bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of a First-order Perturbation Theory for the Direct Correlation Function of Dense Fluids
Authors: Brelvi S. W. , O'Connell J. P.
Published: May 2006

An approximate expression for the direct correlation function of a real fluid in terms of its intermolecular potential and hard-sphere distribution functions is examined. Calculations for argon using the Percus–Yevick hard-sphere distribution functions are compared with molecular correlation functions from X-ray scattering data and the macroscopic integral of the correlation function related to the isothermal compressibility. The results are not satisfactory for any pair potential unless the parameters are made state dependent. However, since partial compensation occurs on integration, fairly good correlation of the isothermal compressibility can be obtained up to twice the critical density (except near the critical point itself) using Lennard–Jones (6–12) potential parameters obtained from second virial coefficient data and the Barker–Henderson hard-sphere diameter.
Synthesis of 8,3′-Thioanhydroguanosine
Authors: Ogilvie Kelvin K. , Slotin Lewis A. , Lin Denis C. K. , Westmore John B.
Published: May 2006

The synthesis of 8,3′-thioanhydroguanosine is described. The anhydro ring is formed by displacement of bromine from position-8 and methanesulfonate from the 3′-position using thiourea in refluxing n-butanol. The 8,3′-thioanhydroguanosine is converted by Raney nickel reduction to 3′-deoxyguanosine, an analogue of cordycepin.
A Positive-Ion Reaction Mechanism for the Radiation Induced Oxidation of Carbon Monoxide in the High Dose Rate Radiolysis of CO–O2 Mixtures
Authors: Willis C. , Boyd A. W. , Bindner P. E.
Published: May 2006

Carbon dioxide and ozone yields have been measured in the irradiation of CO–O2 mixtures with single pulses of electrons. The yields of CO2 at 2 × 1027 ev g−1 s−1 are large G(CO2) = 15 ± 1 from 20–60% O2. These decrease by ∼50% at 1028 eV g−1 s−1. Although the results are somewhat irreproducible the addition of c-C4F8, an electron scavenger, increases these CO2 yields at both dose rates by up to a factor of 15. They are reduced to G(CO2) < 2 by the addition of positive ion scavengers. These results are consistent with a chain reaction similar to that proposed for low dose rate studies involving [Formula: see text], [Formula: see text], and [Formula: see text] as chain carriers.The ozone yields are consistent with a total oxygen atom yield of G(O) = 1.4 in pure CO from neutral processes.
E.S.R. Studies of γ-Ray Irradiated Single Crystals of D-Tartaric Acid
Authors: Mulchinock J. K. , Hallett F. R. , Adam F. C.
Published: May 2006

Electron spin resonance (e.s.r.) studies on single crystals of normal and deuterated D-tartaric acid have been carried out as part of a larger investigation of radical production and migration in biologically related single crystals. The D-tartaric acid system is especially interesting since the second and third carbon atoms of the molecule, which are chemically identical in solution, become conformationally non-equivalent in the unit cell. The effects of this conformational difference on the e.s.r. spectra are discussed. The radicals identified in this study are consistent with the work of others on similar systems.
Thiohydantoins. XI Kinetic Studies of the Alkaline Hydrolysis of 1-Acyl-2-thiohydantoins
Authors: Congdon Wayne I. , Edward John T.
Published: May 2006

1-Acyl-2-thiohydantoins ionize in alkaline solution (pK ∼ 7). In solutions more alkaline than pH > 11 they are rapidly hydrolyzed to 2-thiohydantoin and a carboxylic acid, by attack of a hydroxide ion on the conjugate base of the 1-acyl-2-thiohydantoin. Possible mechanisms to accord with the entropy of activation, which is less negative than usual for base-catalyzed amide hydrolyses, are discussed. 1-Benzoyl-2-thiohydantoin hydrolyzes more rapidly than 1-acetyl-2-thiohydantoin, possibly because the ground state of the former molecule is destabilized by steric effects.
Ruthenium and Arsenic Electrode Potentials in Fused LiCl–KCl Eutectic
Authors: Folkman T. , Plambeck James A.
Published: May 2006

Electrode potentials of the Ru(III)/Ru(0) and As(III)/As(0) systems were measured in dilute solutions of the ionic species in fused LiCl–KCl eutectic at 450 °C. Standard molar electrode potentials of these couples of −0.107 ± 0.007 V and −0.460 ± 0.017 V against a standard molar platinum electrode were calculated. The As(V)/As(III) potential was found to be beyond the potential range of the melt.
Location of Energy Barriers. V. Scaling the Energy-Surface for AB + CD → AC + BD
Authors: Perry D. S. , Polanyi J. C.
Published: May 2006

In order to make use of the sliding-mass analogy for AB + CD four-center exchange reactions it is necessary to know how to scale the "diagnostic" potential-energy surface. This note describes the method of scaling, and exemplifies it for the case of H2 + I2
Paramagnetic Ring Current in Cyclooctatetraene: Evidence from 1H Nuclear Magnetic Resonance Shifts of Fused Benzo Derivatives
Authors: Buchanan G. W. , McCarville A. R.
Published: May 2006

The 1H n.m.r. aromatic spectral regions of benzocyclooctatetraene and several related compounds have been analyzed using the LAOCOON 3 program. Assignments are based on the analysis of the 13C satellite spectrum of the parent compound. Results are interpreted in terms of appreciable π-electron delocalization in the 8π-electron eight-membered rings giving rise to measurable paramagnetic anisotropic effects.
Complexes d'hematoporphyrine IX avec le platine(II): synthese, intermediaires, spectres, interet biologique
Authors: Macquet J. P. , Theophanides T.
Published: May 2006

The platinum–porphyrin (HP•Pt) complex was prepared from hematoporphyrin IX (HPH2) and potassium chloroplatinate(II). An intermediate complex was isolated corresponding to the formula HPH2•PtCl2. U.v., visible, and i.r. spectra of the complexes are obtained and are discussed. The complex HPH2•PtCl2 is the first intermediate identified in these reactions. A biological application of this intermediate for the treatment of tumors is sought.
Etude de quelques polymères obtenus lors de la déshydratation en système statique d'alcools allyliques disubstitués
Authors: Roux Claude , Daoust Hubert
Published: May 2006

