bluuebunny/crossref_metadata_2025 huggingface dataset:
Triplet state of orotic acid and orotic acid methyl ester in solution
Authors: Yip R. W. , Riddell W. D. , Szabo A. G.
Published: May 2006

Flash photolysis of orotic acid and orotic acid methyl ester in aqueous solution was studied. The transients were identified as triplet excited states on the basis of their lifetimes, sensitization, quenching, and self-quenching experiments. The rate constants for self-quenching and for decay of the triplet were measured and discussed in terms of dimerization and competing unimolecular and pseudo-unimolecular processes. A triplet energy of 60 kcal mole−1 was deduced for both orotic acid and orotic acid methyl ester from triplet energy transfer measurements.
Radiolysis of ethane. I. Liquid phase at 195°K with added cyclopentene
Authors: Holland P. T. , Stone J. A.
Published: May 2006

The radiolysis of liquid ethane at 195°K gives as major products H2, C2H4, and n-C4H10. Minor products are CH4 and C3H8. The initial yields of H2 and C2H4 can only be determined indirectly due to the high rate of H-atom addition to product ethylene. c-C5H8 in low concentration effectively scavenges H atoms and hence protects C2H4. The derived initial yields are: G(H2) = 5.97, G(C2H4) = 2.96, G(CH4) = 0.44, and G(C3H8) = 0.55. The yields of scavengeable H atoms and C2H5 radicals are 2.29 and 5.81, respectively. The problem of direct measurement of initial G(H2) values for saturated hydrocarbons at low temperatures is discussed.
Ozonolysis of podocarpic acid
Authors: Bell R. A. , Gravestock M. B.
Published: May 2006

Low temperature ozonolysis of methyl podocarpate in methanol – methylene chloride results in the formation in high yield of 8β-hydroperoxy-8α-hydroxy-(13 → 17)-pentanorlabd-9(11)-en-12,19-dioic acid 19-methyl ester 8 → 12-lactone 4. Ozonolysis followed by hydrogen peroxide work-up gives the lactone-acid 14a, whilst ozonolysis followed by reduction with sodium borohydride gives keto-acid 3a and lactones 16 and 17 derived from peroxide 4 together with δ-lactone 19 possessing all 18 carbon atoms of methyl podocarpate. The lactone 16 is shown to possess an 8β-configuration by application of the nuclear Overhauser effect.
Studies of specifically fluorinated carbohydrates. Part VI. Some pentofuranosyl fluorides
Authors: Hall L. D. , Steiner P. R. , Pedersen C.
Published: May 2006

Detailed analyses of the 1H and 19F nuclear magnetic resonance spectra of seven pentofuranosyl fluoride derivatives are reported. With the help of 1H-{19F} heteronuclear decoupling experiments, some unexpectedly large 4J couplings have been detected between F and H-4; when these substituents are trans the coupling is 5.5–7.9 Hz while the cis relationship gives couplings of 1.0–1.8 Hz. The 4J couplings between F and H-3 are smaller when these groups are trans (< 0.7 Hz) than when they are cis oriented (1.7–2.4 Hz). These, and the other coupling constants are discussed in terms of the favored conformations of these derivatives. The ring conformations of the anomeric tri-O-benzoyl-D-ribo-furanosyl fluorides differ from each other.
Spectrophotometric determination of the hydrolysis constant of bromine at 25 °C
Authors: Pink Judith M.
Published: May 2006

A spectrophotometric determination of the equilibrium constant for the hydrolysis of bromine in water is described.
Reaction of CF3 radicals with methylchlorosilanes
Authors: Bell T. N. , Zucker U. F.
Published: May 2006

Arrhenius parameters have been measured for H abstraction from the alkylchlorosilanes CH3SiCl3, (CH3)2SiCl2, and (CH3)3SiCl, and also for (CH3)4Si[Formula: see text]where k is in ml mole−1 s−1. Halogen abstraction does not occur with these compounds nor with SiCl4. CF2CH2 is formed from the hot molecule produced when the silylmethyl radical combines with CF3[Formula: see text]
Electron spin resonance spectra of nitric oxide adsorbed on zeolites
Authors: Gardner C. L. , Weinberger M. A.
Published: May 2006

Electron spin resonance (e.s.r.) spectra of NO adsorbed on the 4 zeolites Linde 4A, 5A, 13X, and hydrogen mordenite were measured at 77°K. No e.s.r. signal was observed for NO on silica gel. By use of expressions for the line shapes of polycrystalline samples, assuming axially symmetric g-tensors, and taking into account also isotropic coupling, values of [Formula: see text] and line width were derived by an iterative procedure. From these, the crystal field splitting, Δ, of the 2pπ levels, which become non-degenerate on adsorption, were calculated. By relating Δ to the interaction of the non-axial components of the quadru-pole moment with the corresponding electric field gradients, the non-axial component of the latter is estimated for the surface fields of the zeolites.
Cyclobutanes in organic synthesis. Part I. Fragmentation to 1,4-dicarbonyl compounds. General considerations
Authors: Hunter N. R. , MacAlpine G. A. , Liu H. J. , Valenta Z.
Published: May 2006

Photo-cycloaddition of vinyl acetates to 2-cyclohexenones followed by hydrolysis of the acetate group and by oxidative fragmentation leads to 2-alkyl-2-cyclohexenones in which the newly introduced alkyl group bears a 2′-carbonyl group. A similar, less generally applicable method, involving photo-cycloaddition, bromination, and heterolytic fragmentation is also described. Possible applications of this sequence in organic synthesis are discussed.
Etude spectroscopique de l'intermédiaire des migrations d'acyle O → N dans le β-éthyl triacétyl-3,4,6 désoxy-2 amino-2 D-glucoside
Authors: Fodor Gabor , Letourneau Francine , Mandava Nagabhushanam
Published: May 2006

not available
Application of proton magnetic resonance to rotational isomerism in halotoluene derivatives. II. α,α,2,4,6-Pentachlorotoluene
Authors: Fuhr B. J. , Goodwin B. W. , Hutton H. M. , Schaefer T.
Published: May 2006

