bluuebunny/crossref_metadata_2025 huggingface dataset:
High field kinetic processes in anodic oxide films on aluminium. I. Current transients for linearly changing electric field strength
Authors: Dlgnam M. J. , Ryan P. J.
Published: May 2006

Anodic oxide films were formed on high purity aluminium (99.996 %) under steady-state conditions (current and field strength constant) in a glycol–borate electrolyte until the film reached a predetermined thickness at which point the anodic overpotential was changed rapidly and in a linear manner. As little film growth occurred during these linear sweeps, the conditions corresponded to linearly changing field strength. From these data, the transient differential field coefficient, β1, defined by[Formula: see text]where i and E are the ion current density and electric field strength and Es the steady-state formation field strength, was determined β1 was found to vary linearly with Es in the manner [Formula: see text] with [Formula: see text] A recent theory proposed by one of us (M. J. D.) predicts that the parameter [Formula: see text] should have the same value as that deduced from the field dependence of the steady-state differential field coefficient,[Formula: see text]Such agreement was indeed found, two independently determined 'steady-state' values of [Formula: see text] being 3.53 ± 11% and 3.11 ± 14% ÅV−1. A direct comparison of the present results with previous steady-state results gave βs/β1 = μs/μ1 = 3.09. More complex features of the transients were also found to be in accord with the above theory, but could be accounted for almost as well by an earlier theory, the so-called high field Frenkel defect theory.Dielectric constant values determined from the current discontinuity appearing upon application of the linearly increasing field gave K1 = 8.35 ± .1 for transients commencing from steady-state conditions and K1 = 8.85 ± .2 for films formed then 'aged' at E = 0 before measurement. Certain anomalies with regard to the charging current were apparent.
Magnetic properties of pyridine copper (II) chlorobenzoates
Authors: Lin Y. C. , Thompson R. C.
Published: May 2006

Magnetic susceptibility studies have been made on the bispyridine adducts of copper(II)m-chloro-benzoate and copper(II) p-chlorobenzoate and on samples of composition Cu(ClC6H4CO2)2(C5H5N)x, where 2 > x ≥ 0. Results show that whereas the bispyridine adducts are essentially magnetically dilute the monopyridine and hemipyridine adducts of these copper chlorobenzoates are antiferromagnetic, exhibiting magnetic properties typical of binuclear molecules.
Infrared study of the self-association of water dissolved in 1,2-dichloroethane
Authors: Jolicoeur C. , Cabana A.
Published: May 2006

The infrared spectra, in the 3 micron region, of H2O or HDO dissolved in 1,2-dichloroethane are presented. Self-association of the solute molecules is revealed by the appearance of a shoulder on the low frequency side of the OH stretching bands of monomeric H2O or HDO. From the linear increase of the intensity of the shoulder with the third power of the solute concentration, it is inferred that trimers constitute the main polymeric species present in these solutions. The small frequency shifts of the OH stretching mode of trimeric water favors a cyclic rather than an open-chain structure. The observation of a single band for the trimer correlates with this last assertion.
Orthobaric data of certain pure liquids in the neighborhood of the critical point
Authors: Campbell A. N. , Chatterjee R. M.
Published: May 2006

The orthobaric densities of liquid and vapor, and the vapor pressure, have been determined for the three pure liquids, acetone, chloroform, and benzene. It is shown that the nose of the curve, representing orthobaric densities (or volumes) as a function of temperature, though very flat, is probably not a horizontal straight line. Nevertheless, critical phenomena can be observed over a range of total volume, at the critical temperature.
Reaction of sulfur dioxide with dimethylzinc and dimethylmercury
Authors: Carey N. A. D. , Clark H. C.
Published: May 2006

Dimethylzinc and sulfur dioxide give the products (CH3)2Zn•SO2 and (CH3)2Zn•2SO2 for which the formulations CH3ZnO.SO•CH3 and (CH3SO•O)2Zn are proposed. With dimethylmercury, sulfur dioxide gives products best formulated as (CH3Hg)2SO2 and CH3HgSO•OCH3.
Signs of long-range proton–fluorine spin–spin coupling constants in 2-amino-5-bromobenzotrifluoride
Authors: Blears D. J. , Danyluk S. S. , Schaefer T.
Published: May 2006

The signs of the spin–spin coupling constants between the fluorine nuclei in the trifluoromethyl group and the ring protons in 2-amino-5-bromobenzotrifluoride are reported. [Formula: see text] and [Formula: see text] are negative while [Formula: see text] is positive. These signs are in agreement with fluorine contact shifts in certain Ni(II) chelates and therefore provide evidence for hyperconjugation of the CF3 group with the ring. The magnitude of [Formula: see text] is rather larger than expected on the basis of a relationship between the square of the bond order between the relevant ring carbons and the size of the coupling.
Concerning a relationship between long-range ring proton – methyl proton coupling constants and mobile bond order
Authors: Blears D. J. , Danyluk S. S. , Schaefer T.
Published: May 2006

Long-range proton – methyl proton coupling constants in propene, mesitylene, 9-methylphenanthrene, and acenaphthene appear to be linearly related to the square of the mobile bond order between the carbon atoms bonded to the methyl group and the proton. However, substituent-induced changes in the charge on and hybridization state of the carbon atoms, in excitation parameters and in potential barriers to rotation of the methyl group, may also affect the coupling. Such changes must be considered in the application of a possible linear relationship.
Reaction of ethyl with isobutyl and t-butyl free radicals
Authors: Terry J. O. , Futrell J. H.
Published: May 2006

