bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrothermal preparation of magnetite from iron chelates
Authors: Booy Meindert , Swaddle Thomas Wilson
Published: May 2006

The hydrothermal decomposition of iron(II) or iron(III) aminopolycarboxylate complexes can produce well-crystallized, stoichiometric Fe3O4. Best results were obtained when 0.1 m nitrilotriacetatoiron(III) was decomposed under N2 in 0.2–0.4 m NaOH at 497 K for 70 h or more.
Aminocyclitols. 2,5-Dideoxystreptamine and derivatives
Authors: Kavadias Gerry , Velkof Stephan , Belleau Bernard
Published: May 2006

2,5-Dideoxystreptamine (11) was synthesized via the cyclic hydrazine intermediate 10, itself obtained by reaction of the cis-1,4-diepoxycyclohexane (7) with hydrazine. Compound 11 was converted into d,l-N-ethoxycarbonyl-2,5-dideoxystreptamine (12) and the latter resolved into its optical isomers (1N-ethoxycarbonyl- and 3N-ethoxycarbonyl-2,5-dideoxystreptamines 16 and 14). 1,6-.N,O-carbonyl-3N-ethoxycarbonyl-2,5-dideoxystreptamine (1) and 3,4-.N,O-carbonyl-1N-ethoxycarbonyl-2,5-dideoxystreptamine (2) were synthesized from 14 and 16 respectively. A practical process for the preparation of cis-1,4-diepoxycyclohexane is described.
The microwave spectrum and structure of cyclopropyl carbinol. II. Four deuterated forms
Authors: Brooks W. V. F. , Sastri C. K.
Published: May 2006

The microwave spectra of four deuterated species of cyclopropyl carbinol have been studied. The rotational constants A, B, and C (in MHz) are: C3H5CHaDbOH, 11 742.86, 3205.17, 2830.41; C3H5CDaHbOH, 11 853.44, 3188.10, 2878.28; C3H5CHaDbOD, 11 321.30, 3145.87, 2762.23; C3H5CDaHbOD, 11 433.85, 3129.30, 2809.81. The measured dipole moments of C3H5CHaDbOH and C3H5CHaDbOD are, respectively, 1.91 and 1.873 D. This confirms the essential details of the conformation proposed in an earlier paper.
The chemistry of some 6-methyl-4-hydroxy-2-pyridones
Authors: Findlay John A. , Tam Wah Hung John , Krepinsky Jiri
Published: May 2006

Some oxidations and reductions of 4-hydroxy-6-methyl-2-pyridones are discussed. A remarkable reduction–cyclization of 4-hydroxy-3-(1′-hydroxy-2′-oxopropyl-)-6-methyl-2-pyridone (2b) produces the novel system 10a.
Fluxional behaviour of potentially bidentate phenanthroline, naphthyridine, and phthalazine ligands in palladium complexes
Authors: Brandon J. Bradley , Collins Michael , Dixon Keith R.
Published: May 2006

The synthesis of a series of palladium complexes, cis-[PdCl(PEt3)2L][Y]; L = 1,10-phenanthroline, 1,8-naphthyridine, or phthalazine; Y = BF4− or ClO4−; is reported. Variable temperature 1H and 31P nmr spectra are discussed in terms of square planar structures in which the heterocyclic ligands are essentially monodentate and fluxional with the palladium exchanging between the two nitrogen atoms. Above ca. −10 °C a dissociative exchange mechanism operates in all three complexes and, when L = 1,10-phenanthroline or 1,8-naphthyridine, exchange continues at lower temperatures by an intramolecular process.
Fonction d'acidité relative aux amines secondaires: un critère de validité du postulat de Hammett
Authors: Carpentier Jean-Marie , Lemetais Patrick
Published: May 2006

An acidity function has been determined spectrophotometrically in aqueous sulphuric acid, at 298 K, by using seven secondary amine indicators. This function is the same as that based on primary amines and so differs from that relative to tertiary amines. Therefore, the first two types of amines are the indicators of the same acidity function. It is concluded that for a given acidity function, the Hammett postulate is only verified for all the compounds characterized by the same value of a τ structural parameter: apparent ratio of solvation.
Nitration of 1-chloro-2,3-dimethylbenzene in acetic anhydride. Formation and rearomatization of adducts
Authors: Fischer Alfred , Greig Colin Campbell
Published: May 2006

Nitration of l-chloro-2,3-dimethylbenzene in acetic anhydride gives the cis and trans isomers of 3-chloro-4,5-dimethyl-4-nitrocyclohexa-2,5-dienyl acetate (29%) and l-chloro-2,3-dimethyl-4-nitro- (46%), -5-nitro- (5%), and -6-nitrobenzene (20%). In formic acid and acidified methanol, exchange of acetate for formate and methoxyl, respectively, occurs and the diastereoisomers of 3-chloro-4,5-dimethyl-4-nitrocyclohexa-2,5-dienyl formate and methyl ether, respectively, are formed. Rearomatization of each isomer of 3-chloro-4,5-dimethyl-4-nitrocyclohexa-2,5-dienyl acetate in acetic acid results in initial isomerization to form the pair of diastereoisomers and subsequent elimination of nitrous acid to form 3-chloro-4,5-dimethylphenyl acetate. In 25% trifluoroacetic acid in deuteriochloroform elimination of acetic acid and migration of the nitro group to form 1-chloro-2,3-dimethyl-4-nitro-benzene and a lesser amount of its 6-nitro isomer is the dominant reaction. In the presence of mesitylene the formation of the nitro derivatives is suppressed and 3′-chloro-2,4,4′,5′,6-pentamethylbiphenyl is obtained. It is proposed that cyclohexadienyl cations are significant intermediates in ail of the reactions. Pyrolysis of the adducts gives 1-chloro-2,3-dimethylbenzene as the major product.
Re-examination of the Kirkwood–Westheimer theory of electrostatic effects. II. Possible conformations of α,ω-amino-acids in aqueous solutions, as deduced from dissociation constants
Authors: Edward John T. , Farrell Patrick G. , Job John L. , Poh Bo-Long
Published: May 2006

