bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetic Isotope Effect Studies on the Reaction of Benzyl Nitrate with Base in Varions Solvents
Authors: Pollock Carol A. , Smith P. J.
Published: May 2006

The role of solvent and base on the nature of the transition state for the concerted one-step carbonyl elimination reaction of benzyl nitrate has been examined using rate and kinetic isotope effect techniques. The primary hydrogen–deuterium isotope effect was found to increase with increasing strength of the abstracting base, kH/kD = 5.94 and 6.41 at 30° for reaction with EtO−/EtOH and t-BuO−/t-BuOH, respectively. The nitrogen isotope effect decreased with increasing strength of the abstracting base, 2.07, 1.82, and 1.54% for reaction with OH−/40 vol % EtOH–H2O, EtO−/EtOH, and t-BuO−/t-BuOH, respectively. The conclusion is reached that an increase in the strength of the abstracting base leads to a more reactant-like transition state with decreased rupture of both the C—H and O—N bonds. The role of solvent on the nature of the transition state was examined by determining rates and nitrogen isotope effects for reaction in various ethanol–water and ethanol–dimethyl sulfoxide mixtures. The nitrogen effect was found to remain essentially constant in solvent mixtures ranging from 65 vol % EtOH–H2O on the one hand to 80 vol% EtOH–DMSO on the other hand where the rate constants differed by a factor of 100 fold. It is concluded that solvent plays only a very minor role in determining transition state structure for the concerted elimination reaction of a neutral substrate with base.
The Thermal Behavior of Methyl Dehydroabietate at 600–800 °C
Authors: Severson Ray F. , Schuller Walter H. , Lawrence Ray V.
Published: May 2006

Methyl dehydroabietate was pyrolyzed on Vycor rod at 600, 700, and 800 °C with varying contact times. Some 40–60 products were observed upon g.l.p.c. analysis, with the number of products decreasing with increasing temperature and increasing contact time at 800 °C. Considerable carbon formation was found to occur at 800 °C and long contact times. The 24 major products which could readily be separated by preparative g.l.p.c. methods were collected and identified. The high yield of naphthalene-related compounds obtained is explained by the thermal rupture of the A-ring which is initiated by elimination of the carbomethoxy moiety.
Base-catalyzed Deuteration of Tricarbonylchromium Complexes
Authors: Ashraf M.
Published: May 2006

Hydrogen–deuterium exchange in tricarbonylchromium complexes of anisole, ethylbenzoate, and N,N-dimethylaniline has been studied for solutions in ethanol-O-d1, containing sodium ethoxide. The extent of deuteration has been estimated mass spectroscopically and the position of deuteration by n.m.r. spectroscopy. In this kinetically controlled reaction ortho-substitution has been found to be predominantly preferred in case of anisole complex, whereas random substitution was observed (n.m.r.) for ethylbenzoate complex. The results are interpreted in terms of chelative, inductive, mesomeric, and steric effects of the substituents.
Aqueous Solutions of Nonpolar Compounds. Heat-Capacity Effects
Authors: Wauchope R. D. , Haque R.
Published: May 2006

The method of Clarke and Glew has been used to obtain estimates of the precision of measurement of the thermodynamic functions for the solution of hydrocarbons, the noble gases, and inert diatomic gases in water. In some cases, the precision of the data is such that a statistically significant value for the temperature coefficient of the heat-capacity change for the solution process is obtained. Comparison with the theory of Nemethy and Scheraga shows that their calculations of heat-capacity changes at 25 °C are better than previously believed, but that their prediction of a positive temperature coefficient for this quantity is in contradiction with most data.
Mössbauer and Infrared Spectra of Octahedral Complexes of Iron(II) Halides with Amides and Related Ligands
Authors: Birchall T. , Morris M. F.
Published: May 2006

A number of complexes of FeCl2 and FeBr2 with amides, ureas, aniline, and benzothiazole have been prepared and characterized by means of Mössbauer and i.r. spectroscopy, and magnetic measurements. The stoichiometries FeX2L, FeX2L2, FeX2L3, FeX2L4, and FeX2L6 have been found in which the iron is six coordinate. With the exception of an isobutyramide complex which is formulated as [Fe(BUA)6][FeCl4], complexes of the first three types are polymeric with bridging halogens, while FeX2L4 is monomeric and FeX2L6 is formulated as [FeL6]Cl2.
The Reaction of O-Benzylidene Sugars with N-Bromosuccinimide.: VI. A New Synthesis of 2′-Deoxyuridine and some of its Selectively Substituted Derivatives
Authors: Ponpipom M. M. , Hanessian S.
Published: May 2006

A new synthesis of 2′-deoxyuridine and its selectively substituted derivatives has been developed, based on the reaction of appropriately substituted 2′,3′-O-benzylideneuridines with N-bromosuccinimide (NBS). The preponderant products are uridines containing bromine and benzoate groups in the 2′- and 3′-positions respectively.
Total Synthesis of (+)-Occidentalol
Authors: Sergent M. , Mongrain M. , Deslongchamps P.
Published: May 2006

A synthesis of (+)-occidentalol (1) has been realized in six steps, starting from the readily available enonealcohol 3.
The Racemization and Geometrical Isomerization of Oxiranes
Authors: MacDonald Helen H. J. , Crawford Robert J.
Published: May 2006

Optically active trans-2-phenyl-3-p-tolyloxirane and cis-2-phenyl-3-p-tolyloxirane were synthesized and the kinetics of their racemization and geometrical isomerization were studied.The slower rate of racemization of the cis-isomer compared with that of the trans is attributed to the conrotatory opening of the oxirane ring.
The Basicity of Aliphatic Ethers
Authors: Lee Donald G. , Cameron Ronald
Published: May 2006

The [Formula: see text] values of aliphatic ethers have been calculated from n.m.r. chemical shift data to be approximately −6.4.
Application of Factor Analysis to Gas–Liquid Chromatography
Authors: Weiner Paul H. , Howery Darryl G.
Published: May 2006