1,1′-Azoisobutane, 2,2′-azoisobutane, 1-isobutyl azoethane, and mixtures of azoethane with 2,2′-azoisobutane were photolyzed under high intensity conditions in order to study the disproportionation of isobutyl and t-butyl free radicals and their cross reactions with ethyl radicals. The relative rates of disproportionation to combination which were determined for the various radical interactions are as follows: Δ(i-C4H9, i-C4H9), 0.078; Δ(t-C4H9, i-C4H9), 2.32; Δ(C2H5, i-C4H9), 0.04; Δ(C2H5, t-C4H9), 0.498; Δ(i-C4H9,C2H5), 0.04; Δ(t-C4H9, C2H5), 0.283.
Erratum: Spontaneous decarboxylation of oxalacetic acid
Authors: Tsai C. S.
Published: May 2006

not available
Carbodihydrazones and oxalyl dihydrazones
Authors: Wiles D. M. , Suprunchuk T.
Published: May 2006

Carbodihydrazones and oxalyl dihydrazones have been prepared using the reaction between aldehydes and carbohydrazide and oxalyl dihydrazide, respectively. The structures of these new series of compounds have been established by comparing their infrared absorption spectra with those of related compounds.The potential scope of the synthetic method has been indicated by the preparation of analogous derivatives from two aromatic aldehydes and from two simple ketones.
Stereochemical vs• polar control in the preparation and LiAlH4 reduction of cis-and trans-2-alkoxy-3,4-epoxytetrahydropyrans
Authors: Sweet F. , Brown R. K.
Published: May 2006

2-Methoxy- and 2-t-butoxy-5,6-dihydro-2H-pyran react with m-chloroperoxybenzoic acid to give mixtures of trans- and cis-2-alkoxy-3,4-epoxytetrahydropyrans in which the trans to cis ratio is 3:1 and 9:1 for the 2-methoxy and 2-t-butoxy homologues respectively. This selectivity is attributed to the steric effect of the 2-alkoxy group.Lithium aluminium hydride attacks the ring in these cis and trans compounds exclusively at the epoxide carbon remote from the alkoxy substituent to form only 2-alkoxy-3-hydroxytetrahydropyrans. This selectivity of hydride attack is attributed to the polar influence of the two geminal oxygen atoms. Steric factors in this hydride reduction are apparently completely submerged by this polar effect.
Zinniol: a major metabolite of Alternaria zinniae
Authors: Starratt A. N.
Published: May 2006

Zinniol, a compound recently obtained from the phytopathogenic fungus Alternaria zinniae, is shown to be 1,2-bis(hydroxymethyl)-5-(3′,3′-dimethylallyloxy)-3-methoxy-4-methylbenzene (1) by chemical and spectroscopic studies. Attempts to isolate other metabolites are described briefly.
Phenoxazinones by oxidative dimerization of aminophenols
Authors: Gerber Nancy N.
Published: May 2006

Several 2-amino-3H-phenoxazin-3-ones, including cinnabarin, were obtained from the appropriate o-aminophenols by oxidative dimerization on thin-layer plates in air. Shake-flask fermentation of Pycnoporus cinnabarinus also gave cinnabarin.
The measurement of angles and distances in molecular models. III. A general device
Authors: ApSimon J. W. , Craig W. G. , Demayo A. , Raffler A. A.
Published: May 2006

A measuring device which can be attached to any bond of Dreiding molecular models for the estimation of angles and distances is described.
New calorimeter for measurement of the enthalpy of mixing of liquids. The enthalpy of mixing of benzene with carbon tetrachloride and of n-hexane with cyclohexane
Authors: Watts Harry , Clarke E. C. W. , Glew D. N.
Published: May 2006

A high-precision, mixing calorimeter is described for the direct measurement of the enthalpy of liquid mixing under constant pressure conditions. Tests of the calorimeter using the benzene – carbon tetrachloride system at 25 °C show a reaction between mercury and carbon tetrachloride which leads to systematically high values for the heat of mixing. Tests with the n-hexane–cyclohexane system at 25 °C give a maximum enthalpy of mixing Δmh = 222.14 + 0.21 J/mole at 0.586 cyclohexane mole fraction.
Free radicals by mass spectrometry. XXXVIII. Primary steps in the mercury-photosensitized decompositions of dimethyl sulfide and dimethyldisulfide
Authors: Jones A. , Yamashita S. , Lossing F. P.
Published: May 2006

The reaction between mercury (3P1) atoms and dimethylsulfide at 55 °C has been shown to be exclusively[Formula: see text]Two primary modes of dissociation have been established for the corresponding reaction with dimethyldisulfide.[Formula: see text]The former reaction accounts for ~20% of the primary decomposition at 55 °C. No reaction leading to H-atom removal was found for either compound.The subsequent reactions of CH3S and CH3SS radicals, chiefly combination and disproportionation, have been investigated briefly.
Crystal structure of CdZn2(PO4)2 and Cd2Zn(PO4)2
Authors: Calvo C. , Stephens J. S.
Published: May 2006

The crystal structures of two solid solution phases found to occur in the Zn3(PO4)2–Cd3(PO4)2 system, one with composition near to CdZn2(PO4)2 and the other near to Cd2Zn(PO4)2, have been determined. Although these compounds are closely related structurally, there is a miscibility gap between the two phases and an apparent phase transition in only one of these. The compounds, named Bss and Css respectively, have lattice parameters a = 9.032(4) Å, b = 11.417(5) Å, c = 5.952(6) Å, β = 98.8(2), and Z = 4 for the former compound, and a = 9.056(8) Å, b = 11.86(1) Å, c = 6.190(9) Å, β = 100.1(2) and Z = 4 for the latter. Both compounds are monoclinic and crystallize with the space group P21/c with closely related, but not identical, structures to that of the mineral graftonite. The anions are slightly irregular PO43− tetrahedra with average P—O bond distances of 1.538 Å and 1.545 Å for those in Bss and 1.55 Å and 1.56 Å for those in Css. The cations are found to be coordinated to 7, 4, and 5 oxygen atoms for the 3 independent sites per unit cell. In Css the second cation site has a fifth oxygen atom at 2.57 Å in comparison with a length of over 2.9 Å for this same interatomic distance in Bss. The cations appear to be ordered with Cd++ preferentially in site 1 in Bss and Zn++ preferentially in site 2 in Css.
An accurate determination of the crystal structure of triclinic potassium dichromate, K2Cr2O7
Authors: Brandon J. K. , Brown I. D.
Published: May 2006

