bluuebunny/crossref_metadata_2025 huggingface dataset:
Theory of Enthalpy of Mixing in Reactive Charge Asymmetrical Molten Salt Systems. Part I. Binary Solutions
Authors: Flengas S. N. , Kucharski A. S.
Published: May 2006

The enthalpies of mixing for the charge asymmetrical molten salt systems; MnCl2-ACl, FeCl2–ACl, CoCl2–ACl, NiCl2–ACl, MgCl2–ACl, and CdCl2–ACl (where A represents Li, Na, K, Rb, and Cs) have been calculated by separating the mixing process into two parts. One part of enthalpy of mixing results from the "reaction" to form a tetrahedral complex, MCl42−, and another part of the enthalpy of mixing arises from the "mixing" of the complexed species with the remaining free components. The "complex" species are treated as orderly configurations defined by shorter anion to cation distances within which the central metal cation interacts with the surrounding other metal cations through bridging chloride ions. The model takes into account the difference in the coordination number of the mono- and divalent components. The interaction parameters are shown to depend upon the radii of the alkali metal cations.
Electron Spin Resonance Studies of Reactions of Photo-generated Organic Radicals with Hydrogen Peroxide in Aqueous Solution
Authors: Burchill C. E. , Jones P. W.
Published: May 2006

The reactions with H2O2 of free radicals derived from 2-propanol, methanol, dimethoxymethane, and tetrahydrofuran have been investigated by e.s.r. using in-cavity photolysis with acetone photosensitization to generate the radicals in flowing aqueous solutions. The variation in the concentrations of the radicals derived from a particular solute with addition of H2O2 is attributed to the selective oxidation of one radical by H2O2, propagating a secondary chain reaction, e.g.,[Formula: see text]The rate constant for the oxidation of the acetone ketyl radical ((CH3)2ĊOH) by H2O2 is estimated to be 5 × 105 M−1 s−1.The results and conclusions of this study are demonstrated to be consistent with the results of previous investigations employing γ-radiation, photolysis, and the reaction of Ti(III) with H2O2 for initiation.Results are also reported for the direct photolysis of aqueous malonic acid in the presence of H2O2.
Kinetics of Proton Transfer Reactions of Carbon Acids. II. Reaction of Di-(4-nitrophenyl)methane with Alkoxide Bases
Authors: Jarczewski A. , Leffek K. T.
Published: May 2006

The second-order rate constants have been measured over a range of temperatures for the proton-transter reactions from di-(4-nitrophenyl)methane to ethoxide, isopropoxide, and t-butoxide ions in solvents consisting of the corresponding alcohols containing 10% toluene by volume. The activation parameters ΔH≠ and ΔS≠ have been calculated and an interpretation of them is given in terms of solvation effects during the activation process. A comparison between the activation parameters for proton transfers and E2 olefin-forming β-elimination reactions is made and discussed with respect to transition state character of the latter reactions.
Vapor Phase Catalytic Transformations of Terpene Hydrocarbons in the C10H16 Series. I. Isomerization of α-Pinene over Alumina
Authors: Stanislaus A. , Yeddanapalli L. M.
Published: May 2006

The isomerization of α-pinene in the vapor phase over alumina catalysts of varying acid strength has been studied. The isomerization proceeds via two parallel paths, one giving bi- and tricyclic products such as camphene, β-pinene, tricyclene, and bornylene and the other giving rise to monocyclic compounds such as dipentene, terpinolene, α-terpinene, γ-terpinene, p-cymene, and p-menthene. Dependence of the distribution of reaction products on space time reveals that camphene, β-pinene, tricyclene, dipentene, and terpinolene are the primary products. The acid strength of alumina catalysts has a remarkable influence on the selectivity ratio of bi- and tricyclic to monocyclic products, the strong acid sites favoring the formation of monocyclic products. From the study of the reactions of camphene and tricyclene over the same catalysts under similar conditions it has been concluded that the decrease in the selectivity ratio with increasing acid strength of the catalysts is mainly due to the further isomerization of the bi- and tricyclic compounds to monocyclic products which takes place only on the strong acid sites.
Chlorocuprate(II) and Chlorocobaltate(II) Salts of the Aminodiphenyl-phosphonitrileaminodiphenylphosphonium Ion
Authors: Clipsham R. M. , Whitehead M. A.
Published: May 2006

Two new compounds [NH2(C6H5)2PNP(C6H5)2NH2]2[CoCl4] and [NH2(C6H5)2PNP(C6H5)2NH2][CoCl4]CH2Cl2 have been isolated, and characterized by spectrometry, as examples of the general series of quaternary amine transition metal chloride salts. Three other compounds containing the same cations, with empirical formulae, CuP2N3C25H32OCl3 (1), CuP2N3C24H28Cl3 (2), and Cu3P4N6C50H64O2Cl8 (3) have been isolated and studied by spectrometry. The formulae [NH2(C6H5)2PNP(C6H5)2NH2]2[Cu2Cl6] and [NH2(C6H5)2PNP(C6H5)2NH2]2[Cu2Cl6]. 2CH3OH are proposed for (2) and (1) by comparison with the cobalt compounds, and interpretation of the electronic structure. These compounds were produced during attempts to synthesize mixed ring compounds of (PN) and (SN) units.
Stereochemistry of some Altersolanol B Derivatives and their Correlation with Bostrycin
Authors: Gordon M. , Stoessl A. , Stothers J. B.
Published: May 2006

The results of a complete analysis of the proton spectra of altersolanol B acetonide indicate that this compound exists preferentially in the half-chair conformation corresponding to that favored by the parent pigment in the solid state, as shown by previous X-ray studies. In contrast, the triacetate derivative apparently adopts the alternative half-chair conformation.
An Examination of the Heat Capacity of Activation for the Hydrolysis of t-Butyl Chloride in Water
Authors: Scott J. M. W. , Robertson R. E.
Published: May 2006

