)2(PPh2OH2], [MX(PPh2O)(PPh2OH)2], [MX(PPh2O)(PPh2OH)(PEt3)], and [M(PPh2O)2]n where M = palladium or platinum, X = chloride or bromide, Ph = phenyl, and Et = ethyl. [Pt(PPh2O)2(PPh2OH)2] and [Pt2(PPh2O)4(PPh2OH)2] are also described and all the complexes are assigned structures on the basis of their infrared spectra.
Studies of β-Diketone Complexes of Rhenium. I. Trispentane-2,4-dionatorhenium(III) and Tris(1,1,1,5,5,5-hexafluoropentane-2,4-dionato)rhenium(III)
Authors: Courrier W. D. , Forster W. , Lock C. J. L. , Turner G.
Published: May 2006

Pure samples2 of Re(hfac)3 and Re(acac)3 have been prepared and their physical properties studied by ultraviolet–visible and infrared spectroscopy, mass spectrometry, magnetic susceptibility measurements, and X-ray diffraction. The compounds are monomeric and the physical properties may be explained if the rhenium atom sits in an essentially octahedral ligand field. Re(hfac)3 has a hexagonal unit cell and the acetyl-acetone complex adopts the monoclinic cell of the α-form of the three typical crystal structure types which Astbury (1) observed for trispentane-2,4-dionatometal(III) compounds. The properties observed for trispentane-2,4-dionatorhenium(III) differ from those reported previously (2, 3). The difficulties experienced in obtaining pure Re(C5H7O2)3 were caused by the ease with which the material is oxidized.
Diffusion of some Hydrocarbons in Air: a Regularity in the Diffusion Coefficients of a Homologous Series
Authors: Elliott Robert W. , Watts Harry
Published: May 2006

Diffusion coefficients in air at 298.2 °K and 1 atm pressure are reported for ethane, ethene, ethyne, cyclopropane, propene, propadiene, propyne, butane, 1-butene, 2-methylpropene, cis-2-butene, trans-2-butene, 1,3-butadiene, 1-butyne, 2-methylbutane, 2,2-dimethylpropane, cyclopentane, and 1-pentene.A linear relationship, valid for alkanes and alkenes, has been found between the diffusion coefficient and the reduced molecular weight of the members of a homologous series and air.Diffusion coefficients calculated by ten prediction equations were generally lower than those observed.
Mössbauer and Infrared Spectra of Tetrahedral Complexes of Iron(II) Halides with Thioamides and Related Ligands
Authors: Birchall T. , Morris M. F.
Published: May 2006

A number of complexes of iron(II) halides with thioamides and ureas have been prepared and characterized by means of Mössbauer, infrared spectroscopy, and magnetic measurements. These complexes are shown to have distorted tetrahedral structures.
The Reaction of O-Benzylidene Sugars with N-Bromosuccinimide.: VII. Stereochemical and Mechanistic Aspects in the Pyrimidine Nucleoside Series
Authors: Ponpipom M. M. , Hanessian S.
Published: May 2006

The reaction of 2′,3′-O-benzylideneuridine with N-bromosuccinimide (NBS) leads to 3'-O-benzoyl-2′,5-dibromouridine. The stereoselectivity of bromination in the sugar ring can be explained by invoking the sequential formation of benzoxonium ion and 2,2′-anhydronucleoside intermediates. Protonation of the appropriate 2,2′-anhydronucleoside, followed by treatment with NBS, recreates the conditions which prevail in the original reaction of the benzylidene acetal with NBS.
(+)-Occidentalol: Absolute Stereostructure and Total Synthesis
Authors: Amano Young , Heathcock Clayton H.
Published: May 2006

Hydroxy ketone 7 has been prepared from both (+)-dihydrocarvone (3) and (+)-occidentalol (2), thus establishing the absolute stereostructure of the latter. The three-stage conversion of compound 7 into (+)-occidentalol constitutes a total synthesis of the sesquiterpene.
Nuclear Magnetic Resonance Experiments on Acetals. 35. Proton Magnetic Resonance Spectra and Quantitative Conformational Analysis of 4-Fluoromethylated-6-Me-1,3-dioxanes
Authors: Dirinck P. , Anteunis M.
Published: May 2006

4-Substituted ([Formula: see text] and CH2F)-6-Me-1,3-dioxanes together with model derivatives (cis- and trans-4-CHnF3−n-6-t. Bu-1,3-dioxane, and 2-Me-4,6-disubstituted 1,3-dioxanes) were prepared and their p.m.r. spectra analyzed, using i.a. INDOR techniques. Special features which correlate configuration and p.m.r. data are discussed and especially the fluorine–hydrogen (long-range) couplings have been studied. From vicinal (ring) coupling data (using appropriate models), from the vicinal exo-couplings 3J(H4,CF3−nHn) and from absolute shift values, the equilibria were obtained in the conformational heterogenous trans-4-CHnF3−n-6-Me-1,3-dioxanes (n = 0 → 2). The results, according to the different methods, are mutually in excellent agreement, as is also the case for ΔG0(CF3), obtained approximately from dipole moment measurements. The anomeric effect is pronounced, and the conformer with the axial fluoromethylated substituent is the preferred one (CF3:76%; CF2H:62%) at room temperature in CS2. For CH2F the contrary seems to be the case (presumably for entropy reasons also). Finally ΔH0(chair–twist) was evaluated at 3.7 kcal/mol [Formula: see text] using 2J(H2) criteria in trans-4-CF3-6-t. Bu-1,3-dioxane.
Sur la réduction par les hydrures complexes de quelques benzylidène-3 camphres
Authors: Richer Jean-Claude , Rossi Armand
Published: May 2006

Reduction by LiAlH4, LiAlH (OtBu)3, lithium tetrakis-(N-dehydropyridil)aluminate (LDPA), and NaBH4 of several 3-benzylidene camphors have been studied. The relative amounts of the 1:2 vs. 1:4 addition are determined. The results obtained are discussed with respect to the nature of reductive species, solvents, and withdrawing and repulsive effects of the aromatic ring substituents.
Addition of Pseudohalogens to Unsaturated Carbohydrates. V. Addition of Iodine Trifluoroacetate
Authors: Ritchie R. G. S. , Szarek W. A.
Published: May 2006