The first and second dissociation constants of the ten homologous a, α,ω-amino-acids [Formula: see text] have been determined by a potentiometric method at different temperatures, and hence the thermodynamic parameters ΔG0, ΔH0, and ΔS0 were computed. Calculation by Kirkwood–Westheimer theory of ΔG10 for the first (carboxyl) dissociation, assuming the conformation of the polymethylene chain to be intermediate between the random-coil and the fully extended conformation, gives results in good agreement with experiment for the longer chains. A similar calculation of ΔG20 for the second (ammonium) dissociation gives results in fair agreement with theory for the very long chains (n = 7–10), but in disagreement for shorter chains. A tentative explanation based on electrostatic effects on hydration of the ammonium group is advanced.
Base-catalyzed enolization of 2,5-norbornanediones. Evidence for homoenolic assistance
Authors: Werstiuk Nick Henry , Taillefer Roland , Banerjee Sujit
Published: May 2006

The rate enhancements relative to the monoketones, for base-catalyzed exo and endo hydrogen isotope exchange in 2,5-norbornanedione (2), 3,3-dimethyl-2,5-norbornanedione (3), and 1,3,3-trimethyl-2,5-norbornanedione (4) have been determined at 25 ± 0.05 °C in 60% dioxane–40% D2O. After the increase in rate due to the inductive and strain effects of the second carbonyl group is taken into account, the homoenolic-assistance factors are extracted from the overall rate enhancements: for exo exchange in 2,3, and 4, the factors are 13, 39, and 32; for endo exchange in 2,3, and 4, the factors are 26, 64, and 71, respectively.
Construction of a novel generator for use in HF adsorption studies
Authors: Kimmerle Frank M. , Archambault A. , Dube Ghyslain
Published: May 2006

An HF generator based on the dissociation pressure of an alkali bifluoride is described. Sodium bifluoride salt was found to yield HF pressures of the order of 0.001 to 0.3 mm in the temperature range 60 to 135 °C due to the equilibrium [Formula: see text]. The HF generator allows a dry carrier gas (typically N2) to pass through a thermoregulated chamber filled with the crystalline bifluoride and furnishes HF concentrations from 5 to 1000 ppm at flowrates up to 5 ℓ/min for periods up to one year. The HF concentrations thus generated were stable to within 1% after a 40 min warm up period. Described also is the associated control system which allows the operator to send alternately dry carrier gas with or without trace HF concentration to an external cell or analyser.
Influence des groupes tert-butyle, triméthylsilyle et triméthylgermyle sur la stéréochimie de réactions d'addition en série cyclohexénique. II. Epoxydation des dérivés vinyliques et ouverture des époxydes par LiAlH4, MeOH/H+ et H2O/H+
Authors: Richer Jean-Claude , Poirier Marc-André , Maroni Yvette , Manuel Georges
Published: May 2006

Epoxidation of 1-tert-butyl (1a), 1-trimethylsilyl (1b), and 1-trimethylgermyl (1c) 4,4-dimethylcyclohexenes is described and the stereochemistry of the ring opening of the resulting epoxides (3a, 3b, 3c) by lithium aluminium hydride as well as methanol and water in acidic medium is examined. The regiochemistry of the ring opening of 3a is completely reversed, in the case of 3b and 3c, by the electronic effects of the trimethylsilyl and trimethylgermyl groups.
Phase-transfer catalyzed synthesis of activated cyclopropanes
Authors: McIntosh John M. , Khalil Hamdy
Published: May 2006

The phase-transfer catalyzed condensation of diethyl bromomalonate (7d) with Michael acceptors 8–12 leads to cyclopropanes in high yields. More hindered acceptors and other haloesters do not react, while condensation of 7d with crotonaldehyde leads to a 2:1 adduct via a subsequent Darzens condensation. The synthetic potential of the products is also outlined.
Fluorinated alkoxides. Part XII. Studies on potentially tridentate fluorinated diols; zwitterionic and five-coordinate complexes of Ni2+ and Cu2+
Authors: Loeb Stephen J. , Martin John W. L. , Willis Christopher J.
Published: May 2006

The complexing ability towards Ni2+ and Cu2+ of the potentially tridentate ligands HOC(CF3)2CH2C(O)CH2C(CF3)2OH, HOC(CF3)2CH2CH(OH)CH2C(CF3)2OH, and HOC(CF3)2CH2CH2N:C(CH3)CH2C(CF3)2OH has been studied. The first two act as bidentate ligands, uninegative or dinegative according to the extent of ionization of the fluorinated alcohol groups; when both were ionized, the complexes had a zwitterionic structure. The third ligand was exclusively tridentate in its complexes; this difference is ascribed to its greater flexibility. Both four- and five-coordinate complexes of nickel were observed, the latter being produced either by choice of co-ligands or by solvation, but no six-coordinate complex was formed in this series. Limitations on coordination for the metal are ascribed to steric effects.
Phenyl phosphorodichloridate in the synthesis of cyclic phosphate diesters of biological interest
Authors: Penney C. L. , Belleau B.
Published: May 2006

The general usefulness of phenyl phosphorodichloridate (PPDC) in the synthesis of non-nucleoside cyclic phosphates is described. The method is illustrated with several examples including cyclic phosphates incorporating six to nine members. However, the reagent could not be used for the preparation of five-membered cyclic phosphates or 3′,5′-cycloadenylic acid (cAMP) from adenosine. Based on a number of observations, the conclusion was reached that PPDC cannot be used for the synthesis of strained or reactive cyclic phosphates. A convenient synthesis of cis- and trans-2-hydroxycyclopentanemethanol and a simple, quantitative method of separation of the two isomers is described. A number of cyclic phosphates were tested as substrates and inhibitors for cyclic purine phosphodiesterase and protein kinase.
ESCA studies of the uracil base. The effect of methylation, thionation, and ionization on charge distribution
Authors: Peeling James , Hruska Frank E. , McKinnon David M. , Chauhan Mohender S. , McIntyre N. Stewart
Published: May 2006