The influence of ion-pair intermediates on solvolytic displacement reactions is considered for cases where the observed rate constant is complex.Such complex and composite rate constants under certain conditions may show deviations from the Arrhenius temperature dependence law. The deviations will manifest themselves as "spurious" positive and/or negative heat capacities of activation, superimposed on the real heat capacity terms.The hypothesis of Albery and Robinson (1) which proposes that the heat capacity of activation for t-butyl chloride is entirely "spurious" in the sense outlined above, is critically evaluated and rejected. An alternative hypothesis that considers the heat capacity to be a manifestation of solvation effects is retained.The mechanism of the hydrolysis of both the methyl and t-butyl halides in water is discussed and the kinetic laws appropriate to each are shown to be consistent with real heat capacities of activation. The mechanism proposed differs from the classical SN1–SN2 description. Both series of substrates are considered to give rise to intimate-ion-pairs but in the case of the methyl halides these react further by a path which involves the nucleophilicity of the solvent in a kinetically significant way. In the cases of the tertiary compounds, solvent separation of ion-pairs becomes kinetically significant. The nucleophilic component which characterizes the destruction of the solvent-separated ion-pairs for the tertiary compounds is kinetically insignificant.
Etude des oxynitrates de plomb (II). Synthèse des oxynitrates de plomb hydratés et de l'oxyde de plomb anhydre ou hydraté
Authors: Brusset H. , Martin J. J. P. , Martin-Lefevre C. , Repelin Y. , Husson E. , Despagne B.
Published: May 2006

Potentiometric and conductimetric measurements of solutions of sodium hydroxide and lead nitrate at 27 ± 0.2 °C have established the existence of hydrated lead monoxynitrate, dioxynitrate, heptoxytrinitrate and pentoxynitrate. It was shown that the presence of silica inhibits the formation of anhydrous lead oxide but favors that of hydrated lead oxide. The preparation of lead oxynitrates and hydrated lead oxide was carried out over a wide range of temperatures at various concentrations of reactants.
The Electroreduction of Substituted Benzofurazans
Authors: Fawcett W. R. , Forte P. A. , Loutfy R. O. , Prokipcak J. M.
Published: May 2006

The electroreduction of 4- and 5-substituted benzofurazans was investigated at a platinum electrode in acetonitrile. Standard potentials for the reactions were linearly related to the energy of the lowest vacant molecular orbital as estimated by Hückel theory. Standard rate constants for electron transfer decreased as standard potentials in the series became more cathodic. This decrease is attributed to a double layer effect. No correlation was obtained between standard rate constants and observed hyperfine splitting constants for the anion radicals.
Hydrogen Bonding in the case of Self-associated Fluoroalcohols
Authors: Planckaert A. , Sandorfy C.
Published: May 2006

The OH stretching band of polymeric fluoroalcohols exhibits a much higher rate of shifting with temperature but it is less anharmonic than the corresponding band of ordinary alcohols. The degree of self-association in their solutions is discussed.
The Relative Rates of the Reaction of Active Nitrogen with Perfluoro-olefins and Perfluorobutyne-2
Authors: Rujimethabhas M. , Jones W. E.
Published: May 2006

A formulation of the diffusion-kinetic model based on the spherical diffusion flame method is presented and discussed. The application of this technique has been made to obtain the relative rates of the reaction of active nitrogen with perfluoroethylene, perfluoropropene, perfluorobutadiene-1,3, and perfluorobutyne-2.
The Deamination of the 3α- and 3β-Aminocholestanes and their Amide Derivatives
Authors: Bachelor F. W. , White E. H.
Published: May 2006

The nitroso acetamides, naphthamides, and benzylcarbamates of 3α- and 3β-aminocholestanes were decomposed in various solvents and the nitrous acid deaminations of the free amines in acetic acid and aqueous acetic acid mixtures were studied. In these reactions the intramolecular process leads to products with high degrees of retention of configuration, whereas the intermolecular process leads to products which are predominantly equatorial. Diazoalkanes were shown not to be intermediates in these deaminations.
Nuclear Magnetic Resonance Experiments on Acetals. 36. Proton Magnetic Resonance Spectra and Quantitative Conformational Data in 5-Fluoromethylated-5′-Me-1,3-Dioxanes
Authors: Anteunis M. , Dirinck P.
Published: May 2006

A proton magnetic resonance study of [Formula: see text] and 5-CH2F-5′-Me-1,3-dioxanes and the corresponding 2-Me-substituted derivatives enables approximate conformational insights. The system prefers an equatorial polar substitutent at C-5. This is very pronounced for CHF2, and to a lesser but still important extent for CH2F (ΔΔH0 = 488 cal/mol; ΔΔS0 = −3.0 e.u.).
An Electron Spin Resonance Study of a Rhodium(I) Molecular Oxygen Complex in Solution
Authors: James B. R. , Ng F. T. T. , Ochiai Ei.
Published: May 2006

Electron spin resonance studies on the oxygenation of the rhodium(I) cyclooctene complex [RhCl(C8H14)2]2, in N,N-dimethylacetamide (DMA) solution containing chloride show the presence of a paramagnetic species. This is thought to involve a rhodium(II)–superoxide [Formula: see text] species which is likely responsible for some previously reported autoxidation reactions.
13C Nuclear Magnetic Resonance Studies. XVI. 13C Spectra of some Substituted Acrylic Acids and their Methyl Esters. A Correlation of Olefinic Shieldings in α,β-unsaturated Carbonyl Systems
Authors: Brouwer H. , Stothers J. B.
Published: May 2006

The carbon-13 n.m.r. spectra of 26 α,β-unsaturated methyl esters and 16 substituted acrylic acids have been determined and the 13C shieldings are discussed. These data are compared with the recently reported values for several α,β-unsaturated carboxylic acids. Linear regression analysis of the olefinic shielding data for several α,β-unsaturated carbonyl derivatives yields a set of parameters which correlate the results with reasonable precision. The solvent dependence of the 13C shieldings of acrylic acid and methyl acrylate has been examined briefly. The proton results for the methyl esters are discussed briefly.
2,4-Diazapentadienes. I. Prototropy, Cyclization, and Addition–Elimination
Authors: Hunter D. H. , Sim S. K.
Published: May 2006