At temperatures below −40 °C the proton magnetic resonance of α,α,2,4,6-pentachlorotoluene in toluene-d8 or methylcyclohexane is an ABX spectrum where X is the methine proton. The C—H bond of the dichloromethyl group lies in the plane of the ring and its proton couples to one ring proton only. As the temperature increases the mean lifetime before interconversion of the "mirror image" isomers decreases and at 70 °C the proton spectrum is A2X. A density matrix formalism is used to calculate the line shape as a function of the lifetime before exchange. The free energy barrier to rotation of the dichloromethyl group is 15.0 ± 0.1 kcal/mole in both solvents. In toluene-d8 the entropy of activation is near zero. The high energy transition state is very likely one in which the C—Cl bonds of the ring and the dichloromethyl groups are eclipsed.
Heats of mixing in the system acetone – acetic anhydride – carbon disulfide, and the corresponding binary systems, at room temperature
Authors: Campbell A. N. , Kartzmark E. M. , Anand S. C.
Published: May 2006

A simple calorimeter has been devised by means of which the heats of mixing (molar excess heats) of the following systems have been determined at 22 °C: acetone – acetic anhydride; acetone – carbon disulfide; acetic anhydride – carbon disulfide; and a pseudo-binary section of the ternary system acetone – acetic anhydride – carbon disulfide. From these data the partial molar excess heats have been obtained. All systems are very non-ideal except the system acetone – acetic anhydride, which is almost ideal.For the partially miscible system acetic anhydride – carbon disulfide, the excess thermodynamic quantities of mixing, GE, HE, and TSE, have been calculated,
Reactions of acid chlorides with ethers in the presence of iron pentacarbonyl
Authors: Alper Howard , Edward J. T.
Published: May 2006

Iron pentacarbonyl catalyzes the cleavage of alkyl ethers by acid chlorides to form alkyl chlorides and alkyl esters.
Mössbauer spectra and electric dipole moments of organotin(IV) complexes with organic ligands
Authors: Mullins F. Patricia
Published: May 2006

Mössbauer spectra, electric dipole moment, and infrared data are reported for several complexes of the type (i) RSnX3(AA) and (ii) RSnX(AB)2 (where R = C4H9, C6H5; X = Cl, NCS; AA = α,α′-dipyridyl, o-phenanthroline, 8-aminoquinoline; AB = oxinate, 2-pyridinethiol 1-oxide). Quadrupole splittings and dipole moments indicate a similar octahedral structure is present in all the complexes studied; in type (i) two X groups are trans and in type (ii) the R and X groups are cis to each other. Isomer shifts reveal an order of bond polarity Sn—O ≈ Sn—NCS > Sn—Cl > Sn—S.
Fluorocarbon-bridged ditertiary phosphine derivatives of rhodium carbonyl halides
Authors: Cullen W. R. , Thompson J. A. J.
Published: May 2006

The ditertiary phosphines, [Formula: see text] (n = 1,2) react with [Rh(CO)2X]2 (X = Cl, Br) via unsymmetrical cleavage of the halide bridges to give ionic complexes [(P—P)2Rh]+ [cis-(CO)2RhX2]−. However the diarsine, [Formula: see text] (ffars) reacts in an anomalous manner to give the neutral dimer, [(ffars)Rh(CO)Cl]2. With an excess of the phosphines, (n = 1, 2 or 3) the ionic complexes [(P—P)2Rh]+Cl− are obtained. The physical and spectroscopic properties of the new compounds and the tendency of the ions, [(P—P)2Rh]+, not to undergo facile oxidative-addition reactions are discussed.
Remarkable stereoselectivity in the hydrolysis of dioxolenium ions and orthoesters fused to anchored six-membered rings
Authors: King J. F. , Allbutt A. D.
Published: May 2006

Hydrolysis of dioxolenium (acyloxonium) ions fused to anchored six-membered rings gives almost exclusively that hydroxyester in which the ester function is axial (and the hydroxyl group equatorial). With the exception of the orthoformate, a group of related orthoesters reacted similarly. The potential utility of these observations in stereoselective synthesis is suggested by the following examples, (a) With trans-decalin-cis-2,3-diol (21) formation of the mono-benzoate via the orthoester leads to the axial ester (23d) in good yield; this procedure is complementary to reaction with benzoyl chloride and pyridine, which gives the equatorial ester (24d) as the only isolated product, (b) The action of silver acetate and iodine in wet acetic acid (the Woodward–Prevost reaction) on trans-Δ2-octaIin gives the axial acetate–equatorial alcohol (23b) again as the only significant product. The generality of this stereoselectivity is further supported by a number of individual examples drawn from the chemistry of carbohydrates. A rationalization is offered which qualitatively accounts for the observed stereoselectivity and its absence in the hydrolysis of the orthoformate, and which is based on the differences in steric strain among the possible transition states that fulfil the stereoelectronic requirements of dialkoxycarbonium ion formation.
Some potentially physiologically active β, β-diphenylethylamines derived from adrenaline
Authors: Forrest Janet E. , Kašpárek S. , Heacock R. A. , Forrest T. P.
Published: May 2006

The reaction that occurs between adrenalin (1) and phenols in the presence of hydrochloric acid, to form potentially physiologically active β,β-diphenylethylamine derivatives, is described. The products obtained include adrepine (7), formed from 1 alone, and others obtained by the interaction of 1 with a second phenolic component, such as epinine or 4-methylcatechol. The nuclear magnetic resonance and mass spectroscopic data obtained for these products and a number of related compounds are presented and discussed.
Coordination complexes of gallium(III) and indium(III) halides. V. Trialkyl and mixed alkyl–aryl phosphine complexes of indium(III) chloride, bromide, and iodide
Authors: Carty A. J. , Hinsperger T. , Boorman P. M.
Published: May 2006

