bluuebunny/crossref_metadata_2025 huggingface dataset:
Spectroscopic studies on some chromones
Authors: Gallivan James B.
Published: May 2006

Absorption and luminescence spectra were measured for chromone, 4-chromanone, and four photoproducts formed by the addition of extramolecular multiple bonds to photo-excited chromone. Absorption spectra in polar and non-polar solvents at room temperature revealed a low lying n → π* singlet transition in all of these systems. The cycloaddition products and 4-chromanone showed a weak fluorescence in polar solvents which was not observed in non-polar solvents, suggesting a solvent reordering, or at least increased mixing of low lying n,π* and π,π* singlet states. No fluorescence could be detected from chromone in either type of solvent. At 77 °K in polar solvents, all of these systems displayed a concentration independent, intense phosphorescence of intermediate lifetime (25 to 200 ms). The lifetime data, combined with the vibrational analyses of the phosphorescence spectra, phosphorescence polarization results, and oxygen induced singlet–triplet absorption spectra support the concept of a lowest energy triplet state of mixed orbital character. More detailed studies on chromone demonstrated a concentration dependent phosphorescence in non-polar solvents, with the "normal" chromone phosphorescence dominant below 10−4 M. At higher concentrations a lower energy, broad band phosphorescence was observed, which in spite of physical aggregation in the ground state, can be ascribed to a chromone exciplex.
Interaction of s-butyl peroxy and alkoxy radicals
Authors: Hiatt R. , Zigmund Ludek
Published: May 2006

Contrary to previous suggestions, the interactions of 2 s-butyl peroxy radicals yields no di-s-butyl peroxide. Di-s-butyl peroxide has been shown to result from mixing s-butyl hydroperoxide with oxalyl chloride, presumably via 2 s-butyoxy radicals produced in a solvent cage from homolysis of di-s-butyl peroxyoxalate formed insitu.
Electron Paramagnetic Resonance Study of some Alkyl Substituted Cycloalkenyl Radicals
Authors: Gee D. R. , Wan J. K. S.
Published: May 2006

Well-resolved electron spin resonance (e.s.r.) spectra are reported and analyzed for the radicals produced when samples of solid adamantane doped with alkyl substituted cycloalkenes are γ-irradiated at room temperature.
Fluorinated Carbohydrates. Part VII. 2-Deoxy-2-fluorohexopyranosyl Fluorides
Authors: Hall L. D. , Johnson R. N. , Adamson J. , Foster A. B.
Published: May 2006

The 1H and 19F n.m.r. spectra of the α- and β-anomers of 3,4,6-tri-O-acetyl-2-deoxy-2-fluoro-D-glucopyranosyl fluoride and of the corresponding D-manno derivatives have been fully analyzed. The signs of most of the 19F–1H and of all the l9F–19F couplings have been determined by a heteronuclear double-resonance method. The vicinal 19F–19F couplings are absolutely negative in sign, with Ja,a = – 20.0 Hz, and Ja,e and Je,e = – 13.5 to – 18.8 Hz. Sizeable long-range couplings (4J) between an axial fluorine and an axial proton are absolutely positive in sign.
Mechanism of Sulfonation of 4-Hydroxyazobenzene
Authors: Buncel E. , Strachan W. M. J. , Cerfontain H.
Published: May 2006

The mechanism of sulfonation of 4-hydroxyazobenzene and of 4-hydroxyazobenzene-4′-sulfonic acid in concentrated sulfuric acid media is examined through rate correlations and comparison is drawn with sulfonation of alkyl- and halogenobenzenes by means of [Formula: see text] plots. It is concluded that several mechanisms are operative in the hydroxyazobenzene system and that the curvature of the plot is the result of a change in rate-determining step from σ-complex formation to proton abstraction.
The Triplet State of Borazine
Authors: Young W. F. , Grein F. , Passmore J. , Unger I.
Published: May 2006

An attempt has been made to experimentally locate the triplet state of borazine. Borazine vapor was added to benzene vapor excited at 2580 Å. Borazine vapor has no effect on the first excited singlet state of benzene but does strongly quench the triplet state. A comparison of the experimental findings with theoretical predictions has been carried out.
The Mass Spectrometry of para-Substituted Benzyl Nitrates
Authors: Smith P. J.
Published: May 2006

The mass spectra of several para-substituted benzyl nitrates have been measured at 70 and 15 eV. The major fragmentation pathways have been established using deuterium labelling and measurement of metastable peaks. The formation of the para. Y.C6H4.CH2O+ ions from the parent ions approximately correlate with the Hammett sigma constants. A hydrogen-deuterium isotope effect of approximately 1.8 was found for the loss of hydrogen (deuterium) from the C6H6CHDO+ ion at 10 eV.
Applications of Quantum Chemistry. I. Energetics and Bonding in Conjugated Free Radical Chains
Authors: Baird N. C.
Published: May 2006

The heats of formation at 25 °C and the equilibrium carbon–carbon bond lengths are calculated by the neglect of nonbonded differential overlap molecular orbital theory for a series of conjugated, acyclic free radicals containing from one to nine unsaturated carbon atoms. The total bonding energies in the radicals exceed the values expected from polyene bond terms by 5–9 kcal/mol, depending on the length and branching of the chain.
Chemistry of the Aminochromes. Part XIV. Noradrenochrome
Authors: Powell W. S. , Heacock R. A.
Published: May 2006

The preparation, in pure crystalline form, of noradrenochrome and its monosemicarbazone, together with some of their more important properties is described.
The Photolysis in Acidic Aqueous Solutions of the Monooxalato-bisethylenediamine Chromium(III) Cation and the Bisoxalatomonoethylenediamine Chromate(III) Anion: Photolysis Modes and Quantum Yields
Authors: Kirk A. D. , Moss K. C. , Valentin J. G.
Published: May 2006