The crystal structure of triclinic potassium dichromate has been determined by single crystal X-ray diffraction. The cell constants are a = 13.367, b = 7.376, c = 7.445 Å, α = 90.75°, β = 96.21°, γ = 97.96° with four K2Cr2O7 units per cell. Refinement of 2600 reflections in both the space groups P1 and [Formula: see text] leads to the same structure. This is in agreement with the results of anomalous dispersion measurements, confirming that [Formula: see text] is the correct space group. The final agreement index, R, is 0.054. The two crystallographically independent dichromate ions are similar, deviating only slightly from C2v) symmetry. The Cr—O (terminal) distance is 1.63 Å, the Cr—O (bridging) distance is 1.79 Å and all angles at the chromium atoms are tetrahedral except for one of the O(bridging)—Cr—O(terminal) angles in each ion which is 106°. The angles at the bridging oxygen atoms are 124° and 128°. The geometry of the anion is compared with that found in a number of similar groups.
Interactions in aqueous alkali metal nitrate solutions
Authors: Irish D. E. , Davis A. R.
Published: May 2006

Raman (R) and infrared (I) spectra of aqueous alkali metal nitrate solutions have been recorded at 25 °C for a wide range of concentrations. In dilute solution the nitrate ion is perturbed by solvent water; the effects attributed to cations are nonspecific. The solvated nitrate ion generates the following spectrum: 1404 cm−1 (I, R), 1348 cm−1 (I, R), 1049 cm−1 (R), 825 cm−1 (I), 719 cm−1 (I, R). In more concentrated solutions band positions, intensities, and especially half-widths show a marked concentration and cation dependence. Changes in band half-width with concentration have been related to hydrated radii of the cations and are discussed in terms of interaction of solvated ions. For solutions of lithium and sodium nitrate more concentrated than 7 M a splitting of the ν4(E′) mode of nitrate ion into components at 720 and 740 cm−1 has been detected. Contact between ions is believed to account for the spectral changes observed for these high concentrations although water is shown to still markedly influence the interaction.
Isomerization of dideuteroethylene photosensitized by Cd(3P1)
Authors: Tsunashima Shigeru , Hirokami Shun-Ichi , Sato Shin
Published: May 2006

An investigation of the Cd(3P1)-photosensitized isomerization of dideuteroethylene has been made over the temperature range 275–350 °C. Principal primary products in the reaction of trans-1,2-dideu-teroethylene are cis-1,2- and asym-1,1-dideuteroethylenes. Minor products are ethane, acetylene, and n-butane, in amounts which are about three orders of magnitude smaller than those of the isomers.Decomposition of ethylene into hydrogen and acetylene, which is the principal mode of reaction in the case of Hg(3P1), was scarcely observed for the Cd(3P1)-photosensitized reaction.The two-excited-states mechanism previously proposed (1, 2) has been applied to explain hydrogen atom scrambling and cis–trans isomerization. It has been found necessary to modify the above mechanism to explain the results.
Reactions of thiyl radicals. III. Photochemical equilibrium in the photolysis of liquid disulfide mixtures
Authors: Sayamol K. , Knight A. R.
Published: May 2006

The photolysis of mixtures of liquid methyl disulfide and ethyl disulfide at room temperature at wavelengths greater than 2300 Å has been investigated. The sole detectable product is methyl ethyl disulfide which reaches a photostationary state concentration after relatively short irradiation periods. For various initial mixtures, the concentration of the three disulfides in the photostationary state can be correlated in terms of an equilibrium constant, K = [RSSR′]/[RSSR]1/2[R′SSR′]1/2, whose value is 2.05 ± 0.04. The quantum yield of unsymmetrical disulfide formation in the initial stages of the reaction is 330 for an absorbed intensity of 4.70 × 10−2 μeinstein/min when the incident radiation is confined to λ = 2600 + 50 Å. The exceptionally high efficiency of the overall process is ascribed to the chain-propagating step[Formula: see text]which likely proceeds through attack of the thiyl radical on the S—S disulfide linkage.
On the selectivity of acylation of unprotected diamino acids
Authors: Leclerc Jean , Benoiton Leo
Published: May 2006

p-Nitrophenyl acetate and other esters except formates, will acylate the unprotected diamino acids homolysine, lysine, and ornithine, exclusively at the ω-amino group at pH 11. At lower alkaline pH's, the reaction is preferential but not selective. The reaction with diaminobutyric acid and diaminopropionic acid is not selective at any alkaline pH. ε-N-Acetyllysine can be prepared directly by the action of excess phenyl acetate on lysine at pH 11.
Silicon-containing condensation polymers
Authors: Migdal Shmuel , Gertner David , Zilkha Albert
Published: May 2006

Condensation polymers were prepared starting from difunctional silicon-containing carboxylic acids or diols. Dimethyl bis(p-carboxymethylphenyl)silane was condensed with various diols to yield polyesters and with various diamines and diisocyanates to yield polyamides. Dimethyl bis(p-carboxymethylphenyl)silane and dimethyl bis(p-hydroxymethylphenyl)silane were condensed with dicarboxylic acids to yield polyesters, with diisocyanates to yield polyurethanes, and with ethyl chloroformate to yield a polycarbonate. Some of the properties of the polymers were compared with those of the corresponding polymers prepared from dimethyl bis(p-carboxyphenyl)silane.
Studies of the chemistry of azole derivatives. IV. New N-substituted 2-aminothiazoles
Authors: Singh Jag Megh
Published: May 2006