The new complexes InX3L (X = Cl, Br, I; L = tricyclohexylphosphine), InX3L2 (X = Cl, Br, I; L = trimethylphosphine, triethylphosphine, dimethylphenylphosphine), InX3L2 (X = Cl, Br, L = diphenylethylphosphine), InX3L3 (X = Cl, Br; L = dimethylphenylphosphine) have been prepared and characterized by far-infrared, Raman, and molecular weight studies. Structures of the types trans trigonal bipyramidal InX3L2 and C3υ ψ-tetrahedral InX3L can be readily characterized by virtue of their typical infrared and Raman spectra. Nuclear magnetic resonance chemical shifts and coupling constants for adducts of trimethylphosphine, triethylphosphine, dimethylphenylphosphine, and diphenylethylphosphine are discussed.
Temperature dependence of the 35Cl nuclear quadrupole resonance in the trimethylamine – boron trichloride complex
Authors: Gilson D. F. R. , Hart R. M.
Published: May 2006

A 35Cl nuclear quadrupole resonance study of the trimethylamine – boron trichloride complex has revealed line-width and frequency changes which correlate with transitions observed in the wide-line proton magnetic resonance study.
Lithiation of five-membered heteroaromatic compounds. The methyl substituted 1,2-azoles, oxadiazoles, and thiadiazoles
Authors: Micetich R. G.
Published: May 2006

The lithiation of various methyl substituted isoxazoles, isothiazoles, pyrazoles, oxadiazoles, and thiadiazoles using n-butyllithium has been studied. Three types of reactions, namely, lateral lithiation, ring cleavage, and addition of butyllithium to the ring, have been found. 3,5-Dimethylisoxazole, 3-phenyl-5-methylisoxazole, 3,4-dimethyl-1,2,5-oxadiazole, 2,5-dimethyl-1,3,4-thiadiazole, 3-phenyl-5-methyl-1,2,4-oxadiazole, and 3,5-dimethyl-1,2,4-thiadiazole all undergo lateral lithiation to give the respective acetic acids after carboxylation. 1-Methyl-3,5-disubstituted pyrazoles form the 1-lithiomethyl derivatives, while 1-phenyl-3,5-disubstituted pyrazoles are converted to the 1-ortholithiophenyl-3,5-disubstituted pyrazoles. 4-Methylisothiazole is lithiated mainly at C-5, but also suffers ring cleavage to form 1-n-butylthio-2-cyanoprop-1-ene. Heteroaromatic compounds containing an N—S bond, such as 3,4-dimeth yl-1,2,5-thiadiazole, 4-methyl-5-phenyl-1,2,3-thiadiazole, and 3,5-dimethylisothiazole, undergo nucleophilic attack at sulfur with resulting ring cleavage. 3,5-Dimethylisothiazole produces 2-n-butylthiopent-2-en-4-one. 3-Methyl-5-phenyl-1,2,4-oxadiazole gave 3-methyl-5-phenyl-5-n-butyl-1,2,4-dihydroöxadiazole by addition to the azomethine bond. The results of these lithiations are discussed. 3-Methyl-5-lithiomethylisoxazole was converted to various derivatives. Nuclear magnetic resonance spectral analysis was used to establish the identity of the products.
Studies on hydrogen–oxygen systems in the electrical discharge. III. Surface effects
Authors: Brunet Paul E. , Deglise Xavier , Giguère Paul A.
Published: May 2006

Surface effects in the reactions of dissociated hydrogen–oxygen systems and the products condensed therefrom have been investigated. Water vapor at about 0.1 Torr was streamed at high velocity through an electrodeless discharge confined in tubes of different materials or with various surface coatings. In all cases the products trapped in liquid nitrogen evolved oxygen gas on warming, but the relative amounts varied considerably from one type of surface to another. In some cases there was clear evidence that the walls of discharge tube were attacked by hydrogen atom bombardment. The decomposition, both thermal and electrical, of pure hydrogen peroxide vapor was studied likewise. The pyrolysis products gave off very little oxygen on warming. By contrast the products from electrical decomposition, even at low power level, evolved much oxygen, most of it above the melting point.It is concluded that there is always some decomposition of hydrogen peroxide in the trapped products. However, this does not seem sufficient to account for all the evolved oxygen; at least not in the case of dissociated water vapor.
Infrared studies of some N-methylacetamide complexes
Authors: Shaw Y. H. , Li N. C.
Published: May 2006

Hydrogen bonding of N-methylacetamide (NMA) with dimethylsulfoxide (DMSO) and N,N-dimethylacetamide (DMA) in carbon tetrachloride and CCl4/CHCl3 mixed solvent was studied by a near-infrared method, which consists of measuring the effects of various concentrations of DMSO or DMA on the molar absorptivity of 0.06 M NMA at 6800 cm−1, corresponding to the first overtone of the uncomplexed NH stretching vibration. The association constants for the formation of 1:1 NMA–DMA and NMA–DMSO complexes in CCl4 are 10 and 121/mole, respectively, at 25°. In order to obtain an association constant for the formation of NMA–DMSO in CCl4/CHCl3 mixed solvent, it is necessary to have data on association constants of CHCl3–DMSO complexes in CCl4, and we have obtained these by determining the effects of various concentrations of DMSO on the proton magnetic resonance frequency of 0.05 M CHCl3 in CCl4. The association constants for the formation of NMA–DMSO and NMA–DMA in CCl4/CHCl3 mixed solvent are slightly higher than in CCl4, presumably due to hydrogen bonding between Cl3CH and C=O in NMA. NMA was chosen as the simplest molecule containing the peptide amide group and hence can be regarded as a structural unit of the polypeptide chain. Our results show that DMSO and DMA are effective in disrupting the interamide bonds, by acting as hydrogen acceptors to the NH group.
Absolute rate constants for hydrocarbon autoxidation. XIX. Oxidation of some α-substituted toluenes
Authors: Howard J. A. , Korcek S.
Published: May 2006