The preparations and reactions of a series of 1,3,5-triaryl-2,4-diaza-1,3-pentadienes (1) have been investigated. Products of cyclization (2 and 4), prototropy 3 and addition–elimination (5, 6, and 7) have been characterized. Also, the preparations and reactions of 3, a new isomer of 1, have been studied.
Cancentrine. III. Dehydroderivatives
Authors: MacLean D. B. , Baczynskyj L. , Rodrigo R. , Manske R. H. F.
Published: May 2006

The structures of dehydrocancentrine-A and -B are elucidated by a combination of physical and chemical methods.
Determination of Conditions for the Suppression of CH3 + Sb(CH3)2→Sb(CH3)3 and Evaluation of D[(CH3)2Sb—CH3]
Authors: Price S. J. W. , Richard J. P.
Published: May 2006

The pyrolysis of trimethylantimony has been studied in a toluene carrier flow system over the temperature range 690–803 °K (total pressures 3.6–173.4 mm, contact times 1.0–13.5 s, decomposition 3.9–89.5%). The progress of the reaction was followed by measuring the amount of methane, ethane, and ethylbenzene formed. In 23 runs the undecomposed alkyl was also determined. The quantity found was in agreement with that expected from the product analysis if three methyl radicals are released for each molecule undergoing reaction. No heterogeneous reaction was detected.Deuterium labeling led to the conclusion that regeneration of the parent alkyl occurred during the course of the decomposition. This regeneration reaction was effectively eliminated by working at toluene pressures above 150 mm. Least squares analysis of the results obtained under conditions where regeneration should not be important givenLog10k/s−1 = 15.33 − (55 900 ± 1 000)/2.3RTThe activation energy should be a good approximation to D[(CH3)2Sb—CH3].Significant decomposition of SbCH3 probably does not occur. It seems most likely that free Sb is formed via 2Sb(CH3) → Sb(CH3)2 + Sb.
The Kinetics of the Insertion Reaction of Tin(II) Chloride with a Mono-substituted Derivative of Cyclopentadienyliron Dicarbonyl Dimer
Authors: Barrett P. F. , Jacobs W. J.
Published: May 2006

The kinetics of the thermal insertion reaction of SnCl2 with the metal–metal bonded complex (π-C5H5)2Fe2(CO)3P(OC6H5)3 have been studied by following the change in the visible spectrum in THF over the temperature range 40.0 to 55.0 °C. The data are consistent with a two-stage mechanism involving the formation of an intermediate in which the iron–iron bond has been broken but the carbonyl bridges are left intact. From the activation enthalpy of 23.4 ± 0.5 kcal/mol for the formation of the intermediate it is concluded that the triphenyl phosphite has brought about a weakening of the iron–iron bond.
Secondary Kinetic Isotope Effects in Bimolecular Nucleophilic Substitutions. V. The Role of the Solvent in the Reaction Between Methyl Iodide and Pyridine
Authors: Leffek K. T. , Matheson A. F.
Published: May 2006

Secondary kinetic deuterium isotope effects are presented for the reaction of methyl-d3 iodide and pyridine in four different solvents. Calculations on mass and moment of inertia change with deuteration in the initial state and an assumed tetrahedral transition state, together with internal rotational effects, are used to rationalize the inverse isotope effects. It is concluded from the variation of the isotopic rate ratio, that the transition state structure varies with solvent.
Kinetic Study of the Pyrolysis of Formaldehyde
Authors: Chen C. J. , McKenney D. J.
Published: May 2006

Kinetics of the thermal decomposition of pure formaldehyde were studied over a temperature range of 466–516 °C and a pressure range of ~ 50–160 Torr. Arrhenius parameters and rate laws were determined for carbon monoxide, hydrogen and methanol as follows:[Formula: see text]A mechanism is postulated which is qualitatively consistent with the experimental results but the activation energy for reaction 1[Formula: see text]is ~15 kcal/mol lower than predicted from recent thermochemical data, suggesting the possibility of a heterogeneous reaction.
Epimerization of Monosaccharides in Acetic Acid and Acetic Anhydride. Synthesis of D-Altrose
Authors: Sowa Walter
Published: May 2006

Acetolysis of 1,2;5,6-di-O-isopropylidene-α-D-allofuranose occurred with inversion at C-2 in a medium composed of acetic acid, acetic anhydride, and sulfuric acid. D-Altrose was isolated in 45% yield by deacetylation and chromatographic separation of the mixture of products. Unsubstituted D-allose did not epimerize under the same reaction conditions.
The Electron Paramagnetic Resonance Spectrum of the Phenalane Anion
Authors: Paskovich D. H. , Reddoch A. H.
Published: May 2006

The phenalane anion has been prepared by the reaction of alkali metals in ether solutions of both phenalane and phenalene. The electron paramagnetic resonance spectra of both the radical and of its ion pairs with sodium and with lithium in THF are reported. At room temperature there is an alternating linewidth involving the β protons caused by conformational interconversion of the axial and equatorial positions. At −80 °C the γ protons are not equivalent and the corresponding coupling constants are resolved.
An Unusual Oppenauer Oxidation of (±) Ophiocarpine
Authors: Šmula V. , Manske R. H. F. , Rodrigo R.
Published: May 2006

The Oppenauer oxidation of (±) ophiocarpine has been carried out to yield 3-(2′-vinyl-3′,4′-methylenedioxy) phenyl-4-hydroxyisoquinoline (2). Photolysis of this compound gave 3,4-dimethoxy-11,12-methylenedioxy-8,9-dihydro[1]benzoxepino(2,3-c) isoquinoline (7), whereas photolysis of the methyl ether of 2 produced N-norchelerythrine.
Evaluation of Unbonded O—H Groups for HDO in Liquid D2O from Infrared Absorptivity Measurements
Authors: Clarke E. C. W. , Glew D. N.
Published: May 2006