The photolysis reactions of the complex ions [Cr(en)2ox]+ and [Cren(ox)2]− have been studied in the pH range 1 → 3 and at temperatures from 0 to 25 °C. It has been found that both ions photoaquate to a monodentate protonated ethylenediamine complex which then undergoes further aquation thermally with loss of the ethylenediamine ligand. Quantum yields for these aquations were measured for irradiation into the ligand field bands, the values obtained being 0.18 and 0.02, respectively. The results are discussed in terms of known empirical correlations for Cr(III) complexes. Assuming these reactions may occur from the 4T2g state as precursor, arguments are presented that the correlation between quantum yield and ΔE may depend on mixing of the 4T2g and 2Eg states, and its effect on the intersystem crossing rate constant.
Structure of Lycoctamone and its Analogues
Authors: Benn M. H. , Connolly J. D. , Edwards O. E. , Marion L. , Stojanac Z.
Published: May 2006

The lactams derived from the lycoctonine family of diterpenoid alkaloids undergo acid-catalyzed dehydration of the vic-glycol system to produce pinacolones. More vigorous acid treatment converts these to 'lycoctamone' analogues, which are now shown to be α,β unsaturated aldehydes containing in addition an inert allylic alcohol system. Proof of structure and a mechanism for the formation of these compounds involving bond migration and fission are presented. A steric driving force for the reaction leading to these compounds is suggested. Lycoctamone and its analogues are of potential value in the stepwise degradation of the lycoctonine skeleton for biosynthetic studies.
The Crystal and Molecular Structure of Bis-(2,4-pentanedionato)-4-aminopyridinecopper(II)
Authors: Bushnell G. W.
Published: May 2006

The crystal structure of bis-(2,4-pentanedionato)4-aminopyridinecopper(II) has been refined to an R value of 0.070 from photometric Weissenberg film measurements. The cell is monoclinic with a = 836 ± 3 pm, b = 1475 ± 3 pm, c = 1435 ± 3 pm, β = 112.14 ± 0.20°. The space group is P21/c (No. 14) with four molecules per cell. The density is 1.44 ± 0.01 g cm−3 (measured), 1.442 ± 0.013 g cm−3(calculated). The geometry about each copper atom is approximately that of a tetragonal pyramid, with the copper atom 22 pm above the basal plane. The apex of the pyramid is occupied by an oxygen atom, the heterocyclic nitrogen is in the basal plane, and the 4-amino group is uncoordinated and hydrogen bonded to oxygen in a neighboring molecule.
Some Factors Affecting the Synthesis of Hindered Diphenyl Ethers
Authors: Chandler W. D. , Bergman J. J. , Haas G. H.
Published: May 2006

A study is presented which shows how, in the Hems synthesis of two tri-ortho-substituted diphenyl ethers, the nature of the leaving group of the substrate is important in determining yield. The yield increases in the order: OTosyl (p-OSO2C6H4CH3) < Cl < F. As well, a synthetic method, involving reaction of an activated substrate with a sodium phenoxide in dimethyl sulfoxide, has been investigated in a similar way and a number of highly-hindered diphenyl ethers, which cannot be synthesized by the Hems synthesis, have been prepared.
Derivatives of 1-Phenylphthalan, 2-Methyl-1-phenylisoindoline, and 5H-Dibenzo[a,d]cycloheptene Oxides; Synthesis and Conformational Aspects
Authors: Fraser Robert R. , Renaud Roger N.
Published: May 2006

For the purpose of correlation of chemical shifts and geminal coupling constants with stereochemistry a number of compounds of fixed geometry have been synthesized. These include seven 6-substituted 1-phenylphthalans, five 6-substituted 2-methyl-1-phenylisoindolines, and six 2-substituted 5H-dibenzo-[a,d]cycloheptene oxides. The geometrical properties of the three ring systems are discussed and arguments in favor of a quasi-equatorial epoxide substituent in the latter series are supported by n.O.e. measurements.
Valence Force Field Calculations for Octahedral Anions
Authors: Qureshi A. M. , Hardin A. H. , Aubke F.
Published: May 2006

Vibrational force constants for the octahedral anion AsF6−, SbF6−, SnF62−, and SnCl62− in the corresponding potassium salts are calculated using a simple valence force field treatment, with the intention of obtaining better agreement with recently reassigned bending modes in these compounds and to arrive at improved values for the inactive mode ν6[F2u].
Hydrogen Abstraction from Methyl Formate by Methyl Radicals
Authors: Donovan T. R. , Dorko W. , Harrison A. G.
Published: May 2006

The reactions of CH3 radicals with methyl formate and CD3 radicals with methyl formate and methyl formate-d have been studied. The CH3 and CD3 radicals were produced by the photolysis of acetone and acetone-d. The Arrhenius parameters (log A, A in 1 mol−1 s−1; E, in kcal mol−1) for hydrogen abstraction are as follows[Formula: see text]
Reaction of trans-Chlorocarbonylbis(triphenylphosphine) Iridium(I) and its Analogues with Oxidizing Metal Salts
Authors: Cash D. N. , Harris R. O.
Published: May 2006

The effect of several oxidizing metal salts on the square planar iridium(I) complexes trans-[IrI(CO)-(PPh3)2X] (where X− = Cl−, Br−, I−, N3−, NCO−, NCS−, and NO2−) has been investigated. With nitrate salts of Ce(IV), Fe(III), and Cu(II), several of the reactions gave products characterized by analysis and i.r. spectroscopy as [IrIII(CO)(PPh3)2X(NO3)2]. With CuCl2•2H2O and CuBr2 several of the same starting materials gave products, [IrIII(CO)(PPh3)2XY2] (where X− = NCO−, NCS−, NO2− and Y− = Cl−; and X− = NCO−, NCS−, Br−, NO2− and Y− = Br−). These have been similarly characterized. An iridium(III) complex, [IrIII(PPh3)2(NO3)2H] has also been characterized.
Etude des spectres de vibration du benzothiazole et des oscillations des liaisons CH de quelques uns de ses dérivés
Authors: Panizzi Jean-Claude , Davidovics Gisèle , Guglielmetti Robert , Mille Gilbert , Metzger Jacques , Chouteau Jacques
Published: May 2006

The i.r. spectra of benzothiazole and those of 29 of its derivatives, mono, di, and trisubstituted have been analyzed. In each series, at least one compound has been studied in the vapor state, except the heterocycles having a substituent in position 7. Three Raman spectra, one of which is the benzothiazole, have also been examined. The ν(CH) stretching and γ(CH) out-of-plane deformation vibrations have been assigned, as well as the majority of the other fundamentals of benzothiazole.Four dichloro and one trichloro derivatives have been synthetized, in order to make easy the interpretation of the γ(CH) vibrations.
The Spontaneous Resolution of Oxalatobis(ethylenediamine)cobalt(III) Chloride
Authors: Brewer D. G. , Kan K. T.
Published: May 2006