Diolefins, produced by thermal dehydration of disubstituted allyl alcohols in a static system, polymerize as they are formed giving low molecular weight polymers. The microstructure of the product is similar to that of thermal polymers of 1,3-dienes. Number- and weight-average molecular weights, partial specific volumes, and molecular weight distributions have been studied for the polymers obtained from 3-methyl-2-butene-1-ol and 3,3-dimethyl-allyl alcohol.
Dielectric Constants of a Binary Solution Near the Critical Solution Temperature
Authors: Lubezky I. , McIntosh R.
Published: May 2006

The dielectric constants and dielectric losses of solutions of nitrobenzene and 2,2,4-trimethyl pentane have been measured near the critical solution temperature over a concentration range of 22–75% by weight and in the frequency regions of 5–60 and 1000 – 4000 kHz. It was found that below a critical concentration of 35% maxima existed in ε′ and ε″ at a temperature of 0.3 °C above the critical solution temperature. At higher concentrations the maxima disappeared and phase separation was preceded only by changes in the thermal coefficients dε′/dT and dε″/dT. The present study combined with others indicates that two regions of loss exist for the system near the critical temperature: low frequency losses of a conductive nature and high frequency losses of the Debye type. The published experimental knowledge of such systems remains insufficient to enable a thorough test of the theoretical studies published recently by Snider.
Magnetic Susceptibilities of some Compounds of Sulfur
Authors: Kennedy M. B. , Lister M. W. , Marson R. , Poyntz R. B.
Published: May 2006

Magnetic susceptibilities are reported for a number of compounds containing sulfur–oxygen bonds; the sulfur may also be bonded to organic groups or to halogen. The results are compared with earlier measurements on the phosphorus–oxygen or halogen–oxygen systems, and with other data on the sulfur–oxygen compounds which give information on the bond order. Though some trends similar to those in phosphorus–oxygen or halogen oxygen systems are noted, it does not seem to be possible to correlate the magnetic susceptibilities with the bond orders in any simple way.
Iridoids of Mentzelia decapetala (Pursh). I. Mentzeloside
Authors: Danielson Terry John , Hawes Edward Miles , Bliss Carman Arthur
Published: May 2006

Mentzeloside (1), rel-(1R,4aR,5R,6R,7S,7aR)-6,7-epoxy-1-O-β-D-glucosyl-5-hydroxy-1,4a,5,6,7,7a-hexahydro-4-methylcyclopenta(c)pyran, was isolated from flowers and seed pods of Mentzelia decapetala. The preparation of various chemical derivatives and the examination of spectral (i.r., u.v., and 1H n.m.r.) data allowed a complete structure to be proposed for the title compound.
Radiolysis Free Ion Yields and Electron Ranges in Polar and Nonpolar Liquids: Fluoromethanes
Authors: Robinson Maurice G. , Freeman Gordon R.
Published: May 2006

The free ion yields at zero applied electric field strength in the liquid fluoromethanes are Gfi0 in CH3F, 1.9 in CH2F2 and 1.1 in CHF3, all at 183 °K, and 0.07 in CF4 at 143 °K. Median ranges ymcd of the secondary electrons were estimated by fitting the electric field dependence of Gfi to a model equation: ymcd = 41 Å in CH3F, 39 Å in CH2F2 and CHF3, and 132 Å in CF4, at the above-mentioned temperatures. The average number of collisions, n, required to thermalize a secondary electron is about 64 000 in liquid Ar, 7 700 in CH4, 660 in C(CH3)4, 360 in CF4, 110 in C3H8, 44 in CH3F, 39 in CH2F2, 35 in CHF3, 17 in H2O, and 12 in CH3OH. The value of n with nonpolar molecules (up to neopentane in size) tends to decrease with increasing molecular complexity and with decreasing sphericity. Presence of a large dipole moment in the molecule decreases n further, and hydrogen bonds reduce n still more. Energy transfer between the electrons and rotational modes of the molecules appears to be important.
Determination of the Stoichiometry of the Adducts Formed between some Heterocyclic Bases and Copper(II) Bis(diethyldithiocarbamate) in Various Solvents
Authors: Farmer J. B. , Herring F. G. , Tapping R. L.
Published: May 2006

The stoichiometry of the adducts formed between copper(II) bis(diethyldithiocarbamate) and pyridine in benzene, toluene, and chloroform and between 3-picoline, 4-picoline, and 3,4-lutidine in benzene are shown to be 1:1. The method employed is that of Scatchard using electron paramagnetic resonance studies.
Studies on Lactoperoxidase. VI. Kinetics of the Oxidation of p-Cresol by Compound II
Authors: Maguire R. James , Dunford H. Brian
Published: May 2006

The kinetics of the oxidation of p-cresol by compound II of lactoperoxidase have been studied over the pH range 2.1–11.2 by the stopped-flow technique. The reaction is kinetically first-order with respect to p-cresol over the entire pH range. Use is made of the diffusion-controlled limit that can be placed on a bimolecular rate constant to show that p-cresol reacts in the unionized form. The complexity of the pH-rate profile is discussed in terms of acid dissociation constants of groups in the enzyme and the ionization of the substrate.
1H and 13C Nuclear Magnetic Resonance Spectroscopy of Some Derivatives of Nitro Sugars
Authors: Gurudata N. , Rajabalee F. J. M.
Published: May 2006

Eight 2,3-dideoxy-2-amino-3-nitrosugar derivatives have been obtained by an elimination–addition reaction on the α and β anomers of methyl-4,6-O-benzylidene-3-deoxy-3-nitro-glucopyranoside-2-acetate. P.m.r. is used to show that the compounds exist in the CE conformation. 13C.m.r. data are presented for three anomeric pairs. Trends in the C-13 chemical shifts are found to be similar to those reported in other studies of carbohydrates. Exceptions in direction and magnitude of chemical shift differences are discussed.
13C Chemical Shifts of Highly Substituted Bicyclo[2.2.1]heptanes
Authors: Werstiuk N. H. , Taillefer R. , Bell R. A. , Sayer B. G.
Published: May 2006

not available
Complete Variational Treatment of the Hydrogen Molecule. I. The Full Electronic Hamiltonian
Authors: Kari R. E. , Chan A. C. H. , Hunter G. , Pritchard H. O.
Published: May 2006

