bluuebunny/crossref_metadata_2025 huggingface dataset:
13C magnetic resonance studies. 119. Tricyclo[3.3.0.0] and [3.2.1.0]octanones from substituted norbornenones via cyclopropanation and homoketonization
Authors: Ragauskas Arthur J. , Stothers J. B.
Published: May 2006

Simmons–Smith cyclopropanation of the trimethylsilyi enoi ethers of 7-isopropylidene- and two 7-spirocyclopropyl-norbomenones leads directly to the 8-substituted 2-trimethylsilyl ethers of homoquadricyclene. Homoketonization of the unsaturated ether proceeds regiospecifically to the corresponding tricyclo[3.3.0.02.8]octan-4-one while the others give the tricyclo[3.2.1.02.6]octan-4-ones exclusively, all with high stereoselectivity favoring inversion of configuration. This difference in the regiochemistry of homoketonization can be attributed to a directive effect of β-functionalization overcoming thermodynamic control of cleavage.
Hydrogen bonding of alcohols with AOT in carbon tetrachloride: an infrared study
Authors: Ménassa Pierre , Sandorfy Camille
Published: May 2006

The interaction of the inverted micelles of AOT (sodium di(2-ethylhexyl)sulfosuccinate) with different alcohols due to hydrogen bonding has been studied by means of infrared spectroscopy. Spectra of solutions of the alcohols with increasing concentrations of AOT showed a decrease in the intensity of the free OH stretching band. At the same time a new OH band due to a H-bonded alcohol-inverted micelle complex appears and its intensity increases as the intensity of the free band decreases. Calculated values of the equilibrium constants for the formation of the complexes n-alcohol–AOT, showed a decrease in alcohol–AOT association with the increase of the length of the aliphatic chains in the n-alcohols. Surprisingly, cholesterol behaved like a short chain while other cyclic alcohols like long chain alcohols.
Adducts of diphenyllead diselenocyanate with some O- and N-donor ligands
Authors: Wharf Ivor , Wojtowski Ryszard , Onyszchuk Mario
Published: May 2006

The preparation and properties of Ph2Pb(SeCN)2 have been reinvestigated. Infrared spectra show that the solid is polymeric with stronger Pb—Se and weaker Pb—N bonds. In N,N-dimethylformamide (DMF) solution v(CN) values are consistent with complete ionization to NCSe−, but coordinated N- and Se-bound selenocyanate species are observed when DMF/CH2CI2 mixtures are used as solvents. The first 1:2 adducts of Ph2Pb(SeCN)2 with hexamethylphosphoramide (HMPA), triphenylphosphine oxide (Ph3PO), pyridine-N-oxide (pyO), 2,4,6-collidine-N-oxide (collO), and dimethyl sulphoxide (DMSO) have been prepared, while with 4-picoline-N-oxide (4-picO) a 1:4 adduct is obtained. Infrared data show Ph2Pb(SeCN)2•2L (L = HMPA, Ph3PO, collO) are in fact isoselenocyanates, but the pyO and DMSO adducts are selenocyanates. Amine adducts Ph2Pb(SeCN)2•2L (L = morpholine (morph), quinoline (quin), piperidine (pipy)) and Ph2Pb(SeCN)2•3LL (LL = α.α′-dipyridyl (dipy), 1,10-phenanthroline (phen)) have been prepared. Infrared data suggest that amine adducts most probably have N-bonded selenocyanate groups, in some cases with ionic selenocyanate also present. The adduct with 4-picO also contains ionic selenocyanate.
The mechanism of an intramolecular Michael addition: a MNDO study
Authors: Ellis Graham W. L. , Tavares Donald F. , Rauk Arvi
Published: May 2006

The 5-endo-trig cyclization reactions of α′-hydroxy α,β-unsaturated carbonyl compounds to form the 3-furanone ring system has been investigated by means of MNDO calculations. In acid medium, the activation energy for ring formation is reduced by protonation of the carbonyl oxygen and by electron-releasing β-substituents, both of which facilitate torsion about the α,β-CC bond. Rotation about the α,β-CC bond is essentially complete when the transition structure is achieved. In reverse ring opening, heterolytic rupture of the C—O bond is aided by prior enolization since induced polarization of the enol π system acts to stabilize the developing cationic centre at the β-carbon. In basic medium, ring closure is hindered by the combined effects of the intrinsic barrier to cyclization and solvation of the intermediate alkoxide. Ring opening in basic medium is prevented by prohibitively high intrinsic barriers except when a strongly electron-releasing group such as p-O(−)-phenyl is at the β-carbon.
Structural studies of organoboron compounds. XXII. Preparation and crystal and molecular structure of tetramethylammonium-2,4,6,6-tetraphenyl-1,3,5-trioxa-2,4- dibora-6-boratacyclohexane
Authors: Kliegel W. , Motzkus H.-W. , Rettig Steven J. , Trotter James
Published: May 2006

Details of the preparation and physical properties of (Me4N)+ (Ph4B3O3)− are given. Crystals of tetramethylammonium 2,4,6,6-tetraphenyl-1,3,5-trioxa-2,4-dibora-6-boratacyclohexane are orthorhombic, a = 18.130(2), b = 11.9745(7), c = 12.5187(5) Å, Z = 4, space group Pna21. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.056 and Rw = 0.064 for 1460 reflections with I ≥ 2σ(I). The crystal structure consists of discrete tetramethylammonium cations and tetraphenylboroxinate anions, the first such anion to be structurally characterized. The six-membered B3O3 ring is significantly non-planar, having a flattened O(1)-envelope conformation (maximum deviation from the mean plane = 0.074(4) Å for O(1)). The boroxine ring in the anion shows significant deviations from the D3h symmetry observed for neutral boroxines. Important mean structural parameters: B(sp3)—O = 1.494(2), B(sp2)—O[B(sp3)] = 1.320(9), B(sp2)—O[B(sp2)] = 1.389(3) Å, O—B(sp3)—O = 110.5(5), O—B(sp2)—O = 121.7(6), B(sp2)—O—B(sp2) = 118.9(5), and B(sp3)—O—B(sp2) = 122.9(1)°.
Discussion on 13C nuclear magnetic resonance spectra of nucleoside derivatives. Reflection of structural alterations on 13C chemical shifts
Authors: Uzawa Jun , Anzai Kentaro
Published: May 2006

not available
The cleavage of aspirin by α- and β-cyclodextrins in basic aqueous solution
Authors: Tee Oswald S. , Takasaki Bryan K.
Published: May 2006