Treatment of 5,6-dideoxy-1,2-O-isopropylidene-α-D-xylo-hex-5-enofuranose (1) with silver trifluoroacetate and iodine in acetonitrile gave 3,6-anhydro-5-deoxy-5-iodo-1,2-O-isopropylidene-α-D-gluco(and β-L-ido)furanose (2) and 5-deoxy-5-iodo-1,2-O-isopropylidene-6-O-trifluoroacetyl-α-D-gluco(and/or β-L-ido)furanose (3). Component 2 was converted into 3,6-anhydro-5-deoxy-1,2-O-isopropylidene-α-D-xylo-hexofuranose (5) by hydrogenation over Raney nickel, and component 3 was converted into 5-deoxy-1,2-O-isopropylidene-α-D-xylo-hexofuranose (6) by treatment with methanol, followed by hydrogenation. Treatment of 5,6-dideoxy-1,2-O-isopropylidene-3-O-trifluoroacetyl-α-D-xylo-hex-5-enofuranose (7) with silver trifluoroacétate and iodine in acetonitrile gave the addition product 8, but no 3,6-anhydro derivative; 8 was converted into the iodohydrin 4 by treatment with methanol. The preparation of the 5-deoxy derivative 6 by way of the iodohydrin 4 represents an overall anti-Markovnikov hydration of the olefin 1; the reactions described are a convenient alternative to the hydroboration–oxidation procedure for the preparation of 6.
Studies on Fluorinated Vinylic and Aromatic Alcohols and Esters
Authors: Chang I. S. , Price J. T. , Tomlinson A. J. , Willis C. J.
Published: May 2006

Synthetic studies and pKa measurements are reported on a number of highly fluorinated tertiary alcohols and diols, namely (CF2CF)C(CF3)2OH, (CF2CF)2C(CF3)OH, (C6F5)C(CF3)2OH, (C6F5)2C(CF3)OH, (C6F5)3COH, (C6H5)C(CF3)2OH, [(CF3)2COH]2, and [(C6F5)C(CF3)OH]2. General agreement is found with earlier work reporting a correlation between pKa values and differences between free and H-bonded O—H stretching frequencies.The reaction of C6F5Li with the acyl halides CF3COCl and C6F5COCl in appropriate molar ratio gives the esters (C6F5)2C(CF3)OCOC6F5 and (C6F5)3COCOC6F5, respectively; this constitutes a useful preparative route to fully fluorinated esters.
Conformational Studies of Substituted Trimethylene Sulfites by Proton Magnetic Resonance
Authors: Wood Gordon , Buchanan G. W. , Miskow M. H.
Published: May 2006

Proton n.m.r. chemical shifts and coupling constants are reported for trimethylene sulfite and 10 alkyl derivatives in CCl4. Data are discussed in terms of possible chair and non-chair conformations and results are compared with those from dipole moment studies. The shift reagent Eu(dpm)3 is used to aid configurational assignments. Conclusions from n.m.r. and dipole moments are consistent and indicate that several of the sulfites exist to a considerable degree in non-chair conformations.
Pyrochlores. VII. The Oxides of Antimony: an X-Ray and Mössbauer Study
Authors: Stewart David J. , Knop Osvald , Ayasse Conrad , Woodhams F. W. D.
Published: May 2006

Antimonic acid cannot be dehydrated by heating in air to give products of constant and reproducible weight without simultaneous reduction of some of the SbV to SbIII. Neither anhydrous Sb2O5 nor the hydroxy oxide Sb3O6OH postulated by Dihlström and Westgren can be obtained by this method. Two well-defined products of the dehydration/decomposition are Sb2O4.35(5) = Sb6O13, which forms between 650 and 850°, and β-Sb2O4. The latter, and not Sb2O3, results on heating Sb6O13 to 935°. Sb6O13 has a cubic structure of the defect pyrochlore type, a0 = 10.303(1) Å, x(O2) = 0.4304(14). Combined evidence from X-ray diffractometry, density determination, and Mössbauer spectroscopy leads to Sb3+Sb5+2O6O0.5 as the most probable structural formula.The Mössbauer parameters of β-Sb2O4 are closely similar to those reported for α-Sb2O4, but the isomer shifts (relative to InSb at 77°K) for SbV in antimonic acid and Sb6O13 are significantly larger than those in α- and β-Sb2O4.
Phase Relationships in the Calcium Chloride – Calcium Carbide System
Authors: Maillot J. F. , Morris D. R.
Published: May 2006

The system calcium chloride – calcium carbide has been examined by thermal analysis. The depression of the freezing point of CaCl2 by CaC2 is ideal. The system is a eutectic one, with a eutectic point at 90 mol% CaCl2 at 740 °C. Carbon is believed to be present in the electrolyte as the so called acetylide ion [Formula: see text] The melting point of pure CaCl2 was found to be 775.2 ± 0.6 °C.
Chloroacetylation of 1-Azaphenothiazine
Authors: Steele J. W. , Anderson W. K. , Tracer W. F.
Published: May 2006

The n.m.r. and mass spectral data are used to show that chloroacetylation of 1-azaphenothiazine gave 1-hydroxy-2-chloroacetyl-6-thia-10b-aza-2a-azoniaaceanthrylene hydroxide inner salt and not the expected 10-chloroacetyl-1-azaphenothiazine.
Kinetics of the Mercury-Photosensitized Decomposition of Neopentane. Part III. The Secondary Reactions
Authors: Furimsky E. , Laidler K. J.
Published: May 2006