The hydrogen molecule is treated with the [Formula: see text] regarded as part of the Hamiltonian, rather than as a perturbation as was done by Kolos and Wolniewicz. Specimen results are presented for H2 and D2.
"Transitions vibrationnelles simultanées" d'un donneur et d'un accepteur de proton
Authors: Burneau André , Corset Jacques
Published: May 2006

Absorptions simultaneously involving the vibrations of two molecules are brought out of the near infrared spectra of mixtures containing a proton donor RXH and an acceptor R′AB. The donors under study are: chloroform, water, pentachlorophenol, and methanol, and the acceptors: acetonitrile, acetone, dimethylsulfoxide, and pyridine; for comparison, carbon disulfide and hexachloracetone are also used as solvents. Not only the combinations vXH + vAB and vXH + v3(CS2) are observed, but also vXH + vR′, at about 6500 cm−1, if R′ contains CH bonds; these absorptions at 6500 cm−1 do not exist when fully deuterated bases R′AB are used. A correlation between the intensity increase, through hydrogen bonding, of the vXH bands and that of the simultaneous transitions is suggested by the results. In the assignment of the near infrared spectra of proton donors, it is important to take into account the simultaneous transitions because their intensity is sometimes greater than that of the overtones 2vXH. It is likely that these conclusions, founded on the study of relatively weak hydrogen bonds, may be extended to stronger interactions; but the width of the absorption bands in the case of strong hydrogen bond makes the observation of the simultaneous transitions difficult.
Cobalt(II) Mercury Tetrathiocyanate Complexes with Lewis Bases
Authors: Makhija R. , Pazdernik L. , Rivest R.
Published: May 2006

not available
The Geometry of the Methyloxocarbonium Ion Trimer: A CNDO/BW Study
Authors: Pulfer James Douglas , Whitehead Michael Anthony
Published: May 2006

Within the Boyd–Whitehead CNDO theory three consistent methods were developed to calculate the carbon–oxygen infrared frequency of several oxocarbonium ions. The first method, type I, showed that the parameters of the CNDO/BW theory are not useful for predicting bond angles. Type II established a correlation between the C(α)—C bond length and the carbon–oxygen frequency. Type III predicted the correct trend for the homologous series of alkyloxocarbonium ions; however, the calculated frequency was consistently higher than experiment by 20–50 cm−1. Conjugation effects were estimated by applying the above methods to the phenyloxocarbonium ion.Variations on two possible configurations of the methyloxocarbonium ion trimer were studied. The protonated, planar diacetylmethenyloxocarbonium ion, Ac2HCCO+, was shown to be the most stable. A type II calculation estimated the C(α)—C bond to be about 1.37 Å. A type III calculation showed the possibility of the existence of the methyloxocarbonium ion dimer.
Thermal Unimolecular Isomerization of 3-Methyl-3-vinyldiazirine
Authors: Liu Michael T. H. , Toriyama K.
Published: May 2006

The thermal isomerization of 3-methyl-3-vinyldiazirine in various solvents has been investigated over the temperature range 40–75 °C. The reaction was kinetically first order and unimolecular. The experimental results indicate that this isomerization, as well as the other diazirine decomposition so far investigated, is consistent with a two-step mechanism.
The Reaction of Methyl Radicals with Neopentane
Authors: Pacey Philip D.
Published: May 2006

Neopentane was pyrolyzed in a flow reactor system at 793–953 K and 20–400 mm Hg. The rate constant for the initiation reaction,[Formula: see text]calculated from the observed C2H6 yield, was 1017.7±0.3 exp (−356 ± 6 kJ mol−1/RT)s−1, in good agreement with earlier determinations in other temperature ranges. The rate constant of the reaction,[Formula: see text]calculated from the observed CH4 and C2H6 yields, was 1010.5 ± 0.1 exp (−67 ± 2 kJ mol−1/RT) 1 mol−1 s−1, four to ten times faster than predicted on the basis of earlier work at 404–608 K. From 404–953 K, the Arrhenius plot for this reaction is strongly curved.
The Electrical Polarizations of Mercuric Chloride and Dimethylmercury
Authors: Huber Helmut , Wright George F
Published: May 2006

The apparent dipole moments calculated from solutions of mercuric chloride and dimethylmercury have been found to alternate between high and low values over the temperature range extending from 8.5 to 50 °C. The significance of this alternation is discussed.
Complex Fluoroanions in Solution. IV. Fluorocomplexes involving MoF6, MoF6−, and MoF5
Authors: Brownstein S.
Published: May 2006

Complexes of MoF5 or MoF6− with BF3, AsF5, TaF5, and NbF5 have been prepared and partially characterized by infrared and fluorine resonance spectroscopy and X-ray powder diffraction. MoF6 was not found to form complexes with binary fluorides nor fluoroanions.
N-Methylamino Acids in Peptide Synthesis. III. Racemization during Deprotection by Saponification and Acidolysis
Authors: McDermott John R. , Benoiton N. Leo
Published: May 2006

The racemization of N-methylamino-acid derivatives in aqueous sodium hydroxide and hydrogen bromide in anhydrous acetic acid and other solvents has been investigated by determining the products of the reaction with an amino-acid analyzer after deprotection. Whereas MeIle-OMe, Z-MeIle, and the N-unmethylated derivatives were only slightly racemized ( <2%), Z-MeIle-OMe (18–24%), Z-Ala-MeLeu-OMe (22%), and Z-Ala-MeLeu-OBu′ (7%) were appreciably racemized by aqueous sodium hydroxide. It is suggested that these derivatives racemize because of the absence of an > N—H or carboxyl group whose ionization would suppress ionization of the neighboring α-C—H bond. Z-Melle and Z-Ala-MeLeu were substantially racemized (68% in 4 h and 34% in 1 h, respectively) by 5.6 N hydrogen bromide in acetic acid. The extent of racemization by acid varied with acid strength, polarity of solvent, and time. Incorporation of label into both isomers of Ala-MeLeu from a solution of the tritiated reagent established that ionization at the α-C—H bond had occurred. No racemization was caused by aqueous acid or by hydrogen chloride.
Photo-additions of Naphthalene Derivatives with Substituted Ethylenes: Influence of Methoxy- and Cyano-substituents on the Products
Authors: Chamberlain Terence Richard , McCullough John James
Published: May 2006