The deacetylation of aspirin is promoted by α- and β-cyclodextrins (αCD and βCD) in basic aqueous solution. From saturation kinetics the dissociation constants (Kd) for the aspirin anion – CD complexes are 12 mM (αCD) and 20 mM (βCD). At pH 12.25 the limiting rate constant for ester cleavage is 14 times (αCD) and 7 times (βCD) that in the medium alone. For the 4-chloroaspirin anion (Kd = 3.8 mM) the cleavage induced by αCD is 240 times that in the medium, but 5-chloroaspirin shows a very small effect. The results are discussed in terms of a model derived from that of Bender and co-workers (1967) and are compared to earlier work. For the αCD anion, the 4-chloroaspirin anion is almost as good as "substrate" as m-chloro-and m-tert-butylphenyl acetates. Compared to hydroxide ion, the αCD anion is better at cleaving 4-chloroaspirin (2000×) and aspirin (36×).
Study of interaction of polymeric aluminium hydroxide with fluoride
Authors: Parthasarathy N. , Buffle J. , Haerdi W.
Published: May 2006

The interaction between polymeric aluminium hydroxide, Alp, and fluoride has been investigated to optimize the conditions for removal of fluoride from waste waters of aluminium manufacturing plants using Alp. The results of these studies have shown that the nature of products formed between Alp and fluoride depends on the molar concentration ratio of fluoride to aluminium (rF), pH, and initial fluoride concentration. In the absence of interfering ions, fluoride can be effectively precipitated as Al13(OH)29F10 with Alp, using [Formula: see text] and 4 < pH ≤ 7. At rF > 1, Alp dissociates and fluoride is precipitated as cryolite, and the residual fluoride concentration is controlled by its high solubility.
Layered metal uranyl phosphates. Retention of divalent ions by amine intercalates of uranyl phosphates
Authors: Pozas-Tormo R. , Moreno-Real L. , Martínez-Lara M. , Bruque-Gamez S.
Published: May 2006

HUO2PO4•4H2O (HUP) forms a laminar intercalate with butylamine, c = 29.30(5) Å, which accepts cationic metals in exchange for the n-butylammonium ions. Hydrated uranyl metal phosphates M(UO2PO4)2•nH2O (M = Mn, Co, Ni, Cu, Zn, Cd) are obtained by ionic exchange and were studied by thermal analysis and X-ray diffraction. The tetragonal structures of all these product compounds are derived from HUP. The diffuse electronic reflectance spectra of every sample show characteristic [Formula: see text] absorption bands. In the spectra of the Co, Ni, and Cu phosphates there are other bands in the 500–800 nm zone compatible with their observed aquocation transitions.
The chemistry of peptides related to metabolites of Trichoderma spp. 2. An improved method of characterization of peptides of 2-methylalanine
Authors: Shaw I. M. , Taylor A.
Published: May 2006

4-Chlorobenzoylazide reacts with amino acid and peptide esters to give the 4-chlorobenzoyl derivatives in 60–90% yield, at room temperature, without measurable racemization. The reaction also proceeds smoothly with hindered amines such as methyl 2-methylalaninate and with secondary amines, e.g. methyl L-prolyl-L-valinate. Ten examples of the reaction are reported with peptides, synthesized for the purpose, that might be accessible from hydrolysates of the numerous fungal metabolites now known, which contain a high proportion of 2-methylalanine. The derivatives of di-, tri-, tetra-, and pentapeptides were highly crystalline, with sharp melting points, and could be detected and integrated in the effluent from chromatography columns at about the 10-ng level. This simple method of derivatization might be usefully applied to the resolution of discrepancies in the physical properties of ostensibly the same 2-methylalanyl peptide prepared in different laboratories.
A fast atom bombardment study of the lead isotope ratios in early nineteenth century Niagara Peninsula pottery glazes
Authors: Miller Jack M. , Jones Timothy R. B. , Kenney Tina , Rupp David W. , Green Brian N. , Bardoli Robert S.
Published: May 2006

The application of fast atom bombardment (FAB) mass spectrometry to the determination of lead isotope ratios in nineteenth century pottery glazes from the Niagara Peninsula has been investigated with the aim of determining the source of the lead used in the glazes. Methods of sampling have been compared, including direct analysis of glass chips, analysis of powdered glaze scrapings, analysis of acid extracts of the former, and simple acid leaching of the surface of a piece of pottery. The latter method gave the best results. The FAB data, as obtained on an older mass spectrometer, can distinguish lead from igneous vs. sedimentary deposits, but is not adequate to determine specific mining locations. Although newer FAB instrumentation can narrow this range, the overlap of data from the Niagara Peninsula and England precludes a simple answer to the archeological question as to English vs. Canadian origin of the lead used in the Jordan pottery glazes. However, the data do suggest that the potter used a local source for the lead.
Evaluation of the diffusion coefficient of the zincate ion using a rotating disk electrode
Authors: Pessine Elisabete Jorge , Agostinho Silvia M. L. , Chagas Hélio C.
Published: May 2006

Using a rotating Hg-film disc electrode, the diffusion coefficient of the zincate ion in a 1–4 M aqueous solution of NaOH was measured. Experiments covered a temperature range from 25 to 40 °C. The experimental results are in agreement with the predictions of the Stokes–Einstein theory for diffusivity. The obtained Stokes radii decrease with increasing alkali concentration, but the ratio Dη/T is reasonably constant within the whole range of temperature investigated
Le lithio-2 naphtalène carbonitrile-1 et ses produits de substitutions
Authors: Fraser R. R. , Savard S.
Published: May 2006