The spontaneous partial resolution of oxalatobis(ethylenediamine)cobalt(III) chloride was affected by the crystallization of the complex compound from a supersaturated aqueous solution (1 g/25 ml) at 20 °C without the influence of any dissymmetric agent. Crystals exhibiting in some cases dextro-rotatory properties, and in the others levo-rotatory were obtained with up to 25% optical purity.
Kinetics and Mechanism of the Decarboxylation of Pyrrole-2-carboxylic Acid in Aqueous Solution
Authors: Dunn G. E. , Lee Gordon K. J .
Published: May 2006

The decarboxylation of pyrrole-2-carboxylic acid in aqueous buffers at 50° and ionic strength 1.0 has been found to be first order with respect to substrate at a fixed pH. As the pH is decreased, the rate constant increases slightly in the pH range 3–1, then rises rapidly from pH 1 to 10 M HCl. The 13C-carboxyl kinetic isotope effect is 2.8% in 4 M HClO4 and negligible at pH ~ 3. These observations can be accounted for by a mechanism, previously proposed for the decarboxylation of anthranilic acid, in which the species undergoing decarboxylation is the carboxylate ion protonated at the 2-position of the pyrrole ring. This intermediate can be formed both by ring-protonation of the carboxylate anion and by ionization of the ring-protonated acid. At low acidities ring-protonation is rate determining, but at higher acidities the rate of protonation exceeds that of decarboxylation.
A Synthesis of d,l-Prostaglandin E2 Methyl Ester and Related Compounds
Authors: Ferdinandi E. S. , Just G.
Published: May 2006

A synthesis of d,l-prostaglandin E2 (PGE2) methyl ester is described. Two new acetylenic prostaglandins, methyl 11α,15-dihydroxy-9-oxo-prost-5-yn-13-enoate and its C15 epimer, were obtained as intermediates in this synthesis. A solvolytic rearrangement of a bicyclo[2.1.0]hexane to a cyclopentane vinyl system is discussed.
Conformational Analysis of Trimethylene Sulfites. The Importance of Vicinal Unshared Electron Pairs
Authors: Wood Gordon , McIntosh John M. , Miskow Maurice H.
Published: May 2006

Dipole moments are reported for trimethylene sulfite and 11 alkyl derivatives in a variety of solvents (C6H12, CCl4, C6H6, dioxan). The variation of dipole moment with solvent for one of the 5-t-butyltrimethylene sulfite isomers is confirmed, but this behavior is not shown by the other compounds. This latter fact is used to rule out rapid chair–chair interconversion for these compounds. Recent ultrasonic absorption experiments are reinterpreted in the context of vicinal electron pair interactions and their effect on conformational analysis of sulfites and similar six-membered compounds. The result is a general scheme which is consistent with available information and which we believe is preferable to analysis of these compounds by analogy with cyclohexane.
The Effect of Sulfurhexafluoride on the Photochemistry of Aqueous Solutions
Authors: Rumfeldt R. C.
Published: May 2006

The effect of SF6 as a specific scavenger for eaq− in the photolysis of aqueous solutions has been studied. The photolysis of aqueous solutions of I− with 2537 Å light and Br−, Cl−, and SCN− with 1849 Å light containing [SF6] = 1.4 × 10−3 M results in the formation of F−, the yields of which are [Formula: see text], 1.98 ± 0.05, 2.40 ± 0.08, and 2.07 ± 0.05, respectively. By comparison with [Formula: see text]from N2O saturated solutions the relationship [Formula: see text] was confirmed. Assuming the same ratio, [Formula: see text] for pure H2O and aqueous HPO42− with 1849 Å radiation and [SF6] = 2.4 × 10−4 is 0.013 ± 0.002 and 0.30 ± 0.07, but these are considered minimum values due to the low concentration of SF6. Despite these yields HPO42− could be used as buffer in 1849 Å photolysis due to its low extinction at this wavelength.
Photolysis of Thiolane Vapor
Authors: Braslavsky Silvia , Heicklen Julian
Published: May 2006

The photolysis of thiolane vapor [Formula: see text] was studied at room temperature with 2139 Å radiation. The major product was C2H4, whose quantum yield decreased as the pressure was increased. Next in importance were 1-C4H8, C3H6, and C2H6. Also produced were CH4, c-C3H6, 1,3-C4H6, CH2CHSH, [Formula: see text], 1-C4H9SH, H2, C3H8, n-C4H10, c-C4H8, polymer, and an unstable product tentatively identified as 1-butene-1-thiol. All products were initial products of the reaction. Experiments with added C3H6 showed the absence of sulfur atoms. The results are interpreted in terms of two excited states and an intermediate which might be the diradical •CH2CH2CH2CH2S•.
Carbon Disulfide. II. Reaction with Active Methylene Compounds. The Structures of the Desaurins
Authors: Yates Peter , Moore Donald R. , Lynch Thomas R.
Published: May 2006

The desaurins, high-melting, neutral compounds formed by the reaction of active methylene compounds with base and carbon disulfide, have been shown to be derivatives of 2,4-bismethylene-1,3-dithietane.
Carbon Disulfide. III. Reaction with Active Methylene Compounds. The Infrared and Ultraviolet Spectra of the Desaurins
Authors: Yates Peter , Lynch Thomas R. , Moore Donald R.
Published: May 2006

The position of the carbonyl-stretching bands in the i.r. spectra of the desaurins, 2,4-bis(acylmethylene)- and 2,4-bis(carboxymethylene)-1,3-dithetane derivatives, establishes that there is a strong interaction between the sulfur atoms and the carbonyl groups. This is considered to involve mainly conjugative interaction rather than interaction through space, although the latter may account for the abnormally weak intensity of the carbonyl-stretching bands. These bands are split in the case of several desaurins and related compounds, and evidence has been obtained in one case that the splitting is due to Fermi resonance. The u.v. spectra of the desaurins and related compounds also indicate a strong conjugative interaction between the sulfur atoms and the carbonyl groups.
Studies of Substitution Reactions in Chromium(VI)–Fluorine Species
Authors: Arena A. M. , Brown D. S. , Tuck D. G.
Published: May 2006

