bluuebunny/crossref_metadata_2025 huggingface dataset:
Description de l'effet Overhauser dans les systèmes en échange: application à l'analyse conformationnelle d'aldéhydes hétérocycliques
Authors: Combrisson S. , Roques B. , Rigny P. , Basselier J. J.
Published: May 2006

The equations of the nuclear Overhauser effect (n.O.e.) in exchanging systems predict relative increases for proton signals where the life times for exchange are of the same order of magnitude as the relaxation times. This method allows one to obtain structural informations. Hence, for a temperature sufficiently below that of the coalescence, it allows one to infer a conformational preference by an examination of the relative increase in intensity with respect to spatial position of exchange sites. We have hereby determined the conformations of formyl-2 bromo-4 thiophene and acetyl-2 dibromo-4,5 thiophene. The compounds show at ambient temperature a single rotamer OS-cis. Formyl-2 bromo-4 furan exists at −90 °C in an equilibrium between the rotamers OO-cis and OO-trans. In this case, the results of different irradiations show OO-cis to be the preferred rotamer. Moreover, this method is able to give indications of the life time on different sites. We also give an evaluation of the limits of the method.
Use of a Gettering Material to obtain Oxygen-free Liquid Samples for Nuclear Spin Relaxation Studies
Authors: Sandhu H. S.
Published: May 2006

An investigation into the gettering powers of aluminum, barium, magnesium, and misch metal for removing oxygen from liquid samples has been carried out. The liquids treated with each getter are: H2O, CH2Br2, CH2Cl2, CH2I2, and CH3OH. The results show that aluminum is more suitable for all these liquids even though the other getters are also effective. It appears that as long as there is no strong reaction, any of these getters can be used to remove oxygen from any liquid.
Virial Scaling and Diatomic Force Constants
Authors: Chong D. P. , Gagnon P. J. , Thorhallsson J.
Published: May 2006

The application of virial scaling to calculation of diatomic force constants is studied. The ground states of H2, LiH, BH, and Li2 are used as test cases. We find that three-point calculations with fair-to-good wavefunctions lead to excellent k2, fairly good k3, but poor k4. A wide variety of models for interpolating raw data is also investigated.
Chemistry of Fulvic Acid, a Soil Humic Fraction, and its Relation to Lignin
Authors: Ogner G. , Schnitzer M.
Published: May 2006

Fulvic acid, a water-soluble soil humic fraction, was extracted from a Podzol soil and exhaustively methylated so as to make it soluble in benzene. The resulting material was separated repeatedly by column, thin layer, and preparative gas chromatography until relatively pure components were obtained. The latter were then identified by comparing their mass and micro-i.r. spectra and their gas chromatographic retention times with those of standards of known structures.Twenty-one phenolic and benzene-carboxylic acids were identified as methyl ethers and esters. In addition, a number of polymethoxy-benzene polycarboxylic acids of as yet unknown identity were isolated.A number of the compounds isolated have been reported to arise from the alkaline KMnO4 oxidation of lignin. Since we did not oxidize the fulvic acid in the laboratory, it is likely that it originated from products resulting from the chemical and/or biological oxidation of lignin in the soil. Methylation of the fulvic acid was necessary to make the compounds extractable by organic solvents. Since methylation reduces hydrogen-bonding in the fulvic acid, it is suggested that in fulvic acid phenolic and benzenecarboxylic acids are joined by hydrogen-bonds to form a polymeric structure of yet unknown conformation. Any weakening of hydrogen-bonding will lead to a break-up of this structure.
Circular Dichroism of the Copper(II) N,N′-Bis(alanyl)stilbenediamine Complexes
Authors: Parris M. , Hodges A. E.
Published: May 2006

The preparations of the three diamides, RR(or RS or SS)-N,N′-bis(S-alanyl)stilbenediamine are described. The circular dichroism spectra of the 1:1 copper(II) complexes are compared to those of similar compounds previously described.
An Aspect of the Scope of the Phosphonic Acid Bis Amide – Carbonyl Method in the Synthesis of Exocyclic Olefins
Authors: Jones J. Bryan , Marr Peter W.
Published: May 2006

The synthesis of cyclohexylidene derivatives by condensation of α-lithiocyclohexylphosphonic acid bis(dimethylamide) with some carbonyl compounds has been studied. The desired olefin was obtained when the carbonyl moiety was an aldehyde but, probably for steric reasons, not when ketones were used.
Ion Association Effects on Nuclear Magnetic Resonance Parameters of Aromatic Ions. II. The Anions of Carbazole and 4,5-Methylenephenanthrene
Authors: Cox Richard H.
Published: May 2006

The 1H n.m.r. spectra of carbazole nitranion, 4,5-methylene- and 9,10-dihydro-4,5-methylene-phenanthrene carbanions with various alkali metal cations have been analyzed in terms of chemical shifts and coupling constants. Chemical shifts of the anions depend upon cation and solvent and are related to the type of ion pairs present. The 7Li n.m.r. data indicate that Li is associated with the nitrogen of carbazole nitranion whereas with the 4,5-methylenephenanthrene carbanions, Li appears to be located in the π-cloud of the anions and associated equally with all carbons in the anion. The results are discussed in terms of the types of ion pairs present and the association of cation with anion.
Evidence for a Hydride Shift in the Alkaline Rearrangements of D-Ribose
Authors: Gleason W. B. , Barker R.
Published: May 2006

The synthesis of D-ribose-2-t from D-arabinose is described and its conversions in aqueous alkali in the presence and absence of oxygen reported. In both situations a significant amount of label is transferred from C-2 to -1 and a relatively small proportion is released to the solvent. It is concluded that hydride transfer is occurring and that enolization, which requires the loss of hydrogen from C-2, is not an obligatory first step in base-catalyzed rearrangements of D-ribose.
Proton Magnetic Resonance of the Methyl Derivatives of 2-Fluoropyridine. Sigma and Pi Electron Contributions to Spin–Spin Coupling Constants
Authors: Rowbotham J. B. , Wasylishen R. , Schaefer T.
Published: May 2006