The syntheses of 11 new N-substituted 2-aminothiazoles have been accomplished by condensing ω-chloro-3,4-dihydroxy- and ω-chloro-2,3,4-trihydroxyacetophenone with substituted thioureas.
Densities and magnetic susceptibilities of thallium amalgams
Authors: Foley W. T. , Chiu Rebecca Fai-Ying , Delorey John R.
Published: May 2006

The densities of solid thallium amalgams were measured pycnometrically at −79.0 °C with the following results in g/ml: 13.946, 13.851, 13.465, 13.379, 13.219, 13.263, 13.267, 13.264, 13.184, 13.180, 13.177, 13.132, 13.063, 13.055 for the concentrations in weight % thallium of 8.72, 11.15, 19.45, susceptibilities of the amalgams were measured by the Gouy method over the same concentration range at temperatures from −180 °C to 150 °C. The alloys were diamagnetic and the susceptibilities were compatible with the phase diagram. The densities and the e.m.f. measurements on concentration cells show that the alpha phase at −79 °C extends from 21.35 to 30.7 weight % thallium and at 0 °C the alpha phase extends to 33.75 weight % thallium.
Nonempirical s.c.f. calculations on sulfur atom, hydrogen sulfide, and dihydrogen sulfoxide
Authors: Rauk A. , Csizmadia I. G.
Published: May 2006

This paper reports the first attempt to use Gaussian basis sets in nonempirical self-consistent field (s.c.f.) calculations on sulfur-containing chemical systems. Exponents for Gaussian-type functions (G.t.f.) on S atom are given for the minimal basis set. The optimization procedure is described and the optimized exponents utilized on calculations on S atom, H2S, and the hypothetical dihydrogen sulfoxide (H2SO). Calculations by the minimal basis set of (G.t.f.), using these exponents, gave a value for the HSH angle of H2S that agrees well with the experimentally determined value. Calculations of H2SO support a "multiple bond" picture of the S—O bond.
A simple cell for the electrodeposition of traces of metal on thin metallized plastic films. Applications to the preparation of radioactive sources of Co-60, Ag-110 m, Hg-203, Ni-63, and Zn-65
Authors: Ujihira Y. , Roy J. C.
Published: May 2006

A simple and rapid electrochemical technique for the preparation of uniform and adherent metal deposits on thin metallized plastic films has been developed. It is based on the use of an electrolytic cell, characterized by the separation of the anode and cathode compartments by a fritted glass disc. Furthermore, electrodeposition is achieved from a solution having a volume of only 0.15 ml. The technique and the conditions used to realize the electrodeposition on thin metallized plastic films is described. The cell has been used to electrodeposit many metals, mostly by spontaneous electrodeposition using a magnesium anode and also by application of an external voltage using a platinum anode. In this paper, we describe the experimental conditions and report the results dealing with the electrodeposition of Co, Ni, Ag, Hg, and Zn. Deposits of less than a microgram to several hundred micrograms per square centimeter were obtained with high yields in 10 to 40 min. The use of the technique for the preparation of radioactive sources of Co-60, Ni-63, Ag-110 m, and Hg-203 for absolute rate determinations is reviewed.
Measurement of the vapor pressure of methanol-n-decanol and ethanol-n-decanol mixtures
Authors: Singh Jaswant , Benson G. C.
Published: May 2006

Molar excess Gibbs free energies of mixtures of methanol and ethanol with n-decanol were obtained from static vapor pressure measurements over the temperature range 20–50 °C. The molar excess entropies of the system methanol–decanol are predominantly negative at 25 °C; those of ethanol–decanol are positive.
Studies on the thermodynamics and conductances of molten salts and their mixtures. Part V. The density, change of volume on fusion, viscosity, and surface tension of sodium chlorate and of its mixtures with sodium nitrate
Authors: Campbell A. N. , Kouwe E. T. van der
Published: May 2006

The densities, viscosities, and surface tensions of molten sodium chlorate, and of molten mixtures of sodium chlorate and sodium nitrate, as well as the change of volume on fusion, have been determined.From the dependence of molar volume on temperature and composition, it appears that the mixing of sodium chlorate and sodium nitrate is a process of dilution rather than of interaction. The viscosity of sodium chlorate is found to be much lower than that of lithium chlorate, a possible indication of greater complexity in the lithium chlorate melt. The activation energy of viscous flow for sodium chlorate is less than that of lithium chlorate. For lithium chlorate – lithium nitrate mixtures, at constant temperature, there is pronounced positive deviation from linearity, when viscosity is plotted against molar composition. For sodium chlorate – sodium nitrate mixtures, the deviation is much less marked though still positive.The surface tension of sodium chlorate is almost identical with those of lithium and potassium chlorates. The surface heat of sodium chlorate is higher than that of lithium chlorate but it still indicates some degree of covalency. The Guggenheim formula and Sokolov's rule have been applied. In contrast to melts of mixtures of lithium chlorate and lithium nitrate, the sodium salt melts would appear to have simpler constituents and to be more ionic in character.
Electrochemical reactions at Pbo2 electrodes. Part III. β-PbO2 electrodes in acid perchlorate electrolytes at high overpotential
Authors: Hampson N. A. , Jones P. C. , Phillips R. F.
Published: May 2006

The mechanism of exchange between β-lead dioxide and plumbous ions in solution has been investigated using the galvanostatic technique. Interpretation of the ηD vs.i data is consistent with a change in mechanism from a single two-electron transfer step to two successive single-electron transfer steps as the magnitude of the potential excursion from equilibrium is increased.Analysis of the slopes obtained from the linear-logarithmic region indicates that the slow step in the reaction is that leading to the formation of a Pb(III) intermediate.The orders of reaction with respect to the plumbous and hydrogen ions have been obtained from the dependence of the rate of the reaction on the concentration of the electro-reactive species.A reaction mechanism is suggested on the basis of the kinetic data.
Cyclic voltammetry of diphenylpicrylhydrazyl in tetrahydrofuran
Authors: Funt B. Lionel , Gray Derek G.
Published: May 2006