Nuclear magnetic resonance (n.m.r.) studies show that the exchange between fluorochromate(VI) and fluoride in dimethylsulfoxide is slow, in agreement with previous work on oxygen exchange between water and chromates(VI). No substitution was detected in the system CrO3F−/Cl− in acetonitrile. Mixtures of chromyl fluoride and chromyl chloride show rapid fluorine exchange, both as the pure compounds, and in solution in trichlorofluoromethane. Possible mechanistic implications of these results are discussed.
Photochemistry of the cis- and trans-Dichlorobisethylenediamine Chromium(III) Cations in Acidic Aqueous Solutions. Observation of a Stereochemical Change in Photoaquation
Authors: Kirk A. D. , Moss K. C. , Valentin J. G.
Published: May 2006

The photoreactions of cis- and trans-[CrCl2(en)2]+ have been investigated in acidic aqueous solution at pH 3 and 0 °C. On photolysis in the ligand field bands the cis isomer was found to undergo mainly ethylenediamine aquation, apparently to a thermally unstable monodentate protonated ethylenediamine complex, with a quantum yield of 0.13. In addition chloride aquation occurred with[Formula: see text]. In contrast, the trans isomer underwent exclusive chloride aquation with quantum yield 0.32. The results are qualitatively, but not quantitatively, in agreement with predictions of Adamson's empirical rules. It was found that for trans-[CrCl2(en)2]+ photolysis, the reaction product [CrCl(H2O)(en)2]2+ was produced at least 70% in the cis configuration.
Dissociative Electron Attachment Processes in SO2 and NO2
Authors: Rallis D. A. , Goodings J. M.
Published: May 2006

A trapped electron apparatus has been used to identify the processes involved in negative ion formation for the triatomic oxides SO2 and NO2. Two O− peaks are observed in SO2 with onset values at 4.2 ± 0.15 and 6.3 ± 0.2 eV, and peak values at 5.0 ± 0.15 and 7.4 ± 0.15 eV, respectively. From kinetic energy analysis of the O− ions, both peaks are found to have the same dissociation limit involving SO in its ground state. For NO2, two dissociative electron attachment peaks are observed with onset values at 1.6 ± 0.2 and 7.3 ± 0.3 eV, and peak values at 3.0 ± 0.2 and 8.1 ± 0.2 eV, respectively. The first broad peak is explained by overlapping contributions from two processes having the same dissociation limit involving ground state NO; they differ only in the amount of kinetic energy possessed by the fragments. The second peak appears to involve electronic excitation of the neutral fragment NO* with zero kinetic energy at onset.
Studies on Acyl Alkyl Diimides
Authors: Lynch Thomas R. , Maclachlan Frederick N. , Siu Yum Kuen
Published: May 2006

A number of acyclic acyl alkyl diimides have been obtained by oxidation of the corresponding alkyl hydrazides. A new method for the synthesis of α-cyanoalkyl hydrazides, the reaction of acid hydrazides with ketones in the presence of sodium cyanide, has been explored. All the acyl alkyl diimides so obtained exhibit a medium to weak i.r. band at ca. 1550 cm−1; evidence supporting the assignment of this band to the —N=N— stretch is given. The results of oxidation of 5-methyl and 5-phenyl-pyrazolidin-3-one are reported, together with the synthesis and oxidation of tetrahydro-6-methyl-3(2H)-pyridazinone.
Nucleophilic Attack of Siloxycarbenes on Carbonyl Groups. The Formation of Oxiranes
Authors: Brook A. G. , Pearce Ronald , Pierce J. B.
Published: May 2006

Siloxycarbenes, formed by the photolysis of dimethyl- or diphenylsilacyclohexanone have been trapped as oxiranes or as the ring-opened hydrolysis products of oxiranes, with simple aldehydes and ketones such as acetaldehyde, or cyclohexanone. The reactions are interpreted as arising from the nucleophilic attack of the siloxycarbene on the carbonyl group. The structures of the oxiranes and their hydrolysis products have been established.
The Effect of Trace Impurities on Condensed Electrode and Microwave Discharges through Nitrogen
Authors: Baker R. R. , Jacob A. , Winkler C. A.
Published: May 2006

Traces of various gases have been added to a stream of purified nitrogen gas prior to entering either a microwave or a condensed electrode discharge, and the effect of the presence of these gases on the steady flow rate of nitrogen atoms obtained from the discharge has been measured. Suggestions for the effect of the impurity gases on the possible reactions occurring in the discharge have been put forward. It seems probable that an important feature of the presence of the impurities may be their effect on the electron temperature in the discharge.
Radiolysis of Hydrogen Sulfide at Very High Dose Rates. The Effect of SF61
Authors: Willis C. , Boyd A. W. , Miller O. A.
Published: May 2006

Gaseous H2S has been irradiated with electron pulses from a Febetron 705 at a dose rate of ~2 × 1027 eV g−1 s−1. For single pulse experiments, the yield of hydrogen is G(H2) = 12.0 ± 0.5, independent of pressure from at least 350 to 1600 Torr. Addition of SF6 reduces the yield to G(H2) = 7.9 ± 0.3 which is fairly close to that observed for pure H2S at low dose rates. The reduction, ΔG(H2) = 4.1 ± 0.3, agrees very well with the ion pair yield based on a W value of 25.3 eV.In multi-pulse irradiations, for pure H2S, the yield falls off with dose giving a limiting yield close to G(H2) = 8.0. No similar fall-off is observed for H2S–SF6 mixtures. It is proposed that at high absorbed doses and at low dose rates, there is no contribution to the hydrogen yield from neutralization processes; and that this is due to neutralization of H3S+ by an ion of the type Sn− rather than a free electron.
Kinetics of Reactions of 8-Quinolinol and Acetate with Hydroxyaluminum Species in Aqueous Solutions. 1. Polynuclear Hydroxyaluminum Cations
Authors: Turner R. C. , Sulaiman Wan
Published: May 2006