Irradiation of 2-methoxynaphthalene and acrylonitrile in ethanol affords exo- and endo-7-cyano-6-methoxy-2,3-benzobicyclo[4.2.0]octa-2,4-diene, in the ratio 30:70. The structures are assigned from the n.m.r. spectra. The endo compound is the more stable, and on base equilibration predominates (90%). These adducts eliminate a methoxy-group on treatment with tert-butoxide at 80°, to afford 2,3-naphtho-cyclobutene carboxamide. Irradiation of 2-cyanonaphthalene and methyl vinyl ether in ethanol gives a complicated mixture of adducts which includes the cyclobutane 7-methoxy-6-cyano-2,3-benzobicyclo-[4.2.0]octa-2,4-diene as a major product (35%). Also formed are 7-methoxy-2,3(8-cyanobenzo)bicyclo-[3.3.0]octa-2,7-diene (8%), 8-methoxy-10-cyano-1,2-benzocycloocta-1,3,5-triene (18%), and a dimer of the latter (7%), and 8-methylene-5-methoxy-2,3(10-cyanobenzo)bicyclo[2.2.1]heptene (35%). The structures of the latter adducts are assigned from spectroscopic data, including nuclear Overhauser effects. Possible mechanisms for formation of the latter adducts, and a rule for prediction of regiospecificity in cyclobutane formation, are proposed.
Preparation, Infrared and Raman Spectra, and Stereochemistries of Pentacoordinate Trimethylphosphine Complexes, MX4•P(CH3)3 and MX4•P(CD3)3 where M = Ge or Sn and X = Cl or Br
Authors: Frieson D. K. , Ozin G. A.
Published: May 2006

The 1:1 adducts MX4•PMe3 (M = Ge or Sn; X = Cl or Br) are prepared by recrystallization of the respective 1:2 complexes from excess MX4 acceptor. Solid state infrared and Raman Spectra and X-ray powder photographs suggest that these adducts are all trigonal bipyramidal with the ligand in an axial position. Normal coordinate calculations in C3v symmetry (axial ligand) and Cs symmetry (equatorial ligand) support this assignment. The rather high ν(MP) frequencies indicate unusually strong metal–phosphorus donor bonds in these compounds.
Apparent Molal Heat Capacities and Volumes of Tetrabutylammonium Carboxylates and Related Solutes in Water at 25 °C
Authors: Leduc Paul-André , Desnoyers Jacques E.
Published: May 2006

The apparent molal volumes and heat capacities were measured in water at 25 °C with a flow digital densimeter and a flow microcalorimeter for the following salts: tetrabutylammonium octanoate, tetrabutylammonium butanoate, tetrabutylammonium bromide, ammonium acetate, ammonium chloride, ammonium bromide, sodium octanoate, and sodium acetate. The tetrabutylammonium octanoate and butanoate and sodium octanoate form micelles at 0.13, 0.6, and 0.35 M, respectively. The concentration dependence of the apparent molal volumes of the carboxylate salts is similar to that of typical hydrophobic or hydrophilic electrolytes. On the other hand, in the submicellar region, the concentration dependence of their apparent molal heat capacities is abnormal when compared with model electrolytes. It seems that the heat capacities may be reflecting interactions involving a hydrogen bonding of the carboxylate group with water.
The Master Equation for the Dissociation of a Dilute Diatomic Gas. X. How Rotation Causes Low Arrhenius Temperature Coefficients
Authors: Pritchard Huw O.
Published: May 2006

It is shown that previously calculated nonequilibrium rate constants for the dissociation of H2 and D2 appear to approach a rotationally averaged equilibrium expression at low temperature. This equilibrium form of the rate expression itself has an Arrhenius temperature coefficient for dissociation which is significantly less than the dissociation energy, and the corresponding recombination rate constant has a negative temperature coefficient. The reasons for this are explained.
Some Reactions of 3 β-Mesyloxycholestane-5α,6β-diol and Cholest-2-ene-5α,6β-diol Acetates
Authors: Tsui P. , Just G.
Published: May 2006

Reaction of 3β-mesyloxycholestane-5α,6β-diol 6-monoacetate (1e) with potassium t-butoxide gave the 3α,5α-oxycholestan-6β-ol (4a), which rearranged further to 5β,6β-epoxycholestan-3-ol (5). Treatment of 1c with triethylamine gave cholest-2-ene-5α,6β-diol diacetate (7a), whereas heating diacetate 1c in pyridine–dimethylformamide gave cholestan-3α,5α,6β-triol 3,6-diacetate (2a). Cholest-2-ene-5α,6β-diol diacetate (7a) reacted with m-chloroperbenzoic acid to give the α-epoxide 10. Reaction of 7a with aqueous N-bromosuccinimide gave 2β-bromo-3α-hydroxy-5α,6β-diacetoxycholestane (8). Both epoxide 10 and bromohydrin 8 rearranged in acidic media to the tetrahydrofuran 11.
Photodecomposition of Fe(III) Aminopolycarboxylates
Authors: Carey John H. , Langford Cooper H.
Published: May 2006

Aminopolycarboxylate complexes of Fe(III) and Cu(II) may have an interesting natural water photochemistry. As a convenient model system, the photodecarboxylation of ferric–EDTA complexes was studied at 30.0 °C using 3500 Å light. The hydrolytic forms present at pH of 8.00 and 9.00 were observed to have quantum yields below 0.10 and varying from species to species. The oxo-bridged dimer was unreactive. This is discussed from the viewpoint of the changed spin selection rules and changed spectral states of the dimer as compared to monomer. The reaction products in the ferric–EDTA system were seen to parallel those of the previously studied ferric–NTA system; the primary products of the reaction being CO2, CH2O, Fe(II), and ethylenediaminetriacetic acid.
Crystal and Molecular Structure of Benzylidenimine Trisulfide
Authors: Barrick James C. , Calvo Crispin , Olsen Fredric P.
Published: May 2006