The mathematical method of factor analysis is applied to a data matrix of retention indices for 30 solutes on 23 stationary liquid phases. Eight abstract eigenvectors are required to reproduce the data within experimental error. A gas phase imperfection term based on the van der Waals equation of state tests successfully as a fundamental factor of the space. A test vector termed the uniqueness test is used to determine the extent to which molecules possess a particular property. The uniqueness test is applied to rank solutes in terms of (1) alcohol-like character and (2) electron-donor ability.
Synthesis and Properties of Substituted Germylhydrazines
Authors: Peterson L. K. , Thé K. I.
Published: May 2006

By using reactions between Me3GeBr or Me2GeCl2 and appropriate lithium hydrazide salts, the following new compounds were prepared: Me2NN(R)GeMe3 (R = H, 1; Me, 2; GeMe3, 3; SiMe3, 4), Me3GeN(Me)NHGeMe3, 5a, MeNHN(GeMe3)2, 5b, (Me3Ge)2NN(Me)GeMe3, 6, Me3GeNHNHGeMe3, 7a, (Me3Ge)2NNH2, 7b, (Me)11Ge4N6H, 11, (Me2GeNNMe2)3, 12, Me2Ge[N(R′)NMe2]2 (R′ = Me, 13; SiMe3, 14). Thus the reaction of Me3GeBr with Li(MeN2H2) and with LiN2H3 gave mixtures of disubstituted isomers, 5a and b, and 7a and b, respectively, rather than mono-substituted derivatives. Reactions of Me2GeCl2 gave (i) an unresolvable, highly condensed product with LiN2H3; (ii) the high molecular weight compound 11, with Li(MeN2H2); and (iii) the cyclic trigermazane 12 with Me2NNHLi; the extent of self-condensation is a function of the degree of substitution of the hydrazine moiety. Reactions with protic reagents (H2O, MeOH, anhydrous HCl) effect cleavage of the Ge—N bond in germylhydrazines. New compounds were characterized on the basis of i.r., n.m.r., and mass spectral measurements.
A Synthetic Study in the Tricyclovetivene Series
Authors: Deljac A. , MacKay W. D. , Pan Connie S. J. , Wiesner Karel J. , Wiesner K.
Published: May 2006

The total synthesis of racemic tricyclovetivene (1a) and isomers (1b and 26) is described. The crucial reaction of the synthesis is a cyclization (iii) developed in this laboratory.
Mass Spectra of Some Tropolones and Tropolone Methyl Ethers
Authors: Wright J. L. C. , Jamieson W. D. , Safe S. , Vining L. C.
Published: May 2006

The mass spectra and fragmentation patterns of several tropolones and tropolone methyl ethers are reported. Deuteration studies confirmed that elimination of a formyl radical from 2-methoxytropone upon electron impact involves a specific rearrangement of the methoxyl group but sequential loss of carbon monoxide and a hydrogen radical from the ring are competing reactions. They also showed that in a dimethyl ether of anhydrosepedonin elimination of a formyl radical is completely suppressed. In the methyl ether of stipatatonic acid elimination of carbon monoxide is followed by expulsion of carbon dioxide with no loss of 29 mass units. The mass spectrum of [8-13C]-anhydrosepedonin as well as the energy spectrum for sepedonin have been investigated. These results not only provide a plausible account of the fragmentation of tropolones following electron impact but also illustrate the effect of product ion stability in determining which among a number of alternative modes of fragmentation will be more probable.
Isomeric Pyrimidone and Uracil Derivatives Obtained by Reaction of Barbiturates with Diazomethane
Authors: Neville G. A. , Avdovich H. W.
Published: May 2006

A re-examination of some recently reported studies by Ito etal. (1) of the action of diazomethane on barbituric acid, 1-methylbarbituric acid, and 5-ethyl- and 5-phenylbarbituric acids has resulted in the assignment of structures for some of the various possible positional isomers. These reactions were found to be more complex than previously indicated.
n-Butylamine Adsorption onto Amorphous Silica
Authors: Clark-Monks Colin , Ellis Bryan
Published: May 2006

Gravimetric and infrared spectroscopic observations of n-butylamine adsorption onto silica have shown that strong adsorption is associated primarily with isolated surface hydroxyl groups and also with some vicinal surface groups. Adsorbed material can be totally removed from the surface by outgassing at elevated temperature (to 200 °C) without irreversible changes to the underlying surface. The interaction between adsorbed amine and ethylene oxide vapor has been investigated and a possible reaction mechanism is presented.
Substituent Effects in Dye-sensitized Photooxidation Reactions of Furans
Authors: Young R. H. , Martin R. L. , Chinh N. , Mallon C. , Kayser R. H.
Published: May 2006

The problems encountered in the normal method used to determine β values (rate of decay of singlet oxygen divided by the rate of its reaction with an organic compound) are discussed. The use of dilute solutions of organic acceptors for our measurements was found to give more reproducible values and simplified kinetics. These β values were used to obtain relative rate constants for a variety of substituted furans. Hammett plots were made to quantitate the substituent effects in order to explore the nature of singlet oxygen in the dye-sensitized photooxidation reactions of these furans. The calculated ρ values were compared with other photooxidation and Diels–Alder reactions. Hammett ρ values in a series of solvents were also calculated for the reaction of singlet oxygen with 2-arylfurans and increasing ρ values were correlated with decreasing solvent polarity.
Hydrolysis of Sulfamoyl Chlorides. II. Hydrogen Participation in the Hydrolysis of Diethyl and Methylethylsulfamoyl Chlorides
Authors: Ko E. C. F. , Robertson R. E.
Published: May 2006

Diethylsulfamoyl chloride (2) hydrolyzes eight times faster than dimethylsulfamoyl chloride (1). In 2 the secondary deuterium isotope effect was found to be about 2, hence hydrogen participation is important in the hydrolysis of this compound. The temperature coefficient of the enthalpy of activation [Formula: see text] is exceptional (−39 cal mol−1 deg−1) for a reaction presumably following an SN1 mechanism. The kinetic solvent isotope effect was normal for such a mechanism. The corresponding value of [Formula: see text] for the hydrolysis of piperidylsulfamoyl chloride (4) was about the same as found for 2 while the value for the methylethyl isomer (3) was −66 cal deg−1 mol−1, an intermediate value supporting an explanation based on solvent exclusion. Experiments in mixed solvents support the hypothesis that solvent reorganization is the major factor in determining the value of [Formula: see text]for 2 but not for 4.
Organic Free Radical and Metal Complexes. 2,2-Diphenyl-1-picrylhydrazyl with Cu(I)
Authors: Leh F. , Wan J. K. S.
Published: May 2006