The p.m.r. spectra of the methyl derivatives of 2-fluoropyridine are analyzed. The signs and magnitudes of the long-range spin–spin coupling constants between the methyl protons and the ring protons and between the methyl protons and fluorine are consistent with a model in which the nitrogen atom polarizes the sigma electron system but leaves the pi electron contribution to the coupling constants relatively unchanged. There are dramatic changes in the ring proton – fluorine couplings while the couplings involving the methyl protons vary little from those in the corresponding toluene derivatives. Thus the coupling over six bonds between fluorine and methyl protons is 1.25 ± 0.03 Hz in 2-fluoro-5-methyl pyridine compared to 1.15 ± 0.02 Hz in p-fluorotoluene.
A Glucan from Tremella mesenterica NRRL-Y6158
Authors: Fraser C. G. , Jennings H. J.
Published: May 2006

A dextrorotatory glucan has been isolated in good yields from the culture medium of Tremella mesenterica NRRL-Y6158. The glucan consumed 1.32 mol of periodate and released 0.33 mol of formic acid per mol anhydroglucose and reduction and hydrolysis of the periodate-oxidized glucan yielded glycerol and erythritol in the ratio 1.0:1.9. Partial hydrolysis of the glucan released maltose, isomaltose, panose, isomaltotriose and O-α-D-glucopyranosyl-(1 → 4)-O-α-D-glucopyranosyl-(1 → 6)-D-glucose. The fully methylated glucan was composed of 2,3,4,6-tetra-O-methyl glucose (0.5%), 2,3,4-tri-O-methyl glucose (31.4%), and 2,3,6-tri-O-methyl glucose (67.6%).These results indicate that the glucan was a linear molecule composed of approximately 200 α-D-glucopyranose units linked 1 → 6 and 1 → 4 in the ratio 2:1. Structurally the glucan resembles to varying extents the neutral glucans obtained from the yeast-like fungi of the Pullularia species.
On the Theory of Linear Electro-Optical Rotation. II. The Three-Photon Effect
Authors: Hameka Hendrik F.
Published: May 2006

We present a theoretical description of an effect that we call three-photon electro-optical rotation. We consider a high-intensity beam of polarized monochromatic light, which interacts with an assembly of identical molecules. We calculate the probability of the absorption of two photons from this beam of light and the simultaneous reemission of a third photon, which has the same direction of propagation as the incident light and a direction of polarization that is perpendicular to the incident light. The energy of the emitted photon is the sum of the energies of the absorbed photons. We found that the effect is observable in the presence of a homogeneous electric field F, directed along the direction of polarization of the emitted beam of light. The effect is proportional to F and to the molecular dipole moment and it is inversely proportional to the absolute temperature T.
Aqueous Nonelectrolyte Solutions. Part IX. Enthalpies of Mixing of Water and Deuterium Oxide with Ethylene Oxide
Authors: Glew D. N. , Watts Harry
Published: May 2006

Calorimetric enthalpies of mixing have been measured over the whole composition range for the water – ethylene oxide system at 10.75 and 20.00 °C and for the deuterium oxide – ethylene oxide system at 13.45 and 20.00 °C. Less extensive measurements have been made for dilute ethylene oxide solutions in water at 0.6 °C and in deuterium oxide at 4.1 and 7.3 °C. The experimental S-shaped, enthalpy of mixing – composition curves are interpreted in terms of solution hydrogen bonding changes, with particular reference to the hydrogen bonding of water. At low ethylene oxide mole fractions the deuterium oxide systems are more exothermal and at high ethylene oxide mole fractions more endothermal than the corresponding water systems. A good correlation is found between the enthalpy of mixing and the water proton magnetic resonance chemical shift for solutions with greater than 0.55 mol fraction of ethylene oxide.
Studies on Hydrogen–Oxygen Systems in the Electrical Discharge. V. Raman Spectra of the Trapped Products
Authors: Deglise Xavier , Giguère Paul A.
Published: May 2006

The condensed products (at – 180 °C) of electrically dissociated water vapor and other related systems were examined by means of laser Raman spectroscopy. A new type of total reflection cell had to be developed for the study of metastable species trapped in an amorphous matrix. Besides the characteristic O—O stretching band of hydrogen peroxide at 878 cm−1, always the strongest, another fairly strong band at 500 cm−1, and a third one at about 760 cm−1 were present in all cases. A couple of weaker bands around 820–830 cm−1 and 430–440 cm−1 occurred only in oxygen-rich system (H2O2 vapor or H2O–O2 mixtures). In the latter, the presence of condensed ozone was confirmed by a band at 1025 cm−1, and occasionally another faint one around 1120 cm−1.The relative intensities of the bands varied locally in a given sample, indicating uneven composition.Isotopic shifts with 18O confirmed that these Raman bands arise from vibrations of oxygen atoms. Essentially the same results were obtained in hydrogen as in deuterium systems, except that in the latter case the new bands were appreciably stronger and sharper. The present results support the assignment of previous infrared spectra to hydrogen polyoxides, H2O3 and H2O4.
Reaction of Phenyllithium with Some N,N-Disubstitiited Cyanamides
Authors: Anderson Hugh J. , Wang Nam-Chiang , Jwili E. T. P.
Published: May 2006

Phenyllithium adds to N,N-dialkylcyanamides 1 to form, successively, the metal salts of the amidines 3 and the guanidinylamidines 5 followed by further addition and ring closure to give the phenyl-1,3,5-triazines 8. This proposed course of the reaction is supported by the isolation of intermediates, and compounds derived from them, as well as by determination of product yields with varying ratio of reactants. It appears that 2-thienyllithium reacts similarly with dimethylcyanamide. The reaction of phenyllithium with N-methyl-N-phenylcyanamide gives mostly the tetrasubstituted cyanoguanidine 10.
Steroids and Steroidases. XI. Synthetic Approaches to C-17 Bis(2-hydroxyethyl)-amino Compounds as Potential Precursors of 17-Hydroxyandrostane Nitrogen Mustards
Authors: Jones J. Bryan , Leman Jeffrey D.
Published: May 2006