The effect of varying 8-quinolinol and acetate concentration on the rate of decomposition of poly-nuclear hydroxyaluminum cations was studied. It was found that the concentration of the undissociated 8-quinolinol and acetic acid molecules determined the magnitude of the first order rate constant for the decomposition of the polynuclear hydroxyaluminum cations, except when the acetate concentrations were relatively high. With high acetate concentrations, it appeared that polynuclear acetate species were involved in the reactions. An empirical equation was developed showing the effect of 8-quinolinol and acetic acid molecule concentrations on the pseudo first order rate constant for the decomposition reaction.
Nuphar Alkaloids: 3-Epinupharamine
Authors: Forrest T. P. , Ray S.
Published: May 2006

The structure of a new alkaloid isolated from Nuphar variegatum is shown to be that of 3-epinupharamine (4).
Electron Spin Resonance Detection of Electrochemical Intermediates Formed During Oxygen Evolution
Authors: Gardner C. L. , Casey E. J.
Published: May 2006

Electron spin resonance detection has been made of ozonide ion (O3−) and another unidentified species (X) formed during anodic oxygen evolution in concentrated KOH solutions at low temperature. The relative amounts observed depend on the metal used for the anode. New insight into the mechanism of oxygen evolution results.
The Reaction of the Electronically Excited Oxygen Atom O(1D2) with Nitrous Oxide
Authors: Scott P. M. , Preston K. F. , Andersen R. J. , Quick L. M.
Published: May 2006

An investigation has been made of the relative importance of the possible pathways [2a]–[2d][Formula: see text]for the reaction in the gas phase at room temperature between the excited oxygen atom O(1D2) and N2O, using the photolysis of NO2, O3, and N2O as sources of the excited atom. Measurement of the yields of N2 and NO from the photolysis at 2288 Å of mixtures of NO2 and N2O has led to a value of 1.01 ± 0.06 for k2a/k2b, the ratio of the rate constants for [2a] and [2b], in excellent agreement with the value of 0.99 ± 0.06 obtained from determination of the yields of N2 and NO2 arising from the flash photolysis of O3–N2O mixtures. The isotopic composition of the N2 produced in the photolysis of 15NO2–N2O mixtures indicated that k2c/k2a < 5 × 10 – 3. Furthermore, the value of k2a/(k2b + k2d) = 1.08 ± 0.19, obtained from a study of the effect of CO2 and Xe additions on the yield of N2 from the photolysis of N2O at 2288 Å, suggests that deactivation [2d] does not make an important contribution to the total rate constant for destruction of O(1D2).
The Effect of α-Substituents on Benzylic Spin–Spin Coupling Constants. Derivatives of 2,6-Dichlorotoluene
Authors: Janzen A. F. , Schaefer T.
Published: May 2006

Spin–spin coupling constants between methylene protons and ring protons over six and five bonds, [Formula: see text], are reported for α-substituted derivatives of 2,6-dichlorotoluene. Potential energy calculations suggest that the C—X bond of the CH2X group lies perpendicular to the plane of the ring. The six-bond coupling is dominated by a π electron mechanism and depends on the conformation of CH2X with respect to the aromatic plane and on the electronegativity of the substituent, X. The five-bond coupling is independent of X and it is suggested that the decrease in the π electron contribution to this coupling caused by the increasing electronegativity of X, is compensated by a corresponding increase in the sigma electron contribution.
Cycloaddition Reactions of Silyldiazoalkanes
Authors: Brook A. G. , Jones Peter F.
Published: May 2006

The products of cycloaddition of silyldiazoalkanes with representative alkenes are described, together with their photolysis products. The photolysis of silyldiazoalkanes yields silylcarbenes which undergo typical reactions.
Near Infrared Spectra of Water in Aqueous Solutions of Organic Salts. A Solvation Study of Bu4NBr, , and
Authors: Jolicoeur C. , The Nguyen Dinh , Cabana A.
Published: May 2006

The near-infrared spectrum of water at various temperatures and in aqueous solutions of Bu4NBr, [Formula: see text], and [Formula: see text] is studied in the region 0.8–1.2 µ. The spectra are recorded differentially with respect to water by varying the cell lengths as to take into account density changes or the volume occupied by the solutes. A simple analysis of these spectra illustrates the qualitative similarity between the effects of the Bu4N+ ion and that of a temperature decrement on the spectrum of water. On the other hand striking differences are observed in the differential spectra obtained with Bu4NBr and the phenyl substituted: salts. Further differences are exhibited in the relative solute-solvent interactions of [Formula: see text] and [Formula: see text].
Flash Photolysis with Kinetic Mass Spectrometry
Authors: Strausz O. P. , Barton S. C. , Duholke W. K. , Gunning H. E. , Kebarle P.
Published: May 2006

A flash photolysis apparatus coupled with a fast response conventional sector field mass spectrometer for the rapid time resolved detection of short-lived neutral transients is described. The utility of the apparatus is illustrated by the detection of the Fe(CO)(NO)3 intermediate with a half-life of ~0.1 s in the flash photolysis of Fe(CO)5 in the presence of NO.
Electron Spin Resonance Spectra of Azine – Alkali Metal Triple Ions in Ethereal Solvents
Authors: Al-Baldawi S. A. , Gough T. E.
Published: May 2006

Electron spin resonance spectroscopy has been used to study triple ions formed between pyrazine and tetramethylpyrazine and the cations Li+, Na+, K+ in dimethoxyethane, tetrahydrofuran, and 2-methyl-tetrahydrofuran. Differential line-broadening effects are reported within the hyperfine splitting patterns of the alkali metals incorporated into the triple ions, and a possible application of such effects to the study of ionic association is described.
Sesquiterpene Lactones from Pyrethrum Flowers
Authors: Doskotch Raymond W. , El-Feraly Farouk S. , Hufford Charles D.
Published: May 2006