Reactions of Cu(I)Cl, Cu(II)Cl2, Cu(II) acetylacetonates, and Cu(II) N-methylsalicylalidiiminate with the stable free radical 2,2-diphenyl-1-picrylhydrazyl have been investigated. In all cases Cu(II) was reduced and the organic radical behaved as an electron donor-ligand to form complexes containing Cu(I). These novel free radical Cu(I) complexes were characterized by various spectroscopic methods, including e.s.r.
An Upper Bound to the Mole Fraction of Unbonded H2O in Liquid Water at 25 °C
Authors: Lenzi Fabio
Published: May 2006

Liquid water at 25 °C has been treated as a semi-ideal solution of relatively very volatile unbonded monomer dissolved in non-volatile hydrogen-bonded solvent. A mole fraction of less than 0.0016 has been found for unbonded water, in agreement with Stevenson's conclusion.
The Effect of Heat Treatment of Silica Gels on the Calorimetric Heats of Adsorption of Sulfur Dioxide up to One-twentieth Monolayer Coverage at 423 °K
Authors: Glass R. W. , Ross R. A.
Published: May 2006

Calorimetric heats of adsorption of sulfur dioxide have been determined at 423°K for a series of silica gels heat-treated at 240, 550, 700, 800, and 900 °C. At the lowest surface coverage of 0.01 μmol m−2, heats of 25 to 30 kcal mol−1 were observed. These values dropped rapidly with increasing coverage and approached "limiting" values of 6 to 7 and 12 kcal mol−1 for dehydroxylated and hydroxylated surfaces, respectively. To explain the results at lowest coverages an adsorbed complex involving multiple hydrogen bonds is proposed while at higher coverages it is suggested that single and dual site adsorbed species predominate for the dehydroxylated and hydroxylated surfaces, respectively. Sulfur dioxide adsorption isotherms on all gels at 423 °K obeyed the Langmuir equation.Adsorbents were characterized by nitrogen adsorption–desorption isotherms at 77 °K and pore size distribution data were calculated from the desorption branch.
Primary Processes in the Vacuum Ultraviolet Photolysis of Ethyl Fluoride at 147 nm
Authors: Chan S. C. , Inel Y. , Tschuikow-Roux E.
Published: May 2006

The photolysis of C2H5F at 147 nm was studied at room temperature. The principal products include C2H3F, C2H2, C2H4, CH4, and C2H6. The principal primary photochemical reactions involve the molecular elimination of HF and H2, and, to a lesser extent, C—F and C—C bond fission. The effect of reactant and added inert gas pressure on the product yields has been investigated and it was found that the stabilization/decomposition ratio, C2H4/C2H2, displays opposite pressure dependence with ethyl fluoride and argon. This result is interpreted in terms of the higher energy transfer efficiency of the C2H5F molecule.
Zeise's Salt, K[Pt(C2H4)Cl3], Anhydrous and Monohydrate and the Platinum–Olefin Interaction
Authors: Hubert J. , Kong P. C. , Rochon F. D. , Theophanides T.
Published: May 2006

Zeise's salt, anhydrous and monohydrate, has been prepared by a new method similar to the original method used by Zeise. The infrared and laser Raman spectra of the anhydrous Zeise's salt together with the infrared spectra of the deutero and bromo analogs, are reported and discussed. The vibrational spectra are interpreted in terms of a cyclopropane-like ring structure, obtained by the insertion of the platinum atom into the double bond.
Heterogeneous Interactions of Methylamines on Porous Adsorbents. Part I. The Adsorption of Monomethylamine on Silica Gels and Silica–Alumina
Authors: Cook W. G. , Ross R. A.
Published: May 2006

The adsorption of monomethylamine has been studied near its boiling point, 266 °K, on silica–alumina and on a wide range of silica gels by measurement of adsorption–desorption isotherms and isothermal calorimetric heats of adsorption. In addition, surface areas and pore-size distributions have been determined by low-temperature nitrogen adsorption. Heats of adsorption on Davison "923" silica gel varied from around 33.0 kcal/mol at θ = 0.01 to 6.2 kcal/mol at monolayer completion. Maxima were observed in this heat curve in the regions of θ = 0.15, 0.28, and 0.40. These phenomena are believed to be related to interactions among the adsorbed species in pores of diameters approaching molecular dimensions. Heats of adsorption on silica–alumina fell smoothly from 39.5 kcal/mol at θ = 0.03 to 13.0 kcal/mol at θ = 1.00. Adsorption–desorption characteristics of methylamine were also examined on a series of silica gels with widely different pore structures. The variations in the heats of adsorption with surface coverage are discussed in terms of both the nature of the adsorbed surface species and lateral interactions among the adsorbed molecules.
Reactions of Ethylene with Rhodium (III) Chloride. Part IV. Relative Activity of Tetra-, Penta-, and Hexa-chlororhodate(III) Complexes for the Oxidation of Ethylene to Acetaldehyde in Aqueous Acid Solutions
Authors: James B. R. , Kastner M.
Published: May 2006

The catalytic oxidation of ethylene to acetaldehyde using the rhodium(III) chloride complexes, [Formula: see text] in the presence of iron(III) has been studied kinetically in aqueous acid solutions under mild conditions.[Formula: see text] is inactive due to the absence of a coordinated water (hydroxide) ligand. Solutions containing tetrachloro species are generally more reactive than those containing pentachloro species because of the presence of a greater concentration of highly reactive hydroxy species. The neutral and cationic chloro-complexes are inactive due to their substitution inertness.
High Resolution Nuclear Magnetic Resonance Investigation of the Structure of the Adducts Formed by the Interaction of Benzylidenemalononitriles with Trialkylphosphines
Authors: Fyfe C. A. , Zbozny M.
Published: May 2006