The synthesis of some potential nitrogen mustard precursor 17α-bis(2-hydroxyethyl)aminomethyl androst-17β-ol derivatives has been achieved by two routes. During the investigation, unequivocal proof was obtained that addition of cyanide to 17-keto steroids gives predominantly 17β-hydroxy-17α-cyano epimers.
The Hydrothermal Chemistry of some Common Transition Metal Compounds
Authors: Kong Pi-Chang , Swaddle T. W. , Bayliss P.
Published: May 2006

The stabilities of aqueous solutions of typical salts of manganese(II), iron(II), cobalt(II), cobalt(III), nickel(II), and copper(II) at temperatures up to 300 °C have been investigated. At 200 to 300 °C, hydrolysis of the metal ions can lead to the partial precipitation of metal oxides, or silicates in the cases of nickel(II) and cobalt(II) when a silica vessel is used; except for the M(II) sulfates, which precipitate as MSO4•H2O (M = Mn, Fe, Co, and Ni) and Cu3SO4(OH)4. Manganese(II), iron(II), and cobalt(II) tend to be oxidized at 250 to 300 °C in neutral or acidic solutions, while cobalt(III) in aqueous ammonia is reduced. Aqueous CuCl2 is in equilibrium with CuCl and Cl2 at 300 °C. Hydrolytic precipitation is suppressed by the addition of small concentrations of hydrogen ion or larger concentrations of chloride ion, if oxidation–reduction processes do not interfere.
Thermal Conductivity, Anomaly in Temperature-dependence for Liquids
Authors: Venart J. E. S. , Mani N.
Published: May 2006

Most empirical equations express the thermal conductivity of normal simple liquids as linear functions of temperature. The majority of measurements to date, except water, support such a description. Very precise new measurements on toluene over the complete liquid range at 1 atm (0.299 < Tr < 0.645) show a substantial pre-freezing anomaly. At the freezing point (tf) there is a depression of the expected conductivity of 7.9 × 10−3 W/m °K. This tf behavior is attributed to cluster formation.
Vibrational Spectra of Peroxydisulfuryl Difluoride S2O6F2 and the Halogen Derivatives FOSO2F and ClOSO2F
Authors: Qureshi A. M. , Levchuk L. E. , Aubke F.
Published: May 2006

Vibrational spectra of the halogenfluorosulfates FOSO2F and ClOSO2F are recorded and Cs symmetry is suggested for the molecules. For peroxydisulfuryl difluoride a staggered non-planar configuration with C2 symmetry is indicated by the polarized Raman spectra.
Oxydation des alcènes par l'ion thallique. I. Stéréochimie et mécanisme de l'oxydation des cyclohexènes
Authors: Freppel C. , Favier R. , Richer J.-C. , Zador M.
Published: May 2006

The stereochemistry of the diols obtained by oxidation of 3-t-butylcyclohexene by thallic sulfate indicates that the α hydroxyl group participates in the breaking of the C—T1 bond of the intermediate organothallous compound. The fact that only the trans diols are obtained indicates that an SN2 substitution of the thallium can be excluded. We suggest that the thallic oxidation in aqueous media of olefin of rigid conformation is an excellent one-step method of preparing trans diols. The formation of the trans diaxial diol upon oxidation of 4-t-butylcyclohexene tends to confirm that hypothesis.
Reactions of Tertiary Hypohalites
Authors: Boido V. , Edwards O. E.
Published: May 2006

Metallic silver initiates short-chain homolytic decomposition of tertiary alkyl hypochlorites and hypobromites. Evidence is presented that the reaction of tertiary alcohols with silver oxide – mercuric oxide – bromine involves formation and homolytic decomposition of alkyl hypobromite followed by cyclization of γ-bromo alcohols. A convenient synthesis of tricyclo[4.3.1.03,8]decan-4-one (4-proto-adamantanone) is described.
Protonated Cyclopropanes. VI. Solvolyses of 1-14C-1-Propylmercuric Perchlorate
Authors: Lee C. C. , Law Joyce
Published: May 2006

The solvolysis of 1-14C-1-propylmercuric perchlorate in 10% dioxane –90% H2O, HOAc, or HCOOH gave, respectively, about 0.6, 2.5, or 3.5% isotopic scramblings, the rearranged 14C-label being distributed approximately equally over C-2 and -3. The results are considered in relation to protonated cyclopropanes as possible intermediates.
Szilard–Chalmers Reactions in Dicyclopentadienyldiirontetracarbonyl
Authors: Kanellakopulos-Drossopulos W. , Wiles D. R.
Published: May 2006

In neutron-irradiated [CpFe(CO)2]2 radioactive FeCp2 and Fe(CO)5 are formed, in addition to the radioactive parent compound. The radiochemical yields before annealing are 1.4, 3.2, and 16.0%, respectively. The predominance of Fe(CO)5 over FeCp2 is in keeping with previous observations. The yield of radioferrocene is not affected by subsequent thermal treatment at up to 75°, while the yields of the two carbonyl-containing compounds are increased up to 5.4 and 20.1%. The ferrocene yield is insensitive to irradiation time and temperature. From this insensitivity it is concluded that the Fe—Cp bonds are reformed by epithermal processes. Similarly the Fe—CO bonds are reformed by thermal as well as epithermal reactions.
High Resolution Nuclear Magnetic Resonance Spectra of Bifluoride Ion and its Homologues
Authors: Martin John S. , Fujiwara Fred Y.
Published: May 2006

The high resolution 1H and 19F nuclear magnetic resonance (n.m.r.) spectra of the four bihalide ions have been observed in aprotic solvents. The 1H shielding is, in every case, 14 p.p.m. less than that in the related molecule. The spin–spin coupling in FHF− is 120.5 ± 0.3 Hz.
Aqueous Nonelectrolyte Solutions. Part X. Mercury Solubility in Water
Authors: Glew D. N. , Hames D. A.
Published: May 2006

The solubility of mercury in water has been determined between 4 and 72 °C. Standard thermodynamic functions have been evaluated for mercury transfer from the liquid metal to aqueous solution and from aqueous solution to the gas phase. Mercury in water exhibits large positive deviations from Raoult's Law and shows a high relative volatility of 15 400 at 25 °C.
Influence of Lewis Acids on the Diels–Alder Reaction. IV. Reaction of 2-Methyl- and 2-Phenylfuran with Ethyl Propiolate
Authors: Mcculloch A. W. , McInnes A. G.
Published: May 2006