Wyss and Falk's infrared absorptivities between 10 and 85 °C for HDO in liquid D2O in the fundamental O—H stretch region have been analyzed numerically and show a statistically significant weak band near 3600 cm−1 at each temperature. This band, the Raman analog of which was reported earlier, confirms the presence of HDO species with unbonded O—H groups in the liquid state. The percentage of HDO species with un-bonded O—H groups is found to be 4.6, 6.1, 10.1, and 11.9, respectively, at 10, 35, 60, and 85 °C.The four predominant HDO species in equilibrium at low temperatures are denned together with their equilibrium constant for the [Formula: see text] bond-rupturing process. A standard enthalpy change of ΔH° = 6800 ± 1100 cal is found for the rupture of one mole of [Formula: see text] bonds. This is in contrast with the apparent enthalpy change of 2900 ± 500 cal, as usually derived from the temperature dependence of the equilibrium quotient. Approximate mole fractions for each of twelve differently bonded HDO species are derived from a model for random H- and D-bond statistics. Results show that the four predominant HDO species give a full interpretation of the absorptivities at 10, 35, and 60 °C but that additional minor species contribute slightly to the absorptivity at 85 °C.
Meisenheimer Complex Formation Between 1,3,5-Trinitrobenzene and Hydroxide Ion. Equilibrium Constants for the Dimethylformamide–Water Solvent System
Authors: Symons E. A. , Buncel E.
Published: May 2006

Sigma-complex formation between 1,3,5-trinitrobenzene (TNB) and hydroxide ion has been studied quantitatively as a function of medium composition for part of the dimethylformamide (DMF)–water solvent system by spectrophotometric methods. Only a 1:1 complex is detected under the conditions of measurement, with [TNB] ≥ [OH−]. The equilibrium constant (Keq) for complex formation in 22 mol % DMF has the value 3 × 10−3 l mol−1, compared with 3 l mol−1 in purely aqueous medium. Further increases in Kcq occur as the DMF content of the medium is raised; in 50 mol % DMF Keq ≈ 105, but reliable Keq values could not be obtained in this region of medium composition. The increase in Keq with increasing DMF content is interpreted largely on the basis of hydroxide ion desolvation.
Terpolymerization of Methacrylonitrile, Styrene, and α-Methylstyrene
Authors: Rudin Alfred , Chiang Schumann S. M. , Johnston H. Kirk , Paulin Paul D.
Published: May 2006

The free radical copolymerization of methacrylonitrile, styrene, and α-methylstyrene was studied at 60 °C in toluene solution. Copolymer composition was calculated from the composition of the unreacted monomers, as measured by g.l.c. Reactivity ratios measured previously for the three monomer pairs involved were used with the simple terpolymerization equation to predict polymer composition. Agreement between predicted and experimental polymer compositions was satisfactory. The behavior of α-methylstyrene can be described by a simple model without reference to ceiling temperature or penultimate effects because sequence lengths of this monomer in the terpolymers are short.A true azeotropic feed composition was not investigated, but several monomer mixtures produced copolymers with compositions which varied so little from that of the feed that the systems could be considered to be azeotropic for practical synthetic purposes. This behavior is in accord with expectations.Analytical accuracy of the gas chromatographic techniques was examined and means are suggested to make the best use of this method in copolymerization studies.
The Hydrogenation of Allene. IV. The Reaction of Allene with Hydrogen Catalyzed by Palladium, Platinum, Iridium, Rhodium, Ruthenium, and Osmium Catalysts
Authors: Mann R. S. , Shah A. M.
Published: May 2006

The reaction between allene and hydrogen over unsupported palladium, platinum, iridium, rhodium, ruthenium, and osmium catalysts has been investigated in a static constant volume system between 70 and 149 °C for a wide range of reactant ratios. The orders of reaction with respect to hydrogen and allene were one and zero, respectively, and temperature independent. The overall apparent activation energies for unsupported platinum, iridium, palladium and rhodium were 17.7, 9.1, 6.4, and 17.4 kcal/mol, respectively. The catalytic activities of the unsupported metals were in the sequence Pd > Ir > Rh > Pt > Ru, Os. Selectivity was highest with palladium and rhodium, and least with iridium. The polymerization was highest with platinum and least with indium.
The Synthesis of Delphinine: A Stereoselective Total Synthesis of an Optically Active Advanced Relay Compound
Authors: Wiesner K. , Jay E. W. K. , Tsai T. Y. R. , Demerson C. , Jay Lizzie , Kanno T. , Křepinský J. , Vilím A. , Wu C. S.
Published: May 2006

A stereoselective total synthesis of the optically active delphinine degradation product 3b is described.
An Investigation of Long-range Proton–Proton Coupling Constants in Phenylacetylene Derivatives
Authors: MacDonald C. J. , Hamer G. K. , Peat I. R. , Reynolds W. F.
Published: May 2006

Signs and magnitudes of long-range coupling constants in three phenylacetylene derivatives have been determined. Values of the coupling constants are discussed in terms of the McConnell formulation and compared with results of MO–INDO–FPT calculations. Coupling constants are dominated by π contributions. Estimated values of hyperfine interaction constants for acetylene and methylacetylene groups are respectively QCC≡CH = −12 and QCC≡CCH = +12 G. The theoretical calculations are in excellent agreement with experimental results. Both approaches allow quantitative estimation of nine bond couplings in 4-vinylphenylacetylene.
Evaluation of Some of the Factors Involved in the Selective Hydrolysis of Aromatic Ester Protecting Groups by α-Chymotrypsin
Authors: Jones J. Bryan , Lin Yong Yeng
Published: May 2006