Cyclic voltammetry has revealed four reversible single electron transfer processes in the oxidation and reduction of diphenylpicrylhydrazyl (DPPH) in tetrahydrofuran (THF). These are associated with a cation, a free radical, a monoanion, a dianion radical, and a trianion of DPPH.THF is a good solvent for cyclic voltammetry as evidenced by the stability of the products generated at the electrodes. It is also one of the few excellent solvents for anionic polymerization and is therefore a remarkably suitable medium for studies of electropolymerization phenomena.
Kinetics of neopentyl chloride pyrolysis. I. The molecular decomposition
Authors: Shapiro J. S. , Swinbourne E. S.
Published: May 2006

A detailed investigation of the thermal decomposition of neopentyl chloride over the temperature range of 410–496 °C established that the pyrolysis occurs via two concurrent processes: (i) a unimolecular decomposition accompanied by a Wagner–Meerwein rearrangement giving methylbutenes and hydrogen chloride and (ii) a radical-chain decomposition to methane, isobutene, methyl chloride, 1-chloro-2-methylpropene, 3-chloro-2-methylpropene, 1,1-dimethylcyclopropane, and hydrogen chloride. The molecular reaction accounts for 30–40% of the overall decomposition. The Arrhenius equation for the molecular process is given by k1(s−1) = 1013.26 ± 0.36e−60 000 ± 1640/RT. The nature of the transition state for the decomposition is discussed in terms of the unique molecular structure of neopentyl chloride.
Colorimetric determination of molybdenum with 5,7-dibromo-8-hydroxyquinoline
Authors: Elbeih I. I. M. , Abou-Elnaga M. A.
Published: May 2006

A new method for the colorimetric determination of molybdenum(VI) uses 5,7-dibromo-8-hydroxyquinoline as coloring reagent. Molybdenum(VI) is separated from other elements by paper chromatography using a butanol – nitric acid – acetylacetone solvent mixture.
Chemical shifts for compounds of the group IV elements silicon and tin
Authors: Hunter B. K. , Reeves L. W.
Published: May 2006

Chemical shifts for 29Si in seven series of molecules of the type XnSiY4−n have been measured where Y is an alkyl group and X varies widely in electronegativity. A considerable amount of proton and fluorine chemical shift data has been obtained for the same compounds and in one series (CH3)nSiCl4−n the 13C chemical shifts in the methyl groups have been measured.The gross features of the 29Si chemical shifts are understood by considering the series (Alkyl)3SiX with the electronegativity of X widely varied. The hybridization at silicon is approximately conserved in these series and the theoretically anticipated linear dependence on electronegativity of X is demonstrated. The ligands X = O, N, and F are exceptional and these 29Si chemical shifts have a high field shift. This additional shielding has been associated with (p → d)π bonding. The approximate nature of present chemical shift theories is not likely to provide a measure of the order of (p → d)π bonding.The 29Si chemical shifts in the series XnSiY4−n are discussed and also indicate a net shielding effect with (p → d)π bonding. A comparison is always made with corresponding 13C chemical shifts. A long range proton–proton coupling in molecules Me3SnX and Me2SnX2, H—C—Si—C—H, is observed when and only when X = O, (N?), F.119Sn chemical shifts in a series of alkyltin compounds have been measured. The same dependence on the electronegativity of X in the series (Alkyl)3SnX is noted, but the variation of X is much more limited. Some shielding due to (p → d)π bonding in the series (n-Butyl)nSnCl4−n is suggested. The tin chemical shift has been measured as a function of concentration and solvent for simple methyltin bromides and chlorides. In donor solvents, it has been possible to obtain equilibrium constants for complex formation from tin dilution chemical shifts. The nature of the bonding in complexes suggested previously is consistent with the variations in the coupling constant |JSn–C–H| with concentration. The distinction between ionization and complex formation with the solvent for (CH3)2SnCl2 can be made on the basis of the concentration dependence of |JSn–C–H|The spin–lattice relaxation time T1for 13C and 29Si in natural abundance in several pure degassed compounds has been measured. These are not in the case of 13C (as has been suggested) of the order several minutes, but are always less than 50 s and in one case as low as 3–4 s. Both 29Si and 13C T1 values follow what might be expected on the basis of a dipole–dipole mechanism from the closest protons. The short value of 35 s in CS2 is probably a result of spin–rotation interaction in the liquid state.
Chemistry of phosphorus pentaselenide. II. Its reaction with amines
Authors: Melton Robert G. , Zingaro Ralph A.
Published: May 2006

The reaction of phosphorus pentaselenide with amines may yield, as products, selenophosphoric triamides, (RNH)3PSe; alkylammonium diselenophosphoric diamides, (RNH)2P(Se)Se−RNH3+; or alkylammonium monoacidbis(diselenophosphoric diamides), {[(RNH)2P(Se)Se]2H}−RNH3+, where R is an alkyl group. The preparation of potassium diselenophosphoric diamides, (RNH)2P(Se)Se−K+, is also described.
Correlation of specific rotation with conformation. A new approach to the study of conformational equilibria
Authors: Lemieux R. U. , Pavia A. A.
Published: May 2006

The marked changes in optical rotation which occur on dissolving the methyl 2-deoxy-α-L-and 3-deoxy-β-L-erythro-pentopyranosides in a variety of solvents including chloroform, acetone, acetonitrile, pyridine, dimethylsulfoxide, and water were found by nuclear magnetic resonance to result almost exclusively from changes in conformational equilibria. The changes in rotation are in agreement with those expected from Brewster's rules.
Stable complexes of bromine with some phthalazines
Authors: Hirsch A. , Orphanos D.
Published: May 2006

Bromine complexes of phthalazine and several phthalazine derivatives have been prepared. The yields are quantitative and the compounds exhibit good stability. The complexes may be utilized as sources of bromine in bromination reactions.
Partition coefficient of methyl iodide between vapor and water
Authors: Hasty R. A.
Published: May 2006