The crystal and molecular structure of benzylidenimine trisulfide has been determined. Crystals are orthorhombic with a = 16.610(2), b = 9.984(6), c = 4.386(4), Z = 2 and space group P21212. 773 unique reflections of positive measured intensity, recorded with a Syntex [Formula: see text] Automatic Diffractometer, were refined by full-matrix least-square methods to a conventional R value of 0.023. The molecule has a crystallographic two-fold axis and S—S bond lengths of 2.051(1) Å. These are intermediate in length between the long inner and short outer S—S bonds of the chemically analogous tetrasulfide. The S—N and N—C bond lengths are 1.661(3) and 1.269(3), respectively. The crystal packing is determined by S—S van der Waals interaction between adjacent molecules along the c axis.
Reduction of 5α-Cholestan-3-one with Water as a Hydrogen Donor in the Presence of Precipitated Metals
Authors: Ishige Masayoshi , Shiota Michio , Ideno Yukiko
Published: May 2006

Reduction of 5α-cholestan-3-one with various precipitated metals using water as a hydrogen donor was investigated. Precipitated cobalt in t-BuOH and nickel in dioxane afforded 5α-cholestan-3α-ol favorably. Some multi-component precipitated metals were found to show high activity.
Mercury(II) Complexes of L-Cysteine Methyl Ester
Authors: Neville George A. , Berlin Maths
Published: May 2006

The mercurial complexation of L-cysteine methyl ester hydrochloride with mercury(II) nitrate, chloride, and acetate has been investigated at low pH. Bis(methyl L-cysteineato)mercury(II) hydrochloride hydronitrate monohydrate, following isolation and extensive characterization, was shown to be the substance reported in the literature as the dihydrochloride sesquihydrate complex. The preparation and properties of bis(methyl L-cysteineato)mercury(II) dihydrochloride monohydrate are reported for the first time. The properties and structural features of the complexes are discussed mainly in the context of investigations utilizing infrared, 1H- and 13C-n.m.r. spectroscopy.
Reactions of Nitro Sugars. XXXI. Formation of 2,3- and 3,4-Unsaturated Derivatives in the 6-Deoxyhexose Series
Authors: Baer Hans H. , Chiu Chung-Wai
Published: May 2006

The methyl 3,6-dideoxy-3-nitrohexopyranosides having the α-L-galacto (1), α-L-manno (2), α-L-galacto (3), and α-L-talo (4) configurations and their 2,4-diacetates (6, 11, 16, and 18, respectively) served as starting materials for the preparation of 2,3- and 3,4-unsaturated derivatives. The reactions employed included dehydroacetylation of diacetates and of some monoacetates (5, 7, and 12) that had been obtained by partial acetylation or partial acid-catalyzed de-O-acetylation, and also dehydrations occurring under conditions of acetylation. The following nitroolefins were obtained: methyl 3,4,6-trideoxy-3-nitro-α-L-erythro-hex-3-enopyranoside (8) and its 2-acetate (9), the corresponding α-L-threo isomer (13) and its 2-acetate (10) and 2-O-methyl derivative (20), and methyl 2,3,6-trideoxy-3-nitro-α-L-erythro-hex-2-enopyranoside (14) and its 4-acetate (15) as well as the 4-acetate (17) of the corresponding α-L-threo isomer. In addition, 1,4-di-O-acetyl-2,3,6-trideoxy-3-nitro-α-L-threo-hex-2-enose (19) was obtained by acetolysis of 17. Factors assumed to be responsible for a pronounced regioselectivity in some of the reactions are discussed.
Conformation of Bridged Diphenyls. III. Crystal Structure of 2-(2′-Carbomethoxy-4′-nitrophenoxy)-1,3,5-trichlorobenzene
Authors: Griffith E. A. H. , Chandler W. D. , Robertson B. E.
Published: May 2006

not available
Application of Adiabatic Rapid Passage Nuclear Magnetic Resonance Techniques to the Study of Molecular Motions in Solids
Authors: Ripmeester J. A. , Dunell B. A.
Published: May 2006

The adiabatic rapid passage (ARP) technique was applied to the study of molecular motion in solids. Second moments and spin–lattice relaxation times for solid furan and benzene were derived using ARP methods from 77 °K to the respective melting points. Unusual variations of the ARP signal height and shape with temperature were observed for these solids. These effects were interpreted as being due to the presence of short rotating frame relaxation times. New information regarding molecular motion in solid furan, as well as acetic acid-d1, was obtained. Also some quantitative statements have been made regarding the conditions required to observe an ARP signal in the solid state.
Studies on the Biosynthesis of Antheridiol
Authors: Popplestone C. R. , Unrau A. M.
Published: May 2006

Sexual reproduction in the aquatic fungus Achlya bisexualis is governed by antheridiol, a C29 sterol, secreted by the female plant and which initiates formation of antheridial hyphae on the male plant. Tracer studies showed that naturally occurring fucosterol supplied the necessary carbon skeleton for antheridiol. Labelling and trapping studies with a series of hypothetic sterol precursors have indicated the biological sequence involved in elaboration of the antheridiol side chain.
Conformations of Bridged Diphenyls. V. A Nuclear Magnetic Resonance Comparative Study of the Conformations of Identically Substituted Diphenyl Ethers, Sulfides, Methanes, Ketones, Sulfoxides, and Sulfones
Authors: Benjamins Harm , Chandler W. David
Published: May 2006