Absolute propagation and termination rate constants have been measured for the liquid phase autoxidation of some α-substituted toluenes at 30 °C. Rate constants for reaction of α-substituted toluenes with their own peroxy radical and with the t-butylperoxy radical have been compared. It would appear that the reactivity of an α-substituted benzylperoxy radical depends on the nature of the α-substituent.Reactivities of α-substituted toluenes towards the t-butylperoxy radical, the bromine atom, and the phenyl radical have been compared.
Decomposition of some cyclic dithiocarbamates
Authors: Vandebeek Ronald R. , Joris Serge J. , Aspila Keijo I. , Chakrabarti Chuni L.
Published: May 2006

The stability of some cyclic N,N-disubstituted dithiocarbamates has been studied by the analysis of the decomposition rates at different pH values. It is concluded that the most important factors which determine the relative stabilities of three cyclic dithiocarbamates (DTC) are the solvation of the DTC acid molecule and the ring strain associated with the substituents. This has been proven by a study of (a) the decomposition rates as a function of the dielectric constant of the medium, (b) order of the stability, and (c) activation energy.The molar absorptivities and the apparent acid dissociation constants have been determined for pyrrolidine-, piperidine-, and hexamethylene-dithiocarbamates.
Synthesis and cycloaddition reactions of 2-(2-thienyl)aziridines
Authors: Lown J. W. , Matsumoto K.
Published: May 2006

The synthesis of several new 2-(2-thienyl)aziridines and an examination of their cycloaddition with olefinic and acetylenic dipolarophiles is described.
Stereoselective synthesis of α-bulnesene, 4-epi-α-bulnesene, and 5-epi-α-bulnesene
Authors: Piers Edward , Cheng Kin Fai
Published: May 2006

Lithium–ammonia reduction of the hydroguaiazulene derivative 6, followed by oxidation of the resulting diol 13, gave, in a highly stereoselective manner, the keto alcohol 14. The latter was converted into 5-epi-α-bulnesene (2). In a similar sequence of reactions, 4-epi-α-bulnesene (3) was obtained from compound 9. Photochemical rearrangement of the previously obtained dienone 25 gave the hydroguaiazulene derivative 27. Successive subjection of the latter to acetylation, hydrogenation, and sodium borohydride reduction gave a mixture of the epimeric diols 31 and 32. When this mixture was treated with p-toluenesulfonic acid in pyridine, and the resulting olefinic diester 35 was sequentially subjected to hydrogenation [tris(triphenylphosphine)chlororhodium] and lithium aluminum hydride reduction, the crystalline diol 37 was obtained. The latter was converted into α-bulnesene (1) by standard reactions.
Total synthesis of (±)γ2-cadinene
Authors: Kelly R. B. , Eber J.
Published: May 2006

A total synthesis of (±)γ2-cadinene is described. The synthetic terpene was characterized by conversion to (±)-cadinene dihydrochloride.
Preparation and acceptor power of the pentafluorogermanate ion
Authors: Wharf I. , Onyszchuk M.
Published: May 2006

Preparations of [(C3H7)4N][GeF5], [(C4H9)4N][GeF5], [(C4H9)4N][GeF5(H2O)], and [(C6H5)4As][GeF5] are described and their infrared spectra reported. The pentafluorogermanate ion forms a stable 1:1 adduct with ammonia, with ΔH = 17.5 ± 1.0 kcal mole−1 for the reaction: [(C3H7)4N][GeF5(NH3)] (s) → [(C3H7)4N][GeF5] (s) + NH3(g). The value for the corresponding pentafluorosilicate system is ΔH = 12.0 ± 0.5 kcal mole−1.
Broad-line nuclear magnetic resonance investigation of molecular motion in solid trimethylamine–halogen complexes
Authors: Fyfe C. A. , Ripmeester J.
Published: May 2006

Broad-line nuclear magnetic resonance studies of the charge-transfer complexes of trimethylamine (NMe3) with iodine, bromine, and iodine monochloride indicate the presence of motion in the solid state. Trimethylamine itself was studied for purposes of comparison. The nature of the motional transitions for each species has been determined, and activation energies derived.
Improvements for the preparation of L-idose from D-glucose
Authors: Kovár Jan
Published: May 2006

L-Idose (10) was prepared via its 1,2-O-isopropylidene derivative (9). The latter was prepared by means of the known principle of inverting the configuration of C-5 in sulfonic esters derived from 1,2-O-isopropylidene-α-D-glucofuranose, but a number of new intermediates and variations in procedure were studied in order to achieve practical improvements. Starting compounds were the 3,5-di-p- toluenesulfonate (1), the 3-methanesulfonate-5-p-toluenesulfonate (4), and the 5-p-toluenesulfonate (7) of 6-O-benzoyl-1,2-O-isopropylidene-α-D-glucofuranose, and intermediates were the 3-p-toluene-sulfonate-5-acetate (2), the 3-methanesulfonate-5-acetate (5), and the 3,5-diacetate (8) of 6-O-benzoyl-1,2-O-isopropylidene-β-L-idofuranose. Compound 8 was converted into 9 directly, whereas 2 and 5 gave 9 by sodium reduction of their 5,6-deacylated derivatives 3 and 6.
Partial molal volume behavior of tetraalkylammonium chlorides in aqueous acetone and aqueous dimethylsulfoxide
Authors: Macdonald Digby D. , Hyne J. B.
Published: May 2006

The partial molal volumes of a series of tetraalkylammonium chlorides in aqueous acetone and aqueous dimethylsulfoxide at 25.000 °C are reported as a function of solvent composition. It is shown that for each solvent composition the partial molal volume data are better represented by a quadratic in solute molecular weight than by the linear expression previously employed in similar studies. Extrapolation of molecular partial molal volumes to zero cation molecular weight has permitted evaluation of the partial molal volumes of the ions R4N+ and Cl−. The variation of molecular and ionic partial molal volume as a function of solvent composition is discussed.
Adsorption of water and 18O exchange of surface hydroxyl groups on silica
Authors: Morrow B. A. , Devi A.
Published: May 2006