The AlCl3-promoted reactions of 2-methyl- and of 2-phenylfuran with ethyl propiolate afford as major products ethyl 5-hydroxy-2-methyl- and 2-phenylbenzoates (6a, 6b). Also isolated as minor by-products of these reactions are ethyl 3-(2-furyl-5-methyl)acrylate (5a), ethyl 3-(2-furyl-5-phenyl)acrylate (5b), ethyl 3,3-di(2-furyl-5-methyl)propionate (10a), ethyl 3,3-di(2-furyl-5-phenyl)propionate (10b), and ethyl 2-hydroxy-5-methylbenzoate (8a).
The Preparation of Some Heterocyclic Analogues of Triptycene
Authors: McKinnon D. M. , Wong J. Y.
Published: May 2006

A variety of anthracenes react with dibenzoylethylene and diacetylethylene to give substituted bicyclooctadienes as Diels–Alder adducts. Treatment of these with phosphorus pentasulfide gives derivatives of benzenonaphtho[c]thiophenes, which are thiophene analogues of triptycene. Reaction of the anthracenes with dibenzoylacetylene gave substituted bicyclooctatrienes, which on treatment with phosphorus pentasulfide gave inseparable mixtures of the benzenonaphtho[c]thiophenes and benzenonaphtho[c]-furans. Attempted retro Diels–Alder reactions of the thiophenes were unsuccessful.
The Structure of the Hofmann Base Derived from Lycopodine Methiodide
Authors: Chin-You N. , MacLean D. B. , Prakash A. , Calvo C.
Published: May 2006

A new structure, 4a, based on chemical and X-ray crystallographic data, is proposed for the Hofmann base derived from lycopodine.
A Novel SN1 Displacement: The Reaction of Tertiary Amines with Acetic Anhydride
Authors: Mariella R. P. , Brown K. H.
Published: May 2006

The action of actic anhydride on tertiary amines at reflux may cause the displacement of one of the R groups from the amine. The groups which are displaced are benzyl, t-butyl, benzhydryl, trityl, and cinnamyl; the groups which are not displaced are methyl, ethyl, n-butyl, phenyl, α-naphthyl, iso-propyl, allyl, and propargyl. An SN1 mechanism with special steric requirements is consistent with the experimental results.
Infrared Spectra of Hydroxyl Groups on the Surface of Platinum
Authors: Morrow B. A. , Ramamurthy P.
Published: May 2006

Infrared spectroscopy has been used to show that two types of PtOH species exist on the surface of silica-supported platinum. One of these is produced when O2 is allowed to react with hydrogen covered platinum (ν(OH) = 3497 cm−1) and the other is produced when H2O reacts with a reduced platinum oxide (ν(OH) = 3544 cm−1).
A Novel Phenolic Zwitterion
Authors: Nye M. J. , Scriven E. F. V.
Published: May 2006

Two examples (2-ammonio-3′,5′-dibromo-4′-oxidoacetophenone (4a) and 2-pyridinio-3′,5′-dibromo-4′-oxidoacetophenone (4b)) of a new type of phenolic zwitterion have been synthesized and their i.r., u.v., and p.m.r. spectra are discussed.
The Crystal Structure of Dimethylsulfoxidepentammineruthenium(II) Hexafluorophosphate
Authors: March Frank C. , Ferguson George
Published: May 2006

The crystal structure of dimethylsulfoxidepentammineruthenium(II) hexafluorophosphate ( [Ru(NH3)5DMSO]2+ 2PF6−) has been determined from three-dimensional X-ray data. The crystals are monoclinic, space group P21/c, with four formula units in a unit cell of dimensions a = 8.805(2), b = 17.335(5), c = 12.373(2) Å, β = 94.24(2)°. The structure has been refined by full matrix least-squares methods to a final residual R of 0.054 for 1987 reflections greater than 3σ. The DMSO ligand coordinates through the sulfur atom and the S—O bond distance (1.527(7) Å) is considerably longer than that found for other sulfur–donor complexes of the ligand. The Ru—S bond distance is 2.188(3) Å.
Yields of Free Ions in the X Radiolysis of Some Simple Saturated and Unsaturated Hydrocarbon Liquids: Effects of Molecular Structure and Temperature
Authors: Robinson M. G. , Fuochi P. G. , Freeman G. R.
Published: May 2006

Pulse techniques were used at temperatures ranging from 120 to 293 °K. A quasifree electron conductance transient (k/u overshoot) was observed in liquid methane, but not in ethane, propane, cyclopropane, ethylene, propylene or butene-1. The free ion yield in methane, Gfi = 0.8 at 120 °K, is much larger than those in the other liquids, which at 183°K are: ethane, 0.13; propane, 0.076; cyclopropane, 0.04; ethylene, 0.017; propylene, 0.04; butene-1, 0.027. The activation energies of free ion formation are, in kcal/mol: ethane, 0.6; propane, 0.8; ethylene, 0.5; propylene, 1.0; butene-1, 1.0. The results are interpreted in terms of the coulombic interaction model. The distances that the secondary electrons penetrate the liquid away from their parent ions are greater when the hydrocarbon molecules are more sphere-like, and are reduced by the presence of a π bond in the molecule. Cyclopropane behaves somewhat like an olefin in this regard, a fact that is explained by the unusual bonding in the C3 ring. In the present liquids the only ionization events that contribute appreciably to the free ion yield are those in which the electron penetrates [Formula: see text] from the parent ion.
Oxygen Solubility Measurements in Liquid Paraffin
Authors: Ruppel D.
Published: May 2006

The solubility of O2 in liquid paraffin was determined over the temperature range from 31 to 90 °C under an O2 pressure of 736 Torr. The solubility was also determined at 35 °C over the pressure range from 290 to 834 Torr.
A Regenerable, Solid-Phase Coupling Reagent for Use in Peptide Synthesis
Authors: Brown J. , Williams R. E.
Published: May 2006