Studies have been carried out which delineate some of the factors involved in the exploitation of α-chymotrypsin as a catalyst for the specific hydrolysis of selected aromatic ester protecting groups under mild conditions with a specificity not achievable by non-enzymic reagents. The reactions can be carried out under heterogeneous conditions and examination of a series of diesters has shown dihydrocinnamyl to be the most satisfactory of the hydroxyl protecting groups evaluated so far. The degree of specificity achievable is demonstrated by the fact that α-chymotrypsin-catalyzed hydrolysis of 2-acetoxyethyl dihydrocinnamate at pH 7.8 stops when the latter function has been cleaved. In addition, some guidelines have been developed regarding the application of literature specificity data for predicting the course and rate of preparative scale reactions.
An Electron Paramagnetic Resonance Study of a fast Lewis Acid–Base Reaction between Copper (II) bis(Diethyldithiocarbamate) and Pyridine in Benzene
Authors: Farmer J. B. , Herring F. G. , Tapping R. L.
Published: May 2006

The fast Lewis acid–base reaction between copper(II) bis(diethyldithiocarbamate) and pyridine[Formula: see text]has been studied from 280 to 320 °K in benzene. The method employed is the analysis of electron paramagnetic resonance line positions and line widths using the solutions of the modified Bloch equations in the fast exchange limit. Arrhenius plots, over the temperature range employed, gave values for the thermodynamic data of the process.
The Crystalline Structure of Poly-β,D(1→4′)mannose: Mannan I
Authors: Nieduszynski I. , Marchessault R. H.
Published: May 2006

The crystallographic structure of mannan I has been examined by X-ray fiber diffraction, polarized i.r. spectroscopy, and computer chain-packing methods. The combination of X-ray intensity data and the chain packing analyses have shown that the overall number of permissible structures is very limited so that van der Waals' forces play a major role in packing. It was concluded that the chain senses are anti-parallel. The interpretation of the polarized i.r. spectra in the OH stretching region is in line with the presence of an intra-molecular hydrogen-bond between O(3)… O(5′). The awkward "knobby" shape of the mannan molecule, largely a result of the axial disposition of O(2)—H, lends itself to a close packing mainly determined by van der Waals' forces. The considerable similarity between X-ray and i.r. data from mannans and glucomannans would indicate that structural conclusions about the former might relate to the latter.
The Thermal Decomposition of N-Benzoyl-N′-1-cyanocyclohexyl Diimide
Authors: Lynch Thomas R. , MacLachlan Frederick N.
Published: May 2006

N-Benzoyl-N′-1-cyanocyclohexyl diimide decomposes in toluene in a first-order manner between 81 and 102°, k = 1015.08e−32.54 ± 1.35/RT. The major product is N-benzoyl-N-cyclohexane carbonyl imide.
The Racemization of trans-1,2-Divinylcyclopropane
Authors: Arai Mannosuke , Crawford Robert J.
Published: May 2006

The synthesis of (−)-trans-1,2-divinylcyclopropane and the kinetics of its racemization and conversion to 1,4-cycloheptadiene, presumably through cis-1,2-divinylcyclopropane, are described. It is concluded that the ring opening is not an electrocyclic process.
The Preparation of Iron Carbonyl Complexes of Fluorocarbon-Bridged Ligands
Authors: Chia L. S. , Cullen W. R. , Harbourne D. A.
Published: May 2006

The reactions of the ligands [Formula: see text] L′ = (CH3)2As, (C6H5)2P; n = 4, 6, 8; but not all combinations) with iron carbonyls are described in detail. The nature of the products is discussed as a function of the reaction conditions and the ligands. The mixed ligands yield eight different types of complexes which have been characterized. Two of these types (L—L′)2Fe2(CO)4. and (L—L′)2Fe(CO)3 were previously unknown.
Attempts at the Synthesis of the Penicillin Ring System by Transannular Reactions
Authors: Benn M. H. , Mitchell Robin E.
Published: May 2006

Attempts were made to achieve new syntheses of the penicillin ring system by effecting the transannular cyclization of 3D-carbomethoxy-N-chloro-2,2-dimethyl-5-oxoperhydro-6L-phthalimido-1,4-thiazepine sulfone. However the products obtained were those resulting from ring cleavage and elimination reactions.
A General Synthesis of 8,2′-Thioanhydropurine Nucleosides
Authors: Ogilvie K. K. , Slotin L. , Westmore J. B. , Lin D.
Published: May 2006

The synthesis of 8,2′-anhydro-8-mercapto-9-β-D-arabinofuranosyladenine,8,2′-anhydro-8-mercapto-9-β-D-arabinofuranosylguanine, and 8,2′-anhydro-8-mercapto-9-β-D-arabinofuranosylhypoxanthine is described. The anhydro ring is formed by simultaneous displacement of bromine from position-8 and carbonate from the 2′-position of the parent nucleoside using either sodium hydrogen sulfide or thiourea.
Absolute Rate Constants for Hydrocarbon Autoxidation. XXII. The Autoxidation of some Vinyl Compounds
Authors: Howard J. A.
Published: May 2006

Absolute propagation and termination rate constants have been determined for the autoxidation of some vinyl compounds at 30°. Rates of propagation depend on the structure of both the peroxy radical and the vinyl compound. The reactivity of peroxy radicals towards addition increases as the electron-withdrawing capacity of the α-substituent increases. Rate constants for addition of t-butylperoxy radicals to vinyl compounds, [Formula: see text] fit the equation[Formula: see text]where Es is the estimated stabilization energy of the β-peroxyalkyl radical (in kcal/mol) formed in the addition reaction.
The Addition of 4-Chloro- and 2,4-Dinitrobenzenesulfenyl Chloride to cis- and trans-1-Phenylpropene
Authors: Schmid George H. , Csizmadia Valeria M. , Nowlan Vincent J. , Garratt Dennis G.
Published: May 2006