Infrared spectroscopy has been used to show that the surface hydroxyl groups on highly dehydrated silica will exchange with 18O-labeled water. The degree of exchange depends on the sample temperature and is a maximum at about 400 °C, where approximately 65% of the silanol groups contain 18O. The use of the 18O exchange technique for assigning surface-adsorbate stretching modes is illustrated by considering the infrared spectra of BF3 chemisorbed on silica.
Analysis of periodate oxidation of carbohydrates by polarography
Authors: Corlett R. D. , Breck W. G. , Hay G. W.
Published: May 2006

Experimental conditions using a variety of pH buffers have been established to permit the rapid, accurate determination of periodate and formaldehyde by polarography. The application of these analyses to quantitative studies in the oxidation of carbohydrates was illustrated and the lower limit of detection presently available found to be equivalent to 0.04 μmole carbohydrate.
Mass spectrometric study of the reaction of BF3 with B2O3; the identification and heat of formation of B2OF4
Authors: Bidinosti D. R. , Coatsworth L. L.
Published: May 2006

The reaction of BF3 with B2O3 in a molecular flow reactor has been studied with a mass spectrometer. Over the temperature range 930–1300 K the reaction has been found to produce B2OF4 with the stoichiometry[Formula: see text]From the temperature dependence of the equilibrium constant the enthalpy change for this reaction was determined to be 18.5 ± 3 kcal/mole and ΔHf0 (B2OF4) calculated to be −454 ± 2 kcal/mole at 1100 K.
Studies on metal hydroxy compounds. XI. Thermal analyses, decomposition kinetics, and infrared spectra of cadmium and zinc halide derivatives
Authors: Ramamurthy P. , Secco E. A.
Published: May 2006

The thermal analyses of Cd2(OH)3X type of basic halides reveal that the decomposition occurs via a two-step dehydroxylation pattern, yielding CdOHX as an intermediate product after the initial mode. These results suggest that Cd2(OH)3X is an addition compound of the hydroxide and the 1:1 hydroxy-halide, i.e. Cd(OH)2•CdOHX. Calorimetric measurements along with related enthalpy values for the decomposition reaction are given.The kinetics of thermal decomposition of the compounds are classified into two main groups: (i) two-dimensional contracting plate model equation and (ii) first-order rate law.The infrared spectral data of thirteen Cd and Zn basic halides in the frequency region 4000–250 cm−1 are presented with their assignments.
Titration curves of fulvic acid: the analytical chemistry of a weak acid polyelectrolyte
Authors: Gamble Donald S.
Published: May 2006

The fulvic acid molecular weight fraction studied has two general types of carboxyl groups, one of which is ortho to phenolic —OH groups. The number of each type per gram of fulvic acid has been measured. The acid ionization equilibrium of each type has been calculated as a function of its degree of ionization in 0.1 m KCl at 25.0 °C. In both cases the acid strength decreases with increasing degree of ionization. The sample used shows the potentiometric titration behavior expected of a low molecular weight polyelectrolyte.
π-Bonding between C=C bonds and tin in alkenyltin compounds
Authors: Clark H. C. , Poller R. C.
Published: May 2006

The infrared and nuclear magnetic resonance spectra of a number of allyl-, but-3-enyl-, crotyl-, and vinyl-tin compounds in dimethylsulfoxide have been examined and compared with measurements made on solutions in methylene chloride and carbon tetrachloride. It is concluded from the changes which occur in the positions of the ν(C=C) bands and in the chemical shifts of the olefinic protons that there are no significant π-interactions between the d orbitals on tin and the olefinic π-systems.
d Orbitals in the noble-gas dihalides
Authors: Catton R. C. , Mitchell K. A. R.
Published: May 2006

Model calculations are reported for ArF2, KrF2, XeF2, ArCl2, KrCl2, and XeCl2. The approach is to compare the energies of a number of valence-bond structures for each molecule. The calculations use Slater-type radial functions and simplify the electron repulsion integrals with the Mulliken approximation. Energies are optimized by varying the d orbital exponent and a parameter which governs the ionic character of the covalent bonds. For all the molecules it is found that the structures such as (X—M+X− + X−M+—X) and X−M2+X−, which maintain the octet rule and exclude the use of d orbitals, are less stable than the structure X—M—X which implies localized electron-pair bonds based on pd hybrids at the noble-gas atom M.Approximate molecular wave functions are obtained from a configuration interaction calculation, and the general conclusion is that the valence-bond structures incorporating d orbitals become more important as the atomic number of the central atom increases. A preliminary study of the role of the [Formula: see text] orbital is also presented, but it seems this orbital contributes mainly as a polarization effect.
Structure of sepedonin, a tropolone metabolite of Sepedomumchrysospermum Fries
Authors: Wright J. L. C. , McInnes A. G. , Smith D. G. , Vining L. C.
Published: May 2006

The structures of sepedonin, 3,6,9-trihydroxy-3-methyl-1,3,4,7-tetrahydrocyclohepta[c]pyran-7-one, and its two dimethyl ether derivatives, as well as anhydrosepedonin and its three dimethyl ether derivatives, are unequivocally established from proton magnetic resonance and nuclear Overhauser enhancement parameters.
Photolysis of 4,6,6-trimethyl-5,6-dihydro-2(1H)-pyridone. Intermediates and mechanism
Authors: Cavalieri E. , Gravel D.
Published: May 2006

