bluuebunny/crossref_metadata_2025 huggingface dataset:
Further experiments on the oxidation of sugar acetals and thioacetals byAcetobacter suboxydans
Authors: Williams D. T. , Jones J. K. N.
Published: April 2011

The oxidation by Acetobacter suboxydans of d-galactose diethyl dithioacetal and of the dimethyl acetal yielded ketose derivatives in which the hydroxyl group at C-5, and not the one at C-3 as had been expected, had been oxidized to a keto group. 1-Deoxy-d-galactito1 (l-fucitol) yielded both 1-deoxy-d-threo-d-glycero-3-hexulose and 6-deoxy-l-lyxo-hexulose.
A series of Schiff's bases and secondary amine derivatives from 3-formyl-10-methylphenothiazine
Authors: Kremers W. , Steele J. W.
Published: April 2011

The various recorded methods of synthesizing 10-methylphenothiazine were reviewed, and an improved process is suggested which gives consistent yields of 50–60% purified product. A series of bis-Schiff's bases was prepared by condensation of 3-formyl-10-methylphenothiazine with a number of diamines, and reduction of this series yielded a corresponding series of bis-secondary amines. The secondary amines did not show an NH absorption band in the infrared spectra unless considerably higher than normal concentrations were used, but nuclear magnetic resonance studies in deuteriochloroform confirmed the existence of the ―CH2NH― group. A model compound of the same type (namely, 3-phenyliminomethylene-10-methyl-phenothiazine) was synthesized, and it was found to exhibit exactly the same effects in the infrared spectra and in the nuclear magnetic resonance spectra in deuteriochloroform. In dimethyl sulfoxide-d6, the model compound showed clear evidence of coupling between the NH and the adjacent methylene group, an effect which is rarely seen.Quaternization of the secondary amines was unsuccessful in all but a few cases.
Primary step in the mercury photosensitization of propane and deuterated propanes
Authors: Jakubowski E. , Kebarle P. , Strausz O. P. , Gunning H. E.
Published: April 2011

The primary processes in the mercury-photosensitized decomposition of propane and three deuterated propanes have been studied at low pressures. The primary radicals were trapped by methyl radicals, from the in situ decomposition of dimethyl mercury, and the products measured by gas chromatography. The trapping technique was checked by using 1-chloropropane, 2-chloropropane, and their mixtures. The butane yields were representative of the primary radical yields.The ratio of i-butane to n-butane from the propane reaction was found to be dependent on light intensity, which fact, not having been recognized before, vitiates earlier results. The ratio varied between 0.3 (at high intensity) and 8.5 (at low intensity). The i-propyl to n-propyl split in the primary step of propane is 9.1 to 1.0, as found earlier by Holroyd and Klein.
Enantiomeric 3-hydroxypent-4-enethionamides from thioglucosides of Crambe and Brassica seeds by action of ferrous salts
Authors: Austin F. L. , Gent C. A. , Wolff I. A.
Published: April 2011

epi-Progoitrin, the major thioglucoside of Crambe abyssinica seed, is cleaved by ferrous salts to yield (S)-1-cyano-2-hydroxy-3-butene and (S)-3-hydroxypent-4-enethionamide. The products are the same whether obtained from the purified thioglucoside or from the seed meal. Identical behavior was observed for seed meal of Brassica napus, which gave corresponding derivatives of the opposite configuration. Optical rotatory dispersion and proton magnetic resonance studies suggest the existence of solvent-dependent differences in rotamer composition for the 3-hydroxypent-4-enethionamides.
Cis- and trans-2,4-dimethoxytetrahydropyran. Models for the study of the anomeric effect
Authors: Sweet F. , Brown R. K.
Published: April 2011

Acid-catalyzed methanolysis of 2-methoxy-5,6-dihydro-2H-pyran gave, in good yield, a 4.0:1.0 mixture of trans- and cis-2,4-dimethoxytetrahydropyran. Mild acid hydrolysis of 2-methoxy-5,6-dihydro-2H-pyran followed by acid-catalyzed reaction with methanol gave a cis-trans mixture of 4-hydroxy-2-methoxytetrahydropyran in very poor yield.From the equilibrium mixture of trans- and cis-2,4-dimethoxytetrahydropyran (4.0:1.0), the magnitude of the anomeric effect of the 2-methoxy group was calculated to be 1.4 kcal/mole.
Kinetics of hydrolyses of o-methylbenzylideneaniline and o-hydroxybenzylideneaniline
Authors: Willi Alfred V. , Siman José F.
Published: April 2011