High resolution n.m.r. has been used to determine unambiguously the structure of the adducts formed by the action of trialkylphosphines on para-substituted benzylidenemalononitriles2 as a zwitterionic species formed by attack of the phosphine on the α-carbon atom of the alkene. The relation of this result to possible mechanisms of nucleophilic alkene substitution reactions is discussed.
A Simple Synthesis of 2-Methoxy and 2-Ethoxytetrahydrofuran
Authors: Frehel Daniel , Deslongchamps Pierre
Published: May 2006

Ozonolysis of dihydropyran gives 4-formyloxybutyraldehyde which is then easily converted into 2-methoxy or 2-ethoxytetrahydrofuran.
Isotopic Exchange Between Hydrogen and Water Vapor over Supported Metal Catalysts. Part I. Kinetics of the Exchange
Authors: Rolston J. H. , Goodale J. W.
Published: May 2006

Some rate data for the transfer of a deuterium atom tracer between hydrogen and water vapor, catalyzed by platinum supported on γ-alumina, are reported. Above 100 °C the transfer rate measured at 1 atm total pressure is shown to be free of mass transfer effects, and obeys an initial first order dependence on water vapor for vapor pressures less than 10 Torr. A near zero order dependence is observed at higher water vapor pressures. At temperatures below 100 °C the transfer rate is essentially independent of water vapor pressure between 5 and 100 Torr suggesting that surface adsorbed water is involved in the rate limiting transfer step.
Pyrrole Chemistry. XIV. Some Chemical and Physical Properties of 3-Pyrrolecarbaldehyde and 1-Methyl-3-pyrrolecarbaldehyde
Authors: Anderson Hugh J. , Nagy H.
Published: May 2006

3-Pyrrolecarbaldehyde (1) has been prepared on an increased scale. A general survey of the physical and chemical properties of the 3-aldehyde and 1-methyl-3-pyrrolecarbaldehyde has been carried out. The results indicate similar chemical properties to those of the corresponding 2-aldehydes. The physical properties are generally predictable on the basis of earlier studies.
Neothiobinupharidine Sulfoxide, a New Alkaloid of Nupharluteum
Authors: Wróbel J. T. , Iwanow A. , Szychowski J. , Poplawski J. , Yu C. K. , Martin T. I. , MacLean D. B.
Published: May 2006

A new alkaloid (C30H42N2O3S), isolated from Nupharluteum, is shown to be neothiobinupharidine sulfoxide. The mass spectra of neothiobinupharidine and the new alkaloid are discussed.
The Hydration of Ketones in Mixtures of Water and Polar Aprotic Solvents
Authors: Stewart Ross , Van Dyke John D.
Published: May 2006

The hydration of a series of ring-substituted trifluoroacetophenones (Z) has been studied by means of u.v. and n.m.r. spectroscopy in DMSO–water and sulfolane–water mixtures. The W0 function is defined as [Formula: see text] where Kd is the equilibrium constant for the reaction [Formula: see text]Mixtures of water and sulfolane in all proportions have a dehydrating effect compared to water but mixtures of water and DMSO down to 15 mol % water are more hydrating with respect to the carbonyl group of trifluoroacetophenones than is pure water. An analysis of activity coefficient behavior indicates that the diol, ZH2O, has a higher requirement for solvation by water molecules than does water itself.The rate of the uncatalyzed hydration in aqueous sulfolane drops drastically as the water content of the medium decreases, whereas the rate of the acid-catalyzed reaction is not greatly affected by changes in the solvent composition; a plot of log k for both catalyzed and uncatalyzed reactions is approximately linear in W0.
Applications of Lanthanide Shift Reagents to the Identification of 13C Resonances
Authors: Armitage Ian , Campbell John R. , Hall L. D.
Published: May 2006

The 1H and 13C shifts of 2,2-dimethyl-1-propanol (1) have been measured by the 1H–{13C} INDOR technique in the presence of various concentrations of the tris{dipivalomethanato} derivatives of europium (2), thulium (3), and praseodymium (4). All sets of shifts vary with the concentration of added lanthanide; the methylene-13C resonance is shifted more than the methyl-13C resonance. It is shown that tris{dipivalomethanato}gadolinium(III) does not induce chemical shift changes and this further supports the contentation that the pseudo-contact mechanism predominates for lanthanide shift reagents.
Stereochemistry of 3-Methyl-4-phenylpiperidines Derived from Corresponding 4-Phenyl-4-piperidinols
Authors: McErlane K. M. J. , Casy A. F.
Published: May 2006

Catalytic reduction of 3- and 5-methyl-4-phenyl-1,2,5,6-tetrahydropyridines is stereospecific and gives cis-3-methyl-4-phenylpiperidines. Hydrogenolysis of 1-t-3-dimethyl-4-r-hydroxy-4-phenylpiperidine (β-prodinol) by Raney nickel also gives a cis product. Stereochemical assignments are made on the basis of p.m.r. spectroscopic data. Hot-plate activities in mice of 1-methyl- and 1-phenethyl-c-3-methyl-4-phenylpiperidine are reported.
Studies in Solvolysis. Part V. Further Investigations Concerning the Solvolysis of Primary, Secondary, and Tertiary Trifluoroacetates
Authors: Barnes D. J. , Cole (née Morrissey) M. , Lobo S. , Winter J. G. , Scott John M. W.
Published: May 2006

The rate of solvolysis of ethyl trifluoroacetate has been investigated in a series of H2O/D2O mixtures at 9.97 °C. The secondary isotope effects related to the hydrolysis of the isotopic pairs, methyl/methyl-d3, ethyl/ethyl-d5, i-propyl/i-propyl-β-d6 and t-butyl/t-butyl-d9 trifluoroacetates have been established as well as the temperature dependence for the hydrolysis of t-butyl trifluoroacetate. The significance of all these measurements with respect to the mechanism of these reactions is discussed.
The Measurement of the Activity Coefficient Ratios of Protonated and Neutral Forms of Hammett Indicators in Several Strong Acids
Authors: Essig T. R. , Marinsky J. A.
Published: May 2006