Lithiation of 1-naphthonitrile provides the 2-lithio derivative exclusively. Reaction of this intermediate with ten different electrophiles produces 2-substituted derivatives in moderate to good yields. 2-Alkyl-1-naphthonitriles are readily lithiated and further alkylated to provide alkyl substituents modified at the α position. The pKa values for the hydrogen at the 2-position of 1-cyanonaphthalene and 2-methyl-1-cyanonaphthalene have been determined to be 36.3 and 28.5, respectively.
Diastereoselectivity and asymmetric induction in the Diels–Alder reaction of o-quinodimethanes
Authors: Charlton James L.
Published: May 2006

The extent of asymmetric induction in the bimolecular Diels–Alder reactions of chiral o-quinodimethanes with dimethyl fumarate, methyl acrylate, and maleic anhydride has been studied. o-Quinodimethanes with chiral α-alkoxy groups were prepared from 1-alkoxy-1,3-dihydrobenzo[c]thiophene-2,2-dioxides 4a–f or 1-alkoxy-3-phenyl-1,3-dihydrobenzo[c]thiophene-2,2-dioxides 4g–h by thermolysis. These alkoxybenzosulfones were prepared from the corresponding hydroxybenzosulfones 8 and 1-phenylethanol, 2-phenyl-1-propanol, 4-phenyl-2-butanol, 1-phenyl-2-propanol, 3,3-dimethyl-2-butanol, or 1-cyclo-hexylethanol. The 1-phenylethoxy substituent yielded the largest asymmetric induction. The absolute configurations of the major cycloadducts of methyl acrylate with the o-quinodimethanes generated from 1-(R- 1-phenylethoxy)- and 1-(S-1-phenylethoxy)-1,3-dihydrobenzo[c]thiophene-2,2-dioxides 4i and 4j have been determined to be 1S,2S-1-(R-1-phenylethoxy)- and 1R,2R-1-(S-1-phenylethoxy)-2-carbomethoxy-1,2,3,4-tetrahydronaphthalene 11i and 11j, respectively. The proposition that a chiral alkoxy substituent can block one face of the o-quinodimethane towards addition of a dienophile is discussed.
A study of lone-pair interactions of tetracyclic diamines by ultraviolet photoelectron spectroscopy
Authors: Werstiuk Nick Henry , Butler Douglas Neve , Datta Sushil
Published: May 2006

The ultraviolet photoelectron spectra of 2,7-diazatetracyclo[3.3.3.0.4,90.8,11]undecane (1) and its N,N-dimethyl- and methylene-bridged analogues 2 and 3 are documented. The spectrum of 2, which exhibits a nitrogen lone-pair splitting of 0.95 ± 0.1 eV, is interpreted on the basis of an interaction of "inside" lone pairs of the 1,2-diamine. Apparently this is the first report of a study of such an interaction. The spectrum of 1 is consistent with our view that 1 is an intramolecularly hydrogen bonded species in which the lone pairs are "inside–outside".
Cation transport in gaseous nitrogen: density and temperature effects
Authors: Wada Toshinori , Gee Norman , Freeman Gordon R.
Published: May 2006

The density-normalized mobility of nμ of cations in nitrogen gas at densities up to nc = 6.7 × 1027 molecules/m3 increases with temperature. At n ≤ 5.7 × 1025 molecules/m3 and T > 250 K, the dominating ion is N4+. At lower temperatures and higher densities, relatively loosely bound clusters N4+(N2), N4+(N2)2, … form. Momentum transfer cross sections for N4+–N2 are governed at low energies by the polarization potential, and at high energies by the hard body potential. The cross section for N2+–N2 at high energies is larger than that for N4+–N2.
Open chain nitrogen compounds. Part X. Thermolysis of α-diazoacetanilides in methanol: a convenient synthesis of α-methoxyacetanilides from ethyl N-(arylazo)glycinate
Authors: Nicholas Kumudini U. K. Gamage , Vaughan Keith
Published: May 2006

α-Diazoacetanilides (4), which are readily available from the open-chain triazenes (2), undergo thermolysis in methanol solution to afford the α-methoxyacetanilides (5), an apparently rare type of ether/amide derivative. The methanolic thermolysis is inhibited by the presence of a tertiary amine in the solvent, suggesting that a carbocation, rather than a carbene, intermediate is involved in the conversion of the diazo-amide to the methyl ether. This hypothesis is supported by the retardation of the reaction in the presence of an electron-withdrawing group in the para position of the anilide. The conversion 4 → 5 was also observed, on a small scale, under photolytic conditions. It is suggested that the α-diazoacetanilide represents a useful synthetic equivalent for the synthon ArNHCOCH2+.
Cyclic hydroboration of geraniol derivatives: a synthesis of the left-hand portion of X-14547A
Authors: Whitney Ralph Allen
Published: May 2006

The stereochemical consequences of the cyclic hydroboration–oxidation of geraniol derivatives have been examined; moderately high selectivity (85–88%) for the formation of one major diastereomer has been observed, presumably as a consequence of remote asymmetric induction in the cyclic hydroboration of these 1,5-dienes. An approach to the synthesis of the left-hand portion of the ionophore antibiotic X-14547A is described.
The structures of huperzine A and B, two new alkaloids exhibiting marked anticholinesterase activity
Authors: Liu Jia-Sen , Zhu Yuan-Long , Yu Chao-Mei , Zhou You-Zuo , Han Yan-Yi , Wu Feng-Wu , Qi Bao-Feng
Published: May 2006

Huperzine A and B, two new Lycopodium alkaloids isolated from Huperziaserrata (Thunb.) Trev., are shown to possess structures 1 and 3, respectively, on the basis of chemical and spectroscopic data.
Extraction of alkaline-earth metal ortho- and para-nitrophenoxides from aqueous media by crown ether and cryptand complexing agents
Authors: Cox B. G. , Buncel E. , Shin H. S. , Bannard R. A. B. , Purdon J. G.
Published: May 2006