Rates of hydrolysis have been measured for o-methylbenzylideneaniline, o-hydroxybenzylideneaniline, and benzylideneaniline in various buffer solutions in 20% (by volume) aqueous methanol at 29.9 °C. Rate constants for the o-CH3 compound and the unsubstituted Schiff base agree within experimental error which indicates that there is no appreciable rate retarding steric effect. The o-OH group decreases the hydrolysis rate at pH = 5.6 – 6.6 by approximately one power of ten. This effect is caused by the hydrogen bond between the OH group and the azomethine N, which renders the Schiff base less accessible to acid-catalyzed hydrolysis.
Effect of substituents on the chemical shift of benzylic protons: evidence for a conformational dependence
Authors: Fraser Robert R. , Gurudata  , Reyes-Zamora Cesar , Swingle Robert B.
Published: April 2011

The benzyl proton shifts in 11 series of para-substituted toluenes bearing different α substituents have been determined. In each series, a plot of the benzylic shift against the Hammett σ values of the para-substituent is linear. The slope of these plots varies from 0.2 to 0.0 p.p.m./σ. The variation is found to be conformationally dependent, a fact which is not explicable by current theory. A hyperconjugative interaction is proposed to account for these results and for several anomalies in the literature.
Enthalpy of formation of some alkaline earth halides
Authors: Finch Arthur , Gardner P. J. , Steadman C. J.
Published: April 2011

The enthalpies of reaction of crystalline magnesium oxide in aqueous hydrogen bromide and iodide solutions have been determined. The enthalpies of precipitation of magnesium, calcium, and strontium fluorides and the enthalpies of solution of magnesium iodide and bromide have also been determined and the following data are derived: ΔHf0 (298 °K) of MgBr2(c), MgI2(c), CaF2(c), NaMgF3(c), SrF2(c) are −125.3 ± 0.4, −88.1 + 0.35, −291.9 ± 0.2, −406.7 ± 0.3, −291.2 ± 0.3 kcal mole−1 respectively. NaMgF3 is an ideal mixed crystal.
Solvent LiCl–KCl in the nephelauxetic series for trivalent rare earths
Authors: Johnson K. E. , Sandoe J. N.
Published: April 2011

The spectra of trivalent Ce, Pr, Nd, Sm, Eu, Tb, Dy, Tm, and Yb ions in molten LiCl–KCl at 450 °C are reported over the range 0.28 to 2.8 μ and the baricenters of terms are tabulated for a wide variety of crystal and liquid hosts. These hosts can be arranged in a nephelauxetic series and for Pr3+ actual nephelauxetic parameters, β, can be calculated by comparing average multiplet energies.
Reaction of active nitrogen with perfluorinated olefins
Authors: Madhavan N. , Jones W. E.
Published: April 2011

The reactions of the fluorocarbon olefins, C2F4, C3F6, and C4F8-2, with active nitrogen were studied in a flow system. The active nitrogen was produced by a microwave discharge at a concentration of 2.1 × 10−6 mole/s. The major gaseous products of the reactions are fluorocarbons and their production was studied quantitatively at the temperatures 25, 250, and 400 °C and at a large number of reactant flow rates to a maximum of approximately 3 × 10−6 mole/s.Three nitrogen-containing compounds, FCN, N2O, and a polymer of composition (C3F5N)n were detected as products in all three reactions; FCN and N2O are found only in very small amounts.Mechanisms for each of the reactions are discussed.
3d orbitals and bonds of second row atoms. 2. π bonding in phosphoryl compounds
Authors: Mitchell K. A. R.
Published: April 2011

The concept of 3dπ orbital bonding in molecules of second row atoms is tested by making some model calculations on phosphoryl molecules, X3PO. Values of exponents for 3s, 3p, and 3d orbitals of phosphorus have been calculated in an electrostatic calculation where X is F, Cl, C, and H. For F3PO, estimates have also been made on the effect of interatomic exchange. The main conclusion for F3PO is that the molecular environment strongly contracts the 3d orbitals at phosphorus with π symmetry with respect to the P—O bond, thereby indicating the feasibility of double bond interactions with oxygen 2pπ orbitals.
Studies on metal hydroxy compounds. V. Heats of decomposition of zinc and cadmium halide (Cl,F) derivatives
Authors: Ramamurthy P. , Secco E. A.
Published: April 2011