The activity coefficient ratio for several indicators has been estimated for the protonated and neutral forms of the same indicator molecule over a large range of acidity in H2SO4, HClO4, and HCl systems. The activity coefficient (fB) of the neutral form of a number of Hammett indicators was determined via solubility measurements. The observed linear relationship between log fB and [Formula: see text] then permitted estimate by extrapolation of log fB not experimentally accessible for the more basic indicators. Solubility studies of the pentacyanopropenide (PCP−) salts of these more basic protonated indicators were referred to a reference standard, tetraethylammonium pentacyanopropenide (TEA+PCP−) according to the method developed by Boyd to obtain the activity coefficient ratio [Formula: see text] By synthesizing the term [Formula: see text] the approach to a meaningful value of [Formula: see text] is believed to be facilitated. This function is uniquely related to the water activity of the various acid systems examined to support the suggestion by Hammett that [Formula: see text] is a constant for primary aniline indicators at a specified acid concentration.
Effect of Pressure on the Solvolysis of Dimethyl-t-butyl Sulfonium Iodide in Ethanol–Water Mixtures
Authors: Davis Claude S. , Hyne J. B.
Published: May 2006

The pressure dependence of the rate of solvolysis of dimethyl-t-butyl sulfonium iodide has been studied in ethanol–water mixtures at 60.00 °C. Determination of the partial molal volume of the substrate ions has enabled the volumes of activation to be dissected into initial and transition state components. The solvent composition dependence of the partial molal volumes of the two states provides further details of the nature of the reaction mechanism.
Hydrogen Atom Recombination on Glass Surfaces
Authors: Bader L. W. , Gesser H. D.
Published: May 2006

The adsorption and recombination of H atoms at temperatures between 77 and 110 °K have been studied on various silicate glass surfaces consisting of fused silica, porous Vycor with surface adsorbed water, and porous Vycor with chemically altered surfaces achieved by replacement of the surface functional hydroxyl group by chlorine, fluorine, and methoxy substituents.The concentration of adsorbed H atoms was determined by a measurement of the e.s.r. signal and the kinetics of the disappearance of the hydrogen atoms were observed to be second order in mobile atoms, consistent with a diffusion controlled recombination process.The results require that there be at least two types of surface adsorbed atoms, namely, weakly physically adsorbed atoms that are mobile and immobile. Identification of these adsorbed atom types with a particular surface functional feature leading to the adsorption is proposed.The activation energy for the second order decay of hydrogen atoms at the surface was found to vary from 1.0 to 2.3 kcal/mol, depending upon the chemical nature of the surface. A correlation between this activation energy and an electronegativity function of the surface group is presented.
Thermal Rearrangement of Acyl Groups in Anhydronucleosides. A Convenient Synthesis of 5′-O-Acetylanhydrouridine
Authors: Ogilvie K. K. , Westmore J. B. , Taylor G. , Lin D. , Iwacha D. , Wayborn H. , Dunn G. E.
Published: May 2006

The mass spectra of acylanhydronucleosides suggested that the acyl groups undergo a thermal rearrangement. This was confirmed by studying the melting profiles of these compounds in a differential scanning calorimeter. The results have led to a convenient synthesis of 5′-acetylanhydrouridine.
The Far Ultraviolet Photolysis of Alkenes: The Use of Hydrogen Sulfide as a Radical Scavenger
Authors: Collin Guy J. , Perrin Patrick M. , Gaucher Christian M.
Published: May 2006

The far u.v. photolysis of cis-2-butene, n-1-pentene, and cis-2-pentene was carried out in the presence of various quantities of hydrogen sulfide. We showed that in these systems, hydrogen atoms add to the double bond and are not scavenged by 5–10% hydrogen sulfide. On the other hand, alkyl radicals such as methyl, ethyl, s-butyl, and s-pentyl react with hydrogen sulfide, and the formation of the corresponding alkanes may be used to measure the absolute yields of the radical species. The same holds true for vinyl radicals. We also report some experiments published elsewhere. In particular, in the case of 1,3-butadiene, identification of the principal radicals is possible; however, measurement of absolute yields becomes more difficult.
The Barrier to Rotation in Cyclopropylmethyl Cations
Authors: Brown Allister , Schmid George H.
Published: May 2006

The barrier to rotation of a cyclopropyl ring around the planar carbon of a cyclopropylmethyl cation has been estimated from rates of solvolysis to be 14 kcal/mol. This value is obtained by a comparison of the rates of solvolysis of molecules which contain conformationally rigid cyclopropane rings. The results obtained compare favorably with estimates made by other methods.
The 13C Fourier Transform Spectrum of Heparin. Evidence for a Biose Repeating Sequence of Residues
Authors: Perlin A. S. , Kin N. M. K. Ng Ying , Bhattacharjee S. S. , Johnson L. F.
Published: May 2006

Carbon-13 Fourier transform n.m.r. spectra of the biopolymer, heparin, are described. The proton-decoupled spectrum corresponds to that of a molecular structure based on 12 carbon atoms, and the observed chemical shifts are shown to be consistent with a previously-proposed alternating sequence consisting of (1 → 4) linked residues of α-D-idopyranosyluronic acid 2-sulfate and 2-deoxy-2-sulfamino-α-D-glucopyranosyl 6-sulfate. Line-broadening of the C-6 signal of the latter residue indicates that spin–spin relaxation of the 13C nucleus of this sulfated primary carbinol group is more effective than for the 13C nuclei of the sugar rings. Among model compounds utilized for assignment of the signals from heparin is a disaccharide, 4-O-(α-L-idopyranosyluronic acid 2-sulfate)-2,5-anhydro-D-mannose 6-sulfate, prepared in 65% yield by deaminative degradation of heparin.
The Photolysis of 4-Hydroxybenzil and the Effect of Triethylamine on the Photolysis of Benzil and 4-Hydroxybenzil
Authors: Bunbury David L. , Chan Theresa Mak
Published: May 2006