ESCA core line spectra have been obtained for uracil, the thiouracils, and some 1-methyl and 3-methyl analogues. In addition, anionsof the mono methyl derivatives have been prepared and studied. Core line binding energy shifts for all solid compounds, ionic and neutral, are found to correlate reasonably with CNDO/2 charge distributions calculated for the free molecules. The correlation line for ionic molecules is offset from that for neutrals by a constant factor ascribed to an intermolecular potential term. Specific effects of methylation, thionation, and ionization on the charge distribution are described. Methylation at either nitrogen leads to electron release from the nitrogen into the ring. Thionation results in a decrease in the charge at the site of thionation, while the electron density at adjacent atoms increases. The alterations in charge density are somewhat different for neutral and ionic compounds. Upon ionization of either N(1) or N(3) sites, much of the residual charge is located on the keto oxygens. The presence and position of the thionated carbon during ionization mainly affects the change in electron density at the C(6) position.
Oxidative ozonolysis of a polyunsaturated fatty acid in BF3–MeOH medium
Authors: Sebedio J. -L. , Ackman R. G.
Published: May 2006

The ozonolysis of the methyl ester of a typical naturally-occurring polyunsaturated acid (linoleic) in BF3–MeOH medium was investigated. Referring only to difunctional products, yields of the principal reaction product, dimethyl azelate, were approximately 96%. The characteristic secondary product, the dimethyl ester of the acid with one less carbon, was formed only to the extent of 2% or less. Other intermediates and difunctional secondary products which have been identified include the C9 methyl half-ester, half-aldehyde, and the corresponding dimethyl acetal. Dimethyl malonate was not recovered quantitatively under the conditions employed. Monofunctional products qualitatively and quantitatively duplicated the difunctional products.
Solvent effects on the structure of SN2 transition states
Authors: Westaway Kenneth Charles
Published: May 2006

Two research groups have used heavy atom leaving group kinetic isotope effects to determine how the structure of an SN2 transition state is affected by a change in solvent. Two completely different types of behaviour were observed in these studies. In one case, the leaving group kinetic isotope effect, and thus the transition state structure, changed markedly when the solvent was varied over a reasonably narrow range. In the other study, the leaving group kinetic isotope effect (transition state structure) remained constant over a wide range of solvents. A model describing the interaction between solvent molecules and SN2 transition states is developed and a SolvationruleforSN2reactions which rationalizes the different experimental results is explained and justified. Finally, predictions based on the solvation rule are shown to be in agreement with the results of theoretical calculations of solvent effects on SN2 transition states and secondary α deuterium kinetic isotope effect measurements.
Standard thermodynamic transfer functions from water to water + acetone mixtures for a n-nonylcarbon chain attached to different ionic groups
Authors: Bury Raymond , Treiner Claude
Published: May 2006

The standard enthalpy of transfer of trimethyldecylammonium bromide, tetramethylammonium bromide, methyl and decylsodium sulfate have been determined from water to water + acetone mixtures from calorimetric measurements at 298.15 K. The standard entropy function has been calculated using standard Gibbs free energy of transfer data for the same compounds. It is shown that the standard enthalpy and entropy of transfer of a n-nonylhydrocarbon chain attached to the sulfate or to the trimethylammonium groups are quite different whereas the standard Gibbs free energy functions are practically equal in the mixed solvents. It is concluded that the sign of the charge on the ionic groups is responsible for this behaviour and that the influence of this effect extends to a large number of solvent molecules. It is suggested that a similar effect may contribute to the standard enthalpy of so called reference ions: e.g. tetraphenylboron ion casting some doubt on the reliability of these extrathermodynamic approaches at least in mixed solvents, as far as the standard enthalpy function is concerned.
Synthesis of two in vivo metabolites of N-(n-propyl)phentermine
Authors: Coutts Ronald T. , Benderly Abraham , Mak Allan L. C. , Taylor Wesley G.
Published: May 2006

The phenolic metabolite, 1-(4-hydroxyphenyl)-2-methyl-2-(n-propylamino)propane (1e) was prepared by a Ritter reaction from either 3-(4-methoxyphenyl)-2-methyl-1-propene or 3-(4-methoxyphenyl)-2-methyl-2-propanol and propionitrile. Three other products of the Ritter reaction were isolated and identified by interpretation of their mass spectra. Another phenolic metabolite, 1-(4-hydroxy-3-methoxyphenyl)-2-methyl-2-(n-propylamino)propane (1f) could not be prepared by a Ritter reaction but was obtained from the product of the reaction between 3-(4-benzyloxy-3-methoxyphenyl)-2-methyl-1-propene and iodine isocyanate.
C-Stannane derivatives of carbohydrates
Authors: Hall Laurance D. , Steiner Paul R. , Miller Diane C.
Published: May 2006

Triphenyltin lithium (1) was reacted separately with 1,2:3,5-di-O-methylene-6-O-tosyl-α-D-glucofuranose (2), with methyl 2,3-anhydro-4,6-O-benzylidene-α-D-allopyranoside (4), and with methyl 2,3-anhydro-4,6-O-benzylidene-α-D-mannopyranoside (6), to form in each case a sugar-stannane derivative having a stable carbon-tin bond. These products have been studied by 1H and 13C nmr spectroscopy.
Circular dichroism of palladium(II) and platinum(II) diamine complexes
Authors: Sullivan E. A.
Published: May 2006

An identifiable relationship exists between the absolute configuration of chiral diamine ligands and the circular dichroism of their complexes with palladium(II) and platinum(II). Complexes which contain simple C-substituted diamines with the R-absolute configuration show positive circular dichroism in the region associated with the 1A1g → 1Eg transition, both in solution and the solid state. There is no general consistency in the sign of the 1A1g → 1A2g transition, and only for solution does the sign of the net circular dichroism show a correlation with the absolute configuration of the ligands.
On the syntheses and the optical properties of optically active 2-pyrazoline compounds
Authors: Mukai Makoto , Miura Takashi , Nanbu Masahiro , Yoneda Toshinobu , Shindo Yohji
Published: May 2006