The heats of decomposition of the following hydroxy compounds are reported: Zn(OH)2, Zn(OH)Cl, Zn(OH)F, Cd(OH)2, Cd(OH)Cl, and Cd(OH)F.
Synthesis of D-glycero-D-gulo-heptose, D-glycero-D-ido-heptose, and 2-deoxy-D-gluco-heptose from D-glucose
Authors: Williams D. T. , Perry M. B.
Published: April 2011

D-Glucose was condensed with nitromethane to yield 1-deoxy-1-nitro-D-glycero-D-ido-heptitol and 1-deoxy-1-nitro-D-glycero-D-gulo-heptitol which were converted via the Nef reaction to D-glycero-D-ido-heptose and D-glycero-D-gulo-heptose respectively. The acetylated 1-deoxy-1-nitro-D-glycero-(D-ido- and D-gulo-)-heptitols were converted to 3,4,5,6,7-penta-O-acetyl-1,2-dideoxy-1-nitro-D-gluco-hept-1-enitol and reduction of this derivative afforded 3,4,5,6,7-penta-O-acetyl-1,2-dideoxy-1-nitro-D-gluco-heptitol which underwent the Nef reaction to give 2-deoxy-D-gluco-heptose.
Transmission of polar effects. Part XI. Polar and steric effects in the reactions of arylaliphatic carboxylic acids
Authors: Bowden Keith , Young R. C.
Published: April 2011

The rate coefficients for the reaction with diazodiphenylmethane in ethanol at 30° and the acid-catalyzed esterification with methanol at 60° of a number of arylaliphatic carboxylic acids and their pKa values in 80% 2-methoxyethanol–water have been measured. Rate coefficients have also been measured for the alkaline hydrolysis in 70% dioxan–water of their 2-diethylaminoethyl esters at 45°. The pKa values and diazodiphenylmethane esterification rate coefficients were also measured for a series of 2-substituted fluorene-9-carboxylic acids. The latter results have been correlated by Hammett equations and the transmission of polar effects in fluorene is discussed. Polar and steric substituent constants are evaluated for the arylaliphatic systems. These values are used to successfully correlate the hydrolysis and ionization reactions using the Taft–Ingold equation.
Reactions of nitro sugars. XI. Formation of 2,3-unsaturated hexonolactones by denitration of methyl deoxynitroglycosides
Authors: Baer Hans H. , Rank Werner
Published: April 2011

Treatment of methyl 4,6-O-benzylidene-3-deoxy-3-nitro-β-D-glucopyranoside (1) and its α-anomer (3), as well as of methyl 4,6-O-benzylidene-2,3-dideoxy-3-nitro-β-D-erythro-hex-2-enopyranoside (2) and its α-anomer (4), with basic aluminum oxide in refluxing toluene, leads to loss of the nitro and glycosidic methoxyl groups. As a common product an α,β-unsaturated lactone, 4,6-O-benzylidene-2,3-dideoxy-D-erythro-hex-2-enono-1,5-lactone (5), was isolated in crystalline form. The β-D-manno isomer (6) of 1 incurs epimerization to 1 and partial conversion to 5. Methyl 4,6-O-benzylidene-3-deoxy-3-nitro-β-D-galacto-pyranoside (7) and methyl 4,6-O-benzylidene-2,3-dideoxy-3-nitro-β-D-threo-hex-2-enopyranoside (8) similarly yield a crystalline lactone, 4,6-O-benzylidene-2,3-dideoxy-D-threo-hex-2-enono-1,5-lactone (9). The mechanism of this novel reaction is discussed, and certain differences in reactivity in the gluco and galacto series are pointed out. Base-catalyzed additions of methyl alcohol, ethyl alcohol, and piperidine to 8 afford methyl 4,6-O-benzylidene-3-deoxy-2-O-methyl-3-nitro-β-D-galactopyranoside (10), its 2-O-ethyl analogue (11), and methyl 4,6-O-benzylidene-2,3-dideoxy-3-nitro-2-piperidino-β-D-galacto-pyranoside (12), respectively.
Diterpene chemistry III. Chemistry of some epoxides derived from methyl pimarate
Authors: ApSimon J. W. , Krehm H.
Published: April 2011