Irradiation of dihydropyridone 1a in water yields mainly the unsaturated amides 3 (73%), 4 (8%), and acetone. A 1.3% yield of photohydration product 5a is also obtained. Irradiation of 1a in anhydrous methanol yields carbinolamidoether 8 (57%), whereas in t-butyl alcohol enamide 7 is the reaction product. Irradiation of the N-methyl derivative of 1a (1b) yields 90% of starting material and 5% of a photohydrate 5b. The mechanistic path of the reaction is shown to involve the cleavage of compound 1a to the enolic form 9 of the acylimine 6 which reacts differently depending on the solvent used.
Electron spin resonance spectra of the triple ions [Na2-pyrazine]+ and [Na2-tetramethylpyrazine]+
Authors: Al-Baldawi S. A. , Gough T. E.
Published: May 2006

Reduction of pyrazine (P) and tetramethylpyrazine (TMP) by sodium in the presence of sodium tetraphenylboride produces Na2P+ and Na2TMP+, respectively. The electron spin resonance spectra of these species are presented and compared with those of the corresponding ion pairs. From line-broadening effects within the sodium hyperfine multiplets of the triple ion spectra, it is deduced that the sodium ions occupy positions close to the N–N axes of the ring systems.
Free radicals in γ-irradiated disodium succinate. Part 1. Monoclinic crystals
Authors: Vyas H. M. , Janecka J. , Fujimoto M.
Published: May 2006

Crystals of disodium succinate have two distinct modifications, monoclinic and triclinic. These were recognized by electron spin resonance (e.s.r.) studies of. the free radicals produced by γ-irradiation. In the monoclinic crystals, e.s.r. spectra and radiation processes appear similar to those observed in γ- (or x-) irradiated succinic acid. The situation in triclinic crystals is more complex (see Part 2). In monoclinic crystals irradiated at 77 °K, two types of radical coexist. They were identified as −O2CCH2CH2ĊO22−, 1, together with a distorted conformation of the radical −O2C(ĊHCH2)*CO2−, 2. On warming to room temperature the former species disappears while the latter changes irreversibly to a stable conformation −O2CĊHCH2CO2−, 3.
Determination of the molecular conformation of uridine in aqueous solution by proton magnetic resonance spectroscopy. Comparison with β-pseudouridine
Authors: Blackburn Barry J. , Grey Arthur A. , Smith Ian C. P. , Hruska Frank E.
Published: May 2006

A complete analysis of the 220 MHz proton magnetic resonance spectrum of aqueous uridine is reported. From the data a model for the molecular conformation is presented and compared with that of β-pseudouridine. It is concluded that in both compounds the ribose rings are in rapid equilibrium between classical puckered structures. The temperature-independence of the ribose proton coupling constants and chemical shifts suggests that all the conformers involved in this equilibrium have very similar energies. Both compounds exhibit a preference for the gauche–gauche rotamer about the exocyclic 4′—5′ bond; this conclusion is shown to be independent of the parameters in the Karplus equation or the energy minima chosen for the rotamers. The anti conformation of the uracil base is shown to exist in both compounds. It is proposed that the special structural significance of β-pseudouridine in transfer RNA must be due to the potential hydrogen bond that may be formed by the nitrogen atom at position one in uracil.
Aryl complexes of platinum(II). A study of the bonding between platinum and tertiary phosphine, arsine, and stibine
Authors: Westland A. D. , Northcott M.
Published: May 2006

Phenyl and fluorophenyl complexes but not alkyl complexes of platinum may be prepared from (Et3Sb)2PtCl2 by Grignard reactions. Dipole moment and 19F nuclear magnetic resonance studies indicate a slight gradation in electronic properties which correlates with previous equilibrium studies.
The preparation and kinetics of complex formation of hexadimethylsulfoxidovanadium(III) perchlorate
Authors: Langford Cooper H. , Chung Fine Man
Published: May 2006

We report the synthesis of the ion V(DMSO)63+ and kinetics of its reactions with SCN−, sulfosalicylic acid, and 2,2-bipyridine. The complex formation rates show some dependence on the ligand. The value of ΔS≠ found for the reaction with bipyridine is quite negative. A definite mechanistic assignment cannot yet be made.
Branched-chain aminodeoxy sugars. Methyl 3-C-aminomethyl-2-deoxy-α-D-ribo-hexopyranoside and methyl 3-C-aminomethyl-2-deoxy-α-D-arabino hexopyranoside
Authors: Rosenthal Alex , Ong Khong-Seng
Published: May 2006

Addition of methyl 4,6-O-benzylidene-2-deoxy-α-D-erythro-hexopyranosid-3-ulose (1) to excess nitromethane and 1 molar equivalent of sodium methoxide in methanol gave methyl 4,6-O-benzylidene-2-deoxy-3-C-nitromethyl-α-D-ribo-hexopyranoside (2) and the arabino stereoisomer 3 in 63 and 22% yields, respectively. The proof of structure of the branched-chain deoxy nitro sugars is described. Debenzylidenation of the nitro sugars afforded the partially blocked nitro sugars 4 and 5. Catalytic hydrogenation of the latter or of 2 and 3 yielded the branched-chain aminodeoxy sugars 7 and 9 (7 characterized as its N-acetyl derivative and 9 as its N-2,4-dinitrophenyl derivative).
Thermal and photochemical rearrangements of methyl-substituted cyclopentadienes
Authors: McLean Stewart , Findlay D. M.
Published: May 2006

5,5-Dimethylcyclopentadiene undergoes a thermal rearrangement by migration of a methyl group, the kinetics of which have been studied, but no rearrangement product was observed on u.v. irradiation. However, methylcyclopentadiene is converted photochemically to 2-methylbicyclo[2.1.0]pentene, which is thermally unstable.
Mass spectral studies of metal chelates. VI. Mass spectra and appearance potentials of β-diketonates of copper(II)
Authors: Reichert C. , Westmore J. B.
Published: May 2006