The incorporation of the peptide reagent EEDQ (1) into an insoluble polymeric form is described. The utility of this reagent in peptide syntheses is investigated and its application in automated processes considered.
Infrared Studies on Rotational Isomerism. V. 2-Nitroethanol
Authors: Giguère Paul A. , Kawamura Tokiji
Published: May 2006

The i.r. spectra of 2-nitroethanol in the three physical states were measured between 4000 and 250 cm−1. The liquid and the crystal were also studied in Raman effect. In all three states the molecules exist as gauche and trans isomers, the former being stabilized by a weak intramolecular hydrogen bond. Definite evidence for a third isomer, previously reported in dilute CCl4 solutions, could not be ascertained from the vapor spectra as a function of temperature. On the other hand this study revealed appreciable decomposition of the vapor above 80 °C, with formation of nitroethylene and also some aldehyde. For that reason it was not possible to evaluate the enthalpy of isomerization. The difficulty of securing a pure sample of 2-nitroethanol is emphasized. Only one crystalline phase was obtained.
Synthesis of Some Stable 7-Halo-1,4-thiazepines. Potential Substituted Penam Precursors
Authors: Blondeau P. , Berse R. Gauthier C. , Gravel D.
Published: May 2006

The synthesis of some new 3-carbomethoxy-5-oxoperhydro-1,4-thiazepines is described. Halogenation studies led to the preparation of three potential substituted penam ring precursors: 6,7-dibromo-3-carbomethoxy-5-oxoperhydro-1,4-thiazepine, 3-carbomethoxy-6,7-dichloro-5-oxoperhydro-1,4-thiazepine, and 3-carbomethoxy-7-chloro-6,6-dimethyl-5-oxoperhydro-1,4-thiazepine. Preliminary studies on the reactivity of these α-halothioethers showed that methanolysis to the corresponding methoxy-thiazepines may be carried out in nearly quantitative yields in the case of the first two derivatives; the third compound, on the other hand, led to an open-chain dehydrohalogenated product where C-7 is converted to the corresponding dimethyl acetal.
On the Chemistry of the Isomeric Dichlorodiphenylacetaldehydes Related to DDT. Stereoelectronic Effects in the Hydrolysis of their Cyclic Acetals
Authors: McKinney J. D. , Hawk R. E. , Boozer E. L. , Suggs J. E.
Published: May 2006

The chemistry of the isomeric dichlorodiphenylacetaldehydes related to DDT was investigated to aid in delineating their possible role in the metabolism of this pesticide. In the case of the p,p′-isomer, the most important system under consideration, several literature syntheses were shown to be incorrect. The failure of at least one of these methods was attributed to the preferred oxidative involvement of the benzhydryl carbon via rearrangement of a β-hydroxy enol ether which normally led to the isolation of the p,p′-dichlorobenzophenone instead of the desired aldehyde. The o,p′-isomer exhibited chemistry similar to that of the p,p′-isomer although the steric effect of the ortho-substituted chlorine on the benzhydryl proton was notable. The o,o′-isomer was normal in that it did not undergo reactions involving the benzhydryl carbon. Some possible mechanistic and biological implications of the work are discussed.
Sulfur Dioxide Formation in the Photo-oxidation of Methanethiol
Authors: Graham D. M. , Sie Billy K. T.
Published: May 2006

Photolysis of methanethiol in the presence of oxygen has been investigated at 228.8 and 254–265 nm. The major products detected were 2,3-dithiabutane and a liquid, tentatively identified as hydrogen peroxide. The quantum yield of sulfur dioxide was found to be small (3 × 10−5) at 25 °C, increasing only by an order of magnitude at 125 °C. It has therefore been concluded that the reaction between CH3S and oxygen is very slow if it occurs at all.
Shock-Tube Study of Cr* Chemiluminescence During the Induction Period of the C2H2–O2 Reaction
Authors: Gutman David , Matsuda Shimpei
Published: May 2006

The Cr* (a7S–y7P) chemiluminescence at 360 nm during the induction period of the C2H2–O2 reaction was studied behind reflected shock waves. When the reaction gas mixture containing 10 p.p.m. Cr(CO)6, 0.5% C2H2, 1.0% O2, and 98.5% Ar was shock heated to 1650 °K, the emission intensity of Cr* grew exponentially with a growth constant equal to the chain branching constant. This observation indicates that reaction(s) leading to Cr* chemiluminescence involve only one chain carrier during the induction period of the C2H2–O2 reaction. The mechanism of the chemical excitation of Cr is discussed.
A Complex Ion Model for Molten Halides
Authors: Pelton A. D.
Published: May 2006

The formation of complex anions in molten halide systems is treated semi-quantitatively by a discrete complex anion model. The treatment is a more general application and extension of an approach reported previously by the author. By assuming the existence of discrete MY42− tetrahalo complex anions, the model gives good agreement to experimental enthalpies and entropies of mixing and electrical conductivities in a large number of different halide systems of the general formula MY2–AY, where M is a divalent metal, and A is an alkali. Very few adjustable parameters are required. The parameters provide semi-quantitative basicity (or acidity) scales by which molten salts and slags may be classified. The relationships of these basicity scales to ionic radii, ligand field stabilization energies, etc. are shown. General thermodynamic and mathematical aspects of the problem of complexing are discussed, particularly as regards the proper method of calculating the degree of dissociation of the complexes.
Chaleur de dilution de solutions aqueuses d'acide polyacrylique, de son sel de sodium et de l'acide propionique
Authors: Cartier Jean-Pierre , Daoust Hubert
Published: May 2006

With a Tian–Calvet microcalorimeter, heats of dilution at 25 °C have been measured for aqueous and acid (0.2 N HCl) solutions of polyacrylic acid and of propionic acid, and for aqueous solutions of the sodium salts of polyacrylic acid. The results are interpreted in terms of the change in structure of water resulting from the lengthening of the solute molecule. The heat of dilution of moderately concentrated solutions of sodium polyacrylate can be explained by the theory of Eigen and Wicke.
Differential Thermal Analysis Studies on Ag2CO3
Authors: Nagy G. D. , Vergette J. B. , Connolly J. P.
Published: May 2006