Some chemistry of the α- and β-epoxides derived from a methyl pimarate degradation product (vinyl group transformed into a methoxycarbonyl) is described. The α-epoxide was found to be a very reactive species leading, by an intramolecular process, to a hydroxy-γ-lactone even on standing in hexane solution. A possible explanation for the reactivity is given, based on a conformational argument. The β-epoxide undergoes a cleavage reaction with Lewis acid to give a 'backbone' rearrangement product, although a non-rearranged compound was observed in minor yield.
Diterpene chemistry. IV. The oxymercuration–demercuration of methyl pimarate and methyl sandaracopimarate
Authors: ApSimon J. W. , Krehm H.
Published: April 2011

The oxymercuration–demercuration procedure was explored for methyl pimarate and methyl sandaracopimarate. In the first case a dimercurial-monoether was obtained yielding a cyclic ether on demercuration. In the second, a monomercurial was obtained arising from attack on the vinyl group only, and demercuration gave a mixture of alcohols which were oxidized to a methyl ketone, which on hypoiodite degradation yielded a known degradation product of methyl sandaracopimarate. The difference in behavior between the two series is attributed to the proximity of the double bonds in methyl pimarate.
α,β-Epoxy sulfones. The Darzens condensation with α-halosulfones
Authors: Vogt Peter F. , Tavares Donald F.
Published: April 2011

Darzens type condensation of chloromethyl p-tolyl sulfone with benzaldehyde, acetaldehyde, acetone, benzophenone, and cyclohexanone, with potassium tert-butoxide as base, gave good to excellent yields of the corresponding α,β-epoxy sulfones (1). The condensation of α-chloroethyl p-tolyl sulfone and bromomethyl p-tolyl sulfone with benzaldehyde also gave excellent yields. With the aldehydes only the trans-epoxides were formed, which is shown by nuclear magnetic resonance spectroscopy. The mechanism and stereochemistry are discussed.
Galactomannan from Cassiaabsus seed. I. Nature of sugars present, methylation, and periodate oxidation studies
Authors: Kapoor V. P. , Mukherjee S.
Published: April 2011

A galactomannan composed of D-galactose (1 mole) and D-mannose (3 moles) was isolated from the seed of Cassiaabsus. Methylation and hydrolysis of the galactomannan produced 2,3,4,6-tetra-O-methyl-D-galactose (2 moles), 2,3,6-tri-O-methyl-D-mannose (4.2 moles), 2,3-di-O-methyl-D-mannose (1 mole), and 4,6-di-O-methyl-D-mannose (1 mole). Periodate consumption was 1.09 moles for each hexose unit with concomitant liberation of 0.26 mole of formic acid. The periodate oxidized and the reduced galactomannan afforded, on hydrolysis, glycerol (1.94 moles), erythritol (5 moles), and D-mannose (1.08 moles).On the basis of the above findings, a structure for the galactomannan can be proposed in which mannose units form the main chain and the galactose units are present as branches, the former being attached mostly through 1 → 4 (ca. 85%) and the rest which is nearly half the branch points through 1 → 3 or 1 → 2, and branches of single galactose units are attached through 1 → 6 (ca. 50%) and the rest through 1 → 2 or 1 → 3.
Some O-isopropylidene derivatives of D-ribose diethyl dithioacetal
Authors: Lance D. G. , Szarek W. A. , Jones J. K. N.
Published: April 2011

Acetonation of D-ribose diethyl dithioacetal using anhydrous copper sulfate as catalyst gives predominantly 2,4- and 4,5-O-isopropylidene derivatives. The structures of the compounds were established by chemical and nuclear magnetic resonance spectroscopic methods.
Synthesis of 3-O-α-D-glucopyranosyl-D-ribose and 3-O-α-D-glucopyranosyl-D-arabinose by the nitromethane method
Authors: Furda I. , Perry M. B.
Published: April 2011