The thero-anti-Markownikoff and threo-Markownikoff adducts are the products of addition of 4-chloro-and 2,4-dinitrobenzenesulfenyl chloride to cis-1-phenylpropene while only the erythro Markownikoff adduct is the product of addition to trans-1-phenylpropene. The addition reaction follows second order kinetics, first order in both olefin and arylsulfenyl chloride, with the rate of addition to the trans-olefin faster than to the cis. These results are consistent with a mechanism involving bridged transition states in both the rate and product determining steps.
Examination of Two Theories for Absorption of Microwave and Far Infrared Radiation by Polar Liquids
Authors: Benson M. , Martin G. D. , Walker S. , Warren J. , Wilson R.
Published: May 2006

The far infrared spectra of twenty polar organic liquids have been obtained using a cube interferometer spectrometer. Some new liquids have been examined and some of the previously studied liquids have been re-examined over a wider frequency range and the integrated absorption of the broad band with its peak absorption frequency below about 100 cm−1 evaluated, while any contribution from any overlapping higher frequency band has been subtracted. In general, this has not been taken into account in previous such work. Two approaches which have been previously examined to account for the far infrared absorption of such liquids have been tested for a wider variety of liquids and neither mechanism appears to explain quantitatively the observed absorption intensities. Thus the absorption cannot be accounted for by a simple rotational type of mechanism based on Gordon's equation, plus a contribution similar to that which is found in a non polar liquid as has been suggested earlier. In addition, the parameters of the continuous distribution function approach do not match up to those determined experimentally.
High Stereoselectivity in the Deuteration of a Primary Carbon L-Threose-4-d (4S)
Authors: Maradufu A. , Mackie D. M. , Perlin A. S.
Published: May 2006

Chemical synthesis of a deuterated primary carbinol, L-threose-4-d (4S), has been effected with virtually complete stereoselectivity. It involves deuteride reduction of 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide, conversion of the resulting 1,5-anhydride-1-d into the corresponding 4-deoxy-6-aldehydo-hex-4-ene derivative, and then ozonolysis, without deuterium scrambling. In this way, C-4 and stereoselectively- deuterated C-1 of the hexose have been interconverted to become, respectively, C-1 and stereoselectively- deuterated C-4 of the L-threose molecule. This study also furnishes support for previous evidence that D-galactose oxidase catalyzes removal of the pro-S 6-hydrogen atom of D-galactose.
The Infrared and Raman Spectra of Dimethyliodoarsine
Authors: Shurvell H. F. , Gold M. R. , Norris A. R.
Published: May 2006

The infrared and laser–Raman spectra of liquid dimethyliodoarsine, (CH3)2AsI, have been recorded. Assignments of the observed frequencies have been made to the 24 normal modes of vibration of the molecule. A normal coordinate calculation has been carried out in support of the assignment.
Hypersonic Velocities in Molten Salts by Brillouin Spectroscopy
Authors: Reinsborough V. C. , Valleau J. P.
Published: May 2006

Hypersonic velocities in three molten nitrates have been obtained by Brillouin spectroscopy. Velocity dispersions in molten AgNO3 and Ca(NO3)2• 4H2O suggest that these two melts are more complex structurally than molten NaNO3•
The Photolysis of Tetra(trifluoromethyl)thiophene Vapor
Authors: Wiebe H. A. , Braslavsky Silvia , Heicklen Julian
Published: May 2006

The photolysis of tetra(trifluoromethyl)thiophene (TTFT) at 2139 Å or by mercury sensitization at 2537 Å yields hexafluorobutyne-2 and 1,2,3,4-tetra(trifluoromethyl)5-thiabicyclo[2,1,0]pentene-2 (also called tetra(trifluoromethyl)cyclobutadiene episulfide) as the principal gas phase products. The latter is colored a pale yellow and is stable at room temperature. These results suggest that a possible mechanism for the reaction of photoexcited thiophenes is via the formation of valence bond isomers as intermediates.
The Ultraviolet Flash Photolysis of Ozone and the Reaction of O(1D) with H2O
Authors: Fortin C. J. , Snelling D. R. , Tardif A.
Published: May 2006

The decomposition of gas mixtures containing ozone has been studied following a short duration u.v. light pulse. From an analysis of the O3 decomposition curves for O3:N2 and O3:H2O mixtures, it is shown that the relative rate of O(1D) reaction with H2O and N2 is [Formula: see text] It is also shown that less than6% of the O2, formed directly by photolysis, is in the [Formula: see text] state. The water catalyzed decomposition of ozone is also discussed.
Studies on Nucleation from Solution of some Nickel Dioximates
Authors: Hanna J. D. , Hileman Jr. O. E.
Published: May 2006

Nucleation studies on two nickel dioximates have been carried out by using a direct mixing technique coupled with rapid particle counting. It is concluded that homogeneous nucleation was being observed. The Volmer–Weber, Becker–Doring model of the nucleation process was used to correlate the data.
Etude de la réaction gaz–solide organique entre l'isobutène et le paraphénylphénol
Authors: Lamartine R. , Perrin R.
Published: May 2006

Within the scope of the study of organic gas–solid reactions, we considered the reaction of gaseous isobutene with solid paraphenylphenol doped with sulfuric acid. Parallel to the polymerization of isobutene leading to C8 and C12 hydrocarbons, there is a very good yield of 2,6-di-t-butyl-4-phenylphenol production as compared to initial phenol. The corresponding alkylation reaction is apparently of the order 1 as compared to paraphenylphenol; the activation energy of the reaction is equal to 21 kcal/mol.The reaction spreads out from active centers and is transmitted to almost the entirety of the solid substance; the proton is probably the migrating entity.
Solvent Structure Effects and Diffusion Control in the Reaction Between Solvated Electrons and Solvated Protons in Alcohols and Water
Authors: Jha K. N. , Bolton G. L. , Freeman G. R.
Published: May 2006