The Ostwald's partition coefficient for the solubility of methyl iodide in water was determined from 4.85 to 68.5 °C. The partition coefficient measured for 10−7 to 10−8 M solutions was found to be from 20 to 30% lower than for 10−2 M solutions. A new rapid gas chromatographic technique is described for the determination of partition coefficients in dilute systems.
La détermination de la température optimale de précipitation de l'iodate de thorium
Authors: Collée R.
Published: May 2006

not available
Temperature dependence of the electron resonance spectrum of the hydrazine positive ion
Authors: Falle H. R.
Published: May 2006

A temperature study of the hydrazine positive ion, N2H4+, showed that the ratio of the nitrogen hyperfine splitting to the proton hyperfine splitting, |aN/aH| increased with increasing temperature. The increase in |aN/aH| was approximately 3%, while the increase in aN itself was less than 1% over the 50 °C temperature range. This effect is attributed to torsional vibration about the N—N bond and is assessed on this basis.
Recherches sur le point isohydrique et les équilibres acido–basiques de condensation ou association en chimie. XXVI. Quelques nouvelles remarques et commentaires théoriques
Authors: Carpéni Georges
Published: May 2006

The experimental data so far obtained relative to titration networks showing isohydric points (i.p.) permit us to affirm that (a) the classical electrochemical law which governs all the acid–base equilibria is in fact valid only for "sufficiently diluted" media and (b) in "sufficiently concentrated" media, the dissolved acid–base chemical systems always give rise to (isopoly-)condensation or -association equilibria which are simultaneously superposed on those of dissociation; the presence of the isopolycondensed species (under their molecular and (or) ionic forms) appears unquestionably in the titration networks, ph = f(X,c), which are always "isohydric".The theoretical interpretation of the i.p. is based on a postulate that, around the i.p., attributes a prominent importance to the most condensed species which has its stoichiometric equivalence approximately equal to the isohydric abscissa Xi; whence follows the fundamental relation[Formula: see text]the multiplicity index m being found by calculation. The above relation is sustained and justified by several experimental and theoretical arguments.Until further knowledge is obtained, the above postulate can be held to be true, as its validity has never been known to fail.Some remarks concerning the analogy in representation between the isohydric and isobestic points can be found in the Appendix.
Relative efficiencies of triplet–triplet energy transfer from benzene (3B1u) to monoolefins and 1,3-butadiene
Authors: Morikawa A , Cvetanović R. J.
Published: May 2006

Relative efficiencies of quenching of the benzene triplet (3B1u) in the gas phase by a number of monoolefins, 1,3-butadiene, and several inorganic gases (SF6, Xe, CO2, N2O) have been determined by a competitive technique. Most of the data have been obtained at room temperature (~26 °C) and some measurements have been made at 30 and 70 °C. The latter indicate that the efficiency of the energy transfer to the monoolefins and 1,3-butadiene increases with increasing temperature. The mechanism of the "energy transfer" to the olefins appears to involve a chemical interaction with the benzene (3B1u) molecules. The inert gases are inefficient quenchers.The kinetic data obtained with 1,3-butadiene indicate that this diolefin quenches also to an appreciable extent the first excited singlet of benzene (1B2u). This has been confirmed by direct fluorescence measurements.
Relation entre la structure de la kröhnkite et la dissymétrie des spectres de résonance magnétique nucléaire de l'échantillon polycristallin
Authors: Tiggelen Pierre J. Van
Published: May 2006

not available
Photoinduced paramagnetism in the 1,3,5-trinitrobenzene – cyanide ion system
Authors: Norris A. R. , Breck A. , Wan J. K. S.
Published: May 2006

Photoinduced paramagnetism has been observed in the 1,3,5-trinitrobenzene – cyanide ion system and evidence is presented to indicate that the radical species is generated via the 1,3,5-trinitrobenzene – cyanide ion σ-complex.
Synthesis and properties of some formylferrocene thiosemicarbazones
Authors: Wiles D. M. , Suprunchuk T.
Published: May 2006

Twelve new substituted thiosemicarbazones have been prepared from formylferrocene and 2- and 4-monosubstituted and 4,4-disubstituted thiosemicarbazides. The infrared spectra of these compounds are discussed in some detail. Copper complexes of three of them were synthesized and their structures established. They were found to be strongly paramagnetic. The electronic absorption spectra of the thiosemicarbazones and the copper complexes are reported.
Synthesis and properties of some β-diketimines derived from acetylacetone, and their metal complexes
Authors: McGeachin S. G.
Published: May 2006

The synthesis of a number of diketimine ligands of structure 1 is reported. These give bis-bidentate chelates of type 2 with Cu(II), Ni(II), and Co(II). Optical spectra, magnetic moments and, in a number of instances, solution molecular weights are recorded for these complexes. On the basis of these, it is concluded that the complexes unsubstituted on nitrogen, adopt a square planar stereochemistry in contrast to the others which are all pseudotetrahedral.
Essential oils and their constituents. XLII. Isomerization of epoxides on active alumina
Authors: Nigam Ishwar C. , Levi Leo
Published: May 2006

When chromatographed on active alumina, epoxides isomerize yielding chiefly the corresponding α,β-unsaturated alcohols. Side reactions were observed in some cases. Limonene oxide yielded cis-1 (7), 8 p-menthadien-ol-2, cis- and trans-carveol, perillyl alcohol, trans-8p-menthene-diol-1,2, and cis- and trans-dihydrocarvone. α-Pinene oxide was converted to pinocarveol, cis- and trans-pinocamphone, campholenic aldehyde and an unidentified alcohol. Caryophyllene oxide yielded three isomeric unsaturated alcohols which were converted to a ketone of known structure.
Deuterated 4-hydroxycoumarin derivatives
Authors: Knight Allan R. , McIntyre J. S.
Published: May 2006