2-O-α-D-Glucopyranosyl-D-erythrose condensed with nitromethane in the presence of sodium methoxide to yield a mixture of 1-deoxy-3-O-α-D-glucopyranosyl-1-nitro-D-ribitol and 1-deoxy-3-O-α-D-glucopyranosyl-1-nitro-D-arabinitol which were converted via the Nef reaction to 3-O-α-D-gluco-pyranosyl-D-ribose and 3-O-α-D-glucopyranosyl-D-arabinose.
Reaction of m-methoxyphenol with trichloromethanesulfenyl compounds. A novel route to sulfines
Authors: Thorn G. Denis
Published: April 2011

The reaction of m-methoxyphenol with various compounds containing the trichloromethanesulfenyl moiety gives 3,6-dimethoxyxanthione-S-oxide.
Phospholipids. Part I. Synthesis of phosphatidyl ethanolamines
Authors: Rakhit S. , Bagli J. F. , Deghenghi R.
Published: April 2011

This paper deals with a simple and general method of preparation of polyunsaturated 1,2-diacyl glycerol-3-phosphate and the synthesis of phosphatidyl ethanolamines. Dilinolenyl phosphatidyl ethanolamine was found to inhibit invitro production of angiotensin 1 by renin from renin substrate.
The barrier to the conformational interconversion of 1,4-dimethylenecyclohexane and related compounds
Authors: St-Jacques Maurice , Bernard Michel
Published: April 2011

The proton magnetic resonance spectra of 1,4-cyclohexanedione, 1,4-dimethylenecyclohexane, and 1,4-difluoromethylenecyclohexane have been studied at various temperatures; the spectra of the last two compounds were found to be temperature dependent. ΔF≠ values of 7.5 and 6.5 kcal/mole, respectively, were estimated from the spectral changes.
Lyoluminescence and spin trapping
Authors: Ettinger Kamil V , Forrester Alexander R , Hunter Charles H
Published: April 2011

The chemical origin of lyoluminescence has been probed using spin trapping techniques. Radicals derived from amino acids and saccharides by γ-irradiation in the solid state have been identified after trapping with aliphatic and aromatic nitroso compounds. Most of the radicals trapped were secondary alkyl radicals. Reaction of peroxyl radicals derived therefrom are thought to produce the emitting species (excited carbonyl compound and/or singlet oxygen). The effect which thermal annealing of the solids after γ-irradiation has on (a) the concentration of radicals in the solid, (b) the concentration of trapped radicals, and (c) the light yield has been investigated. One new water-soluble spin trap has been prepared.
An electron paramagnetic resonance study of the reaction of nitrosobenzene with cholesterol
Authors: Sridhar Rajagopalan , Floyd Robert A
Published: April 2011

The reaction of nitrosobenzene with cholesterol(Δ5-cholesten-3β-ol) producesa fairly stable aminoxyl (nitroxyl) derivative. This steroidal aminoxyl is presumed to be the oxidation product of the hydroxy lamine formed by Alder-ene addition of nitrosobenzene to cholesterol. Evidence is presented to show that, in this ene reaction, the double bond in the Δ5 position of the steroid shifts to the Δ4 rather than the Δ6 position.
Spin trapping of the azide radical with nitroso compounds
Authors: Kremers Walter , Koroll Grant W , Singh Ajit
Published: April 2011

Azide radicals (N3·) are formed in aqueous solutions by the reaction of hydroxyl radicals (·OH) with azide anions (N3aq−). Azide radicals have been spin trapped with three nitroso spin traps: nitrosodurene (ND), 2,6-dideutero-3,5-dibromo-4-nitrosobenzene sulfonate (DDNBS), and 2-methyl-2-nitrosopropane (MNP). The electron spin resonance (esr) spectra show the presence of two molecules of the spin traps in the spin-trapped species.
Spin-trapping in early and some recent nitroso chemistry
Authors: de Boer Th. J
Published: April 2011