Benzil is photoreduced in neat triethylamine and mixtures of triethylamine and 2-propanol. In neat 2-propanol the principal products are; benzil pinacol, 20%; benzoin benzoate, 19%; benzoin, 18%; and benzoic acid, 12%. When the amine concentration is as low as 0.2 mM the benzil pinacol formation is almost completely suppressed. At amine concentrations higher than 0.36 mM the principal product is benzoin, 80%. At intermediate amine concentrations benzoin benzoate is important. The rate of benzil disappearance reaches a maximum and then declines as either the benzil concentration in triethylamine is increased or the amine concentration in 2-propanol is increased.4-Hydroxybenzil is not photoreduced by 2-propanol. It is reduced by triethylamine. The quantum yield of disappearance is 0.04 at a concentration of 47.8 mM and in solutions containing at least 0.36 M of amine. 4-Hydroxybenzoin is the principal product but at low starting 4-hydroxybenzil concentrations 4,4′-dihydroxybenzil is important. A rate maximum is also observed in this case.4,4′-Dihydroxybenzil is not photoreduced by 2-propanol. It does undergo photoreaction in neat triethylamine but no products were isolated.Triethylamine also appears to suppress biacetyl pinacol formation in the photoreaction of biacetyl with 2-propanol.
Coordination Compounds of Indium. Part XV. The Stability Constants of some Trifluoromethyl-β-diketonate Complexes of Indium (III)
Authors: Bowden Keith , Tanner (Mrs.) G. M. , Tuck D. G.
Published: May 2006

The stability constants K1 and K2 have been measured for the interaction of indium(III) with the ligands R•CO•CH2•CO•CF3 (R = 2-furyl, 2-thienyl, phenyl, 2-naphthyl, i-butyl, and (t-butyl). The pKa values for these compounds, and for R = 3-pyridyl and methyl, are also reported. A conventional potentiometric technique was used; the results refer to 46% aqueous acetone, at an ionic strength of approximately 0.1 M. The results are compared with published values for complexes of these ligands with divalent cations in other solvent systems.
Mobilities and Ranges of Electrons in Liquids: Effect of Molecular Structure in C5–C12 Alkanes
Authors: Dodelet Jean-Pol , Freeman Gordon R.
Published: May 2006

X-radiolysis free ion yields and electron mobilities were measured in a series of branched chain hydrocarbons at several temperatures. The numbers listed after the following compounds are the temperature (K), Gfi, most probable penetration range of the secondary electrons (Å) and thermal electron mobility (cm2/V s): 2,2-dimethylpropane (neopentane), 294, 1.09, 213, 50; 2,2,3,3-tetramethylbutane, 379, 0.80, 130, –; 2,2,4,4-tetramethylpentane, 295, 0.83, 158, 24; 2,2,5,5-tetramethylhexane, 293, 0.67, 138, 12; 2,2,6,6-tetramethylheptane, 293, 0.47, 113, –; 2,2,7,7-tetramethyloctane, 383, 0.58, 100, –; 2,2,3,3-tetramethylpentane, 295, 0.42, 102, 5.2; cyclohexane, 294, 0.16, 67, 0.45. The difference between the activation energies of the reactions[Formula: see text]and[Formula: see text]is (E15–E14) ≈ (2 to 3)RT for twenty two different hydrocarbons, including olefins and benzene. The rate of energy loss by epithermal electrons in liquid hydrocarbons increases with increasing anisotropy of polarizability of the molecules or groups; the range of the electron interaction in a given molecule appears to be about two C—C bonds in series (groups up to neopentyl in size). There is a correlation between the mobilities of thermal electrons in liquids and the penetration ranges of the secondary electrons in the liquids. The electron mobility in a liquid alkane appears to be limited by inelastic scattering. The inelastic scattering cross sections for both thermal (< 0.1 eV) and epithermal (~ 1 eV) electrons in liquid alkanes are affected in similar ways by the anisotropy of polarizability of the molecules. In both instances the scattering apparently involves rotational (librational) excitation of the medium.
The Use of Polymer Supports in Organic Synthesis. The Synthesis of Monotrityl Ethers of Symmetrical Diols
Authors: Leznoff Clifford C. , Wong Jack Y.
Published: May 2006

A modified Merrifield polymer containing acid chloride groups was used in the selective synthesis of the monotrityl ethers of the symmetrical diols, HO—(CH2)n—OH, where n = 2, 4, 6, 8, and 10. This procedure constitutes a unique method of blocking one functional group of a completely symmetrical difunctional compound.
Automatic Sorting of Signals in Shift Reagent Spectra
Authors: ApSimon J. W. , Beierbeck H. , Fruchier A.
Published: May 2006

This communication shows a simple algorithm for the automatic sorting of signals in shift reagent spectra with an implicit plot of chemical shifts vs. improved shift reagent coordinates.
Alkyl Shifts in Cyclohexenyl Cations
Authors: Rajeswari K. , Sorensen T. S.
Published: May 2006

The possible ways in which alkyl rearrangements can occur in cycloalkenyl cations are described. With cyclohexenyl cations, two rearrangements unique to this system are discussed and experimental evidence for both of these is presented. Use is made of the n.m.r. spin saturation transfer technique in one case.In the final part of the paper, we show how, by repeatedly using both rearrangements, it is possible in theory to scramble the relative positions of all of the carbon atoms with respect to both the different positions within a cyclohexenyl cation framework and with respect to the bonding order of consecutive atoms within the framework. In the unsubstituted case, this corresponds to a 360-fold degenerate rearrangement.
Conformations of Bridged Diphenyls. I. Crystal Structure of 2-(3′-Methyl-4′-nitrophenoxy)-1,3-diisopropylbenzene
Authors: Griffith E. A. H. , Chandler W. D. , Robertson B. E.
Published: May 2006

The structure of 2-(3′-methyl-4′-nitrophenoxy)-1,3-diisopropylbenzene, C19H23NO3, has been determined by X-ray diffraction. The crystals are triclinic, a = 12.422(24), b = 13.180(25), c = 11.241(30) Å, α = 89.99(20), β = 95.81(15), γ = 105.46(12)°, [Formula: see text] with Z = 4. The intensities of 8153 independent reflections were measured on a four circle diffractometer, of which 3701 were used in the refinement of the structure to give a final least-squares weighted residue of 0.053.The ether oxygen bond angle in each of the two independent molecules is 120°. The two phenyl rings are nearly orthogonal in each case, while the ring containing the electron withdrawing nitro group is conjugated with the ether oxygen atom. The rings show significant deviations from hexagonal symmetry and the nitro-substituted ring is bent away from the other ring.
The Triterpenes of Lycopodiumlucidulum Michx.
Authors: Orito K. , Manske R. H. , Rodrigo R.
Published: May 2006