Three new sesquiterpene lactones, dihydro-β-cyclopyrethrosin (3), chrysanin (4), and chrysanolide (5) were isolated from the flowers of Chrysanthemum cinerariaefolium and their structures determined by physical and chemical methods. The configuration at C-1 of pyrethrosin (2) was established as R by its conversion to dihydro-β-cyclopyrethrosin (3), a hydrogenation product of β-cyclopyrethrosin (1), which had the C-1 hydroxyl group assigned by the Horeau procedure and Brewster's benzoate method. The preparation and properties of the C-11 epimers, 12 and 17, of dihydropyrethrosin are reported and their stereochemistry established.
Absolute Rate Constants for Hydrocarbon Autoxidation. Part XX. Oxidation of Some Organic Sulfides
Authors: Howard J. A. , Korcek S.
Published: May 2006

Absolute rate constants for the liquid phase autoxidation of some organic sulfides at 30 °C have been measured. The reactivities of organic sulfides towards t-butylperoxy radicals are equal to or somewhat less than the reactivities of structurally analogous ethers. The α-alkylthiylalkylperoxy radicals appear to be about 3–5 times more reactive in hydrogen atom abstraction than the α-alkoxyalkylperoxy radicals.
Free-ion Yield in the Radiolysis of Dimethylsulfoxide
Authors: Cooper T. K. , Walker D. C.
Published: May 2006

Dimethylsulfoxide is a dipolar aprotic solvent of high basicity having a large dielectric constant (ε = 48) but very low solvating power for negative ions. The radiation yield of "free ions" in this liquid is in accord with the dielectric constant, G(free ions) = 1.8 ± 0.2, but these "free ions" do not resemble the strongly solvated electrons found in other polar media such as water and aliphatic alcohols. Evidence for this conclusion is based principally on competitive reactions involving a wide range of scavengers in competition with nitrous oxide. The radiation yields of gaseous products from pure liquid dimethylsulfoxide are G(H2) = 0.20 ± 0.01, G(CH4) = 3.3 ± 0.1, and G(C2H6) = 0.49 ± 0.03.
Metal Oxide Trialkylsilyloxide Polymers. Part VI. Aluminum Oxide Trimethylsilyloxides
Authors: Bradley D. C. , Lorimer J. W. , Prevedorou-Demas C.
Published: May 2006

Tris(trimethylsilyloxy)aluminum, [Al(OSiMe3)3]2, was hydrolyzed under controlled conditions in dioxane at 25 °C. The soluble initial products [AlOx(OH)z(OSiMe3)3−2x−z]n, with x = 0.03–0.65, underwent disproportionation when heated at 120–150 °C under vacuum to give final products with x = 0.8–1.1. Molecular weights were determined by cryoscopy in cyclohexane, and the linear dependence of 1/n on x was combined with an extension of the theory of regular polymer series to show that the number of OH groups, z, was small compared to the number of bridging oxygen atoms, x, per Al atom. The initial products consist of dimeric units, each linked to an adjacent unit by one or two oxygen bridges between aluminum atoms. The degree of polymerization is 1 to 4, based on the dimer unit. The final products have much higher degrees of polymerization (10–40, based on the dimer), and appear to contain a higher proportion of Al—O—Al bridges.
Electronic Raman Spectra. VII. Raman Spectra of the Lanthanides
Authors: Koningstein J. A. , Grunberg P.
Published: May 2006

Additional experimental data are reported on electronic Raman scattering of trivalent lanthanides, making the observation of this effect of the series nearly complete. The bulk of the information now available points to the fact that the intensity of electronic Raman transition is strongest for the rare earth ions in the middle of the series. The most profound differences of polarization features of electronic transitions and phonons is observed in the situation where the lanthanide ions have an odd number of 4f electrons. Antisymmetric scattering tensors play a less important role.
The Electron Spin Resonance Spectra of the Photochemically Produced Perfluorobenzophenone Ketyl and Anion Radicals
Authors: Sargent F. P. , Bailey M. G.
Published: May 2006

The electron spin resonance spectra of the ketyl and radical anion of perfluorobenzophenone were generated in alcoholic solution by means of a photochemical method. The radical anion was prepared in alkaline solutions by means of a flow system to prevent nucleophillic degradation of the perfluorobenzophenone prior to photolysis. A comparison is made of the fluorine nuclear hyperfme coupling constants to those reported for partially fluorinated radical anions.
Cyclic Alkoxyoxosulfonium Ions in the Chlorination of Hydroxy Sulfoxides
Authors: Durst T. , Tin K.-C.
Published: May 2006

Chlorination of β-, γ-, and δ-hydroxy sulfoxides with SO2Cl2 in CH2Cl2 at −78° resulted in the formation of the corresponding β-, γ-, and δ-chloro sulfones. Stereochemical evidence is presented that cyclic alkoxyoxosulfonium salts (O-alkylated sulfones) are intermediates in these transformations.
Structure and Nuclear Magnetic Resonance Spectrum of N-Nitrosocamphidine
Authors: Apsimon J. W. , Cooney J. D.
Published: May 2006

The 220 MHz n.m.r. spectrum of N-nitrosocamphidine is interpreted in terms of a 1:1 syn-anti isomer mixture. Benzene solvent-induced shifts and the spectrum of the tris(dipivalomethanato)europium(III) – nitrosocamphidine complex are used to assign the methyl resonances.
An Electron Spin Resonance Investigation of the Mechanism of the Intramolecular Cation Migration of Alkali Metal Semiquinone Ion-pairs
Authors: Gough T. E. , Hindle P. R.
Published: May 2006

A systematic survey of the kinetic characteristics of the intramolecular cation exchange reactions of semiquinone ion-pairs is described. A linear correlation exists between the free energy of activation for the exchange and the strength of the ionic interaction within the ion pair; however, this correlation does not extend to the enthalpy of activation. The significance of the kinetic parameters is discussed in terms of the role solvation plays in determining the course of the exchange process.
The Aqueous Chemistry of Chromium(III) above 100 °C: Hydrothermal Synthesis of Chromium Spinels
Authors: Swaddle T. W. , Lipton J. H. , Guastalla G. , Bayliss P.
Published: May 2006