4-Hydroxycoumarin exchanges rapidly with heavy water, resulting in deuterium replacing both the 3- and the 4-hydroxy proton. Preparation of the following deuterated coumarin derivatives is described: 4-chlorocoumarin-3-d1, 4-piperidylcoumarin-3-d1, and 4-anilinocoumarin-3-d1.
A new simple absolute viscometer for use in experimental systems with limited access to the liquid
Authors: Nagarajan M. K.
Published: May 2006

A novel type of vertically oscillating bob viscometer for liquids is described. The mathematical theory of a solid sphere oscillating in a viscous liquid is developed, and results in an exact equation depicting the relationship between the logarithmic decrement of the oscillations of the sphere and the viscosity of the liquid surrounding the bob. The use of this technique for the determination of absolute viscosity of liquids is demonstrated. Using five sample liquids, at room temperature, the average error between the absolute viscosities determined and those of previous measurements is ± 1.5%.The viscometer consists of a quartz spring, which suspends a solid gold sphere, hanging vertically. The oscillations of the system are sensed by electrically recording the output of a linear variable differential transformer, the core of which forms a part of the oscillating system. The oscillations are stimulated electrically; the positioning of the transducer core is precisely adjustable with the use of an electric motor driven mechanism. Thus, the viscometer can be entirely remotely controlled and is, therefore, recommended for experimental situations which make the liquid not easily accessible, e.g. inside furnaces, pressure vessels, vacuum chambers, etc.
Electrical conductivities of quaternary ammonium salts in acetone.: Part II. The mechanisms of transport
Authors: Adams W. A. , Laidler K. J.
Published: May 2006

The limiting equivalent conductivities of tetramethylammonium iodide, tetraethylammonium iodide, and tetra-n-propylammonium iodide in acetone solution have been interpreted in terms of activated-complex theory; the energies of activation for conductivity at constant pressure and at constant volume, and the volumes of activation for conductivity, were calculated.The hole free-volume theory of liquids has been discussed and found to give a satisfactory explanation for the observed pressure and temperature coefficients of conductivity, viscosity, and self-diffusion in several solvents. The magnitude of the limiting ionic equivalent conductivity has been shown to depend in a critical way on the ionic radius and on the relative strengths of the ion–solvent and the solvent–solvent interactions.
Infrared spectra of triphenylboron and triphenylborate
Authors: Shurvell H. F. , Faniran J. A.
Published: May 2006

The infrared spectra of triphenylboron and triphenylborate have been obtained in the region 4000 to300 cm−1. The analysis of the spectra supports a propeller-shaped structure with symmetry D3 for triphenylboron and a planar structure with symmetry C3h for triphenylborate. The Urey–Bradley force field has been applied to the calculation of approximate vibrational force constants for the BC3 and BO3 groups.
Group vibrations and the vibrational analysis of molecules containing the CD3 group
Authors: Freeman J. M. , Henshall T.
Published: May 2006

The procedure introduced by King and Crawford for the simplification of the molecular vibrational problem by factorization from the secular determinant of characteristic group frequencies, and applied by them to the CD3 group, has been reexamined and programmed in English-Electric KDF-9 Algol. A few small corrections have been made to their results, and equations are given for the calculation of CD3 group frequencies in molecules bearing such groups.The group factorization procedure has also been applied to the calculation of the skeletal frequencies of ααα-d3-dimethyl sulfide and d6-dimethyl selenide.
Longitudinal spin-lattice relaxation in aqueous solutions of dysprosium(III) and copper(II) ions as an indicator of complex formation
Authors: Bock E.
Published: May 2006

Spin-lattice relaxation times of aqueous solutions of Dy(III) and Cu(II) in the presence of acetate ions were determined. The experimental results suggest that the coordination number with respect to the acetate ion appears to be 3 and 2 for the Dy(III) and Cu(II) ion respectively.
Dielectric studies. Part XIX. Molecular relaxation of some rigid molecules
Authors: Crossley J. , Hassell W. F. , Walker S.
Published: May 2006

The dielectric absorption at five microwave frequencies of solutions of seven rigid polar molecules in nonpolar solvents has been examined as also has cyclohexanone. Furan, pyridine, and thiophene have their dipole moments along the major axis and their dielectric absorption should be characterized by a single relaxation time. Unlike the monohalobenzenes, camphor, pentamethylene sulfide, tetrahydropyran, and s-trioxan, however, furan, pyridine, and thiophene have non-zero distribution coefficients at 25 °C, whereas for pyridine at 50 °C and cyclohexanone at 25 °C the value is zero. The non-zero distribution coefficients are to be related to either weak solute-solute or solute-solvent interactions, resulting in the polar molecule experiencing a variety of local environments. The observed relaxation times of furan, pyridine, and thiophene are comparable with those of other rigid molecules of similar shape and size. For such cases, even though the distribution parameters are not zero, it is not feasible to analyze the dielectric data into contributions from more than one relaxation process.
Thermal rearrangement of methyl cis-2-alkylcyclopropanecarboxylates
Authors: McGreer Donald E. , Chiu Norman W. K.
Published: May 2006

Seven alkyl substituted methyl cyclopropanecarboxylates with an alkyl group cis to the ester group have been found to ring open to the isomeric γ,δ-unsaturated ester through a 1,5-hydrogen shift upon heating to 259.4 °C in a sealed tube. Methyl cyclopropanecarboxylates which do not have a cis 2-alkyl group are unaffected when heated for longer periods at this or higher temperatures and thus a simple method for determining geometrical isomers in this series is now available. The reactions are first-order, with ΔH† between 25 and 38 kcal/mole and ΔS† between −8 and −37 e.u. This and other information fully supports a cyclic hydrogen transfer mechanism.
Synthesis of methyl 2,3-anhydro-4-deoxy-6-O-methyl-α-DL-lyxo-hexopyranoside
Authors: Sweet F. , Brown R. K.
Published: May 2006