The decomposition and phase transitions that occur during the heating and cooling of Ag2CO3 were studied by differential thermal analysis at heating rates of 7 to 14° per min. In helium, the Ag2CO3 was partially decomposed evolving CO2 (7–35% depending upon the method of preparation) giving rise to peaks at 190 to 200°; at 350 to 400°, two endothermic peaks were observed at which CO2 and O2 were given off simultaneously, leaving silver metal. In CO2 the initial partial decomposition gave rise to a peak at about 265°. The partially decomposed Ag2CO3 (Ag2O•nCO2, where n is less than one) gave the same X-ray diffraction pattern as Ag2O, which slowly converted to that for Ag2CO3 if left exposed to air or CO2. The Ag2O•nCO2 undergoes two distinct "reversible" phase transitions at 180 and 197° on subsequent reheatings. The Ag2O•nCO2 behaves like a clathrate-type of structure in which CO2 can be entrapped in the Ag2O lattice.
Collisional Deactivation Rates of Electronically Excited Molecular Ions. II
Authors: Mackay G. I. , March R. E.
Published: May 2006

Total deactivation rate constants have been determined for N2+(B2Σu+) and the (A2Πu) and (B2Σu+) states of CO2+ with a number of quenchers. The energy specific total deactivation rate constant is compared to the total radiative lifetime of the excited species. A particular novelty of the technique is that it does not require a complete knowledge of the formation modes for the excited species. The results are compared with theoretical values obtained from the ion-induced dipole model. Individual deactivation rate constants are presented for N2+(B2Σu+) ions in the v = 0, 1, and 2 vibrational levels quenched by N2, O2, H2, and CO2; and for the(A2Πu) and (B2Σu+) states of CO2+ quenched byCO2, N2, O2, NO, and H2. Charge transfer is the most probable mode of deactivation except in the CO2+–H2 reactions where H-atom abstraction is more probable.
Selectivity in NBS Bromination. I. The Reaction of Methyl Enol Ethers of Cyclohexane-1,3-diones. A Reexamination
Authors: Awang D. V. C. , Vincent A. , Wilson W. L. , Avdovich H. W.
Published: May 2006

The n.m.r. spectral analysis utilising solvent- and Eu(DPM)3-induced chemical shifts demonstrates that the reaction of N-bromosuccinimide with the methyl enol ethers of cyclohexane-1,3-dione and dimedone leads to bromine substitution at the carbon atom allylic to the olefinic bond, and not at the olefinic site or α to carbonyl, respectively, as previously claimed.
Etude des mouvements de molécules linéaires en phase liquide par analyse du profil des bandes d'absorption infrarouge.: II. Bande v3 du sulfure de carbonyle
Authors: Bize A. M. , Soussen-Jacob J. , Vincent-Geisse J. , Legay D. , Perchard J. P.
Published: May 2006

The band width and profile of v3 mode of carbonyl sulfide (OCS) dissolved in about 30 solvents have been examined. The study of temperature broadening permits the separation of the vibrational and rotational effects and the determination of the potential barrier to rotation. Correlation functions have been plotted from the experimental results; the mean squared torques acting on carbonyl sulfide in various solvents have been calculated from the second and the fourth moments. The obtained results bear evidence of a dominant rotational effect for solutions in saturated hydrocarbons while, for the other solvents, vibrational broadening proves important.
Chemistry and Synthetic Utility of α-(Dimethylamino)benzylidene and 1-(Dimethylamino)ethylidene Acetals
Authors: Hanessian S. , Moralioglu E.
Published: May 2006

N,N-Dimethylbenzamide and N,N-dimethylacetamide dimethyl acetals react with vicinal cis-diols to give cyclic α-(dimethylamino)benzylidene and 1-(dimethylamino)ethylidene acetals respectively. In aqueous methanol, the acetals are hydrolyzed to the original diol. At pH 4–5, cleavage occurs to give benzoate and acetate esters, presumably by the sequential formation of acyloxonium and orthoacid intermediates. The acetals are thus useful as temporary protecting groups for vicinal diols and can be used for indirect, selective benzoylation and acetylation. They are compatible with the reaction conditions of acylation (acetylation, benzoylation, tosylation) and nucleophilic displacement [Formula: see text]
Addition of ICl to Norbornene. The Preparation and Photochemical Isomerization of syn-7-Iodonorbornene
Authors: Werstiuk N. H. , Vancas I. , Warkentin J. , Clark F. R. S.
Published: May 2006

The addition of ICl to norbornene in the presence of pyridine yields nortricyclyl iodide (1c), endo-2-chloro-exo-3-iodonorbornane (2c), and syn-7-iodo-exo-2-chloronorbornane (3b) as the major products. Base-catalyzed elimination of HCl from 3b yields syn-7-iodonorbornene (6a) which is isomerized photochemically to anti-7-iodonorbornene (6b).
Paniculatin, a New Coumarin from Murraya paniculata (L.) Jack
Authors: Steck Warren
Published: May 2006

The coumarin derivatives osthol and coumurrayin were isolated from foliage of Murrayapaniculata (Rutaceae). In addition, a new coumarin, paniculatin, was obtained. By means of chemical degradation and u.v., n.m.r., and mass spectroscopy, the new compound was identified as 7-methoxy-8-(isovaleryloxy-2-keto-3-methylbutyl)coumarin.
Isomérisation des époxydes
Authors: Jankowski Kryzsztof , Daigle Jean-Yves
Published: May 2006

not available
A Novel Phosphate Protecting Group for Oligonucleotide Synthesis
Authors: Wightman R. H. , Narang S. A. , Itakura K.
Published: May 2006

2-Phenylmercaptoethanol is found to be a very stable phosphate protecting group during oligonucleotide synthesis. However, when necessary it can be easily removed, after activation.
Measurements of Deuterium Chemical Shifts by 1H–{2H} INDOR Spectroscopy
Authors: Campbell J. R. , Hall L. D. , Steiner P. R.
Published: May 2006