A study has been performed on the extraction of alkaline-earth metal ortho- and para-nitrophenoxides, from aqueous medium into methylene chloride, in the presence of crown ether and cryptand complexing agents. The results are analyzed in terms of the various constituent complexation and extraction equilibria involved. Comparison is drawn with our previously reported study on extraction of potassium p-nitrophenoxide. The different anion stoichiometries in the two systems result in relatively more favorable extraction of M+ systems at low anion concentrations. Furthermore, while extraction of MX (X = o- or p-nitrophenoxide) can be carried out in the presence of excess MOH, this is not possible in the case of MX2 due to the limited solubility of M(OH)2. The addition of excess MOH leads to more efficient extraction of M+-phenoxides and prevents hydrolysis to free phenols. A noteworthy point in both MX and MX2 systems is that at high concentrations of complexing agent a saturation effect occurs, which limits the overall extent of extraction achievable. Under these conditions the extraction is governed by the equilibrium constant, Kdcs, representing the partitioning of the complexed salt between the aqueous and organic phases, and is independent of the amount of ligand present.
Fastigiatine, a lycopodium alkaloid with a new ring system
Authors: Gerard Robert V. , MacLean David B. , Fagianni Romolo , Lock Colin J.
Published: May 2006

Fastigiatine, C19H28N2O, is a minor component of the alkaloids of Lycopodiumfastigiatum R•Br•collected in New Zealand. Its structure and relative configuration have been resolved by an X-ray analysis of the free base. The pentacyclic ring system of fastigiatine has not been previously observed in the Lycopodium family of alkaloids or elsewhere. A proposal is presented for its derivation from the tetracyclic flabellidane ring system that is widely distributed among Lycopodium species. The mass spectrum and the 13C and 1H nmr spectra of fastigiatine are discussed.
Solvolysis of 2-substituted-9-(otrho-substituted phenylmethyl)fluoren-9-yltrimethylammonium ions in various solvents. The effect of steric crowding on alkene formation
Authors: Smith Peter James , Pradhan Jyotsna
Published: May 2006

The solvolytic reaction of several 9-(ortho-substituted phenylmethyl)fluoren-9-yltrimethylammonium salts has been investigated in several different solvents. Substitution and elimination products were found for the reactions in all the solvents studied, with the exceptions that reaction in both tert-butyl alcohol and chloroform led exclusively to the alkene product. The observed rate constants for alkene formation and the percent alkene were measured and it was found that the di-ortho compounds reacted at a faster rate but produced less alkene than the reaction of the corresponding mono-ortho salts. Hydrogen–deuterium isotope effects were also determined for the various reactions. The results are discussed in terms of the reaction proceeding by way of the E1 mechanism, where steric acceleration promotes the loss of the bulky ammonium leaving group to give the carbocation intermediate.
Reactions of the 1-hydroxy-1,4-dimethylcyclohexadienyl cation, an intermediate in the solvolysis of 1,4-dimethyl-4-nitrocyclohexa-2,5-dien-1-ol
Authors: Fischer Alfred , Henderson George N. , Smyth Trevor A.
Published: May 2006

Solvolysis of 1,4-dimethyl-4-nitrocyclohexa-2,5-dien-1-ol in mixed aqueous organic solvents gives the diastereomers of 1,4-dimethylcyclohexa-2,5-diene-1,4-diol, 1,4-dimethylcyclohexa-3,5-diene-1,2-diol, 2-nitro-p-xylene, 2,4-dimethylphenol (all derived from the title cation, itself formed by ionization of the nitro group as nitrite), and 2,5-dimethylphenol. In aqueous methanol the diastereomers of 4-methoxy-1,4-dimethylcyclohexa-2,5-dienol are also obtained. Significant yields of 2,5-dimethylphenol are only obtained on the acid-catalysed further reaction of the dienediol (or the methoxydienol) and involve the intermediate formation of 1,4-dimethylcyclohexa-3,5-diene-1,2-diol. In the absence of added base the acid released in the solvolysis catalyses this reaction and leads to the aromatization of the dienes.
An MNDO SCF-MO study of proton transfer from fluoroethanols
Authors: Anhede Bo , Bergman Nils-Åke , Kresge A. Jerry
Published: May 2006

Proton exchange between β-fluorinated ethanols and ethoxide ions has been studied using the MNDO SCF-MO method. Calculations were performed on reactions of ethoxide ion with ethanols substituted in the β-position with 0, 1, 2, and 3 fluorine atoms as well as on reactions where both the ethanol and the ethoxide ion were substituted with the same number (1, 2, 3) of fluorine atoms in the β-position. The energies obtained for the ion–molecule reactant complexes and the transition states from these reactions have been analyzed using the Marcus equation. Through the calculated force-constant matrices of reactants and transition states we also calculated the kinetic isotope effects for the proton-transfer reactions. The semiclassical isotopic rate constant ratios (kH/kD)s were found to be of rather normal magnitude and showed a variation with the energy of reaction. The calculated ratios of tunnel correction factors, QtH/QtD, proved to be unrealistically high. These factors were also calculated with the frequencies scaled down by 10% and this was found to reduce the QtH/QtD ratios to more realistic values.
Sulphite-promoted delignification of wood: identification of paucidisperse lignosulphonates
Authors: Bialski Alec M. , Luthe Corinne E. , Fong Jenny L. , Lewis Norman G.
Published: May 2006

Paucidisperse lignosulphonates, previously described as a distinct group of compounds called "hemilignins" [Formula: see text] were conclusively shown to be a complex mixture of monomeric (C9) sulphonic acids. Since these compounds are rapidly solubilized only during the early stages of delignification from softwoods (≤30% lignin removal), it can be concluded that they are selectively removed from the secondary wall and not from the middle lamella. This result gives chemical support to the hypothesis that morphological differences in lignin structure exist. It is proposed that the generation of monolignols and their sulphonated derivatives may occur via an α-O-aryl bond cleavage rather than β-O-aryl cleavage as previously suggested. For softwoods, several other major constituents were isolated, which may be derived from sulphonation of a β-hydroxylated form of coniferyl alcohol.
The internal rotational potential in benzyl chloride
Authors: Schaefer Ted , Sebastian Rudy , Penner Glenn H.
Published: May 2006