The mass spectra of several copper complexes of β-diketones are discussed. The extent of fragmentation of the molecular ions depends upon the nature of the substituents on the chelate ring, being larger for electron-withdrawing, and smaller for electron-releasing substituents. In a number of fragmentations, migration of an aryl group to the copper atom occurs. Hydrogen atom migrations are also observed in some fragmentations. Attempts are made to correlate the appearance potentials of the molecular ions with acid dissociation constants of the β-diketones, formation constants and polarographic reduction potentials of the complexes, and Hammett σ constants of the substituents.
Thermodynamics of proton dissociations from imidazolium ion, 6-uracilcarboxylic acid, and protonated hypoxanthine in aqueous solution
Authors: Woolley Earl M. , Wilton Richard W. , Hepler Loren G.
Published: May 2006

Equilibrium constants have been determined potentiometrically for proton dissociations from imidazolium ion, 6-uracilcarboxylic acid (pK1 and pK2), and protonated hypoxanthine (Pk1, pK2, and pK3) in aqueous solution at 25 °C and used for calculation of ΔG° values for the corresponding reactions. Enthalpies of these same proton dissociations have been measured calorimetrically and combined with the ΔG° values to yield ΔS° values for these reactions.
Reactivities of ions and ion-pairs in the base-catalyzed reaction of phenyl glycidyl ether and benzoic acid in various solvents
Authors: Tanaka Yoshio , Okada Akira , Suzuki Mitsuo
Published: May 2006

The conductance of pyridinium benzoate has been measured in various solvents such as nitrobenzene, benzonitrile, o-dichlorobenzene, monochlorobenzene, and toluene, and its dissociation constant, K, was determined, using the Kraus and Bray's equation with the Λ0 value estimated from Walden and Ulich's rule and Stokes's law. The logarithm of K was found to be linear with the reciprocal of the dielectric constant, ε, or with the Kirkwood–Laidler–Eyring function, (ε − 1)/(2ε + 1). Kinetic studies for pyridine-catalyzed reaction between phenyl glycidyl ether and benzoic acid were also made in these solvents. Both the free ions and ion-pairs including the molecular addition complex participate in the reaction. The apparent rate constants, k″, of the reaction were shown to be linear with 1(K/c)1/2, c being the concentration of pyridinium benzoate. The intercepts of such lines give the rate constant for formation of ion-pairs, ki and the slopes yield the rate constant for formation of free ion, kf. The free ion rate constant increases fairly rapidly as the dielectric constant decreases, while the ion-pair reaction constant drifts downward comparatively slowly. A plot of the logarithm of kf or kf(K/c)1/2 against 1/ε or (ε − 1)/(2ε + 1) is found to be linear, but the plots of log ki against the same function are curved. The tangent of the curve is steeper for polar solvents than for non-polar solvents. The results have been compared with those predicted from classical dielectric theory.
Photochemical rearrangement of diene endoperoxides
Authors: Maheshwari K. K. , Mayo P. de , Wiegand D.
Published: May 2006

It has been shown that the direct irradiation of cyclic peroxides such as ascaridole, and those derived from cyclohexadiene, 1,3,5,5-tetramethylcyclohexadiene, and levopimaric acid methyl ester rearrange on irradiation. The bisepoxides are obtained, as in the thermal rearrangement, together with, where the structure permits, the ketoepoxide. The reaction can be induced by triplet–triplet energy transfer.
The radiolysis of ethane. II. Liquid phase at 195°K; effect of electron and positive ion scavengers
Authors: Holland P. T. , Stone J. A.
Published: May 2006

H atoms and•C2H5 radicals in the radiolysis of liquid ethane have both ionic and non-ionic precursors. The use of SF6 as an electron scavenger leads to very low C2H4 yields which is consistent with the addition of•SF5 radicals to this product. H and D atoms produced by neutralization of ND3H+ can either add to C2H4 or abstract from C2H6 at 195°K.
Quaternization of quinazoline with methyl iodide
Authors: Bunting John W. , Meathrel William G.
Published: May 2006

Contrary to previous reports, the methylation of quinazoline with methyl iodide has been shown to produce both 1-methylquinazolinium iodide and 3-methylquinazolinium iodide. These quaternary salts are formed in the ratio of 5:1 in favor of the latter isomer.
The vibrational spectra of ClF2SbF6, BrF2SbF6, and ClO2SbF6
Authors: Carter H. A. , Aubke F.
Published: May 2006

Infrared and Raman spectra of ClF2SbF6, BrF2SbF6, and ClO2SbF6 are reported. Vibrational frequencies for the BrF2+ cation are assigned. In all compounds various degrees of anion–cation interaction are found. The symmetry of the anion is reduced but no internal similarity between the three spectra is recognizable. In addition, strong coupling of vibrational modes for BrF2SbF6 is observed.
Studies on hydrogen–oxygen systems in the electrical discharge. IV. Spectroscopic identification of the matrix-stabilized intermediates, H2O3 and H2O4
Authors: Giguère Paul A. , Herman Kazimiera
Published: May 2006

The infrared absorption of the products from electrically dissociated H2O or D2O vapor and other hydrogen–oxygen systems trapped at liquid nitrogen temperature was measured between 4000 and 300 cm−1. Four new absorption bands were found in the deuterated systems at 857, 820, 760, and about 440 cm−1. By isotopic substitution of 18O the frequencies are shifted to 806, 775, 717, and ~420 cm−1 as expected for O—O vibrations. In the hydrogen systems this region is obscured by the strong libration bands of H2O and H2O2 molecules. Temperature and composition effects show that more than one new species is involved. Accordingly the new spectra are assigned to the often postulated polyoxides, H2O3 and H2O4, stabilized in the water–peroxide matrix. The more abundant, and also more stable, H2O3 has a half-life of some 5 h at −65 °C.The observed frequencies are consistent with zigzag chain structures linked by single covalent bonds as in hydrogen polysulfides. Relative concentrations of the polyoxides are estimated at 5 to 10 mole% depending on the composition of the starting material. Possible mechanisms of formation and decomposition are discussed.
The complexing characteristics of insoluble selenides. 1. Silver selenide
Authors: Mehra M. C. , Gubeli A. O.
Published: May 2006