Heteronuclear 1H–{2H} INDOR spectroscopy has been used to measure the deuterium chemical shifts of acetone-d5 dimethylsulfoxide-d5, and of 1,2:5,6-di-O-isopropylidene-α-D-allofuranose-3-d.
Valence-shell Transitions in the Vacuum-Ultraviolet Spectra of Fluorobenzenes
Authors: Gilbert R. , Sauvageau P. , Sandorfy C.
Published: May 2006

The vacuum–ultraviolet spectra of a nearly complete series of fluorinated benzene derivatives were measured. The assignments of π* ← π and σ* ← σ valence-shell type transitions are discussed as well as the influence that the fluorine substituents exert on these.
A Critical Test of the Hammett Acidity Function
Authors: Yates Keith , Shapiro Stanley A.
Published: May 2006

The applicability of the H0 acidity function to primary aromatic amines in general has been tested by using a set of five aniline indicators bearing no nitro-substituents. Up to 45% sulfuric acid the scale generated by these bases is the same (within experimental uncertainty) as that based entirely on nitro-anilines.
Rearrangement Studies with 14C. XXXV. The Absence of Isotopic Scrambling in the Photolysis of 2-14C-3-Phenylpropionaldehyde.
Authors: Lee C. C. , Unger D.
Published: May 2006

The photolytic decarbonylation of 2-14C-3-phenylpropionaldehyde gave isotopically unrearranged β-l4C-ethylbenzene, indicating that under the experimental conditions employed, there was no detectable amount of 1,2-phenyl shift in the reaction.
The Role of HgH in the Hg(63P0) Photosensitized Decomposition of the Alkanes and Hydrogen
Authors: Vikis A. C. , Roy D. J. Le
Published: May 2006

Mercury hydride, arising from the Hg(63P0) photosensitized decomposition of hydrogen containing molecules, has been detected in the presence of H2, D2, CH4, C2H6, C3H8, and n-C4H10. For the alkanes, this is the first experimental evidence that HgH is formed in the primary process Hg(63P0) + RH → HgH + R.
Thermal Decomposition of Methyl Titanium Chlorides
Authors: McCowan J. D. , Hanlan J. F.
Published: May 2006

The thermal decomposition of CH3TiCl3 and (CH3)2TiCl2 in C2Cl4 and C6H6 has been examined over the range 20 to 110 °C under a nitrogen atmosphere utilizing n.m.r. spectroscopy, mass spectroscopy, and elemental analysis. The reaction products are found to be the result of at least four separate, simultaneous, and competing reactions.
Kinetic Evidence for Predominant Oxygen Protonation of Amides
Authors: Smith Clinton R. , Yates Keith
Published: May 2006

Comparison of rate data for the acid-catalyzed hydrolysis of amides, and model compounds for O- and N-protonated amides, provides strong evidence that amides protonate predominantly on oxygen in dilute as well as in concentrated aqueous acids, contrary to a recent proposal that the protonation sites are different in the two media.
Steroids and Steroidases. XIII. Illustrations of the Potential of Lithiodithiane–Epoxide Reactions for the Stereospecific Introduction of Substituents into the Steroid Nucleus
Authors: Jones J. Bryan , Grayshan Roger
Published: May 2006

The reactions of 2-lithio-1,3-dithiane with both 2α,3α- and 2β,3β-oxiranyl-5α-cholestane have been used to prepare both epimers of 2-methyl-3-oxo- and 3-methyl-2-oxo-5α-cholestane. The results obtained illustrate the potential of the dithiane-epoxide route as an attractive and versatile general procedure for the stereospecific introduction of substituents into alicyclic compounds. Furthermore, since for six-membered ring compounds the epoxide ring is opened in a trans-diaxial manner, the substituent is introduced into the thermodynamically less stable orientation. Subsequent isomerization to the preferred equatorial isomer is thus possible and accordingly, both epimers are obtainable from the same synthetic sequence.
Reactions of 1,2,5-Triphenylphosphole and its Oxide, Sulfide, and Selenide with some Transition Metal Halides
Authors: Budd D. , Chuchman R. , Holah D. G. , Hughes A. N. , Hui B. C.
Published: May 2006

Reactions of 1,2,5-triphenylphosphole (TPP) and 1,2,5-triphenylphosphole oxide (TPPO), sulfide (TPPS), and selenide (TPPSe) with some transition metal halides have been studied in dry, oxygen-free organic solvents. The reactivity of these ligands is clearly a function of the oxidation states of the metal, with the order being M(II) < M(III) < M(IV) < M(V). For example the ligands do not react with the metal(II) halides (Mn, Fe, Ni), while rapid reactions occur with niobium(V) and tantalum(V). Iron(III) and copper(II) are both reduced by TPP. The complexes resulting from these studies are mostly simple adducts of the various metal halides, although other species such as phospholium salts [Formula: see text] and oxytrichloride adducts, MOX3•TPPO(M = Nb, Ta) are also described. In the phospholium salts, the phosphole ring is protonated at the phosphorus atom which is in direct contrast to pyrrole derivatives. The origin of the oxygen atom in the oxytrichloride complexes is discussed and compared with data on the analogous triphenylphosphine oxide systems, where cleavage of the P=O bond occurs.
Photoreactions of Nitroso Compounds in Solution. XXI. Stereochemical Course of Photoaddition of Nitrosamines to some Cyclic Olefins and Conformational Isomers Generated by A1,3-Interaction
Authors: Chow Y. L. , Chen S. C. , Pillay K. S. , Perry R. A.
Published: May 2006

The results of the photoadditions of N-nitrosopiperidine and N-nitrosodimethylamine to three substituted cyclohexenes are discussed in terms of an "electrophilic" free radical attack of the aminium radicals generated from the photolysis of the nitrosamines. The photoaddition to 4-t-butylcyclohexene gave all four possible oximes; the axial approach of the aminium radical was preferred over the equatorial approach. The photoadditions to 3-methylcyclohexene are highly stereoselective giving oxime pairs 1–2 and 4–5. Both oximes in each pair have 2-amino and 6-methyl substituents in trans-relation; but locked in the alternative conformations through A1.3 interaction of the oximino group. In this addition the aminium radical almost exclusively approaches the C-1 carbon of the most stable conformer from the axial side. The steric hindrance to all possible axial and equatorial approaches to conformers of olefins have been compared. Piperidinium radicals, however, abstract an allylic hydrogen from Δ9,10-octaline since the steric hindrance in the addition process is too great to overcome. The hydrogen abstraction process leads to an intermolecular hydrogen–nitroso group exchange reaction which is similar to that in the photolysis of nitrosamides. A pathway is suggested to account for the generation, insitu, of the heteroannular diene 28 from which oxime 17 could be derived by photoaddition in 1,4-mode.
Electron Spin Resonance of γ-Irradiated Acetylacetone in Adamantane Matrix
Authors: Wolodarsky W. H. , Wan J. K. S.
Published: May 2006