Nine known serratane triterpenoids have been isolated from Lycopodiumlucidulum Michx. mostly as their acetates. Serratenediol is the major one and is accompanied by significant amounts of serratriol. Moderate quantities of serratenediol-3-acetate, tohogenol, and episerratenediol were present together with minor amounts of 16-oxoserratriol, tohogeninol, and the phlegmanols A and E.
Chemistry of Aminochromes. Part XV. The Reaction of Epinochrome with Thiols
Authors: Powell W. S. , Heacock R. A.
Published: May 2006

Epinochrome (5) has been shown to react with thioglycollic acid to give mainly 5,6-dihydroxy-1-methylindoline and a 4-thiosubstituted 5,6-dihydroxy-1-methylindoline. The acetyl derivatives of these compounds (i.e. 7b and 15), along with that of the corresponding 4-thiosubstituted 5,6-dihydroxyindole (i.e. 11), were isolated after acetylation of the reaction mixture. The latter compound is probably a secondary product of the reaction, having arisen from the 4-thiosubstituted 5,6-dihydroxy-1-methylindoline which is formed initially.
Electrochemical Fission of Vicinal Diketals to Orthoesters
Authors: Couture R. , Belleau B.
Published: May 2006

Anodic methoxylation at a platinum electrode of α,α′-dimethoxystilbene yielded benzil tetramethylketal (2) which upon further electrolysis in methanol gave a 62% yield of trimethyl orthobenzoate. The mechanism of this new anodic fission reaction is briefly discussed.
Primary Bond Formation in the Addition of Cyclopentenone to Chloroethylenes
Authors: Loutfy R. O. , Mayo P. De
Published: May 2006

The cycloaddition of cyclopentenone to all the halogenated ethylenes has been studied. There is no evidence, as has been previously suggested, that specific β addition takes place as the first step. The details of the two-step closure are discussed and it is concluded that spin relaxation is probably of no relevance for the stereochemical outcome.
Nitration Studies on 2-Isopropylimidazole
Authors: Glass R. S. , Blount J. F. , Butler D. , Perrotta A. , Oliveto E. P.
Published: May 2006

The nitration of 2-isopropylimidazole has been studied under a variety of conditions involving nitration of the unprotonated imidazole, the imidazole anion, or an imidazole radical. From the reaction of nitronium tetrafluoroborate with 1-trimethylsilyl-2-isopropylimidazole there was isolated a dinitro compound the structure of which was shown by X-ray crystallography to be 1,4-dinitro-2-isopropylimidazole.
Equilibria Studies on Tetraalkylcyclohexenyl Cations
Authors: Ananthanarayan K. A. , Sorensen T. S.
Published: May 2006

A cyclohexenyl cation equilibria which effectively "pits" alkyl groups against one another yields equilibrium constants in the hyperconjugative order direction; however the size of the free energy differences are only about 60% of those observed for the identical cyclopentenyl cation member. The rate of the equilibrium reaction was studied, as was the rate of several aberrant ion–ion rearrangements, one on the t-butyl substituted ions causing particular problems. Unfortunately, the results appear consistent with either a steric or a hyperconjugation argument.
Intermediate Binary Carbonyls of Palladium Pd(CO)n where n = 1–3; Preparation, Identification, and Diffusion Kinetics by Matrix Isolation Infrared Spectroscopy
Authors: Kündig E. P. , Moskovits M. , Ozin G. A.
Published: May 2006

The co-condensation reaction of atomic palladium with a dilute CO–argon mixture (1:1000) at 10°K yields intermediate carbonyls of palladium Pd(CO)n where n = 1–3 as well as very small amounts of Pd(CO)4. Isotopic substitution experiments using 12C18O were used to aid the spectral assignments. The probabilities of forming the various Pd(CO)n carbonyl species as a function of the CO concentration in Ar are analyzed and compared with the experimental observations. An analysis of the diffusion kinetics demonstrates their usefulness in assigning bands to various species in a series of compounds such as Pd(CO)n. The data make possible the assignment of infrared absorptions at 2070, 2060, 2044, and 2050 cm−1 to tetrahedral (Td) Pd(CO)4, trigonal planar (D3h) Pd(CO)3, linear (D∞h) Pd(CO)2 and linear (C∞v) PdCO, respectively. Cotton–Kraihanzel force constants are calculated for Pd(CO)n and are compared with those for the analogous intermediate carbonyls of nickel, Ni(CO)n.
The Structure and Physical Properties of μ-oxo-bis{oxotrichloro(O-perrhenylchloride)rhenium(VI)}, and the Non-existence of β-ReOCl3
Authors: Calvo C. , Frais P. W. , Lock C. J. L.
Published: May 2006

The compound previously reported as β-ReOCl3 has been shown by analysis and single crystal X-ray diffraction to be μ-oxo-bis{oxotrichloro(O-perrhenyl chloride)rhenium(VI)}, (Re2O3Cl6)(ReO3Cl)2. The crystals were triclinic, a = 6.112(5), b = 12.876(9), c = 6.020(5) Å, α = 88.30(5), β = 95.88(5), γ = 105.36(5)°, [Formula: see text]. Intensities were measured by a densitometer from photographs recorded on an integrating precession camera. The structure was refined by full matrix least squares to give a final R2 of 0.072. The molecule is composed of a dimeric Re2O3Cl6 unit with a bridging oxygen atom on the center of symmetry and an Re—O (bridge) distance of 1.847(1) Å. The remaining oxo-group on each rhenium is cis to the bridge and is strongly bonded (1.69(2) Å), and the position trans to the terminal oxo-group is filled by a weak bond to an oxygen atom of a perrhenyl chloride molecule. The infrared spectrum of the compound has been explained in terms of the structure.
Préparation simple et configuration de dérivés des bicyclo[3.3.1]nonanol-2 ones-9 endo et exo. Utilité de la fonction trichloro-2,2,2 éthoxycarbonyle comme groupe protecteur d'aldols
Authors: Gravel D. , Rahal S. , Regnault A.
Published: May 2006