The 1H nmr spectra of benzyl chloride in dilute CS2 and acetone-d6 solutions are analyzed. The long-range coupling constants are consistent only with a low-energy conformation in which the C—Cl bond lies in a plane perpendicular to the benzene plane. Geometry optimized computations at the STO 3G level of molecular orbital theory agree with this conclusion and yield a nearly pure twofold barrier to internal rotation of 8.6 kJ/mol. In CS2 solution the long-range couplings yield 8.8 kJ/mol, rising to 11.2 kJ/mol in acetone solution. This increase in the internal barrier in a polar solvent is similar to that found for benzyl fluoride, but in the latter the barrier itself is very much smaller than in benzyl chloride.
13C magnetic resonance studies. 124. Preparative ring expansions of bicyclic ketones by homoketonization of cyclopropoxide analogs
Authors: Patel Vijay , Ragauskas Arthur J. , Stothers J. B.
Published: May 2006

Homoketonization of some readily prepared cyclopropoxides provides a new synthetic method for ring expansion of the [2.2.1] and [2.2.2] ring systems. Cyclopropanation of the trimethylsilyl enol ethers derived from a variety of polycyclic ketones affords the required cyclopropyl silyl ethers, which may be ketonized directly or hydrolyzed to the corresponding cyclopropanols before ketonization. The results for fourteen examples serve to define the scope of the ring expansion process, and the silyl enol ethers, cyclopropyl silyl ethers, and most of the corresponding cyclopropanols have been characterized by 13Cmr. The stereochemistry of the ketonization leading to ring expansion has been established by deuterium labelling experiments.
Metabolites produced by the Scleroderris canker fungus, Gremmeniellaabietina. Part 1
Authors: Ayer William A. , Hoyano Yumiko , Pedras M. Soledade , Altena Ian van
Published: May 2006

The metabolites produced in liquid culture by the Ascomycetous fungus Gremmeniellaabietina (Lagerb.) Morelet, the causative agent of Scleroderris canker in pines, have been investigated. The major metabolite, which we have named sclerodin, is (−)-4,7-dihydroxy-2,3,3,9-tetramethyl-2,3-dihydronaphtho[1,2-b]furan-5,6-dicarboxylic anhydride (1), the enantiomer of the so-called "naphthalic anhydride from atrovenetin". Several highly colored compounds, including the enantiomer of atrovenetinone (3), the blue compound 6, the red acenaphthenequinone derivative 8 (sclerodione), and the yellow 8-hydroxysclerodin (12) were also obtained. The blue compound 6, named Scleroderris blue, has been prepared from 3, and sclerodione (8) has been transformed into sclerodin (1).
Excess volumes, viscosities, enthalpies, and Gibbs free energies for mixtures of methyl isobutyl ketone + n-pentanol and methyl isobutyl ketone + isoamyl alcohol at 298.15 K
Authors: Riggio Roque , Martinez Hector E. , Solimo Horacio N.
Published: May 2006

Three excess functions (molar volumes, viscosities, and molar enthalpies) for the methyl isobutyl ketone + n-pentanol and methyl isobutyl ketone + isoamyl alcohol systems at 298.15 K were calculated from measured densities, viscosities, and enthalpies, respectively. The UNIFAC group contribution method was used in order to estimate the activity coefficients which were then employed to calculate the excess molar Gibbs free energy. An attempt to explain the experimental results in terms of molecular interactions was made.
The effects of high temperatures (29–123 °C) on critical micelle concentrations in solutions of potassium n-octanoate in deuterium oxide: A nuclear magnetic resonance study
Authors: Desando M. A. , Reeves L. W.
Published: May 2006

Critical micelle concentrations have been determined for potassium n-octanoate in deuterium oxide over a wide temperature range, 29–123 °C, from the concentration dependence of proton nmr spectral parameters (peak positions, and vicinal splitting values of the α-CH2 multiplet) and carbon-13 nmr chemical shifts. The c.m.c. varies from ca. 0.30 m at ca. 30 °C to ca. 0.50 m at ca. 120 °C and is at a minimum (0.30–0.35 m) in the temperature range ca. 30–50 °C. 23Na+ spin-lattice relaxation times reveal that a co-counterion (Na+) different from that of the surfactant counterion (K+) reflects the micellization process. A second critical micelle concentration has been observed around 1.0 m at ca. 30 °C.
Properties of a strong intramolecular OHO hydrogen bond in 2-(N,N-diethylamino-N-oxymethyl)-4,6-dichlorophenol
Authors: Koll A. , Rospenk M. , Sobczyk L. , Glowiak T.
Published: May 2006

The crystals of 2-(N,N-diethylamino-N-oxymethyl)-4,6-dichlorophenol chosen as a representative of the Mannich base N-oxides were found to be monoclinic, P21/c space group, with a = 11.729(3), b = 16.232(4), c = 13.689(3) Å, β = 107.37(3)°, and Z = 8. The structure solved by the direct method was refined to R = 0.033 for 3170 independent reflections. Two slightly different molecules denoted as A and B in the unit cell with very short (2.42 and 2.40 Å) OHO intramolecular hydrogen bonds were detected. Both a X-ray diffraction study and the ir and uv spectra indicate a symmetric type of bridge in this compound.
Ionic dissociation in pyridine–iodine solutions
Authors: Aronson Seymour , Wilensky Stuart Bryan , Yeh Taun-Iuan , Degraff Darnel , Wieder Grace Marilyn
Published: May 2006

An electrochemical technique has been employed to study the ionization of the pyridine–iodine complex in pure pyridine and in 1,2-dichloroethane. A mechanism for the ionization in accord with the experimental data is proposed. The results indicate that, for wide ranges of iodine and pyridine concentration, one quarter of the I2 is dissociated into ionic species.
Cation–anion combination reactions. 26. A review
Authors: Ritchie Calvin D.
Published: May 2006