The hydrothermal deposition of CrO(OH) from aqueous chromium(III) chloride, nitrate, and perchlorate, and of Cr3(SO4)2(OH)5•H2O and Cr(OH)SO4•2H2O(?) from aqueous chromium(III) sulfate, has been investigated. Aqueous chromium(III) is oxidized to chromium(VI) by 0.4 M perchloric acid above 225 °C, and by molecular oxygen above 250 °C. Aqueous chromium(III) can react at 300 °C with iron or steel, cobalt, and copper to produce FeCr2O4, CoCr2O4, and Cu2Cr2O4, respectively. CrO(OH) reacts with type 316 stainless steel at 440 °C in supercritical water of density 0.7 g cm−3 to yield (Fe,Ni)-Cr2O4, which is the "cubic Cr2O3" of Laubengayer and McCune. The spinels MCr2O4 (M = Mg, Mn, Fe, Co) can be made hydrothermally at ca. 300 °C from Cr(OH)3 and M(OH)2. This information is relevant to corrosion phenomena, and the possible hydrothermal origin of chromite deposits in serpentinized rocks.
Lewis Acid – Base Interactions Between Bis-π-cyclopentadienyl Tungsten and Molybdenum Dihydrides, Cp2MH2, and some Main Group III Moieties
Authors: Storr A. , Thomas B. S.
Published: May 2006

Combination of the Lewis bases Cp2MH2 (where M = W or Mo) with the Group III Lewis acids AlR3 (where R = Me, Et, or Ph) and AlMe2H has yielded a series of 1:1 complexes of the type Cp2MH2•AlR3. A number of the complexes undergoes a slow elimination of hydrogen or alkane in benzene solution. Attempts to isolate mixed hydride adducts of the type, Cp2MH2•M′H3 (where M′ = Al or Ga), were unsuccessful.
Crystal and Molecular Structure of Difluorochlorine(III)-hexafluoroarsenate(V), ClF2AsF6
Authors: Lynton H. , Passmore J.
Published: May 2006

Crystals of difluorochlorine(III)hexafluoroarsenate(V), ClF2AsF6, are monoclinic, space group A2/a, a = 10.676(9), b = 7.673(7), c = 8.064(7) Å, β = 113.40(5)°. The structure was refined by three dimensional least squares methods to R = 0.045 for 185 independent observed reflections. The chlorine atom has two nearest fluorine neighbors at 1.541(14) Å, with a F—Cl—F angle of 103.17(0.70)°, and two longer fluorine bonds at 2.339(14) Å. All five atoms lie in a plane. The arsenic atom is octahedrally coordinated to six fluorine atoms and is connected to two ClF2+ groups via trans fluorine bridges.
Stereoselective Total Synthesis of (+)-Copaborneol, (+)-Copaisoborneol, and (+)-Copacamphor
Authors: Piers Edward , Britton Ronald W. , Keziere Robert J. , Smillie R. Dean
Published: May 2006

A stereoselective total synthesis of the novel tricyclic sesquiterpenoids (+)-copaborneol (1), (+)-copacamphor (2), and (+)-copaisoborneol (3) is described. This work fully corroborates the structure and absolute stereochemistry assigned to the three sesquiterpenoids.
Eistert's Methyl Enol Ethers of Acetylacetone
Authors: Awang Dennis V. C.
Published: May 2006

The configuration and conformation of the two isomeric methyl enol ethers of acetylacetone (1) have been unequivocally demonstrated. The n.m.r. solvent shift data and observation of nuclear Overhauser effects support an s-cis conformation for the more stable isomer 2 bearing acetyl trans to methoxyl while indicating an s-trans conformation for the less stable enol ether 3 having acetyl cis to methoxyl. The facile acid-catalyzed isomerization of 3 to 2 apparently proceeds by reversible protonation of carbonyl oxygen since no deuterium incorporation is observed when the isomerization is performed in acetic acid-d4.
Electrolysis of α-Chloro- and α-Fluorocarboxylic Acids
Authors: Arora Parkash C. , Woolford R. G.
Published: May 2006

The electrolysis of α-chlorovaleric, α-chlorocaproic, and α-chloroisobutyric acids in methanol gave none of the Kolbe dimer; the main products were chloroester and hydrogen ester with aldehydes and acetals formed in lesser amounts. In water, straight chain α-chloroacids gave dimeric esters as the major product. However, Kolbe dimer was formed in fairly good yields together with small amounts of fluoroester and acetal, when α-fluorocaproic and α-fluoroheptanoic acids were electrolyzed in methanol. No Kolbe dimer was produced from 2-fluoro-2-ethylbutanoic and α-fluorophenylacetic acids; the corresponding ketone or aldehyde was the major product.
Mössbauer Spectra and Electric Dipole Moments of Organotin(IV) Complexes with Monodentate Donor Ligands
Authors: Mullins F. Patricia
Published: May 2006

Mössbauer spectra and electric dipole moment data are reported for R2SnCl2 and RSnCl3 complexes with Y type ligands where R = C4H9, C6H5 and Y = Ph3PO, Ph3AsO, Bu3PO, and Ph3P. Quadrupole splittings and dipole moments are consistent with trans C—Sn—C bonds in the R2SnQ2Y2 complexes. In the trigonal bipyramidal Ph2SnCl2Y complexes, the two phenyl groups are assumed to be in equatorial positions. Data for the RSnCl3Y2 complexes suggest that in BuSnCl3(Ph3AsO)2 and BuSnCl3-(Ph3P)2 two Cl atoms are trans and that in BuSnCl3(Ph3PO)2 and PhSnCl3(Ph3PO)2 the three Cl atoms are cis.
Low Surface Coverage Interactions of Sulfur Dioxide on Selected Transition Metal Catalysts from 273 to 423 °K
Authors: Glass R. W. , Ross R. A.
Published: May 2006