The rates of reactions 1 and 2 are diffusion controlled in alcohols[Formula: see text]In water reaction 1 is slower and reaction 2 (where RO− is HO−) is faster than one would estimate from the Debye equation for diffusion controlled reactions. The solvent dependence of the relative values of k1 and k2 is attributed to the solvent dependence of the structures of [Formula: see text] [Formula: see text] [Formula: see text] and H+ and RO− are strong solvent structure makers in alcohols and in water, whereas e− is a weak solvent structure maker in alcohols and a strong structure breaker in water. Effects of the solvent structure making and breaking properties of ions on their reaction rates have been proposed by Gurney and Frank.
N.M.R. Study of Base-Catalyzed Hydrolysis of Trimethylfluorosilane
Authors: Gibson J. A. , Janzen A. F.
Published: May 2006

The diethylamine catalyzed hydrolysis of trimethylfluorosilane in acetonitrile solution has been studied by the nuclear magnetic resonance technique. The concentration and temperature dependence of the preexchange lifetime of a fluorine in the exchange reaction was determined from the collapse of the trimethylfluorosilane doublet. The order with respect to trimethylfluorosilane, water, and diethylamine was experimentally determined. Approximate values of the equilibrium constant for the hydrolysis reaction were obtained at several temperatures.
Preparation, Mössbauer and Vibrational Spectra of some Penta- and Hexacoordinated Addition Compounds of Dimethyl and Diphenyltin(IV) Dichloride
Authors: Llengme B. V. , Randall R. S. , Sams J. R.
Published: May 2006

A number of both mono and bis addition compounds of dimethyl- and diphenyltin dichloride with oxygen donor molecules of the general type RnEO (E = C, N, P, S) have been prepared and characterized by Mössbauer, infrared, and Raman spectroscopies. In the solid state the bis derivatives all have trans methyl or phenyl groups, and with the sole exception of Me2SnCl2•2C5H5NO, all appear to have cis-chlorines and cis-donor molecules. Considerable distortions of the Ph2Sn groups from linearity are suggested. The rather unusual R2SnCl2•L complexes appear to have trigonal bipyramidal structures in which the R groups and one Cl atom occupy equatorial positions, with the donor molecule and second Cl atom in apical positions. Again the C5H5NO adduct of Me2SnCl2 seems to be an exception, with both apices apparently occupied by Cl atoms.
Infrared Investigation of H2S Adsorption and Decomposition on Alumina and on Alumina Supported Molybdenum Sulfide
Authors: Slager T. L. , Amberg C. H.
Published: May 2006

Adsorption and subsequent reaction of H2S on alumina gave major i.r. bands at 1341, 1568, 1625, and 3400 cm−1. Relative band intensities were used to follow the first order decomposition of adsorbed H2S and formation of H2O. Rate constants of the surface reaction at 23, 55, and 80 °C were 0.70, 1.48, and 3.42 × 10−3 s−1, respectively. A mechanism consistent with the observed spectral and kinetic data involved adsorption to an exposed Al ion forming an Al—S surface bond, and hydrogen bonding to neighboring O and OH species. It was assumed that the sulfur remained on the surface as a sulfide. The 1568 cm−1 band was discussed in terms of an Al—O species.With adsorption on MoS2–Al2O3, bands appeared at 1330 and 1575 cm−1. Behavior in all respects was similar to that observed on the alumina support alone.
The Triplet State of Ketones in Solution: Quenching of Triplet Acetone by Amines
Authors: Yip R. W. , Loutfy Rafik O. , Chow Y. L. , Magdzinski L. K.
Published: May 2006

Rate constants for quenching of triplet excited acetone by primary and tertiary amines in solution have been measured directly by flash and pulsed laser techniques. The rate constants were found to be independent of solvent dielectric constant over the range ε 1.9 to ε 80, but were influenced by amine ionization potential. The results are interpreted as supporting a charge-transfer model for the quenching of triplet ketones by tertiary amines. The intervention of free ions in the quenching process is discussed. Free energy calculations indicate that electron transfer from N,N-dimethylaniline to triplet ketones is exothermic but is slightly more favorable for triplet aromatic ketones than for triplet acetone. Evidence for direct hydrogen atom transfer was obtained for quenching of triplet acetone by n-hexylamine.
Oxidations with Potassium trans-1,2-Diaminocyclohexanetetraacetatomanganate-(III). I. Composition of the Complex and the Reaction with Methanol
Authors: Poh Bo Long , Stewart Ross
Published: May 2006

The complex of manganese(III) with trans-1,2-diaminocyclohexanetetraacetic acid has been shown to exist as the crystalline monohydrate, KMnIIICyDTA(H2O), where CyDTA represents the ligand trans-1,2-diaminocyclohexanetetraacetate.In aqueous methanol (2.5% water v/v) three forms of the complex exist: MnIIICyDTA(H2O)− in neutral solution, MnIIICyDTA(OH)2− in base, and HMnCyDTA(H2O) in acid. In basic methanol the complex decomposes by disproportionation following first-order kinetics. When the same solvent system contains acid the disappearance of MnIII is first-order in complex and first-order in acid but in this case methanol is oxidized to formaldehyde.The isotope effects observed in the oxidation of CH3OD, CD3OH, and CD3OD are all small (1.25 or less). This together with the acid dependence indicates that the oxidation proceeds by rate-controlling electron abstraction from methanol by the protonated form of the complex, possibly via an intermediate in which one of the coordinating ligands is replaced by methanol.
Total Synthesis of (±)-Ishwarane, a Tetracyclic Sesquiterpenoid
Authors: Kelly R. B. , Zamecnik J. , Beckett B. A.
Published: May 2006

A total synthesis of (±)-ishwarane, a novel tetracyclic sesquiterpenoid possessing a tricyclo[3.2.1.02,7]octane system, is described. Completion of the synthesis of ishwarane firmly establishes the structure assigned to this sesquiterpenoid and provides corroboration of the structure assigned to the related sesquiterpenoid ishwarone. A total synthesis of (±)-isoishwarane, a transformation product of ishwarone, is also described.
2-Aryloxytetrahydrofurans. Their Reductive Cleavage by Ether Solutions of AlH2Cl and their Cleavage and Rearrangement by Ether Solutions of AlCl3
Authors: Loewen P. C. , Brown R. K.
Published: May 2006