The following were identified as secondary products of the mercury-photosensitized decomposition of neopentane, and their maximal rates measured over a range of conditions: C2H4, C3H6, C3H8, i-C4H10, 2,2,3,3-tetramethylbutane, and 2,2,4,4-tetramethylpentane. A mechanism is proposed which explains the kinetics of formation of these products. It involves the reaction of H atom with i-C4H8 formed as a primary product; this leads to the formation of C4H9 which reacts further; one of its products is C3H6 which also reacts with H atoms.
The Formation of Alkenes by the Thermal Elimination Reaction of N-Methyl-4-alkoxypyridinium Iodides. II. An Investigation of the Mechanism
Authors: Schmid George H. , Wolkoff Aaron W.
Published: May 2006

A comparison of the products from elimination reactions of a number of compounds containing various leaving groups with those containing the N-methyl oxypyridinium leaving group suggests that the elimination is not occurring by means of a simple E1 mechanism. Changing the anion of the salt from iodide to methyl-sulphate and tetrafluoroborate affects the product composition indicating that the anion is taking part in the reaction. The mechanism of this reaction appears to be on the E1-E2 borderline.
Oligoribonucleotide Synthesis. IV. Approach to Block Synthesis
Authors: Werstiuk Eva S. , Neilson Thomas
Published: May 2006

A convenient block synthesis for oligoribonucleotides of predetermined sequence is developed. Preparation and deblocking of protected tetranucleotide, Ph3COCH2CO•O-U(Thp)p(Cl3Et)Abz(Thp)p(Cl3Et)U(Thp)p-(Cl3Et)Abz(Thp)-OH (8) to give UpApUpA is described. Phosphorylation of HO-U(Thp)-OH derivative (1; R = Ph3COCH2CO) and subsequent coupling with HO-Abz(Thp)-OH (4) gave protected UpA (5). Specific removal of triphenylmethoxyacetyl group from 5 is accomplished by dilute methanolic ammonia. 5′-Hydroxyl group of resulting UpA derivative (7) is condensed with the 3′-phosphate derivative of 5 to give 8 in good overall yield.Ease of mild alkaline cleavage, convenient ceric sulfate spray detection and enhancement of solubility, make the triphenylmethoxyacetyl group an excellent choice for 5′-protection of nucleoside derivatives.
Theory of Enthalpy of Mixing in Reactive Charge Asymmetrical Molten Salt Systems. Part II. Ternary Solutions
Authors: Flengas S. N. , Skeaff J. M.
Published: May 2006

The enthalpies of mixing for a reacting charge asymmetrical ternary molten salt system have been calculated on the basis of an extension of a previously developed model for binary systems. The enthalpy of mixing is considered to consist of a reaction term and a mixing term; the former results from the formation of the tetrahedrally coordinated complex species [Formula: see text] and the latter from the mixing of the products of reaction according to quasichemical theory modified to account for charge asymmetry.The ternary model enables the prediction of the integral enthalpies from a knowledge of the interaction parameters determined for the two charge asymmetrical binary systems. The calculations are compared with experimentally measured integral enthalpies of mixing in the ternary system MnCl2–NaCl–CsCl, and shown to give accurate predictions of the behaviour of the system.
Synthesis of 6-O-(4-O-Methyl-β-D-glucopyranosyl)-D-galactose
Authors: Berry J. M. , Dutton G. G. S.
Published: May 2006

6-O-(4-O-Methyl-β-D-glucopyranosyl)-D-galactose has been synthesized by a Koenigs–Knorr reaction. The disaccharide is most readily characterized in the form of the crystalline glycosyl alditol peracetate.
The Cotton Effects of Conjugated Homoannular Dienes. I. The Non-generality of the Rule of Moscowitz
Authors: Lessard J. , Ruest L. , Engel Ch. R.
Published: May 2006

The non-generality of the diene rule of Moscowitz, relating the helicity of a non-planar conjugated homoannular diene to the sign of its Cotton effect, is discussed. We report the preparation of 3β-bromoacetoxy-16α-ethyl-162-cyano-162,21-cyclo-5α-pregna-17,21-diene, the X-ray crystallographic analysis of which confirms, as reported by Ahmed and Pollard, the stereochemistry which we previously assigned to the parent alcohol and acetate. We also report the synthesis of the methyl ketonic analogues of these dienonitriles and show that their sodium borohydride reduction product still has a Cotton effect in contradiction to the diene rule. The implications of these and other experiments are discussed.
Some Thermodynamic Properties of Lithium Chlorate in Water and Dioxane–Water mixtures
Authors: Campbell A. N. , Bhatnagar O. N.
Published: May 2006

Heats of solution and heats of dilution of lithium chlorate in water and dioxane–water mixtures have been determined experimentally. From these data apparent molal heat content, ΦL, and relative partial molal heat contents of solvent, [Formula: see text] and of solute [Formula: see text] have been calculated. The values of ΔG0, ΔH0, and ΔS0are also calculated.
Peptides de l'acide djenkolique. II. Une nouvelle méthode de synthèse du glutathion oxydé
Authors: Marinier Bernard , Bérubé Michèle
Published: May 2006

This paper shows that it is possible to convert a protected peptide containing djenkolic acid to the corresponding peptide containing cystine. Thus, the tripeptide 8 and the pentapeptide 9 were converted to peptides 10 and 11 respectively by treatment with bromine in anhydrous medium followed by an hydrolysis. The pentapeptides 9 and 11 were then deprotected and purified by filtration through Sephadex G-10 to give respectively the pentapeptide bis-γ-L-glutamyl-L-djenkolyl-bis-glycine (7) and oxidized glutathione (2) with overall respective yields of 57 and 38% from djenkolic acid (1).
Triazine Intermediates in the Decomposition of 1-(o-Carbethoxyphenyl)-3-(o-cyanophenyl)-triazene in Aqueous Ethanol
Authors: Vaughan Keith
Published: May 2006

The thermal decomposition of 1-(o-carbethoxyphenyl)-3-(o-cyanophenyl)-triazene (4) in aqueous ethanol has been found to give 2-phenylquinazolin-4(3H)-one (8); the formation of triazine intermediates in the reaction has been established.
L'effet d'anions sur l'oxydation anodique du méthanol
Authors: Belanger Guy
Published: May 2006