The aqueous solubility of the system silver selenide has been investigated in an inert atmosphere of nitrogen at a unit molar ionic strength and constant temperature of 25° C. The experimental evidence indicates the formation of two aqueous species [Ag2(HSe)(OH)], and [Ag(Se)2(OH)]4− in contact with the precipitated selenide in different regions of acidity. The former exists in acidic medium and has a pβ value of 48.49 ± 0.10 while the latter is stable only in alkaline conditions and has a pβ value of 24.07 ± 0.19. A mathematical treatment has been elaborated to identify and calculate the stability constants of such selenide complexes formed through a heterogeneous equilibrium.
Studies on metal hydroxy compounds. XII. Thermal analyses, decomposition kinetics, and infrared spectra of copper basic oxysalts
Authors: Ramamurthy P. , Secco E. A.
Published: May 2006

The thermal analyses of copper basic oxysalts of the type Cu2(OH)2XOy, where X = S, C, Cl, Br, I, N, HC and y = 4, 3, or 2 reveal that decomposition occurs, in most cases, by dehydroxylation with concomitant disproportionation of the oxysalt. An outstanding exception to this pattern of decomposition is the basic sulfate. Calorimetric measurements along with related enthalpic values for the decomposition reaction are given.The kinetics of thermal decomposition of the compounds are classified into three main categories: (i) three-dimensional contracting sphere model, (ii) first-order rate, and (iii) nucleation controlled rate processes.The infrared spectral data of nine copper basic oxycompounds in the frequency region 4000–250 cm−1 are presented with their assignments. The fundamental infrared inactive modes of the anionic species SO42−, NO3−, etc. become active by the presence of the copper hydroxide ligand indicating a lowering of symmetry in the anion.
Studies on microcapsules. VII. Further characterization of sulfonated Polyphthalamide microcapsules
Authors: Takahashi Kikuko , Koishi Masumi , Kondo Tamotsu
Published: May 2006

Characterization was made on the sulfonated polyphthalamide microcapsules (SPPAM) prepared by making use of the interfacial polycondensation reaction of p-phthaloyl dichloride with mixtures of 4,4′-diaminostilbene-2,2′-disulfonic acid and diethylenediamine of varying mole ratios. The specific conductance of dialyzed dispersions of the H form of SPPAM in water was always higher than that of Na form microcapsule dispersions.On the other hand, the former dispersions invariably gave a much lower pH in comparison with the latter. Cation binding experiments established increasing orders, Ca2+ < Sr2+ < Ba2+ and Li+ < K+, NH4+, Na+ < Cs +, for the binding of di-and monovalent cations to SPPAM, respectively. The results were interpreted as showing that less hydrated ions are easier to adsorb on the negatively charged microcapsules. Finally, the feasibility of using SPPAM as ion-exchanger was indicated.
Five-membered rings. II. Inter and intramolecular reactions of simple amines with N-substituted phthalimides. Methylamine as a reagent for removal of a phthaloyl group from nitrogen
Authors: Wolfe Saul , Hasan S. K.
Published: May 2006

A reexamination of the literature on inter and intramolecular reactions of amines with N-substituted phthalimides has led to the demonstration that methylamine is a convenient reagent for removal of a phthaloyl protecting group from nitrogen at room temperature. Application of this procedure (first described in 1896) to the Gabriel synthesis of primary amines and to peptide synthesis is recommended. The simplicity of the reaction is a consequence of the consecutive occurrence of two unexpectedly rapid processes: (1) methylaminolysis of one of the imide bonds; (2) intramolecular catalysis, by an N-methylamido group, of the hydrolysis or aminolysis of an adjacent phthalamido linkage.Some unsuccessful attempts to prepare 2-aminoethylphthalimide are also described.
Chemistry of 2-substituted adamantanes. II. Preparation of 2-adamantanethiol and some of its derivatives. Aromatic solvent-induced shifts in their n.m.r. spectra
Authors: Greidanus J. W.
Published: May 2006

Reduction (NaBH4) of adamantanethione gives high yields of pure 2-adamantanethiol, from which several derivatives including the methyl sulfide, sulfoxide, and sulfone were prepared. The sulfenyl chloride was prepared and used insitu. From the n.m.r. spectra the aromatic solvent-induced shifts Δ = τ(benzene) – τ(CCl4 or CDCl3) were determined, where possible.
Nuclear magnetic resonance studies of multi-site chemical exchange. I. Matrix formulation of the Bloch equations
Authors: Reeves L. W. , Shaw K. N.
Published: May 2006

A concise matrix formulation of chemical exchange effects on a nuclear magnetic resonance (n.m.r.) spectrum using the Bloch equations is described. The method accommodates many-site exchange processes, site-dependent relaxation times, differing site populations, and saturation effects in a steady-state first-order spectrum. The simple two-site exchange system is analyzed in detail and saturation effects in this system are studied numerically. Alternative forms of the basic lineshape equation are derived, all of which are readily adapted to efficient computer calculations for complete lineshape fitting to obtain kinetic data for complicated chemical exchange processes.
Gaseous reactions and luminescence initiated by triboelectricity
Authors: Paoli S. De , Strausz O. P.
Published: May 2006

Mercury shaken at room temperature in the presence of reduced pressure of a hydrocarbon, CO2, acetone, N2–H2 mixture, etc., induces visible fluorescence and chemical transformations in the gaseous material.
Pulse radiolysis of liquid ethanol: reaction kinetics of the radicals
Authors: Fletcher J. W. , Richards P. J. , Seddon W. A.
Published: May 2006

In the pulse radiolysis of alkaline ethanol solutions the conjugate base CH3CHO− is not formed from the α-ethanol radical CH3CHOH, i.e.[Formula: see text]This is contrary to the observation in aqueous alkaline solutions of ethanol of a rapid equilibrium between CH3CHOH and CH3CHO−.The small quantity of CH3CHO− which is produced in the present system is consistent with the formation of the ethoxy radical CH3CH2O and its subsequent reaction with the ethoxide ion CH3CH2O−.