Rate and equilibrium constants for reactions of carbocations, and a few other electrophiles, with anionic and neutral nucleophiles in several solvents are summarized. Equilibrium constants for such reactions are a measure of the carbon basicities of the nucleophiles, and are discussed in the context of differences in proton and carbon basicities. The factors affecting the kinetic reactivities of nucleophiles are not well understood, even though the reactivity patterns are frequently the same toward widely different electrophiles.
Iodine chemistry in the +1 oxidation state. II. A Raman and uv–visible spectroscopic study of the disproportionation of hypoiodite in basic solutions
Authors: Wren J. C. , Paquette J. , Sunder S. , Ford B. L.
Published: May 2006

The kinetics of disproportionation of elemental iodine to iodide and iodate ions has been studied in basic aqueous media using Raman and uv–visible spectroscopy. The IO stretching vibrations for IO− and I2OH− were observed at 430 ± 2 and 560 ± 2 cm−1, respectively. The totally symmetric stretching vibration for [Formula: see text] was observed at 685 ± 2 cm−1. The Raman results indicate that I2OH− is a linear molecule with a stronger I—O bond than IO−. The rate expression at 25 °C in 1 mol dm−3 NaOH was found to be[Formula: see text]where[Formula: see text]The reaction is primarily a reaction of the iodine +1 oxidation-state species IO− and I2OH−. It proceeds through the +3 oxidation-state species [Formula: see text] The following equilibrium and rate constants were determined:[Formula: see text]
Energy partitioning in O(1D2) reactions. III. O(1D2) + NH3 → OH(v′) + NH2
Authors: Aker P. M. , O'Brien J. J. A. , Parsons J. M. , Sloan J. J.
Published: May 2006

The vibrational distribution in the OH created by the reaction of O(1D2) atoms with NH3 has been recorded directly using low pressure infrared emission spectroscopy. The relative kinetic energy of the reagents is Boltzmann at 300 K. The OH product vibrational levels are populated statistically, indicating that the reaction probably involves a long-lived ONH3 intermediate. There is some evidence that this may not be the case at higher reagent translational energies.
Kinetic benzylidenation. Part I. The selective formation of five-membered ring benzylidene acetals from aldose diethyl dithioacetals
Authors: Grindley T. Bruce , Kusuma Srihari , Cameron T. Stanley
Published: May 2006

Reaction of D-arabinose diethyl dithioacetal with one equivalent of benzaldehyde dimethyl acetal in the presence of p-toluenesulfonic acid at −40 °C gave a mixture of the two epimers of 5-O-methoxyphenylmethyl-D-arabinose diethyl dithioacetal initially. After 14 h at −20 °C, the major products were R- and S-4,5-O-benzylidene-D-arabinose diethyl dithioacetal. The structure of the S isomer was determined by X-ray crystallography. The crystal was orthorhombic, with space group P212121, cell dimensions a = 5.179(4), b = 12.469(3), c = 27.150(4) Å, and Z = 4. The crystal structure was solved using the SHELX (76) system and refined to R = 0.060 for 714 reflections. The sugar chain was in a zigzag conformation, the 4,5-O-benzylidene ring in a 0−5Tc conformation, and the plane of the phenyl ring was nearly perpendicular to the plane of the five-membered ring (88° angle). There were two short OH—S hydrogen bonds, one intramolecular and one intermolecular. Reaction of the diethyl dithioacetals of D-glucose, D-galactose, D-mannose, and D-ribose at −20 °C as above also gave mixtures of the terminal five-membered ring O-benzylidene diastereomers.
A water soluble dimeric steroid with catalytic properties. Rate enhancements from hydrophobic binding
Authors: Guthrie J. Peter , Cossar John , Dawson Brian A.
Published: May 2006

Dimeric steroids can be formed by reductive amination of terephthalaldehyde with 3-amino steroids using cyanoborohydride. An amino group in the 11β-position can be blocked using a formyl group, and this can be removed by acid hydrolysis after dimerization. Trifluoroacetyl is not a suitable blocking group; although it can be removed by acid hydrolysis from monomeric steroids, it was only removed from the dimer under forcing conditions which caused degradation. The dimeric steroid is a catalyst for the hydrolysis of arylpropionate esters with good leaving groups. Acylation is markedly accelerated by hydrophobic binding of the aryl group of the substrate to the steroids. Rate enhancements, relative to imidazole, of up to 5.5 × 102 were obtained, and analysis of the data shows that the potential rate enhancement is 1.1 × 105. The magnitude of the hydrophobic binding is consistent with what was seen with earlier catalysts. Aggregation, even at very low concentrations, was a problem with anionic substrates.
Biosynthesis of lupanine: incorporation of [3,3-2H2]cadaverine
Authors: Hemscheidt Thomas , Spenser Ian D.
Published: May 2006

The mode of incorporation of 2H from [3,3-2H2]cadaverine into lupanine (2) and 13α-hydroxylupanine (3) in Lupinusangustifolius was determined by 2H nmr spectroscopy. Lupanine carried deuterium at positions 4α, 4β, 8α, 8β, 13α, and 13β. These six sites were approximately equally enriched. Similarly, 13α-hydroxylupanine carried label approximately equally at five sites, 4α, 4β, 8α, 8β, and 13β. [3,3-2H2]Cadaverine was prepared by borodeuteride reduction in D2O of the p-toluene-sulfonylhydrazone of N-benzoylpiperid-4-one, followed by degradation of the resulting N-benzoyl[4,4-2H2]piperidine into 1,5-dibromo[3,3-2H2]pentane, conversion into 1,5-diphthalimido[3,3-2H2]pentane, and acid hydrolysis.
Synthesis and spectroscopic investigations of 1,4-benzothiazepine derivatives
Authors: Szabó János , Bernáth Gábor , Katócs Ágnes , Fodor Lajos , Sohár Pál
Published: May 2006