Anodic oxidation of methanol in acidic medium (1 N H2SO4) is briefly reviewed with the presentation of polarization and potentiodynamic curves. The possible mechanism of oxidation is presented: the inhibition phenomenon of oxidation is illustrated by the formation of oxides on the surface of platinum. The oxidation current of methanol is sometimes modified by the presence of anions in a low concentration (10−3 to 10−4 N). An attempt is made to relate the inhibitor effect of some anions to theoretical values of binding strength, crystal lattice energy, and heat of hydration. A succinct correlation can be set up between the importance of the inhibition effect and the classification of the anions in hard or soft bases.
Self Association of Folic Acid in Aqueous Solution by Proton Magnetic Resonance
Authors: Lam Yui-Fai , Kotowycz George
Published: May 2006

Proton magnetic resonance experiments on the disodium salt of folic acid in aqueous solutions (pD 7.1) indicate that the folate ion exists in an unfolded, extended conformation in solution. However, based on a temperature and concentration dependence of the proton chemical shifts, folate ions are involved in intermolecular association consisting of a vertical stacking interaction. A stacking model is proposed for the association with the hydrophilic ends of the molecule alternating in orientation with respect to the hydrophobic portion of the neighboring molecules.
Juvenile Hormone Mimics in Conifers. I. Isolation of (−)-cis-4-[1′(R)-5′-Dimethyl-3′-oxohexyl]-cyclohexane-1-carboxylic Acid from Douglas-fir Wood
Authors: Rogers I. H. , Manville J. F.
Published: May 2006

The petroleum ether extract from the whole-wood meal of a British Columbia Interior variety of Douglas-fir has yielded a new and potentially useful juvenile hormone mimic, (−)-cis-4-[1′(R)-5′-dimethyl-3′-oxohexyl]-cyclohexane-1-carboxylic acid (3a). This compound possesses the opposite steric configuration at C-1′ to that of (+)-juvabione (1a), which has been isolated by others from balsam fir. Also, it occurs exclusively as the free acid. Not all Douglas-firs contain this compound and the biological consequences of its formation are being explored.
Photoisomerization of 2-Alkenes in the Presence of Hydrogen Sulfide
Authors: Collin Guy J. , Perrin Patrick M.
Published: May 2006

In far u.v. photochemistry, the radicals formed react with hydrogen sulfide to give, amongst others, thiyl radicals (HS•). These radicals initiate the cis–trans isomerization of 2-olefins in a chain mechanism. We have tried to demonstrate that the thiyl radicals are also chain carriers. Quantum yields for the isomerization of cis to trans compound are probably of the order of 6–7 × 103 and the length of the chain, of the order of 4.7 × 103. We have also studied the radiolysis of these reactions in the liquid phase. The effect of oxygen and of conjugated di-olefins, such as 1,3-butadiene and 1,3-pentadiene is also discussed.
Novel Rearrangement During Alkaline Hydrolysis of 1,1,1-Trichloro-2-alken-4-ones
Authors: Kiehlmann Eberhard , Menon B. C. , Wells J. I.
Published: May 2006

The action of a five-fold excess of potassium hydroxide in methanol on 1,1,1-trichloro-2-penten-4-one (1), 1,1,1-trichloro-6-methyl-2-hepten-4-one (5), and 1,1,1-trichloro-6,6-dimethyl-2-hepten-4-one (9) gives rise to the potassium salt of 5-chloro-2,4-pentadienoic acid (2), the potassium salt and methyl ester of 5-chloro-6-methyl-2,4-heptadienoic acid (7), and the methyl ester of 5-chloro-6,6-dimethyl-2,4-heptadienoic acid (10), respectively.When the same reaction is performed with an equimolar amount of base, 1 is converted into methyl 5-chloro-2,4-pentadienoate (3) as well as 1,1,1-trichloro-2-methoxy-4-pentanone (4); the latter compound (4) is shown to be a true intermediate in the formation of 3.Neither 1,1,1-trichloro-5-methyl-2-hexen-4-one (11) nor 1,1,1-trichloro-5-ethyl-2-hepten-4-one (14) yields the expected dienoic acid or ester when treated with an equimolar amount of potassium hydroxide. Instead, alkaline methanolysis of 11 leads to the formation of a mixture of 1,1,1-trichloro-2-methoxy-5-methyl-4-hexanone (12) and 1,1-dichloro-2,5-dimethoxy-5-methyl-4-hexanone (13), whereas 14 gives predominantly 1,1,1-trichloro-2-methoxy-5-ethyl-4-heptanone (15) and traces of 1,1-dichloro-2,5-dimethoxy-5-ethyl-4-heptanone (16).On the basis of these observations, a mechanism is proposed for the formation of 2, 7, and 10 which requires the presence of two geminal α-hydrogen atoms in the olefinic starting material.
Adiabatic Calorimetric Studies of the Adsorption of Sulfur Dioxide at 423 °K on Heat-treated Magnesias Characterized by Electron Microscopy
Authors: Glass R. W. , Ross R. A.
Published: May 2006

Calorimetric heats of adsorption of sulfur dioxide at surface coverages from 0.2 to 7.7 μmol m−2 have been measured on a series of magnesias heat-treated at 600, 700, and 800 °C. Structural features of the adsorbents have been characterized by analysis of nitrogen adsorption–desorption isotherms and by transmission electron microscopy.Heats of adsorption at 423 °K for adsorbed amounts of 0.3 μmol m−2 were respectively, 86.0, 87.0, and 77.0 kcal mol−1 for the 600, 700, and 800 °C samples. The values for the 600 and 700 °C samples fell rapidly above a coverage of 2.0 μmol m−2 to around 44.0 kcal mol−1 at 5.0 to 7.0 μmol m−2, while the values for the 800 °C sample decreased continuously to 39.0 kcal mol−1 at the same coverage.Crystallite shapes tended increasingly towards the cubic form as the temperature of heat-treatment was increased and average particle sizes were 80, 240, and 320 Å for the 600, 700, and 800 °C samples, respectively.It is proposed that the very high heats obtained on all the samples are due to interactions with high-energy defect centers in the oxide and with the formation of magnesium sulfite initially, and magnesium sulfate towards monolayer completion.
Conformations of Bridged Diphenyls. III. Crystal Structure of 2-(2′-Carbomethoxy-4′-nitrophenoxy)-1,3,5-trichlorobenzene
Authors: Griffith E. A. H. , Chandler W. D. , Robertson B. E.
Published: May 2006