The radical scavenging properties of nitroso compounds were discovered accidentally during investigations of photochemical nitrosation of hydrocarbons with alkyl nitrites. Depending on the nature of substrates and nitrosating agent, various nitroxides can be generated. Identification of these nitroxides by their esr spectra has triggered the development of the spin-trapping technique which has been useful in the elucidation of many organic radical reaction mechanisms. Recent studies have shown that the behavior of nitrosocyclopropanes and α-chloro-nitroso alkanes is unorthodox upon irradiation. Dark reactions of α-chloro-nitroso alkanes with Grignard reagents lead to nitrones by a polar mechanism and to oximes by electron transfer. In the latter case high yields of hydrocarbon dimers are sometimes obtained from the Grignard and other organometallic reagents, despite the presence of nitroso compounds. In the postulated reaction mechanism dimers and higher associates from the organometallic reagent play an essential role.
Involvement of nitroxide radicals in cocaine-induced hepatotoxicity
Authors: Rauckman Elmer J , Kloss Michelle W , Rosen Gerald M
Published: April 2011

Cocaine administration can produce hepatotoxicity in non-induced mice of at least one strain, DBA/2Ha and hepatotoxicity in induced mice of several strains. Metabolic studies and the administration of metabolites indicate that the minor metabolic pathway, cocaine → norcocaine → N-hydroxynorcocaine → norcocaine nitroxide, is responsible for the observed cocaine-induced hepatotoxicity. In vitro experiments show that cytochrome P-450 can oxidize N-hydroxynorcocaine to norcocaine nitroxide. Norcocaine nitroxide is unreactive towards cellular proteins or glutathione but does react directly with reduced pyridine nucleotides and is rapidly reduced enzymatically by the microsomal flavoproteins, NADPH-cytochrome P-450 reductase and FAD-containing monooxygenase. These reactions constitute a futile cycle in which NADPH is consumed and superoxide and hydrogen peroxide are generated. We postulate that the destruction of hydrogen peroxide by glutathione peroxidase results in the accumulation of excess oxidized glutathione which is actively excreted by the cell, since insufficient NADPH is available for glutathione reductase to maintain the GSH/GSSG ratio at an acceptable level. As reduced glutathione levels diminish, the cell can no longer protect itself against toxic lipid hydroperoxides which accumulate as a result of stimulation of lipid peroxidation (caused by the one electron cycling reaction, N-hydroxynorcocaine to norcocaine nitroxide cycle). Finally, as glutathione is depleted below a certain level, the cell loses the ability to maintain the GSH/GSSG ratio in a range consistent with homeostasis resulting in loss of cellular function. Ultimately, necrosis results. This mechanism is consistent with all the information available concerning cocaine-induced hepatotoxicity.
Syntheses of model oligosaccharides of biological significance. 9. Syntheses of trideuteriomethyl di-3,6-O-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-β-D-galactopyranoside: the I antigen branch-point trisaccharide and related disaccharides
Authors: Whitfield Dennis M. , Ruzicka Caroline J. , Carver Jeremy P. , Krepinsky Jiri J.
Published: April 2011

The title trisaccharide, 13c, was synthesized, as well as its two component disaccharides, 10c and 11c. Four disaccharides, 3c, 4c, 5c, and 7c, were also prepared to serve as model compounds for the investigation of the 3-dimensional structure of more complex oligosaccharides. The β-1,3 linkage was formed in 75% yield by coupling 3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl bromide (9) with trideuteriomethyl 2-O-benzoyl-4,6-benzylidene-β-D-galactopyranoside (2a), using silver trifluoromethanesulphonate as a promoter in the presence of the base 2,6-di-tert-butyl-4-methylpyridine. Using a silver zeolite as a promoter under a variety of conditions, both α-1,3 and β-1,3 linkages were formed. The β-1,6 linkages were prepared in high yield using 9 and silver zeolite with either trideuteriomethyl 2,3-di-O-benzoyl-β-D-galactopyranoside (8b) or trideuteriomethyl 2-O-benzoyl-3-O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl)-β-D-galactopyranoside (11b). 2,3,4-Tri-O-benzyl-α-L-fucopyranosyl bromide (1b) was used in the halide ion catalyzed fucosylation of 2a or its 3-O-benzoyl isomer 2b. The glycosylations of 3,6-di-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-2-deoxy-2-phthalimido-β-D-glucopyranosyl bromide (6b) and 4-O-(2,3,4,6-tetra-O-acetyl-β-D-galactopyranosyl)-2,3,6-tri-O-acetyl-α-D-glucopyranosyl bromide (5a) by heptadeuterioisopropanol used silver zeolite as promoter.
Facile calculations of select eigenvalues and the characteristic polynomial of small molecular graphs containing heteroatoms
Authors: Dias Jerry Ray
Published: April 2011