Optically active 2-pyrazolines were synthesized and their optical properties were studied using various spectroscopic techniques to investigate the effects of substituents at the 3 and 5 positions of the 2-pyrazoline ring on their optical activity. It was found that in the case of 5-substituted-1,3-diphenyl-2-pyrazoline derivatives, the substituent at the 5 position has considerable influence on the optical activity, whereas in 3-substituted-1,5-diphenyl-2-pyrazoline derivatives, the substituent at the 3 position has no such influence.
Structures and properties of mixtures of branched chain compounds and lecithin: phytol, α-tocopherol (vitamin E), and phytanic acid
Authors: Cushley Robert J. , Forrest Bruce J. , Gillis Anne , Tribe Jenifer
Published: May 2006

Phospholipid bilayers containing branched chain molecules, phytol (1), vitamin E (2), and phytanic acid (3), have been investigated by 31P nmr, esr, and differential scanning calorimetry (dsc).A 31P lanthanide induced shift study indicated varying permeabilities to Pr3+ in the order phytanic acid > vitamin E > phytol > egg yolk lecithin alone; the half-lives (in days) were 0.002, 0.14, 0.83, and 6.5, respectively. The activation energy for Pr3+ permeation through the egg yolk lecithin–phytol membrane was found to be 84.9 ± 0.8 kJ.The following esr order parameters, S3, were obtained using the extrinsic spin label, 5-doxylpalmitic acid, in oriented mixed multibilayers: S3 (1) = 0.29, S3 (2) = 0.50, and S3 (3) = 0.02.Differential scanning calorimetry revealed a lowering of the gel–liquid crystalline phase transition temperature, Tc, as the concentration of incorporated isoprenoid compound increases, with eventual disappearance of the endotherm. Specific entropy, s, calculated for dipalmitoyl lecithin +25 mol% 3 is 126 J kg−1 K−1 compared to s = 114.2 J kg−1 K−1 for 1and s = 85 J kg−1 K−1 for 2.
New heteropolymetallic complexes of platinum(II) with palladium(II)-, gold(I)-, cadmium(II)-, or mercury(II)-chloride
Authors: Bonati Flavio , Clark Howard C.
Published: May 2006

The platinum(II) complex trans-PtCl(PEt3)2(CH=NC6H4-p-CH3) gives 1:1 complexes with CdCl2, HgCl2, and AuCl and a 1:2 trans-adduct with PdCl2, thus showing its character as a monodentate, N-ligand.
On the use of dilution calorimetry in the study of hydrogen-bonding self-association reactions: benzoic acid in benzene
Authors: Krishnan Trichur , Duer Wayne Carlton , Goldman Saul , Fortier Jean-Luc
Published: May 2006

A calorimetric dilution method was applied to the system benzoic acid in benzene at 25 °C. Two different calorimeters, a batch calorimeter (at Guelph) and a flow microcalorimeter (at Sherbrooke), were used in this study. Our results were inconsistent with an ideal monomerdimer model, which had been used in previous calorimetrie studies on this and other similar systems. Our results were consistent with an ideal monomer–dimer–trimer model, for which we obtained: K2 = 625 ± 100 L/mol, [Formula: see text] for the dimerization and trimerization constants respectively, and ΔH20 = −8.52 ± 0.50 kcal/mol, ΔH30 = −13.48 ± 2 kcal/mol for the molar enthalpies of dimerization and trimerization, respectively.
Electron spin resonance observations of photochemically generated contact ammonium ion-pairs of fluoro-substituted ketones
Authors: Chen K. S. , Foster T. , Wan J. K. S.
Published: May 2006

Contact radical ion-pairs of ammonium and fluoro-substituted ketones were generated in photochemical systems and their here-to-fore elusive esr spectra were characterized.
Nuclear analogs of β-lactam antibiotics. XII. 2-Oxodesthiocephalosporins
Authors: Martel Alain , Doyle Terrence William , Luh Bing-Yu
Published: May 2006

Epoxidation of Δ2-1-carbacephems 2 followed by base treatment gave the allylic alcohols 4. Oxidation of 4 gave the 2-keto-Δ3-carbacephem 9 which could be reduced to the isomeric allylic alcohol 7. Conversion of these intermediates to a series of biologically active cephalosporin analogs 13g–l and 14 is described.
Free energy relationship of the equilibrium ionization constants of disulfonyl carbon acids in 80% (w/w) dimethyl sulfoxide – water solvent at 25°C
Authors: Lee Thomas W. S. , Ang Kok-Peng
Published: May 2006

A series of eight carbon acids, α,α-bis(benzylsulfonyl)toluene and 7 substituted α,α-bis-(benzylsulfonyl)toluenes, was synthesized and their equilibrium ionization constants were determined by spectrophotometric measurement in 80% (w/w) dimethyl sulfoxide – water solvent at 25 °C. From a plot of −log K versus σ for the 'well-behaved' substituents and σ− for para-cyano and para-nitro substituents, a ρ value of 2.53 is obtained. The correlation co-efficient is 0.99. Comparing this ρ value with the reported ρ value of 12 for the substituted toluenes in dimethyl sulfoxide, it shows that the acidities of the disulfonyl toluenes are at least 8 to 9 orders of magnitude less sensitive to substituent effects than are the acidities of substituted toluenes implying that, for disulfonyl toluenes, the negative charge on the benzylic carbon is extensively delocalised into the two adjacent sulfonyl groups.
Hydrogenation during ligand exchange reactions between ferrocene and pyrene
Authors: Lee Choi Chuck , Demchuk Ken J. , Sutherland Ronald G.
Published: May 2006

From ligand exchange reactions between ferrocene and pyrene, carried out in the presence of AlCl3–Al, the η6-pyrene-η5-cyclopentadienyliron, η6-4,5-dihydropyrene-η5-cyclopentadienyliron, and η6-4,5,9,10-tetrahydropyrene-η5-cyclopentadienyliron monocations (2, 3, and 4, respectively) as well as the η6-pyrene-trans-bis-η5-cyclopentadienyliron and η6-4,5,9,10- tetrahydropyrene-trans-bis-η5-cyclopentadienyliron dications (5 and 7, respectively) were isolated and identified. A possible mechanism for the partial hydrogenation of the pyrene ligand is discussed.
Nucleophilic reactions of zwitterionic species from deprotonation of η6-arene-η5-cyclopentadienyliron cations
Authors: Lee Choi Chuck , Steele Barry R. , Demchuk Ken J. , Sutherland Ronald G.
Published: May 2006