The structure of 2-(2′-carbomethoxy-4′-nitrophenoxy)-1,3,5-trichlorobenzene, C14H8NO5Cl3, has been determined by X-ray diffraction. The crystals are triclinic, a = 8.862(10), b = 15.164(10), c = 13.028(14) Å, α = 90.35(8), β = 116.28(8), γ = 97.54(8)°, [Formula: see text] with Z = 4. The intensities of 6417 independent reflections were measured on a four circle diffractometer of which 4526 were used in the refinement to give a final least-squares residue of 0.047. The two independent molecules in the unit cell show a similar conformation to that found in earlier studies of diphenyl ethers, and the conformation appears to be determined partly by steric effects, since conjugation between the nitro-substituted ring and the ether oxygen atoms is less pronounced than found previously.
A Kinetic Study of the Oxidative Addition of Substituted Benzenethiols Towards trans-Halocarbonylbis(triphenylphosphine)iridium(I)
Authors: Gaylor J. R. , Senoff C. V.
Published: May 2006

not available
Free Radical Bromination of Saturated Hydrocarbons using Bromine and Mercuric Oxide
Authors: Bunce N. J.
Published: May 2006

The reaction of alkanes with a mixture of bromine and mercuric oxide gives alkyl bromides in preparatively useful yields. The reagent is significantly more reactive than elemental bromine, and it is believed that bromine monoxide, formed insitu by the interaction of bromine and mercury oxide, is the reactive intermediate. Bromination by bromine monoxide is a free radical chain process in which hydrogen abstraction is carried out predominantly by bromoxy (BrO•) radicals, and to a lesser extent by bromine atoms.
Aqueous Nonelectrolyte Solutions. Part XI. Mercury Solubility in 6.10 molal Sodium Chloride
Authors: Glew D. N. , Hames D. A.
Published: May 2006

The solubility of mercury in aqueous 6.10 m NaCl has been determined between 5 and 70 °C. Solubility equations and thermodynamic functions are derived and compared with those for mercury in water. Salting-out constants are given.
Ambident Ligands. I. Phenylsulfoxyacetic Acid
Authors: Gogan N. J. , Newlands M. J. , Tan (Née Yap) Beck-Yu
Published: May 2006

Phenylsulfoxyacetic acid, C6H5S(O)CH2CO2H, a potential ambident ligand, forms simple salts with magnesium(II), calcium(II), barium(II), manganese(II), cobalt(II), nickel(II), copper(II), zinc(II), silver(I), and mercury(I). With cadmium(II) it forms a simple salt and a complex, oxygen-bonded to the sulfoxide group. With platinum(II) it gives complexes which are sulfur-bonded to the sulfoxide group.
Hydrogen Isotope Exchange in 2-Butanone. Further Measurements and Some Comments
Authors: Cox R. A. , Thorpe J. W. , Warkentin J.
Published: May 2006

The ratio of rate constants for exchange at the methylene and methyl positions of butanone, [Formula: see text], is shown to be near 1.69 in 1:1 acetic acid–acetate buffer; nearly twice the value (0.86) for deuterioxide catalysis at 54.8°. Methods of obtaining rate constants for acetate catalysis from composite rates (acetate and deuterioxide), or from rates in buffered media, are shown to be adequate for estimating rate ratios.Detailed temperature dependence of the relative rate constants for either system is not yet available but the effects are known to be small. For butanone enolizations the isokinetic temperature is in the neighborhood of 35°, when reaction is catalyzed by deuterioxide in aqueous media.
Addition Reactions in the Nitration of Some Polycyclic Aromatic Compounds
Authors: Fischer A. , Leonard D. R. A.
Published: May 2006

Reaction of 3-oxo-1,2,3,7,8,9,10,10a-octahydrocyclohepta[de]naphthalene with nitric acid in acetic anhydride gives two stereoisomeric 4-acetoxy-6a-nitro-3-oxo-1,2,3,4,6a,7,8,9,10,10a-decahydrocyclohepta[de]-naphthalenes as well as the expected nitro substitution products. Formation of these adducts from a substrate containing a meta-directing deactivating substituent shows that the 1,4-addition reaction of acetyl nitrate is more general than previously suspected. 1,4-Acetyl nitrate adducts are also formed from tetralin, benzsuberane, 5,6,7,8-tetrahydrocyclohepta[fg]acenaphthene, and 1,2,3,4,7,8,9,10-octahydrodicyclohepta[de,ij]naphthalene. Decomposition of the last two adducts gives in each case a product with the nitro group substituted into the alicyclic ring.
Oxidations with Potassium trans-1,2-Diaminocyclohexanetetraacetato-manganate(III). II. Reaction of the Complex with Hindered Phenols
Authors: Stewart Ross , Poh Bo Long
Published: May 2006

A series of 4-substituted-2,6-di-t-butylphenols has been oxidized with potassium trans-1,2-diaminocyclohexanetetraacetatomanganate(III) KMnIIICyDTA(H2O), in methanol containing 2.5% water by volume. Addition of either acid or base greatly accelerates the reaction, acid because it produces HMnIIICyDTA(H2O), and base because it produces both MnIIICyDTA(OH)2− and the phenolate ion.In acidic methanol HMnIIICyDTA(H2O) reacts with both methanol and the phenol leading to formation of both methoxy and aryloxy radicals. The latter are stable in some instances and in others undergo further reaction. The methoxy radicals produced by the concomitant oxidation of methanol are competed for by MnIII and by phenol; formaldehyde and MnII being the products in the former case and methanol and aryloxy radicals in the latter case.In basic methanol MnIIICyDTA(OH)2− converts the hindered phenols to aryloxy radicals, some of which are stable and others of which undergo further reaction.Isotope effects, kH/kD, between 5 and 6 are observed for the oxidation of the phenols in acidic or neutral CH3OD. Smaller effects (less than 2) are observed in basic solution. Substituents have a large effect on the reaction only in basic solution. The ρ of 2.69 in base probably reflects the effect of substituents on the ionization of the phenol.
Enthalpies of Dissociation of Ammonia and Amine Adducts of some Tetraalkylammonium Pentafluorosilicates
Authors: Wharf I. , Onyszchuk M.
Published: May 2006