Using n.m.r. methods developed in earlier papers, the conformations of two series, one doubly ortho-substituted and one triply ortho-substituted, of six identically substituted bridged diphenyls were compared. The ethers, sulfides, and methanes have been shown to adopt the same conformation in which the di-ortho-substituted ring is perpendicular to the central bridge plane while the other ring lies in that plane and an ortho hydrogen takes up the "inside" or "proximal" position. The benzophenones and sulfoxides prefer a conformation in which the dihedral angle between each ring and the central plane is about 40–50° and an ortho hydrogen adopts the "outside" or "distal" position. The sulfones adopt a conformation in which the two rings are more nearly perpendicular to the central plane.
Molluscicidal Saponins of Phytolaccadodecandra: Lemmatoxin
Authors: Parkhurst R. M. , Thomas David W. , Skinner W. A. , Cary Lewis W.
Published: May 2006

Lemmatoxin, one of the molluscicidal saponin components of the fruit of Phytolaccadodecandra (endod), has been found to be a derivative of oleanolic acid substituted in the 3 position with a branched trisaccharide containing two glucose units and one galactose unit. A structure is proposed.
Synthetic Cardenolides and Related Products. III. Isocardenolides
Authors: Ferland J. M.
Published: May 2006

The synthesis of novel cardenolides, closely related to naturally-occurring cardiotonic agents, is described. They were obtained from 17β-[3-furyl]androstanes derived from digitoxigenin, gitoxigenin, digoxigenin, and strophanthidin by hypohalous acid or organic peracid oxidation. The preparation of β-D- and α-L-glycosidic derivatives is also reported.
Selective Hydrolysis and Oxidation of the Bismethylenedioxy Protective Group During Angular Methyl Migration in Corticosteroid Analogs
Authors: Makhubu L. P. , Hajos Z. G. , Duncan G. R.
Published: May 2006

An attempt to achieve a 10β → 9β methyl migration in a 9,11α-epoxy-4,4-dimethylated derivative of cortisol (3) using BF3, failed to result in a clean reaction product. In contrast a 9α-amino-11-oxo derivative (9) rearranged smoothly to 20(R)-3β-acetoxy-9β-methyl-17α, 20-methylenedioxy-19-norpregn-5(10)-en-20-ol-11-one-21-oic acid (10) with sodium nitrite and acetic acid. During the migration, the protecting bismethylenedioxy group underwent selective hydrolysis and oxidation. The structure of the product has been established by i.r., n.m.r., and mass spectra analyses and a mechanism has been proposed for its formation. The product is an intermediate in the synthesis of 4,4-dimethylcucurbitacin and cortisol analogs, the goal of this chemical and biological investigation.
Dihydrothiophenes. III. Preparation of Some 3,4-Unsubstituted Examples
Authors: McIntosh John M. , Steevensz Richard S.
Published: May 2006

Using the reaction between four representative vinylphosphonium salts and three α-mercaptoaldehydes, 12 3,4-unsubstituted 2,5-dihydrothiophenes(1) were prepared. The reaction proceeds in excellent yields under mild conditions. The use of these compounds in the synthesis of dienes is indicated.
Complex Formation in Ether–Chloroform Systems: Comparison of Thermodynamic and Spectroscopic Results
Authors: Pasco Neil F. , Fenby David V. , Hepler Loren G.
Published: May 2006

A number of procedures for evaluation of equilibrium constants and standard enthalpies of complex formation from equilibrium liquid–vapor and calorimetric results have been applied to ether–chloroform systems. The results are compared with published spectroscopic values.
The Photobromination of (+)-1-Cyano-2-methylbutane
Authors: Tanner Dennis D. , Ruo Tomoki C. S. , Blackburn E. V.
Published: May 2006

The photobromination of (±)-1-cyano-2-methylbutane with molecular bromine, under varying conditions, yields a mixture of three monobrominated products: 1-cyano-1-bromo-2-methylbutane (relative yield 78–95%), 1-cyano-3-bromo-2-methylbutane (relative yield 1–5%), and 1-cyano-2-bromo-2-methylbutane (relative yield 4–17%). The production of the major monobrominated product is proposed to arise by an acid catalyzed ionic reaction. When the bromination of (+)-1-cyano-2-methylbutane was carried out in the presence of solid N-bromosuccinimide as well as molecular bromine, the three monobrominated products were formed in relative yields that reflected a free radical bromination reaction: (+)-1-cyano-1-bromo-2-methylbutane (5–14%), (±)-1-cyano-2-bromo-2-methylbutane (68–85%), and (+)-1-cyano-3-bromo-2-methylbutane (10–19%).The inability to obtain active 1-cyano-2-bromo-2-methylbutane from these bromination reactions may not be due to the fundamental nature of the bromination of a substrate at a chiral center but may be due to the instability of this particular tertiary bromide.
Simultaneous Electron Spin–Nuclear Spin Transitions in Solid Solutions of Methyl Radicals
Authors: Cazianis C. T. , Eaton D. R.
Published: May 2006

The e.s.r. spectra of methyl radicals produced by the ultraviolet irradiation of Tl(III) acetate show satellites attributed to simultaneous electron spin – nuclear spin transitions involving a proton of a neighboring water molecule. Measurement of the relative intensities of the satellites and the main transitions allows the average separation of the interacting proton from the unpaired electron to be calculated. Such measurements have been carried out over the temperature range −180 to −120 °C. The implications regarding the environment of the methyl radical in the ice matrix are briefly discussed.
The Crystal and Molecular Structure of Diazido-2,2′-bipyridinecopper(II)
Authors: Bushnell Gordon W. , Khan Masood A.
Published: May 2006

The crystal and molecular structure of diazido-2,2′-bipyridinecopper(II), C10H8N2(N3)2Cu, is determined by single crystal X-ray diffraction, and refined to an R value of 0.067. The cell dimensions are a = 664.9(2), b = 843.3(1), c = 1082.0(2) pm, α = 86.99(2)°, β = 87.77(3)°, γ = 78.59(2)°. The space group is [Formula: see text] (No. 2) with 2 molecules per unit cell and the measured density is 1.71(2) g cm−3. The copper coordination is square planar with two additional longer bonds. The coordinate bond lengths in pm to the bipyridine ligand are: Cu—N(1), 201.6(6); Cu—N(2), 201.9(6). The coordinate bonds to the azido ligands are: Cu—N(3), 194.9(6); Cu—N(6), 196.6(6). The longer bonds are: Cu—N(3)″, 268.0(8), Cu—N(6)′ 268.2(8). The N—N bond lengths within each azido ligand are unequal: N(3)—N(4), 118.2(10); N(4)—N(5), 115.4(11); N(6)—N(7), 119.2(9); N(7)—N(8), 114.8(9). The angles at N(3) and N(6) are both 130° and at N(4) and N(7) the angles are both 175(1)°. Each azide takes part in asymmetric bridging through a single nitrogen atom. The results are compared with other structural studies on azido complexes and to a nitrate complex of Ag(II) which is structurally similar.
Dielectric Studies. Part XXXV. Relaxation Studies of Benzaldehyde and Fourpara-Substituted Aideliydes
Authors: Mountain P. F. , Walker S.
Published: May 2006