Bromomethoxylation of 2-methoxymethyl-3,4-dihydro-2H-pyran, 1, at −55° gave in 87% yield a 9:1 mixture of 3α-bromo-2β-methoxy-6α-methoxymethyltetrahydropyran (2) and 3β-bromo-2α-methoxy 6α-methoxymethyltetrahydropyran (3) respectively. Of the mixture of 2 and 3, in refluxing methanol containing sodium methoxide, 2 is dehydrohalogenated much more readily than is 3, giving a product that contains at least 95% of the trans-2-methoxy-6-methoxymethyl-5,6-dihydro-2H-pyran, 4. The identity and configuration of 4 was established by its hydrogenation to the known trans-2-methoxy-6-methoxymethyltetrahydropyran, 5. m-Chloroperoxybenzoic acid slowly and selectively converts 4, in 80% yield, to a mixture of methyl 2,3-anhydro-4-deoxy-6-O-methyl-α-DL-lyxo-hexopyranoside (6) (> 95%) and methyl 2,3-anhydro-4-deoxy-6-O-methyl-α-DL-ribo-hexopyranoside, (7) (< 5%).A rationalization is given for the selectivity observed.
Synthesis of 1,6-anhydro-4-deoxy-β-DL-xylo-hexopyranose
Authors: Sweet F. , Brown R. K.
Published: May 2006

6,8-Dioxabicyclo[3•2•1]octane (2), obtained from acid-catalyzed cyclization of the NaBH4 reduction product of acrolein dimer, has been converted to 4-bromo-6,8-dioxabicyclo[3•2•1]octane 3. Epoxidation of the base-catalyzed dehydrohalogenated product of 3, 6,8-dioxabicyclo [3•2•1]oct-3-ene (4), gave stereoselectively 1,6:2,3-dianhydro-4-deoxy-β-DL-ribo-hexopyranose (5) contaminated with < 5% of the isomeric 1,6:2,3-dianhydro-4-deoxy-β-DL-lyxo-hexopyranose (6). Compound 5, with the contaminating 6, subjected to treatment with aqueous KOH, gave 1,6-anhydro-4-deoxy-β-DL-xylo-hexopyranose (7) whose di-p-nitrobenzoate (8) gave a 100 MHz nuclear magnetic resonance (n.m.r.) spectrum superimposable on that obtained from an authentic sample of 1,6-anhydro-4-deoxy-β-D-xylo-hexopyranose di-p-nitrobenzoate.A first order analysis of the n.m.r. spectrum of 5 showed that the anomeric proton was coupled to all other protons except H-4 exo. Long range coupling over five bonds, as well as over four bonds, is observed. Couplings between H-1 and H-6 or H-5 illustrate that such effects can be obtained when an oxygen atom replaces carbon as in the structural feature [Formula: see text].
Proton magnetic resonance spectra of Trichosporon aculeatum mannan and its borate complex and their relationship to chemical structure
Authors: Gorin P. A. J. , Mazurek M. , Spencer J. F. T.
Published: May 2006

Methylation–fragmentation and periodate oxidation studies show that the mannan of Trichosporon aculeatum is branched with 2-O and 6-O-monosubstituted units and 2,6-di-O-substituted D-mannopyranosyl units. It contains up to five consecutive α-D-(1 → 2)-linkages. The proton magnetic resonance spectrum of the mannan (recorded in D2O at 70° using a VananHA-100 spectrometer) indicates structural differences from other yeast mannans. It contains four distinct H-1 signals, but more than four H-1 environments are present since addition of sodium tetraborate shifts two signals downfleld so that six signals are observed (Fig. 1). Two of the four signals in the mannan spectrum at τ 4.40, and τ 4.20 can be assigned to chemical structures. The former signal arises from nonreducing end units attached to the 2-positions of adjacent mannopyranose units and from 2,6-di-O-substituted units and the latter from 2-O-substituted mannopyranose units. These assignments are based on the above chemical evidence, comparison with H-1 chemical shifts of known compounds, and the magnitudes of the H-1 shifts on borate addition. Downfleld shifts of H-1 proton signals on borate addition to known mannopyranosides vary from a maximum with compounds that can form 2,3-borate complexes to virtually none with 2-O-substituted derivatives. The magnitude of the downfleld shifts observed with α-D-linked mannopyranose derivatives is greater than that of their β-linked counterparts.
Isolation of two arabinobioses from Acacia nilotica gum
Authors: Chalk R. C. , Stoddart J. F. , Szarek W. A. , Jones J. K. N.
Published: May 2006

A new, crystalline arabinobiose, 2-O-β-L-arabinofuranosyl-L-arabinose has been isolated from A. nilotica gum. Another arabinobiose, 3-O-β-L-arabinopyranosyl-L-arabinose, found previously in other Acacia gums, was also present.
Oxidative fragmentation of 3-pyrazolidinones to olefins
Authors: Kent R. H. , Anselme J.-P.
Published: May 2006

The oxidation of 5-aryl-3-pyrazolidinones with mercuric oxide to the corresponding olefins is reported. Diethyl azodicarboxylate also converts 4,5-diphenyl-3-pyrazolidinone to trans-stilbene. The fragmentation of the intermediate cyclic α-carbonyl azo compounds is suggested to account for the observed products.
Complexes of alkyl and aryl cyanides. Part VI. The vibrational spectra of MX2•2RCN, where M = Pd or Pt, X = Cl or Br, and R = Me or Ph, and the assignment of the metal–nitrogen stretching frequency
Authors: Walton R. A.
Published: May 2006

A careful examination of the Raman and infrared spectra of the crystalline planar complexes cis-and trans-MX2•2RCN, where M = Pd or Pt, X = Cl or Br, and R = Me or Ph, reveals intense absorption bands in the 125–80 cm−1 region which can be assigned to modes involving stretching of the metal–nitrogen bonds. Alternative assignments for v(M—N) are also discussed. These results are compared with those for other metal halide – RCN systems. The complexes trans-PtBr2•2RCN are described for the first time.