Condensed phase enthalpies of dissociation of [R4N][SiF5(NH3)], in which R = C2H5, C3H7, and C5H11, are in the order: C2H5 — < C3H7 — < C4H9 — > C5H11 —, and a lower limit of 16.8 ± 0.6 kcal mol−1 is suggested for the gas phase interaction of NH3 with [Formula: see text]. Enthalpies of dissociation of the amine adducts, [(C5H11)4N][SiF5L], in which L = CH3NH2, (CH3)2NH, and (CH3)3N are in the order: [Formula: see text].
A Nuclear Magnetic Resonance Study of some 4-X-Substituted-2,6-Dinitroanisoles and Related Meisenheimer 1,3- and 1,1-Complexes
Authors: Simonnin M. P. , Lecourt M. J. , Terrier F. , Dearing C. A.
Published: May 2006

The structures of transient 1,3-complexes 2 and stable 1,1-complexes 3 formed by the reaction of methoxide ion with various 4-X-2,6-dinitroanisoles in DMSO-d6 are confirmed by n.m.r. spectroscopy. 13C satellites in the proton spectra of anisoles and 1,1-complexes have been used to obtain [Formula: see text] as well as 4JH–H in these symmetrical compounds.The chemical shifts of the ring protons in 1,3- and 1,1-complexes give some information concerning the influence of the substituent X on the delocalization of the negative charge. In anisoles and 1,1-complexes, [Formula: see text] of the ring protons are mainly dependent on the inductive effect of X. Furthermore, a linear relationship is observed in anisoles between the chemical shift as well as [Formula: see text] of the methoxyl protons and the Hammett σP constant of X, thus suggesting an identical geometry of these molecules at C-2,-1, and -6.
Dethioacetalization with Thallium(III) Trifluoroacetate
Authors: Ho Tse-Lok , Wong C. M.
Published: May 2006

Thioacetals undergo facile hydrolysis on treatment with thallium (III) trifluoroacetate.
The Reactions of Organometallic Compounds Involving Silicon. Reactions of Triphenyl-, Diphenylmethyl-, and Phenyldimethylsilyl-lithium with 9-Phenylfluorene in Tetrahydrofuran
Authors: Hamid M. A.
Published: May 2006

Triphenyl-, diphenylmethyl-, and phenyldimethylsilyl-lithium react very rapidly with 9-phenylfluorene in tetrahydrofuran (THF) but the reaction can be followed spectroscopically using the stop-flow technique at low temperatures. The order of reaction, found from the dependence of the initial rate of reaction on the initial reactant concentrations, is unity in both 9-phenylfluorene and the relevant organosilyl-lithium reagent. The thermodynamic constants of activation for the reaction between 9-phenylfluorene and triphenylsilyl-lithium (Ph3SiLi), diphenylmethylsilyl-lithium (Ph2MeSiLi), and phenyldimethylsilyl-lithium (PhMe2SiLi), respectively, are: ΔH≠ = 4.5, 4.0, and 4.0 kcal mol−1; ΔG≠ = 13.0, 12.5, and 12.5 kcal mol−1; ΔS≠ = −34.9, −34.8, and −34.9 cal mol−1 deg−1
The Conformation of Racemic 4,6-Dimethyl Trimethylene Sulfite by Gas Phase Electron Diffraction
Authors: Mustoe Frank J. , Hencher J. Lawrence
Published: May 2006

The molecular geometry of the racemate trans-4,6-dimethyl trimethylene sulfite has been studied in the gas phase by electron diffraction. Six trial conformations were examined by least squares fitting of the intensity data. A significance test applied to the fits obtained for each of the six static models tested indicate that the best single representation of the molecule has a chair conformation, although a mixture containing other conformations could not be definitely eliminated. It was not possible to conclusively discriminate between an axial or an equatorial S=O bond, although the axial position is favored. The following bond distances (rg values) and angles were determined: C—H = 1.119 ± 0.020, C—C = 1.505 ± 0.014, C—O = 1.413 ± 0.013, S=O = 1.480 ± 0.022, S—O = 1.622 ± 0.009 Å; [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text]. The following angles were assumed to be tetrahedral: [Formula: see text], [Formula: see text], [Formula: see text]. The errors are estimated to be at the 95% confidence level. The molecular parameters are in agreement with those of trimethylene sulfite.
The Synthesis of 17β-(4(5)imidazolyl)-5α-androstane-3β,11β-diamine: a Water Soluble Steroid with a Potentially Catalytic Substituent
Authors: Guthrie J. Peter
Published: May 2006

The title compound, 9, has been synthesized in an eight-step process, starting with corticosterone (1). The Weidenhagen reaction on 1 converted the 17-COCH2OH to an imidazole. Reduction with lithium–ammonia–methanol gave 17β-(4(5)-imidazolyl)-5α-androstane-3β, 11β-diol (3) which could be selectively oxidized to the 3β-ol, 11-one, which was then converted to the oxime and hydrogenated to the 3β-ol, 11β-amine, 6. Oxidation of the 3β-ol to the 3-one, oximation and sodium–propanol reduction gave 9.
The Chromyl Chloride Oxidation of α-Pinene
Authors: Bachelor Frank William , Cheriyan Ukken Ouseph
Published: May 2006