A variety of η6-arene-η5-cyclopentadienyliron cations in which the arene ligand has an α-carbon substituent containing one or more hydrogens can be deprotonated with base to give the corresponding neutral zwitterionic species. These zwitterions can react insitu as nucleophiles with different substrates, such as CH3I, CO2, and CS2, to give a wide range of synthetic applications.
Spectrophotometric study of ion pairing in diphenylmethyl alkali metals salts
Authors: Buncel E. , Menon B. C. , Colpa J. P.
Published: May 2006

A spectrophotometric study of diphenylmethyllithium (DPM−Li+) and diphenylmethyl-potassium (DPM−K+) in ethereal solvents has yielded information on ion pairing and solvation phenomena in these carbanion systems. Different spectral absorptions are observed, characteristic of two types of contact ion pairs (unsolvated and partially solvated) as well as the solvent separated ion pair species, on varying the cation and solvent. This contrasts with our previous observations with triphenylmethyl alkali metal salts where only contact and solvent separated ion pairs were observed. The effect of 18-crown-6 polyether and the effect of temperature changes on the ion pairing equilibria are evaluated. Thermodynamic parameters are obtained for equilibria pertaining to the DPM−Li+/THF and DPM−Li+/DME systems. The results are discussed in relation to literature reports on ion pairing in these systems as derived from nmr studies. Comparison with triphenylmethyl alkali metal salts yields information relating to delocalization and steric effects on ion pairing.
Nucleophilic substitution in tris(pentafluorophenyl)phosphine
Authors: Hanna Hanna R. , Miller Jack M.
Published: May 2006

Reaction of tris(pentafluorophenyl)phosphine with various nucleophiles (DMF, HMPA, HEPA, diethylformamide, hydrazine, UDMH, phenylhydrazine, formamide, and aniline) gave exclusively the replacement of all three para fluorines with the exception of aniline, phenylhydrazine, and formamide which gave mixtures of the mono- and bis-4-substituted phosphines. Sodium bisulphide and various alkoxides led mainly to C—P bond rupture though some alkoxides did under certain conditions give some of the expected substitution product. 19F, 31P, and 1H nmr and mass spectral data are presented.
The chlorosulfonyl moiety as a leaving group: hydride reduction of sulfonyl chlorides
Authors: Fong Harvey Owen , Hardstaff William Rayne , Kay Denis George , Langler Richard Francis , Morse Richard Herman , Sandoval Deig-Nevy
Published: May 2006

A series of γ-sulfone sulfonyl chlorides undergo a novel reduction upon reaction with lithium aluminum hydride to furnish the corresponding ethyl sulfones. The reactions appear to proceed in an SN2 fashion with the chlorosulfonyl moiety functioning as the leaving group. In general sulfonyl chlorides furnish mercaptans as hydride reduction products.A novel two-phase hydrolysis is shown to convert a thiol ester to a symmetric sulfide which involves hydrolysis and an SN2 displacement in the aqueous phase.
Studies of β-diketone complexes of rhenium. IX. The preparation and characterization of salts of the trans-dihalobis(pentane-2,4-dionato)rhenate(III) anion and an improved preparation of tris(pentane-2,4-dionato)rhenium(III)
Authors: Lock C. J. L. , Murphy C. N. , Turner M. L.
Published: May 2006

Salts of the anion Re(C5H7O2)Cl2− have been made by the reduction of both cis- and trans- Re(C5H7O2)Cl2 with a number of different reducing agents. The salts have been examined and characterized by physical methods. An improved preparation for Re(C5H7O2)3 is reported.
Crystal and molecular structures of 2,2,4,4,6,8,8-heptamethyl-6-methylamino-1,3,5-triaza-2,4,6,8(PV)-tetraphosphorin and 2,2,4,4,6,8,8-heptamethyl-6-methylamino-7-benzoyl-1,3,5-triaza-2,4,6,8(PV)-tetraphosphorin
Authors: Calhoun Harry P. , Oakley Richard T. , Paddock Norman L. , Rettig Steven J. , Trotter James
Published: May 2006

not available
A study of trapped electrons in LiCl/D2O and other aqueous glasses at temperatures down to 2 K by radiolysis, pulse radiolysis, photolysis, and stimulated luminescence
Authors: Klassen Norman V. , Teather George G. , Kieffer Fernand
Published: May 2006

Pulse radiolysis of 9.5 M LiCl/D2O glass at 6 K produces both types of trapped electrons, evis− and eir−, just as it does at 75 K. However, going from 75 K to 6 K increases the initial yield of eir− and decreases its decay rate, while the yield of evis− decreases and its decay rate increases. These results are attributed to fast trap-to-trap tunnelling of evis− from unrelaxed traps at 6 K and slower tunnelling from deeper traps at 75 K while the eir− traps seem to relax within 100 ns even at 6 K. In 12 M LiCl/D2O at 4–10 K the initial evis− band with λmax = 625 nm decays considerably over minutes revealing a stable band with λmax = 695 nm. The stimulation spectrum and absorption spectrum of this stable band indicate a bound–free transition of 2.0 eV and a bound–bound transition of 1.8 eV. Similar measurements of evis− at 77 K indicate a bound–free transition of 2.6 eV and a bound–bound transition of 2.1 eV. Tryptophan was photolyzed in 9.5 M LiCl/D2O at 2 K to produce eir−.
Kinetics and mechanisms of some reactions of aqueous sodium bromite
Authors: Lee C. L. , Lister M. W.
Published: May 2006