Determination of common eigenvalues by embedding smaller subgraphs onto larger ones is illustrated. A nearly universal expression of the sixth coefficient of the characteristic polynomial valid for all conjugated hydrocarbon polyenes is presented. Its use in a graph theoretical determination of the Hückel MO characteristic polynomial of molecular graphs possessing heteroatoms is detailed.
The direct electrochemical synthesis of some transition metal carboxylates
Authors: Kumar N. , Tuck Dennis G. , Watson Katherine D.
Published: April 2011

The transition metal carboxylates M(O2CR)n (M = Cr, R = C2H5, C6H5, n = 3; M = Mn, Fe, Ni, R = CH3, C2H5, C6H5, n-C7H15, n = 2, not all combinations) have been prepared by oxidising suitable metal anodes electrochemically in solutions of RCOOH in acetonitrile. With Co and Cu, a wide range of carboxylic acids (R = C2H5, c-C3H5, c-C5H9, C6H5, n-C4H9, n-C7H15, 2-ethylhexanoic, oleic, linoleic) has been used successfully to give M(O2CR)2. The advantages of the method are discussed. The preparation of Cu(O2CR)2 involves the prior formation of CuO2CR at the anode, followed by oxidation by the solvent.
Permanganate oxidation of glycine: Kinetics, catalytic effects, and mechanisms
Authors: Perez-Benito Joaquin F. , Mata-Perez Fernando , Brillas Enrique
Published: April 2011

The oxidation of glycine by permanganate ion in aqueous phosphate buffers is autocatalyzed by the soluble form of colloidal manganese dioxide formed as a reaction product. Both the noncatalytic and the catalytic reaction pathways are first order in permanganate, the noncatalytic pathway is also first order in glycine, whereas the catalytic pathway has a kinetic order unity for the autocatalytic agent and a non-integral order (1.31) for glycine. Both reaction pathways are accelerated by an increase in the pH of the medium, whereas an increase in the buffer concentration at constant pH results in an increase in the rate of the noncatalytic pathway and a decrease in the rate of the catalytic one. Additions of potassium chloride to the solutions have no kinetic effect on the reaction. The apparent activation energies of the noncatalytic and catalytic reaction pathways are 64.5 and 62.0 kJ mol−1, respectively. On the other hand, manganese(II), thiosulfate, and hexacyanoferrate(II) ions, as well as benzyltriethylammonium chloride and arabic gum, have all been found to increase the initial reaction rate. Mechanisms in concordance with the experimental findings are proposed.
Transient intermediates in the photolysis of iodonium cations
Authors: Devoe R. J. , Sahyun M. R. V. , Serpone N. , Sharma D. K.
Published: April 2011

Pulsed picosecond laser photolysis of the diphenyliodonium cation indicates that excitation of the allowed transition is followed by rapid (ps) deactivation to a homolytically dissociative state, presumably T1. Steady-state photolysis yields iodobenzene and biphenyl from the primary radical products. Iodobiphenyl is also observed. We infer in-cage recombination of these radical products, with intervention of a carbocationic intermediate. Laser flash photolysis of diphenyliodonium iodide in its charge transfer band yields an initial transient with a lifetime of ca. 200 ps. A strongly absorbing secondary transient is observed on the nanosecond time scale. Iodobenzene is the exclusive reaction product. We infer that it is not formed directly from the primary photoproduct, but through in-cage recombination of phenyl cation with iodide anion, as in benzenediazonium iodide.
Bis(dimethoxymethyl) peroxide and bis(1,1-dimethoxyethyl) peroxide
Authors: Kopecky Karl R. , Molina José
Published: April 2011

The title compounds 1 and 2, the first examples of peroxides polysubstituted at the α and α′ positions by alkoxy groups, are formed by benzophenone sensitized photooxygenation of trimethoxymethane and 1,1,1-trimethoxyethane, respectively. No peroxide was formed from tetramethoxymethane. Allowing 98% hydrogen peroxide and trimethoxymethane to stand results in an 80% yield of 1, so that 1 and 2 are probably formed by such a disproportionation reaction during photooxygenation. Compound 1 is converted quantitatively to methanol, methyl formate, and dimethyl carbonate in pyridine solution at 60 °C. In acidic methanol both 1 and 2 undergo solvolysis rapidly with exclusive cleavage of the carbon – peroxy oxygen bond. Signals for the ether and peroxy oxygens of 1 appear at 34 and 263 ppm and those of 2 appear at 40 and 264 ppm in the 17O nuclear magnetic resonance spectrum. Luminescence results when 1 and 2 are heated to 150 °C.
Charge distributions and chemical effects. XLIII. Bond dissociation energies and radical formation
Authors: Fliszár Sándor , Minichino Camilla
Published: April 2011