The oxidation of α-pinene with chromyl chloride has been investigated and 11 compounds amounting to 81% of the total reaction have been isolated and identified. Besides a small amount of recovered α-pinene these compounds have been found to be products of acid-catalyzed rearrangement (bornyl chloride, borneol, and limonene); products of allylic oxidation (myrtenal, myrtenol, and verbenone); and products of oxidative addition–rearrangement (pinocamphone, pinocarveol, campholenaldehyde, and pinol). In addition, p-cymene was isolated which may arise from several oxidation sequences. The isolation of optically active pinol suggests that at least part of the oxidation of α-pinene is initiated by attack of the chromyl chloride on the same side of the double bond as the dimethyl substituted bridge. An attack by a positive chromium atom on the double bond is ruled out by a deuteration study.
Reactions of Ozonides. IX. A Radioisotopic Dilution Study of Ozonide Methanolysis
Authors: Kerur Dundappa R. , Diaper Dennis G. M.
Published: May 2006

A radioisotopic dilution study indicates that no significant amounts of[Formula: see text]are produced by reacting [Formula: see text] with methanol.
The Crystal Structure of the Platinum Acetylenic Complex, K[Pt((C2H5)2C(OH)C≡CC(OH)(C2H5)2)Cl3]
Authors: Beauchamp A. L. , Rochon Fernande D. , Theophanides T.
Published: May 2006

The complex salt K[Pt((C2H5)2C(OH)C≡CC(OH)(C2H5)2)Cl3] forms monoclinic crystals, a = 10.841(5), b = 9.796(4), c = 17.414(6) Å, β = 100.44(2)°, Z = 4, space group P21/c. Positional and anisotropic thermal parameters were refined to R = 0.069 and Rw = 0.064 by using 1662 independent reflections.The coordination around platinum is planar, and the triple bond of the acetylenic ligand is approximately perpendicular to the coordination plane. The triple bond is 1.18(3) Å and the C≡C—C angles [Formula: see text] show a deformation of the ligand in a direction away from the platinum atom with the two hydroxyl groups in cis configuration, above and below the plane of the PtCl3 group. The cis Pt—Cl bonds are of normal length, but the trans Pt—Cl bond seems to be shorter. The K+ ion is surrounded by four chlorine atoms and two oxygen atoms at relatively short distances. The oxygen–potassium attraction seems to be the predominant direct interaction of the—OH groups with the rest of the crystal.
A Synthetic Route to Dihydrojasmone; Sulfuric Acid as Dethioacetalization Agent
Authors: Ho Tse-Lok , Ho Honor C. , Wong C. M.
Published: May 2006

Dihydrojasmone has been synthesized in three steps from the dithiane 2. Hydrolysis of vinylic chloride and a dithioacetal group was achieved simultaneously using sulfuric acid. The scope of this dethioacetalization procedure has been explored.
Crystal and Molecular Structure of Hexaaquocobalt(II)–Hexafluorosilicate(IV), [Co(H2O)6][SiF6]
Authors: Lynton H. , Siew P-Y.
Published: May 2006

The structure of hexaaquocobalt(II)-hexafluorosilicate(IV) has been determined by the heavy atom method. The compound crystallizes in the space group [Formula: see text], with three molecules in the hexagonal unit cell of dimensions a = 9.358(16), c = 9.712(14) Å. The atomic parameters were refined by block diagonal least squares using anisotropic thermal parameters. The hydrogen atom positions were established but the parameters were not refined. The final agreement residual for 151 observed reflections is R = 0.043.The structure consists of discrete Co(H2O)62+ and (SiF6)2− octahedra joined systematically by [Formula: see text] hydrogen bonds into chains parallel to the [Formula: see text] axis.
Calculated Geometry for Ten-Coordination
Authors: Lin Yeong C. , Williams Donald E.
Published: May 2006

The predicted geometry for coordination of ten ligands of equal size about a central atom was found by minimizing the interligand repulsion energy. The favored arrangement of hard-sphere ligands is of the 2:4:2:2 type, of symmetry C2v. The favored arrangement of soft-sphere ligands is of the 1:3:3:3 type, symmetry C3v, or of the 1:4:4:1 type, symmetry D4d, depending on the degree of softness. The differences in repulsion energy among the three favored arrangements were small, making it likely that any differences in ligand sizes would be an important factor in determining the structure.
The Total Synthesis of Daunomycinone
Authors: Wong Chiu Ming , Schwenk Robert , Popien Donald , Ho Tse-Lok
Published: May 2006

The aglycone of the antitumor antibiotic daunomycin, daunomycinone 1, has been synthesized along with its C-1 isomer.
Studies on Horseradish Peroxidase. XI. On the Nature of Compounds I and II as Determined from the Kinetics of the Oxidation of Ferrocyanide
Authors: Cotton M. L. , Dunford H. B.
Published: May 2006

In order to investigate the nature of compounds I and II of horseradish peroxidase, the kinetics were studied of ferrocyanide oxidation catalyzed by these compounds which were prepared from three different oxidizing agents. The pH dependence of the apparent second-order rate constant for ferrocyanide oxidation by compound I, prepared from ethyl hydroperoxide and m-chloroperbenzoic acid, was interpreted in terms of an ionization on the enzyme with a pKa = 5.3, identical to that reported previously for hydrogen peroxide. The second-order rate constant for the compound II-ferrocyanide reaction also showed the same pH dependence for the three oxidizing substrates. However, with more accurate results, the compound II-ferrocyanide reaction was reinterpreted in terms of a single ionization with pKa = 8.5. The same dependence of ferrocyanide oxidation on pH suggests structurally identical active sites for compounds I and II prepared from the three different oxidizing substrates.
Electrochemical Oxidation of Trifluoroacetic Acid in an Organic Medium. II. In Presence of Propionic Acid
Authors: Renaud Roger N. , Sullivan Donald E.
Published: May 2006

Trifluoropropane could not be prepared by the "crossed" Kolbe reaction from a mixture of trifluoroacetic acid and propionic acid. Instead, a mixture consisting of 3,3,3-trifluoropropene, 1,2-bis(trifluoromethyl)ethane, 1,1,2-tris(trifluoromethyl)ethane, and 1,2,4-tris(trifluoromethyl)butane was obtained. The probable mechanism for the reaction is discussed.
Stereochemical and Steric Effects in Nucleophilic Substitution of α-Halo Ketones
Authors: Thorpe J. William , Warkentin John
Published: May 2006