Simple and efficient preparations of some endo and exo epimeric pairs in the bicyclo[3.3.1]nonan-2-ol-9-one series are described. The configuration of each isomer is established spectroscopically and by chemical correlation. It is shown that the 2,2,2-trichloroethoxycarbonyl group may be used to protect these aldols and that regeneration of the latter does not give rise to epimerization.
Isotopic Studies of the Metal–Ligand Bond. Part I. Further Spectroscopic Studies of Copper Ethylenediamine Complexes: Copper–Nitrogen Vibrations
Authors: Canham G. W. Rayner , Lever A. B. P.
Published: May 2006

Confirmation of the far infrared (500–200 K) spectroscopic assignments of the metal–ligand vibrations in the complexes Cu(N–N)2X2 and Cu(N–N)X2((N–N) = ethylenediamine, symmetric and asymmetric N,N-dimethyl- and N,N-diethylethylenediamine, X = Cl, Br, NO3) has been obtained from copper isotopic substitution measurements. Extension of the series Cu(ethylenediamine)2X2 has provided some exceptions to the straight line correlation between [v(Cu—N)]2 and mean electronic d–d band energy. These are discussed.
Crystal Structure of a New Form of Cu3V2O8
Authors: Shannon Robert D. , Calvo Crispin
Published: May 2006

A new form of Cu3V2O8 was prepared at 30 kbar and 900 °C. The unit cell has dimensions a = 6.2493(9), b = 7.9936(9), c = 6.3776(10) Å, β = 111.49(1)°, and the space group is P2/c. The crystal structure, refined by least-squares to a final R = 0.054, using 848 reflections, is similar to that of Mg3V2O8. Chains of edge-shared M2 octahedra run along the c axis at about y = ± 1/4 with M1 octahedra sharing two edges with the M2 octahedra. These octahedral networks at about y = ± 1/4 are linked by corner-shared V–O tetrahedra. The distortion from the Mg3V2O8 structure can be explained on the basis of the Jahn–Teller effect in which four of the octahedral Cu—O distances shorten to 1.93–1.99 Å and two Cu—O distances lengthen to 2.3–2.6 Å.
Adduct Intermediates in the Side-chain Nitration of 1,4-Dimethylnaphthalene
Authors: Fischer Alfred , Wilkinson Alan Leslie
Published: May 2006

cis and trans isomers of 1,4-dimethyl-4-nitro-1,4-dihydro-1-naphthyl acetate (1) have been isolated from a mixture of 1,4-dimethylnaphthalene and nitric acid in acetic anhydride by quenching at −40°. At room temperature only 1-methyl-4-nitromethylnaphthalene (4) is obtained. The conversion of 1,4-dimethylnaphthalene to 4 and of the cis (1a) and trans (1b) adducts to 4, by nitric acid in acetic anhydride, has been followed by n.m.r. 1,4-Dimethyl-4-nitro-1,4-dihydro-1-naphthyl nitrate (5) appears to be the immediate product from nitration of 1,4-dimethylnaphthalene in acetic anhydride, methylene chloride, or nitromethane. In acetic anhydride 5 is converted into 1. Decomposition of 1 in acetic acid gives 1,4-dimethyl-2-naphthyl acetate and some 4. The formation of 4 in this reaction is suppressed by urea.
Synthesis and Stereochemistry of Some Diastereoisomeric 2-Amino-4-t-butylcyclohexanols and Related Compounds
Authors: Casy A. F. , Wu E. S. C. , Whelton B. D.
Published: May 2006

The synthesis of four RS diastereoisomeric analogs of acetylcholine based on 2-amino-4-t-butylcyclohexanol is described. Preferred conformations of these derivatives, their intermediates, and analogs lacking a t-butyl substituent, are assigned on the basis of 1- and 2-methine and other p.m.r. characteristics. In general, major deviations from preferred chair conformations arise only in quaternary salts which require an axial trimethyl-ammonium group. Certain p.m.r. signals of t-2-amino-c-4-t-butylcyclohexanol (base and hydrochloride) and t-2-dimethylamino-t-5-t-butylcyclohexanol hydrochloride are duplicated at 30°, a result attributed to a slow interconversion of conformational isomers.
A Model Compound for Anhydroryanodol
Authors: Brownlee Brian G. , Ho Pak-Tsun , Wiesner K.
Published: May 2006

The synthesis of the acetoxy lactone 17 by a method potentially suitable for anhydroryanodine is described. In the course of the synthesis several mechanistically unusual reactions were observed. One of them was an attack of Cl+ on an exocyclic double bond in a benzobicycloheptane system from the endo side. Another was a SN2 type displacement of chlorine by chloride or acetate ions in a six-membered ring.
Charge Scavenging by Benzene in γ-Irradiated Liquid Cyclohexane
Authors: Kennedy Michael G. , Stone John A.
Published: May 2006

The effect of benzene on the yield of propane formed by H2 transfer to cyclopropane in γ-irradiated liquid cyclohexane has been used to determine the efficiency of cation scavenging by benzene. The reduction of the hydrogen yield from cyclohexane by the addition of low concentrations of benzene may be accounted for by a combination of cation and H atom scavenging. G(benzene in polymer) found in previous studies correlates well with G(H atoms scavenged).
The Structure of the Capsular Polysaccharide from Klebsiella K-Type 21
Authors: Choy Y. M. , Dutton G. G. A.
Published: May 2006

Methylation, periodate oxidation, and partial hydrolysis studies on the capsular polysaccharide, and on the carboxyl reduced polymer, of Klebsiella K21 show the structure to consist of a repeating unit.[Formula: see text]The anomeric linkages were determined by p.m.r. spectroscopy of isolated oligosaccharides and, in part, by specific enzymes. P.m.r. spectroscopy of the original polysaccharide in methyl sulfoxide-d6 showed clearly a ratio of one pyruvic acid ketal (CH3, τ 8.5) to five anomeric protons (τ 4.65–5.40).