The kinetics of the reactions of aqueous bromite ions with basic aqueous solutions of iodide, sulphite, formate, and thiosulphate ions have been investigated. The products are, respectively, iodate, sulphate, and carbonate ions, and with thiosulphate either tetrathionate or sulphate depending on the conditions. The reaction with formate is autocatalytic, being catalysed by carbonate ions. All the reactions show some dependence on hydroxide concentration, and in general k(apparent) = k1 + k2[OH−]−1. The various rate constants have been obtained, as have the associated kinetic parameters. The relative rates of the reactions of bromite ions parallel those of the corresponding reactions of hypochlorite ions, but at 25 °C K is smaller by a factor of roughtly 105.
9-Oxobenzomorphans. III. Synthesis of derivatives with various substituents at 2-, 2′-, and 5-positions
Authors: Kavadias Gerry , Velkof Stephan , Belleau Bernard
Published: May 2006

5-Allyl-2-cyclobutylmethyl-2′-methoxy-, 5-allyl-2′-benzyloxy-2-methyl-, 5-benzyl-2′-methoxy-2-methyl-, and 5-allyl-2′-benzyloxy-2-cyclobutylmethyl-9-oxo-6,7-benzomorphans were prepared by a previously described process. The process involves bromination of the 5,9b-dihydrobenz[e]indolines to β-bromoiminium bromides followed by treatment with a weak base in aqueous organic solvents. Ammonium bicarbonate and aluminium oxide are effective bases for the conversions of the β-bromoiminium salts to 9-oxobenzomorphans 5a–g. The mechanism of the reaction involves formation of the bromoenamines (fast step) followed by hydration of the latter (slow step) and rearrangement to 5a–g.
The crystal and molecular structure of the molybdenum tetracarbonyl complex of 1,4-diphenyl-2,2′,3,3′5,5′,6,6′-octamethylcyclo-1,4- diphospha-2,3,5,6-tetrasilahexane
Authors: Calabrese Joseph C. , Oakley Richard T. , West Robert
Published: May 2006

The crystal and molecular structure of the molybdenum tetracarbonyl complex of 1,4-diphenyl-2,2′,3,3′,5,5′,6,6′-octamethylcyclo-1,4-diphosph a-2,3,5,6-tetrasilahexane, (PhPSi2Me4)2Mo(CO)4, has been determined by single crystal X-ray diffraction. The crystals are monoclinic, space group P21/n, with a = 15.983(5), b = 19.316(6), c = 10.580(3) Å, β = 99.99(2)° V = 3217(2) Å3, Z = 4, and ρcalcd = 1.356 g/cm3. The structure was solved by Patterson heavy atom methods and was refined by full-matrix least-squares procedures to a final R1 of 3.3% and R2 of 4.3%, for 6342 reflections with intensities greater than 2σ. The coordination of the boat-shaped (PhPSi2Me4)2 ligand to molybdenum tetracarbonyl produces a distorted octahedral environment about the metal. The mean Si—Si (2.358(14) Å) and P—Si (2.275(19) Å) distances are not greatly altered from the values found for them in the free ligand. The structural consequences of P → Si π-bonding in the latter are therefore minimal. The relatively long P—Mo (mean length 2.592(13) Å) distances are interpreted as the result of reduced back-bonding from the metal, caused by the presence of the relatively electropositive silyl groups on phosphorus. Consistently, the equatorial Mo—C bonds, which are trans to the diphosphine ligand, are shorter (mean length 1.968(19) Å) than the corresponding bonds to the axial carbonyl groups (mean length 2.021(15) Å).
Thermodynamics of transfer of Ph4C; scaled-particle theory and the Ph4As+/Ph4B− assumption for single ions
Authors: Abraham Michael H. , Nasehzadeh Asadollah
Published: May 2006

Free energies of transfer of Ph4C from acetonitrile to 20 other solvents have been calculated from literature data. The contribution of the cavity term to the total free energy has been obtained from scaled-particle theory and Sinanoglu–Reisse–Moura Ramos theory. It is shown that there is little connection between the cavity term and the total free energy of transfer, and that there must be, in general, a large interaction term. If the latter is important for transfer of Ph4C, we argue that it must also be important for transfer of the ions Ph4As+ and Ph4B−. Previous suggestions that the interaction term is zero for transfer of these two ions are thus seen to be unreasonable. We also show, for six solvents, that the interaction term for Ph4C is very large in terms of enthalpy and entropy, and that scaled-particle theory seems not to apply to transfers of Ph4C between pure organic solvents.The free energy, enthalpy, and entropy of transfer of Ph4As+ = Ph4B− have been calculated by dividing the total transfer values into neutral and electrostatic contributions; reasonable agreement is obtained between calculated and observed values.
The oxidation potentials of cis- and trans-1,2-diphenylcyclopropane and cis- and trans-2,3-diphenyloxirane
Authors: Arnold D. R. , Wong P. C.
Published: May 2006

The oxidation potentials of cis- and trans-1,2-diphenylcyclopropane (1) and cis- and trans-2,3-diphenyloxirane (2) have been determined by cyclic voltammetry, spectroscopically (using an empirical correlation of the long wavelength transition of the charge-transfer complexes with tetracyanoethylene) and by using an empirical correlation based upon the gas phase ionization potentials measured by photoelectron spectroscopy. The values obtained by these three very different techniques agree to within ±0.15 V. The results are interpreted in terms of the initial formation of the phenyl radical cation with the three-membered ring intact. The higher oxidation potentials of cis- and trans-2, relative to those of cis- and trans-1, are attributed to inductive electron withdrawal from the phenyl group by the oxygen of the oxirane ring. The relevance of these results to the photosensitized (electron transfer) behaviour of these compounds is discussed.
Chemoselectivity in the synthesis of thiocyanates and isothiocyanates: the reaction of alkenes with benzeneselenenyl thiocyanate in methylene chloride
Authors: Garratt Dennis G. , Ryan M. Dominic , Ujjainwalla Mark
Published: May 2006