The reaction of sodium 3,4-dimethoxythiophenolate (1) with 2-bromoethylamine (2) gave 2′-aminoethyl-3,4-dimethoxy-phenyl sulfide hydrochloride (3). Ring closure of the acyl derivatives 4a–c with phosphoryl chloride furnished the 2,3-dihydro-1,4-benzothiazepines 5a–c. In a reaction competing with the cyclization, the acid amides 4 decomposed to 2′-chloroethyl-3,4-dimethoxyphenyl sulfide (7) and the corresponding nitrile. A few derivatives (8–10) of 5c were prepared. Sodium borohydride reduction of 5b, c yielded the 2,3,4,5-tetrahydro-1,3-benzothiazepines 11a, b. With substituted acetyl chlorides, compounds 5c and 10 were converted to the β-lactam derivatives 12a–f and 13, the configurations and conformations of which were determined by nmr spectroscopy; under similar reaction conditions the analogous compounds 5a, b gave the enamides 14, 15, and 16.
Charge transfer fluorescence of some N-benzoylindoles
Authors: Disanayaka Bimsara W. , Weedon Alan C.
Published: May 2006

The fluorescence properties of various N-carbonyl-substituted indoles (compounds 1–7) are examined. The N-benzoyl-indole derivatives 1 and 3–5 are shown to fluoresce weakly and the effect of solvent polarity upon the energy of the emitting state and upon the quantum yield of fluorescence is described. It is concluded that the initially formed singlet excited state is non-emissive and can relax to an intramolecular charge transfer state which is weakly fluorescent. The solvent effects are consistent with a general type of solvent interaction, and the solvent-induced shifts in the wavelength of the fluorescence emission correlate well with the Lippert equation relating the stabilisation of the excited state to a function of solvent dielectric and refractive index. A poor correlation with the empirical ET(30) solvent polarity parameter is observed.
Flash vacuum pyrolysis of anthracenic Diels–Alder adducts, a convenient source of methanethial and methanethial S-oxide
Authors: Vallee Yannick , Ripoll Jean-Louis , Lafon Christophe , Pfister-Guillouzo Geneviève
Published: May 2006

The flash vacuum pyrolysis of Diels–Alder adducts of anthracene constitutes a rapid and selective route to methanethial 1 and methanethial S-oxide 2, as analyzed in the gas phase by photoelectron spectroscopy. Low temperature infrared and nuclear magnetic resonance (1H, 13C) spectra are also reported for sulfine 2.
Structure and magnetic exchange in poly-bis(pyrazine)bis(methanesulfonato-O)-copper(II). One-dimensional exchange in a two-dimensional polymer
Authors: Haynes John S. , Rettig Steven J. , Sams John R. , Thompson Robert C. , Trotter James
Published: May 2006

Crystals of poly-bis(pyrazine)bis(methanesulfonato-O)copper(II) are orthorhombic, a = 8.199(1), b = 13.130(1), c = 6.913(1) Å, Z = 2, space group Pnnm. The structure was solved by conventional heavy atom methods and was refined by full-matrix least-squares procedures to R = 0.025 and Rw = 0.033 for 1226 reflections with I ≥ 3σ(I). The complex contains parallel sheets, each sheet consisting of a square array of copper(II) ions bridged by two types of bidentate pyrazine ligands. The CuN4O2 chromophore is tetragonally elongated; the equatorial plane contains two pyrazine nitrogen atoms (Cu—N(1) = 2.058(2) Å) and two oxygen atoms from monodentate methanesulfonate ligands (Cu—O(1) = 1.956(1) Å); the axial sites are occupied by bridging pyrazine groups with significantly longer Cu—N bond lengths (Cu—N(2) = 2.692(2) Å) Magnetic susceptibility studies (82 to 4.2 K) reveal antiferromagnetic behaviour with a susceptibility maximum at about 6.2 K. Exchange coupling in the complex is considered to take place primarily via the more strongly bound, equatorially coordinated pyrazine ligands. Analysis of the magnetic susceptibility data according to a Heisenberg linear chain of interacting S = 1/2 spins yields best fit values of J = −3.82 cm−1 and g = 2.13. Vibrational and electronic spectroscopic and differential scanning calorimetric studies on the title compound and, for comparison, on the related mononuclear pyridine complex, bis(methanesulfonato)-tetrakis(pyridine)copper(II), are also reported.
Total synthesis of the ravidomycin aglycone (defucogilvocarcin V)
Authors: Findlay John A. , Daljeet Anand , Murray Peter John , Rej Rabindra N.
Published: May 2006

The synthesis of 1-hydroxy-10,12-dimethoxy-8-vinyl-6H-benzo[d]naphtho[1, 2b]pyran-6-one 7, starting from vanillin and 1,5-dihydroxynaphthalene is described. This compound is the aglycone of the antitumor antibiotic ravidomycin and is identical with the recently reported antimicrobial agent, defucogilvocarcin V.
Comment on "Thermodynamics of solvent mixtures. I. Density and viscosity of binary mixtures of N-methylpyrrolidinone – tetrahydrofuran and propylene carbonate – acetonitrile"
Authors: Gee Norman , Freeman Gordon R. , Anantaraman A. V.
Published: May 2006

In the recent work of Anantaraman (Can. J. Chem. 64, 46 (1986)) the conversion from kinematic viscosity to dynamic viscosity was incorrect. We calculated correct values from the tabulated data. We also give corrected values of the ideal mixture viscosity, the Grunberg–Nissan deviation parameter, and the Hind interaction parameter.
Anomalous ozone degradations of 1-chloro substituted conjugated dienes in methanol
Authors: Griesbaum Karl , Bandyopadhyay Ashis R.
Published: May 2006

Diozonolyses in methanol of (E)-4-chloro-2,3-dimethyl-1,3-hexadiene (4a) and of (4E)-5-chloro-3,4-dimethyl-2,4-heptadiene (4b) resulted in complete cleavage of the double bonds and of the single bonds of the respective diene systems. The course of these anomalous cleavage reactions has been established by step-wise ozonolyses of these dienes, and by the identification of labile methoxy hydroperoxides as intermediates.
New nitrogenous sesquiterpenes based on alloaromadendrane and epi-eudesmane skeletons from the marine sponge Axinellacannabina
Authors: Ciminiello Patrizia , Fattorusso Ernesto , Magno Silvana , Mayol Luciano
Published: May 2006