Electron spin resonance spectrum is observed when samples of solid adamantane doped with acetylacetone are γ-irradiated at room temperature. The spectrum is interpreted due to an enolized allylic radical CH3-COCHC(OH)CH2.
Microwave Spectrum, Dipole Moment, and Intramolecular Hydrogen Bond of 2-Methoxyethanol
Authors: Buckley Paul , Brochu Mireille
Published: May 2006

The minimum energy conformation of 2-methoxyethanol (CH3OCH2CH2OH) has been determined from an analysis of its microwave spectrum. The rotational constants of the normal species are: A = 12982.35, B = 2742.48, and C = 2468.10 MHz; the dipole moment components are μa = 2.03, μb = 1.15, [Formula: see text] and μ = 2.36 ± 0.03 D. For the CH3OCH2CH2OD species: A = 12385.71, B = 2724.74, and C = 2431.42 MHz. The conformation consistent with this data is gauche about each of the C—C, C—O(H) and C—O(ether) bonds, having dihedral angles of 57 ± 3°, 45 ± 5°, and 8 ± 3°, respectively. This distorted conformation is one in which the hydroxyl hydrogen atom is approximately aligned with the nearest sp3 lone pair electrons of the ether oxygen atom. Transitions in three excited torsional states have also been observed but no other rotational isomer was detected.
Quenching of Fluorescence of Chloropentafluoroacetone by Saturated Hydrocarbons
Authors: Yarwood A. J.
Published: May 2006

Saturated hydrocarbons can quench the electronically excited singlet state of a simple ketone in the gas phase. Measurements on the quenching of the fluorescence yield of chloropentafluoroacetone at 23 °C show that different saturated hydrocarbons can deactivate the excited singlet state with varying efficiencies. The quenching rate constants are reported and possible relationships considered.
Search for the N–N2 Exchange Reaction
Authors: Lyon Richard K.
Published: May 2006

Since N3 is a stable molecule, one might expect the N–N2 exchange reaction to occur readily; however, if the reaction exists, its rate constant is ≤8 × 106 cc/mols at 1000 °C. An explanation in terms of spin conservation is discussed.
Vibrational Spectra of SiH4 and SiD4–SiH4 Mixtures in the Condensed States
Authors: Fournier R. P. , Savoie R. , The Nguyen Dinh , Belzile R. , Cabana A.
Published: May 2006

not available
Etude spectroscopique des dérivés du peroxyde d'hydrogène. V. Les percarbonates KHCO4 et K2C2O6
Authors: Giguère Paul A. , Lemaire Denis
Published: May 2006

The two percarbonates KHCO4 and K2C2O6 were prepared by chemical or electrolytic methods in order to measure their infrared and Raman spectra. The permonocarbonate is unstable and very hygroscopic. The [Formula: see text] anion forms quite strong intermolecular hydrogen bonds, although somewhat less so than the bicarbonate anion. As for the [Formula: see text] anion, the rather small number of its infrared and Raman bands suggests a planar and centrosymmetric configuration. In both percarbonates the O—O vibration shows nearly the same frequency as in H2O2, presumably due to coupling with neighboring vibrations. For comparison purposes the peroxyhydrate K2CO3.3H2O2 was studied likewise.
The Constituents of Naucleadiderrichii. Part IV. Miscellaneous Substances; Biogenetic Considerations
Authors: McLean Stewart , Murray D. G.
Published: May 2006

Basic substances isolated from the bark of Naucleadiderrichii and not placed in one of the three earlier alkaloidal categories include an alkaloid, C21H26N2O4, designated ND-370, and an amorphous material that appears to be an alkaloidal glycoside. Also isolated were the non-basic substances benzamide and antiarol (3,4,5-trimethoxyphenol), and two monoterpenoids given the names naucleol and naucledal; the spectroscopic characteristics of naucleol, C9H14O3, can be accounted for by structure 1a, and those of naucledal, C10H12O4, by structure 2a, but the data do not establish the structures unequivocally. The structural relationships between the various constituents isolated from this plant and their possible biogenetic implications are discussed.
Complex Fluorides with Perovskite Structure: Thermal Analyses, Calorimetry, and Infrared Spectra
Authors: Patil K. C. , Secco E. A.
Published: May 2006

Thermal decomposition and infrared spectral results are reported for complex fluorides of the type NH4MF3 where M = Cd, Zn, Cu, Ni, Co, Mn.
The Electrochemical Reduction of Compounds with the Group. III as-Triazines
Authors: Pinson Jean , M'Packo Jean-Pierre , Vinot Nicole , Armand Joseph , Bassinet Philippe
Published: May 2006

The electrochemical reduction of as-triazines 3-one or -thione leads to a 1,4-dihydro derivative which rearranges into a 4,5-dihydro compound which is further reducible to an imidazolone or a tetrahydro as-triazine 3-one. In the case of simple as-triazine the 1,4-dihydro compound rearranges either to a 1,2- or to a 4,5-dihydro compound. This last derivative can be reduced to an imidazole or a tetrahydro as-triazine. The mechanisms are discussed.
Hindered Rotation in Carbamates: A Kinetic Anomaly
Authors: Inglefield P. T. , Kaplan S.
Published: May 2006

The energy barriers to hindered rotation in two carbamate structures have been measured by total line-shape analysis of the high resolution n.m.r. spectrum. Conclusions are presented concerning the influence of solvent on the nature of the transition state in such processes and the existence of frequency factors outside the normal expected range for a unimolecular transformation.