Bimolecular substitution reactions of α-halo ketones with acetate and azide ions are remarkably insensitive to steric hindrance. 1-Bromo-4,4-dimethyl-2-pentanone (bromomethyl neopentyl ketone) is only slightly less reactive than bromo acetone in spite of the fact that the carbonyl group in the former is neopentylic. The results are interpreted in terms of a normal SN2 transition state, not involving either special alignment of entering and leaving group with the π-orbital of the carbonyl function (conjugation) or covalent interaction between nucleophile and carbonyl carbon (bridging) for reaction of conformation-ally-mobile systems. Conformationally-fixed systems, on the other hand, may be affected by such factors. trans,-2-Chloro-4-t-butylcyclohexanone is 61-fold more reactive than the cis-isomer, in the SN2 reaction with acetate. Activation parameters support the conclusion that only those α-halo ketones which are stereochemically set up for conjugation and bridging undergo substitution by a mechanism significantly different from that operating in corresponding reactions of alkyl halides.Possible significance of the results to the mechanism of bimolecular elimination is discussed.
The Temperature Dependence of the Diffusion Coefficients of Ar, CO2, CH4, CH3Cl, CH3Br, and CHCl2F in Water
Authors: Maharajh Dow M. , Walkley John
Published: May 2006

Diffusion coefficient values are reported over a 0 to 35 °C temperature range for Ar, CO2, CH4, CH3Br, CH3Cl, and CHCl2F in water. Various empirical theories relating these diffusion coefficient values to the viscosity of water (η) and the size of the diffusing solute molecule are examined. None are found valid though a linear relationship is found to hold between log D and log η for all systems. McLaughlin's hard sphere theory is examined and found in surprisingly good agreement with experiment. It is seen, however, that this theory cannot adequately predict the temperature dependence of the diffusion coefficient of the solute.
The Ultracentrifuge as a Pressure-Densitometer
Authors: Rogers Kenneth S. , Burkat Rosalind , Richard Alfred J.
Published: May 2006

The Spinco E analytical ultracentrifuge has been used to determine specific volumes or densities for organic liquids and water at pressure from 1 to 100 bars. Specific volumes calculated from experimental isothermal compressibilities (βT) were in very close agreement with values from measurements recorded in literature. Bulk modulus (1/βT) vs. pressure plots indicated that the Lennard–Jones 6-12 potential does not satisfactorily describe the molecular interactions for carbon tetrachloride, benzene, cyclohexane, or water. The organic liquids were reasonably approximated by a 7-28 potential or more exactly by a 6-24 potential. None of the two-term potentials could account for the interaction of water molecules.
Liquid Bismuth Calorimetry: Enthalpies of Solution of Copper, Indium, and Tellurium, and Enthalpies of Formation of Cuprous Selenides
Authors: Skeoch Kenneth Gordon , Heyding Robert Donald
Published: May 2006

An isoperibol liquid metal solution calorimeter in which samples are introduced below the surface of the melt is described. Enthalpies of solution in liquid bismuth at ca. 625°K in kcal mol−1 were found to be +0.99 ± 0.05 for copper, −1.41 ± 0.08 for indium, and −1.16 ± 0.07 for tellurium.Enthalpies of formation in kcal mol−1 at 625°K of cubic cuprous selenides are −7.98 ± 0.20 for Cu1.80Se; −7.80 ± 0.19 for Cu1.85Se; −5.92 ± 0.20 for Cu1.90Se; −5.29 ± 0.20 for Cu1.95Se; and −5.21 ± 0.14 for Cu2.00Se.
The Rate Constants for the Reactions of Ozone with Triphenylphosphite and Triphenylphosphine
Authors: Razumovskii Stanislav Dmitrievich , Mendenhall George David
Published: May 2006

The stoichiometry and rate constants for the reaction of triphenylphosphite and triphenylphosphine with ozone were measured at several temperatures. The rate was first order in each reactant, with k = (3 ± 1) × 104 and (5 ± 2) × 103 M−1 s−1 respectively, for the reaction of ozone with triphenylphosphine and triphenylphosphite (2,4-dimethylhexane, −90°). The reaction of ozone with triphenylphosphite has a low activation energy in carbon tetrachloride. The stoichiometry was 1:1 for both compounds under these conditions.
Nucleic Acid Related Compounds. 5. The Transformation of Formycin and Tubercidin into 2′- and 3′-Deoxynucleosides
Authors: Robins Morris J. , McCarthy Jr. James R. , Jones Roger A. , Mengel Rudolf
Published: May 2006

Reaction of tubercidin (4-amino-7-β-D-ribofuranosylpyrrolo[2,3-d]pyrimidine) (1) with α-acetoxyisobutyryl chloride in the presence of excess sodium iodide in acetonitrile gave an acylated iodo intermediate (2) which was converted into 3′-deoxytubercidin (4) by hydrogenolysis and subsequent saponification.Analogous treatment of formycin (7-amino-3-β-D-ribofuranosylpyrazolo[4,3-d]pyrimidine) (5) gave 3′-deoxyformycin (6) and 2′-deoxyformycin (7) in an approximate ratio of 3:2. These purified nucleosides, 6 and 7 were individually deaminated enzymatically to give 3′-deoxyformycin B (8) and 2′-deoxyformycin B(9).Biological rationale, n.m.r., and mass spectra of these antibiotic-derived deoxynucleosides are discussed.
Acid-catalyzed Exchange at 250 °C; a Simple and Quantitative Method for the Replacement of Aromatic Protons by Deuterium
Authors: Werstiuk Nick H. , Kadai Tony
Published: May 2006

Treatment of benzene (1), biphenyl (2) and o- and m-xylene (3 and 4) with 4% v/v concentrated HCl (concentrated DCl) in D2O at 250 °C results in selective deuteration of the aromatic nucleus with excellent isotopic incorporation and quantitative yield.