The dielectric absorption has been determined for benzaldehyde, p-fluoro-, p-chloro-, p-bromo-, and p-nitro-benzaldehyde in p-xylene solution at mainly five or six frequencies in the 6.70 to 70.1 GHz region. For all three p-halo-substituents the mean relaxation time values indicate that some mechanism faster than molecular relaxation occurs whereas none was apparent in benzaldehyde itself. A detailed study has been made of p-chlorobenzaldehyde in p-xylene solution at five temperatures, and the data have been analyzed into contributions from a molecular relaxation process and a shorter relaxation time τ2. In the p-xylene solutions of benzaldehyde the relaxation data indicate weak intermolecular hydrogen bonding between the solute and the solvent which is probably of the type [Formula: see text]
Comments on the Crystal Structure of Polypivalolactone and Deviation of Ester Groups from trans Planarity
Authors: Cornibert J. , Hien N. V. , Brisse F. , Marchessault R. H.
Published: May 2006

The crystalline conformation of polypivalolactone was determined by analysis of the chain conformational energies and it was found that the minimum energy corresponds to a planar trans conformation for the ester group. The result was compared to published X-ray data based on fiber diffraction which show a significant deviation from trans planarity. This difference is discussed in terms of the relative energies involved and by comparison with literature crystallographic results of low molecular weight carboxylic esters. It is stressed that because of the paucity of information in fiber diffraction, internal energy considerations are important for assigning internal rotation angles. Crystallographic results for low molecular weight compounds show that deviations greater than 10° from trans planarity are rare for ester groups.
6H-Dibenzo[b,d]pyrans. II. Boron Trifluoride Catalyzed Acylation of Hydroxy-6H-dibenzo[b,d]pyrans
Authors: Devlin John P.
Published: May 2006

The Friedel–Crafts acetylation of 3-hydroxy-6H-dibenzo[b,d]pyrans (1) with acetic acid in the presence of boron trifluoride is described. Representatives unsubstituted at C-1 acylate exclusively at C-2. A methyl or methoxyl substituent at C-1 directs acylation to the C-4 position. The identities of the individual isomers are established primarily on the basis of n.m.r. spectral interpretations.
Kinetics of Environmental Averaging, and the Stereochemistry of (CH3)ClGe(C5H7O2)2. A Case of a Second Order Kinetic Process
Authors: Hersh Ken A. , Serpone Nick
Published: May 2006

Dynamic n.m.r. studies on the stereochemistry of (CH3)ClGe(C5H7O2)2 (acac = C5H7O2−), indicate that the complex adopts the cis configuration in CDCl3–CCl4 solutions. Kinetics of environmental averaging of the acac ring proton (—CH=) and acac methyl groups between the respective nonequivalent sites in the C1 isomer have been investigated in the temperature range −31.0 to 23.1° by line-broadening techniques. Kinetics of the averaging process are second order in complex concentration. Activation parameters are: Ea = 6.0 ± 0.3 kcal/mol, ΔS≠ = −30 ± 1 e.u., and k25 = 1.6 × 102 M−1 S−1. Rearrangements are viewed as occurring via a germanium–oxygen bond rupture as a first step to yield a five-coordinate intermediate. The rate-determining sequence is thought to involve proper orientation of two five-coordinate species prior to formation of a bis-acac bridged dimer.
A Synthetic Approach to Quassin. Introduction of Functionality and Stereochemistry by a Diels–Alder Reaction
Authors: Stojanac Nada , Sood Ashwani , Stojanac Žarko , Valenta Zdenek
Published: May 2006

Using a Lewis acid catalyzed Diels–Alder reaction as the key step, the crystalline synthetic intermediate (17) has been prepared. Compound 17 contains all C-atoms of quassin (1) and stereochemistry and 0-functionality suitable for the conversion into 1.
The Equivalent Conductivity of Aqueous Solutions of Salts of Carboxymethylcellulose: A Test of Manning's Limiting Law
Authors: Kwak Jan C. T. , Johnston Allan J.
Published: May 2006

Measurements of the equivalent conductivity of aqueous solutions of lithium, sodium, potassium, and cesium salts of carboxymethylcellulose (CMC) at 25 °C are reported. The degree of substitution of the CMC used was 0.86, concentrations of the four salts were varied from 5 × 10−4 to 5 × 10−2 equiv l−1. Results show a decrease of Λ with increasing concentration in each case. In the lower concentration range (up to 10−2N) this decrease is in close agreement with a limiting law for conductivity recently developed by Manning. Above 10−2N the decrease in Λ is less than the decrease predicted by the limiting law. The counterion dependence of Λ is accurately predicted by the theory, and a qualitative agreement is obtained when the theory is used to compare conductance data of polyelectrolytes with different charge densities.
Electron Mobilities and Ranges in Liquid Ethers: Ion-like and Conduction Band Mobilities
Authors: Dodelet Jean-Pol , Freeman Gordon R.
Published: May 2006