The reactions of benzeneselenenyl thiocyanate with some simple alkylsubstituted acyclic and cyclic alkenes have been investigated, and the relative distribution of isomeric adducts determined. The relative distribution of β-thiocyanatoalkyl phenyl selenide to β-isothiocyanatoalkyl phenyl selenide is found to be dependent upon the degree of substitution of the initial alkene. Thus mono- and disubstituted alkenes favour formation of the thiocyanato species, whereas tri- and tetrasubstituted alkenes yield isothiocyanato adducts almost exclusively. Stereospecific anti addition was established in all cases except that of tricyclo[4.2.2.02,5]deca-3,9-diene-7,8-dicarboxylic anhydride which gives a 33:67 mixture of cis and trans adducts.
Excited state properties of nitrobenzene derivatives
Authors: Buemi Giuseppe , Millefiori Salvatore , Zuccarello Felice , Millefiori Arcangelo
Published: May 2006

Gas-phase and solution spectra of methoxy nitroanilines are reported. MIM and PPP configuration analyses were used to calculate the properties associated with the electronic transitions. The excited state dipole moments associated with the first intense electronic transition were evaluated by the solvent shift method. The spectra of the title compounds are tentatively correlated with those of the corresponding disubstituted benzene derivatives. The effect of the methoxy group on the absorption features of the isomeric nitroanilines is briefly discussed.
The reaction of benzeneselenenyl thiocyanate with E- and Z-1-phenylpropene: evidence for anomalous stereospecific syn addition
Authors: Garratt Dennis G.
Published: May 2006

The reaction of benzeneselenenyl thiocyanate with E- and Z-1-phenylpropene has been shown to give products under conditions of kinetic control of net stereospecific syn addition in the Markownikoff orientation. Furthermore, the reactions were highly specific in that a thiocyanato adduct was formed exclusively from the Z-isomer, whereas an isothiocyanato adduct was formed exclusively from the E-isomer.
1H nuclear magnetic resonance study of 2,2′-anhydro-O2-β-D-arabinosyluracil. Four- and five-bond coupling constants in the sugar moiety
Authors: Hruska Frank E. , Dalton James G. , Remin Mieczyslaw
Published: May 2006

A high resolution proton magnetic resonance spectrum for 2,2′-anhydro-O2-β-D-arabinosyluracil in aqueous solution at 80 °C is presented. The spectrum provides evidence for the presence of long-range four-bond (4J1′3′, 4J1′4′, 4J2′4′) and five-bond (5J1′5′, 5J1′5′′, 5J2′5′, 5J2′5′′) coupling interactions involving the furanose hydrogens. The 5J data represent the first reported evidence for the presence of coupling interactions involving the anomeric proton and exocyclic C5′ protons in a furanose system. The relative signs of the 4J and 5J couplings were determined by double resonance methods. The 4J and 5J interactions are discussed using crystallographic data and the theory of long-range couplings.
Thermodynamics of molecular interactions in aniline + benzene mixtures
Authors: Nigam Ram K. , Singh Prem P. , Singh Krishan C.
Published: May 2006

Heats of mixing, HE, of aniline + benzene at 298.15 and 308.15 K have been measured over the entire composition range. The results have been analysed in terms of Barker's and ideal associated model theory of non-electrolyte solutions. It has been observed that the ideal associated model approach which assumes the presence of AB, AB2, A2B2, and B molecular species well describes (within ± 120 J/mol at the worst) the general behaviour of HE with xB (mole fraction of aniline) over the whole composition range for aniline + benzene mixtures. The equilibrium constants for the various association reactions along with the enthalpy of formation of various molecular species have also been calculated.
Specific binding of phenylalanine and tryptophan to β-nicotinamide adenine dinucleotide
Authors: Neurohr Klaus J. , Mantsch Henry H.
Published: May 2006

This 1H nmr study provides the first experimental evidence for specific complex formation between the coenzyme nicotinamide adenine dinucleotide (β-NAD+) and the two aromatic amino acids phenylalanine and tryptophan. It is shown that the interaction is of the stacking type and occurs between the aromatic side chains of these amino acids and the adenine moiety of NAD+. Binding parameters were obtained from dilution studies, taking into account the self-association of NAD+. The apparent microscopic association constants for complex formation of phenylalanine and tryptophan with excess NAD+ in aqueous solutions are 1.35 M−1 and 11.35 M−1, respectively, indicating that the adenine moiety of NAD+ can discriminate between phenylalanine and tryptophan by a stronger binding to the latter. The results are discussed with regard to the interaction of NAD+ with dehydrogenases.
Excess volumes of β-picoline and γ-picoline mixtures with some n-alcohols at 308.15 K
Authors: Singh Prem P. , Sharma Buta R. , Chopra Parkash C.
Published: May 2006

Excess volumes, VE, of binary mixtures of β-picoline and γ-picoline with ethanol, n-propanol, and n-butanol have been measured as a function of composition at 308.15 K by a dilatometric method. The VE data are negative for all the mixtures studied here and suggest that the strong [Formula: see text] interactions outweigh those due to the breaking of the [Formula: see text] bonds.
Free energies of transfer of some single ions from ethylene glycol to its isodielectric mixtures with acetonitrile at 25 °C
Authors: Bose Kumardev , Kundu Kiron K.
Published: May 2006

Free energies of transfer (ΔGt0) of the reference electrolyte Ph4AsBPh4 (Ph = phenyl) from ethylene glycol to its approximately isodielectric mixtures with acetonitrile have been determined at 25 °C from the measurement of the solubilities of KPi, Ph4AsPi, and KBPh (Pi = picrate) in these solvents. Using the assumption [Formula: see text] values for the individual ions K+, Pi−, Ph4As+, and Ph4 s− have been estimated. These, in conjunction with previously determined values of ΔGt0 for MCl (M = Li, Na, K, Rb, Cs, and H), KBr and KI have provided ΔGt0 values for Cl−, Br−, I−, and M+ ions. Ionic ΔGt0's have been interpreted in terms of specific ion–solvent interactions. The contrasting behaviour of ethylene glycol and acetonitrile in ion-solvation is shown to be characteristic of the protic and dipolar aprotic solvent types respectively.
Pentagonal pyramidal lead coordination in the crystal structure of dimeric diaquopyridine-2,6-dicarboxylatolead(II) pyridine-2,6-dicarboxylic acid monohydrate
Authors: Beveridge A. , Bushnell W.
Published: May 2006