Calorimetric beats of adsorption for sulfur dioxide at low surface coverages from 0.004 to 0.600 μmol m−2 on a number of supported transition metal catalysts have been measured between 273 and 423 °K mainly by an adiabatic technique. The catalysts included Fe2O3, Mn2O3, V2O5, MnSO4, and "NiS" ail supported on silica gel.Sulfur dioxide adsorption/desorption isotherms, nitrogen adsorption data, and chemical and infrared analyses were also determined to provide further ancillary information.Heats of adsorption at 423 °K for adsorbed amounts of 0.004 μmol m−2 varied with the adsorbent from nearly 39.0 for Mn2O3 on silica gel to 23.0 kcal mol−1 for the silica gel support medium. With increase in surface coverage to 0.600 μmol m−2 the heat values begin to steady at 6 to 7, 7 to 8, and 8 to 9 kcal mol−1 at 423, 373, and 323 °K, respectively, and less discrimination is observed among the various materials. Preadsorption of small amounts of sulfur dioxide on the supported oxides followed by oxygen admission caused sharp initial falls of as much as 7 to 8 kcal mol−1 in the heat values whereas preadsorption of oxygen followed by sulfur dioxide gave only slight heat increases of around 1 kcal mol−1.It is proposed that sulfur dioxide is chemisorbed on all surfaces with the strongest interactions occurring at the lowest coverages. Sulfates are formed on the oxides as confirmed by chemical analysis, and it is postulated that multiple hydrogen bond formation occurs on silica gel through the interaction of sulfur dioxide oxygen atoms with surface hydroxy groups.
Theoretical Studies of Nonbenzenoid Hydrocarbons: 16 π-Electron Systems
Authors: Birss F. W. , Gupta N. K. Das
Published: May 2006

Hückel and self-consistent-field semi-empirical π-electron molecular orbital calculations on pentalenoheptalene are reported and the results compared to those of pyrene, acepleiadylene, napth[cde]azulene, and cyclohept[bc]acenaphthylene which contain the same number of π electrons. Resonance energies of all molecules calculated by the methods of Dewar and Whitehead are reported. It is suggested that pentalenoheptalene can be treated as two fused azulene nuclei.
Complexes of Tungsten Halides with Group VI Donors: Adducts with Triphenylphosphine Chalcogenides
Authors: Boorman P. M. , Reimer K. J.
Published: May 2006

The preparation of complexes with the empirical formula WCl5L (L = Ph3PS, Ph3PSe) and WBr4•-Ph3PS is reported. The tungsten chloride adducts have been formulated as [W2Cl8L2]2Cl on the basis of infrared spectra, molecular weight, and conductance measurements. The complex WBr4Ph3PS is probably a non-ionic dimer, but solubility problems make this suggestion tentative. No corresponding complex with Ph3PSe could be isolated.The shifts in v(P—X) (X = S, Se) upon coordination are amongst the largest ever reported, and are indicative of bridging behavior by these ligands.
The Trifluoroacetic Acid Solvent System. Part II. Acids
Authors: Harriss M. G. , Milne J.B
Published: May 2006

19F nuclear magnetic resonance (n.m.r.) studies show that SbF5 forms HSbF5(OOCCF3) in tri-fluoroacetic acid. This complex acid does not react with (CF3CO)2O which must be added to carry out conductimetric studies in anhydrous HOOCCF3. However, HClO4, HSO3F, and HNO3 all react with (CF3CO)2O to yield mixed anhydrides CF3COClO4, CF3COSO3F, and NO2OOCCF3. HBF4 reacts with the anhydride to give CF3COF while H2SO4 appears to be simply dehydrated to polysulfuric acids.
Reactions of Alkylthio Derivatives of Aluminum with Aldehydes, Ketones, and Olefins
Authors: Lalancette J. M. , Beauregard Y. , Bhéreur M.
Published: May 2006

The preparation of ((CH3)2CHS)2AlCH3 and (t-CaH9S)2AlCH3 is reported. The reactions of (RS)2AlCH3 (R = CH3, (CH3)2CH, t-C4H9) with ketones give aldol condensations leading to the corresponding conjugated ketones, with the acetyl group R—CO—CH3; with other ketones, a mixture of thioacetal and enolthioether is obtained. With aldehydes, a mixture of thioacetal and enolthioether is observed. With olefins there is an addition of two RS groups on the site of the double bond, with a small percentage of allylic substitution. With conjugated ketone, the saturated ketone is obtained with the alkylthio group in β position. All those reactions proceed with good yields and appear quite general.
Oligoribonucleotide Synthesis III. Synthesis of Trinucleotides Using a Stepwise Phosphotriester Method
Authors: Neilson Thomas , Werstiuk Eva S.
Published: May 2006

A convenient general synthesis for protected di- and triribonucleotides of predetermined sequence is described. Starting with a 5′-p-methoxytrityl-2′-O-tetrahydropyranyl-ribonucleoside, the nucleoside unit destined to become the 5′-terminal of the oligomer, 2′-O-tetrahydropyranyl-nucleosides are coupled together by β,β,β-trichloroethyl 3′–5′-phosphotriester linkages. A two-step process is used for each coupling, (a) the terminal 3′-hydroxyl group is phosphorylated using β,β,β-trichloroethylphosphate activated by triisopropylbenzenesulfonyl chloride (TPS) and (b) re-activation of the newly inserted diphosphate grouping by TPS is followed by condensation with the 5′-hydroxyl of the incoming nucleoside derivative. These phosphotriester derivatives can be isolated and purified in good yield by silica gel column chromatography in methanol – methylene chloride. The fidelity of 3′–5′ linkage is checked. The p.m.r. spectra can indicate the nature and ratio of the bases in these protected oligomers. Deblocking conditions to give free trinucleoside diphosphates are described.
Alkylations of the Side-chain Nucleophiles of Cysteine, Methionine, Histidine, and Lysine Derivatives with Allyl Bromide, 1-Bromo-2-butyne, and 2-Bromoacetophenone
Authors: Jones J. Bryan , Hysert David W.
Published: May 2006

Comparative studies on the reactions of cysteine, methionine, histidine, and lysine derivatives with allyl bromide, 1-bromo-2-butyne, and 2-bromoacetophenone have been carried out in connection with an evaluation of the potential of reagents incorporating ethylenic and acetylenic functions for protein modification.
Photoreactions of Nitroso Compounds in Solution. XIX Stereochemistry of Nitrosamine Photoaddition to Olefin
Authors: Chow Y. L. , Chen S. C. , Chang D. W. L.
Published: May 2006

The stereochemical course of the photoaddition of nitrosamines to a carbon–carbon double bond was shown to follow a free radical mechanism initiated by aminium radicals. The photoaddition to cyclohexene was highly stereoselective in which the addendum approached in anti-diaxial mode. Similar photoadditions to cis- and trans-2-butenes were less stereoselective, giving mixtures of the erythro- and threo-adducts, owing to the rotation of the carbon-carbon single bond in the intermediate stage.