The hydrogenolysis of 2-aryloxytetrahydrofurans by excess AlH2Cl gave, in excellent yield, only those products expected from exo C—O bond cleavage regardless of the nature of the substituent in the aryl ring. None of the 4-aryloxy-1-butanol, the product expected from ring cleavage, was detected. The reaction was very much faster than the corresponding AlH2Cl hydrogenolysis of 2-alkoxytetrahydrofurans which is known to give only ring cleavage products under similar conditions.Treatment of 2-aryloxytetrahydrofurans or pyrans with AlCl3 in ether, resulted in acid-catalyzed cleavage to the corresponding phenol and dihydrofuran or dihydropyran, the latter immediately forming polymeric products. For those 2-aryloxytetrahydrofurans or pyrans, unsubstituted, or substituted with electron donor groups in the aryl ring, another product was obtained which resulted from electrophilic attack of one protonated dihydrofuran or pyran on the ortho or para position of the phenol. These rearrangement products were also obtained in small amounts as byproducts when 2-aryloxytetrahydrofurans were hydrogenolyzed with insufficient AlH2Cl.
The Influence of the Substrate on Hydrogen–Water Deuterium Exchange over Carbon Supported Platinum
Authors: Sagert Norman Henry , Pouteau Rita Mary Louise
Published: May 2006

Rate data for hydrogen–water deuterium isotope exchange are reported for a number of platinum on carbon catalysts whose carbon supports were graphitized to varying degrees before the metal was deposited on the support. The exchange over platinum black was studied for comparison. Over carbon supported catalysts, the rate was almost independent of hydrogen pressure and increased approximately linearly with water pressure. The rate controlling step seems to be the transfer of deuterium between chemisorbed hydrogen atoms and physisorbed HDO.Activation energies for the rate determining step decreased from 14 kcal/mol over unsupported platinum to as low as 2 kcal/mol over highly graphitized supports. Rates increased with heat treatment temperatures up to 2100 °C. These effects are ascribed to electron transfer from the carbon support to the metal, resulting in a weaker Pt—H bond, and faster exchange. However they may be partially the result of non-linear adsorption of water.
Thiohydantoins. X. Kinetic Studies of the Acid Hydrolysis of 1-Acyl-2-thiohydantoins
Authors: Congdon Wayne Irvine , Edward John Thomas
Published: May 2006

The rates of hydrolysis of 22 1-acyl-2-thiohydantoins in aqueous sulfuric acid to give 2-thiohydantoin and a carboxylic acid have been determined. In 0–90% sulfuric acid, hydrolysis takes place by an A-2 mechanism, and the rate reaches a maximum in about 70% acid. In acid more concentrated than about 90%, hydrolysis takes place by an A-1 mechanism, and the rate increases monotonically. Evidence for the two mechanisms comes from Yates r and Bunnett-Olsen [Formula: see text] parameters; from entropies of activation; from pσ and pσ+ relations; and from steric effects.
Metal–Amino Polycarboxylic Acid Complexes. IV. A Polarographic Study of Lead (II) Complexes with Diethylenetriaminepentaacetic Acid in Aqueous Solution
Authors: Letkeman P. , Westmore J. B.
Published: May 2006

The polarographic behavior of the lead ion in the presence of excess DTPA was studied over the pH range 2–10. Three different polarographic waves can be distinguished. The wave occurring at the most negative potentials and highest pH values is assigned to an irreversible reduction of PbHA2−. The kinetic current treatment gives the results[Formula: see text]The wave occurring at intermediate potentials and pH values is also assigned to an irreversible reduction of PbHA2−. The kinetic current treatment gives the results[Formula: see text]Protonation is assumed to occur at different coordination sites. In the former case it occurs at the center carboxyl group; in the latter case it occurs at a terminal nitrogen atom. The reversible wave occurring at the most positive potentials and lowest pH values can be interpreted in either of two ways[Formula: see text]For the stability constant we obtained log KpbA = 19.1. All values above were obtained at 25° and an ionic strength of 0.2.
Solvation of the Sodium Ion. Quadrupolar Broadening of the 23Na Nuclear Magnetic Resonance
Authors: Green R. D. , Martin John S.
Published: May 2006

Sodium ion preferentially forms long lived complexes with dimethylsulfoxide or N,N-dimethylformamide, in mixtures of either of these solvents with either ethanenitrile or propanone. No long lived complexes are observed in solvent mixtures of water or methanol with ethanenitrile or propanone.
Sterically Hindered Aromatic Compounds. V. Solvolysis of p-Methyl-, 2,4,6-Trimethyl-, and 2,4,6-Tri-t-butylbenzyl Chloride. Effect of Solvent and α-Deuterium Substitution
Authors: Barclay L. R. C. , Mercer J. R. , Hudson J. C.
Published: May 2006

Rates, activation parameters, and kinetic α-deuterium isotope effects are reported for solvolysis of p-methyl-benzyl chloride in 80% trifluoroethanol–water, and in ethanol–water and t-butyl alcohol–water of varying solvent compositions. The α-deuterium isotope effect in trifluoroethanol–water (kH/kD = 1.14 per D) indicates approximately limiting behavior. Results in the other solvents (kH/kD = 1.04–1.08) indicate considerable nucleophilic participation by solvent in the transition state. 2,4,6-Trimethylbenzyl chloride gave kH/kD = 1.09 in 80% ethanol–water but kH/kD = 1.16 in 80% trifluoroethanol–water. 2,4,6-Tri-t-butylbenzyl chloride showed kH/kD effects of 1.13–1.15 in t-butyl alcohol–water and 1.15–1.16 in ethanol–water. The higher kinetic isotope effects for solvolysis of these trialkylbenzyl chlorides are discussed in terms of steric hindrance to nucleophilic participation by solvent. N.m.r. chemical shifts give evidence for steric compression of the benzylic protons in 2,4,6-tri-t-butylbenzyl chlorides.