The free ion yields in X irradiated ethers are larger than those in alkanes because the dielectric constants of the former liquids are greater than those of the latter. The relative increase of the free ion yield with temperature is smaller in ethers than in alkanes because the dielectric constants decrease more rapidly with increasing temperature in the former. The density normalized penetration range (thermalization length) bGPd of the secondary electrons in dimethyl ether (DME) is 3.5 × 10−7 g/cm2. As the length of the n-alkyl groups on the ether is increased bGPd increases towards the value obtained for long chain n-alkanes, 4.5 × 10−7 g/cm2. Electron mobilities ue showed two types of behavior: (i) at low temperatures ue approaches a value of about 2u−, where u− is the mobility of the anions formed in the irradiated liquid; (ii) at higher temperatures the ratio ue/u− increases with temperature, and equals 21 in di-n-butyl ether (DBE) at 375 K. The activation energy of electron migration at low temperatures (ion-like mechanism) is similar to that of ion migration, 2–3 kcal/mol, while at high temperatures it increases to ∼6 kcal/mol. The larger activation energy is attributed to thermal excitation of electrons from the solvated state into a conduction band, and is equal to one-half of the optical excitation energy of the solvated electrons. Electrons in water, alcohols, and ammonia at 300 K migrate by the ion-like mechanism. Electrons in alkanes migrate almost exclusively by the conduction band mechanism. A plot of the Arrhenius temperature coefficient of electron mobility against mobility in different liquids at a given temperature displays a maximum which is temperature dependent.
Vibrational Spectra of N2H5HC2O4 and N2D5DC2O4
Authors: Savoie R. , Guay M.
Published: May 2006

Infrared and Raman spectra of N2H5HC2O4 and N2D5DC2O4 have been recorded at various temperatures between 77 and 300 K. The results at 300 K are consistent with the known crystal structures of these solids. A phase transition has been detected at ∼ 240 K in N2D5DC2O4 and although there are similarities between the two stable solid phases of this compound, the low-temperature form appears to be centrosymmetric and to have a larger unit cell than the high-temperature modification.
Photolysis of Pyridazine in the Gas Phase
Authors: Fraser James R. , Low L. H. , Weir Neil A.
Published: May 2006

Pyridazine was photolyzed with long wave ultraviolet radiation (3650–3663 Å) over the temperature range 100–160 °C. Nitrogen and vinylacetylene were the main products, their quantum yields at 110 °C being 0.12 ± 0.05 and 0.09 ± 0.04, respectively. Nitrogen formation is not significantly inhibited by the presence of oxygen and no isomerization of cis-but-2-ene was observed during photolyses. It appears that some reaction occurs from the excited singlet, S (n → π*) A, but this state is efficiently deactivated photophysically. It is suggested that vinylacetylene is formed from a C4H4 diradical by means of a 1,3 H-atom migration, and isotope effects observed for the photolysis of pyridazine-d4 support C—H bond fission.
Structure of Nickel Orthophosphate
Authors: Calvo Crispin , Faggiani Romolo
Published: May 2006

Ni3P2O8 crystallizes in the monoclinic system with space group P21/c with a = 5.830(2), b = 4.700(2), c = 10.107(4) Å, β = 91.22(2)°, and Z = 2. The structure was refined by full-matrix least squares methods to a final R value of 0.035 using 986 symmetry independent reflections. The structure is isotypic with that of sarcopside, which in turn is related to that of olivine with vacant cation sites ordered. The Ni ions are octahedrally coordinated in two types of sites with average Ni—O bond lengths of 2.081 and 2.067 Å. The mean P—O bond length is 1.547 Å although the tetrahedron shows some unusually large distortions with bond lengths ranging from 1.521 to 1.595 Å.
The Crystal Structure of Tripotassium bis(Oxalato)dioxovanadate(V) Trihydrate
Authors: Drew R. E. , Einstein F. W. B. , Gransden Susan E.
Published: May 2006

not available
Theoretical and Experimental Investigation of Primary Reactions in Sodium Diffusion Flames
Authors: Mintz Kenneth J. , Le Roy Donald J.
Published: May 2006

The determination of rate constants of reactions of the type Na + RX = NaX + R by the diffusion flame method is critically investigated, both theoretically and experimentally. More precise methods than those used heretofore are developed for calculating rate constants from experimental data, viz. evaluation of the effective nozzle radius, a generalization of the Heller criterion, an improvement in the theory of the visibility limit, and allowance for wall reaction and halide consumption. These methods were applied to previous data on the reaction Na + C2H5Cl as well as to new data on the reaction of sodium with CH3Cl, CH3Br, CH3I, and C2H5Br.
Conformations of Bridged Diphenyls. X. Crystal Structure of 2-(4′-Carbomethoxy-2′-nitrophenylsulfinyl)-1,3,5-trimethylbenzene
Authors: van der Heijden Simon P. N. , Chandler W. David , Robertson Beverly E.
Published: May 2006

The crystal structure of 2′-(4′-carbomethoxy-2′-nitrophenylsulfinyl)-1,3,5-trimethylbenzene, C17H17NO5S, has been determined by X-ray diffraction. The crystals are triclinic, a = 9.848(11), b = 7.654(10), c = 12.513(15) Å, α = 107.33(8), β = 100.73(8), γ = 106.53(8)°, [Formula: see text] with Z = 2. The intensities of 3850 independent reflections were measured on a four circle diffractometer; 2985 reflections were used in the refinement to give a final least-squares residual of 0.053 and a traditional R factor of 0.052.Repulsion between the sulfoxide oxygen atom and the nitro oxygen atoms forces the molecule into the twist-nitro-proximal conformation as opposed to the nitro-distal conformation which has been observed for other bridged diphenyls in this series.
The Photolysis of Matrix Isolated cis-Thionylimide. 1. The Identification and Infrared Spectra of cis-HOSN, HSNO, and SNO
Authors: Tchir Peter O. , Spratley Richard D.
Published: May 2006

cis-HNSO has been photolyzed in argon matrices using a medium pressure mercury lamp. Examination of the infrared spectra has revealed the presence of four photolysis products. With the aid of isotopic substitution these species have been identified as cis-HOSN, cis-HSNO, trans-HSNO, and SNO, all previously unknown. Assignments have been made for all four products and force fields calculated for cis-HOSN and trans-HSNO. The following reaction scheme has been postulated for the photolysis induced process: cis-HNSO → cis-HOSN → cis-HSNO + trans-HSNO → SNO. The extent of this reaction sequence has been found to depend on reaction time and photolysis energy.