The crystal structure of dimeric diaquopyridine-2,6-dicarboxylatolead(II) pyridine-2,6-dicarboxylic acid monohydrate, empirical formula and asymmetric unit C14H14N2O11Pb, has been solved and refined to R = 0.081, Rw = 0.100. The space group was [Formula: see text] with a = 1073.8(3), b = 1123.2(5), c = 705.0(3) pm, α = 101.28(8)°, β = 95.42(6)°, γ = 92.80(7)°, ρ = 2.37 g cm−3 (meas.). Measurements were done on an automatic 4-circle diffractometer ([Formula: see text], λ = 71.069 pm), and corrected for absorption. The lead complex is dinuclear with an inversion point at the centre of the double bridging. Each lead atom has distorted pentagonal pyramidal coordination with a water molecule at the apex. The basal ligands are water and terdentate pyridine-2,6-dicarboxylate. The double bridging is by one of the coordinated carboxylic oxygen atoms and its inverse. The electron pair geometry is assumed to be pentagonal bipyramidal with a stereochemically active lone pair occupying considerable solid angle in an axial position. Bond lengths (±2 pm) are: Pb—OH2 (apex), 259; Pb—OH2 (basal), 273; Pb—O, 251, 258, 273; Pb—N, 259. The mean of the bond angles at Pb involving the apical oxygen is 77°. The unit cell contains two water and two dicarboxylic acid molecules of crystallisation which are involved in an H-bonding network with one bond for each hydrogen attached to oxygen in the structure.
Variable-temperature Raman spectroscopy as a probe of the supermolecular structure of ionomers
Authors: Neppel A. , Butler S. , Eisenberg A.
Published: May 2006

Raman spectroscopy has been used for the first time to show the presence of multiplets and clusters of ion pairs in ethyl acrylate–sodium acrylate and styrene–sodium methacrylate ionomers and to determine the relative concentrations of ion pairs in these two different kinds of sites.
Electrochemical oxidation of trifluoroacetic acid anion.IV. Synthesis and stereochemistry of products of trifluoromethyl radical addition to some mono- and disubstituted olefins
Authors: Renaud Roger N. , Champagne Philippe J. , Savard Marc
Published: May 2006

The trifluoromethylation of mono- and disubstituted ethylene molecules was performed in good yields via the electrochemical oxidation of sodium trifluoroacetate. The relative quantities of monomeric and dimeric products are a function of the concentration of the substrate.The stereoisomers of the products were separated and identified and, when possible, their stereochemistry was determined by Hnmr and Fnmr spectroscopies.
Electrophilie du ligande η3-allylique de complexes η3-allyl-dicarbonyl-nitrosyl-fer
Authors: Roustan J. L. A. , Houlihan F.
Published: May 2006

Neutral η3-allyl-dicarbonyl-nitrosyl iron complexes react rapidly in THF at room temperature with nucleophiles of the doubly activated type such as malonate anion. Monoallylated organic products are obtained in good yields (80–95%). With unsymmetrical η3-allyl ligands the less substituted carbon is alkylated preferentially.
Apparent molar heat capacities and volumes of aqueous electrolytes at 25 °C: Cr(NO3)3, LaCl3, K3Fe(CN)6, and K4Fe(CN)6
Authors: Spitzer Jan J. , Olofsson Inger V. , Singh Prem Paul , Hepler Loren G.
Published: May 2006

We have used a flow calorimeter and a flow densimeter for measurements at 25 °C of heat capacities and densities of aqueous solutions of four electrolytes of high charge type: LaCl3, Cr(NO3)3, K3Fe(CN)6, and K4Fe(CN)6. Results of these measurements have been used for calculating corresponding apparent molar heat capacities and apparent molar volumes, which have been extrapolated to infinite dilution to obtain the corresponding standard state apparent molar and partial molar properties. Uncertainties resulting from extrapolations of heat capacities are discussed. Results of our measurements are compared with those of earlier related investigations.
Les oxazolines-4 précurseurs de sels d'iminium fonctionnels. Ouverture en milieu anhydre de ces hétérocycles par des acides protoniques: obtention de sels d'iminium fonctionnels, étude de leur structure
Authors: Vaultier Michel , Mullick Gurbachan , Carrié Robert
Published: May 2006

The protonation of 4-oxazolines with protic acids in anhydrous medium, both at low or at room temperature, generally leads to acyclic functional iminium salts. In those cases where the oxazoline ring bears a hydrogen atom in the four position, two diastereoisomeric cyclic iminium salts are obtained. The conditions for preparation of these salts along with the characterization of their structures were determined by the aid of 1H and 13C nmr.
The oxidation of ascorbic acid and hydroquinone by perhydroxyl radicals. A flash photolysis study
Authors: Nadezhdin A. D. , Dunford H. B.
Published: May 2006

The oxidation of ascorbic acid (AH2) and hydroquinone (QH2) by photolytically generated HO2•radicals was studied over a broad range of pH. The rate constants of the following processes were obtained[Formula: see text]and[Formula: see text]depending upon two different possible mechanistic interpretations.
Structure of Ni[Ag(SCN)2]2•2diox and its derivatives
Authors: Singh P. P. , Khan S. A. , Pandey J. P.
Published: May 2006

Ni[Ag(SCN)2]2•2diox and its derivatives have been synthesized. Their structures have been given on the basis of infrared spectral, electronic spectral, magnetic moment, and molar conductance studies. These results demonstrate that Ni[Ag(SCN)2]2 forms two types of complexes: (i) cationic–anionic type of general formula [NiLx]2+[Ag(SCN)2]22− (x = 3, 4, 6) and (ii) polymeric bridged type having a chain structure consisting of zig-zag thiocyanate bridges between nickel and silver. The cationic–anionic type of complexes are formed by pyridine, nicotinamide, 4-aminopyridine, aniline, p-toluidine, thiourea, ethylene thiourea, bipyridine, phenanthroline, pyrazine-2,3-dicarboxamide, and triphenylphosphine, and the polymeric bridged type by dioxane, acetone, and dimethylformamide. All the ligands have been found to prefer to coordinate to nickel instead of silver.