Six new nitrogenous sesquiterpenes (1–6), which form two new isocyanide-isothiocyanate-formamide series, have been isolated from the marine sponge Axinellacannabina. The structure elucidation of these compounds is based upon spectral data, including 2D-nmr, and chemical interconversions. The complete assignment of all proton and carbon resonances in nmr spectra of axisonitrile-2 (7), an isonitrile previously isolated from the same source, is also reported, along with its complete relative stereochemistry.
Solvent and α-substituent perturbations of the 2H/1H isotope shifts in the 13C nuclear magnetic resonance of toluene-α-d3
Authors: Schaefer Ted , Peeling James , Sebastian Rudy
Published: May 2006

The 2H/1H isotope effect on 13C nmr chemical shifts, nΔ, n being the number of intervening bonds between 2H and 13C nuclei, in toluene-α-d3 is solvent dependent. For example, 1Δ ranges from 817 ppb in CD3OH to 869 ppb in acetone-d6 solutions, a positive number indicating increased shielding in the deuterated species. 1Δ is linearly dependent on a function of the refractive index, nD, of the solvent, allowing extrapolation to nD = 1. The hyperconjugative model, in which the C—D bond is a poorer electron donor to the aromatic system than is a C—H bond, is tested for the substituents CH2D, CHD2, CD3, CHDCH3, CD2CH3, CD(CH3)2, C6H5CHD, and (C6H5)2CD. For these substituents, the negative 5Δ is linearly related to the expectation value of sin2 θ; θ is the angle by which the C—D bond twists out of the benzene plane. The model fails quantitatively for C6H5CD2X (X = Cl, COOH, CN, OH). For X = OH, very large negative 5Δ and 3Δ values are observed. nΔ is also reported for 4-ethyltoluene-α-d3 and benzaldehyde-α-d1. For the latter, all nΔ values are positive other than 5Δ, which vanishes in acetone-d6 solution.
Synthesis and properties of phenyl substituted derivatives of 2-phenyl-1,1,3,3-tetramethylguanidine
Authors: Pruszynski Przemyslaw
Published: May 2006

A series of 17 phenyl substituted derivatives of 2-phenyl-1,1,3,3-tetramethylguanidine was synthesized. The structure and purity of these compounds were checked by means of elemental analyses, mass spectrometry, ultraviolet spectrophotometry, and 1H nuclear magnetic resonance. The pKa values were determined and are discussed in terms of substituent effects using Hammett substituent constants. The Hammett reaction constant ρ = 1.84 ± 0.05 was found to be much lower for para and meta substituted compounds than for anilines, even though the phenyl ring is attached directly to the basic centre in both cases.
Prospectives of polymeric liquid crystal stationary phases for capillary column gas chromatographic separations
Authors: Naikwadi K. P. , McGovern A. M. , Karasek F. W.
Published: May 2006

The liquid crystalline polysiloxane substrate offers unique selectivity when used in capillary column gas chromatography. The separation and identification of priority pollutants along with other compounds is very difficult but important. In particular, the separation of isomeric organic compounds having similar volatilities could not be obtained on capillary columns using conventional stationary phases. The complete separation of ortho, meta, and para isomers of certain disubstituted benzenes as well as polycyclic aromatic compounds was achieved on a capillary column using a liquid crystalline polysiloxane stationary phase. The complete separation of octachlorodibenzodioxin from octachlorodibenzofuran was also obtained on this column which is not possible on columns of identical lengths using conventional stationary phases. The separation of polycyclic aromatic compounds in a complex sample of airborne particulate matter extract on the liquid crystal column is demonstrated.
Recent advances in ultratrace analysis of dioxins and related halogenated hydrocarbons
Authors: Afghan B. K. , Carron J. , Goulden P. D. , Lawrence J. , Léger D. , Onuska F. , Sherry J. , Wilkinson R.
Published: May 2006

Analytical methodology for polychlorinated dioxins and furans (PCDDs and PCDFs) in environmental samples is not standardized. Many variations exist for the extraction, cleanup, quantitation, and confirmation of these compounds and reported detection limits and recoveries vary over several orders of magnitude. This paper describes research carried out at the Canada Centre for Inland Waters over the past seven or eight years to develop reliable methodology at ultratrace levels (10−12–10−15 g/g) applicable to a wide range of environmental samples. Extraction techniques are described for biological tissue (fish, clams, leaches, eggs), fly ash, sediments, and water. Detailed cleanup procedures for the various matrices consist of most or all of the following: gel permeation chromatography liquid/liquid extraction with Na3PO4, liquid/liquid extraction with H2SO4, basic alumina chromatography, and carbon fibre chromatography. Preliminary screening of the cleaned extracts is achieved by gas chromatography equipped with a mass selective detector and positive identification by gas chromatography/mass spectrometry operated in electron impact and chemical ionization modes and with full scan and multiple ion detection. Custom software permitting the analysis of a wide range of compounds in a single run by gc/ms is reported. The presence of specific isomers of PCDDs and PCDFs is confirmed by high resolution gas chromatography/mass spectrometry. A radioimmunoassay screening procedure for PCDDs in environmental samples is also described.
Polarized absorption spectra of radical ions of some azanaphthalenes and biphenyls in stretched polymer films
Authors: Hiratsuka Hiroshi , Sekiguchi Ken'ichi , Hatano Yoshihiko , Tanizaki Yoshie , Mori Yuji
Published: May 2006

The stretched polymer film technique combined with -γ-irradiation has been employed to measure the polarized absorption (linear dichroism) spectra of radical anions of quinoline, isoquinoline, quinoxaline, phthalazine, phenylpyridine, 4,4′-bipyridyl, and 2,2′-bipyridyl. Profiles of polarized absorption spectra of all the radical anions are similar to those of the parent naphthalene or biphenyl radical anions. Those of radical cations of isoquinoline and 2,2′-bipyridyl are also similar to those of radical cations of their parent molecules. Quinoxaline radical cations, however, show quite a different spectrum from that of naphthalene radical cations; a long vibrational structure with ca. 550 cm−1 intervals was observed and peaks of these vibrational bands were polarized parallel to the molecular short-axis or normal to the molecular plane.