The problem of bond dissociation, R1R2 → R1• + R2•, is addressed from the viewpoint that the fragments, R1 and R2, may not be individually electroneutral in the host molecule, whereas the corresponding radicals certainly are. The mutual charge neutralization of R1 by R2 during the cleavage of the bond linking R1 to R2 is described by an expression featuring only molecular ground-state properties. This expression translates directly into a new energy formula for the dissociation energy, D*(R1R2) = ε(R1R2) + CNE − E*nb + RE(R1) + RE(R2), where both the molecule and the radicals are taken at their potential minimum. The charge neutralization energy, CNE, profoundly affects the relationship between the dissociation (D*) and contributing bond energy (ε), i.e., the energy in the unperturbed molecule. Nonbonded interactions between R1 and R2, E*nb, are almost negligible. The reorganizational energy, RE, measures the energy difference between R• and the corresponding electroneutral group found in the symmetric molecule RR. Numerical applications to alkanes reveal an important cancellation of individual CNE terms accompanying the mutual charge neutralization of alkyl groups during the cleavage of CC bonds, i.e., [Formula: see text]. Theoretical εCC's lead to valid CC bond dissociation energies. In CH bond dissociations, on the other hand, the sum εCH + CNE remains nearly constant although individual εCH's may differ from one another by as much as 6 kcal mol−1. The appropriate approximation, [Formula: see text], shows in what manner charge neutralization energies disguise genuine contributing CH bond energies to create a perception of seemingly constant CH bond contributions.
1-β-Methylcarbapenem intermediates. Stereoselective synthesis of (3S,4R)-3-[(1R)-1-tert-butyldimethylsilyloxyethyl]-4-[(1R)-3-methoxycarbonyl-1-methyl-2-oxopropyl]azetidin-2-one and its related chemistry
Authors: Endo Masaki , Droghini Robert
Published: April 2011

A chiral intermediate bearing the 1-β-methyl moiety (14a) for 1-β-methylcarbapenem antibiotics (1) was prepared by stereoselective aldol-type reaction between 4-acetoxyazetidinone 3a and the dianion (or corresponding bissilyl enol ether) of a 3-oxopentanoate 12 or 13 in the presence of a metal salt. A major side reaction has also been elucidated.
Thermolysis of trimethylsilyl esters: an ultraviolet photoelectron spectroscopy study
Authors: Werstiuk Nick Henry , Brook Michael A. , Hülser Peter
Published: April 2011

The thermolytic behaviour of trimethylsilyl trifluoromethanesulfonate, 1, trimethylsilyl trifluoroacetate, 2, and trimethylsilyl acetate, 3, has been investigated by ultraviolet photoelectron spectroscopy. Acetate 3 undergoes decomposition only to a small extent at 800 °C via the mechanism shown in Scheme 1 (X = Si); only acetic acid and starting material are detected. In contrast[Formula: see text]with this result, 1 and 2 decompose completely at 725–800 °C and yield products which cannot be derived via the mechanism shown in Scheme 1. Evidence is presented to support our proposal that the thermolysis of 1 yields trimethylsilyl fluoride, 6, and difluorooxathirane dioxide, 7, as primary products. The photoelectron spectra of 1, 2, 3, 6 and trimethylsilanol, 9, are presented. Molecular orbital eigenvalues of dimethylsilene, 4, dimethylsilanone, 5 (calculated using AMPAC and Gaussian 82), 6 and 9 (AMPAC) are reported. Molecular orbital contour diagrams are given for selected MOs of 6 and 9.
Proton transfer reactions between ortho-methyl substituted derivatives of 4-nitrophenylphenylcyanomethane and nitrogen bases in acetonitrile solvent
Authors: Leffek Kenneth T. , Pruszynski Przemyslaw
Published: April 2011

Equilibrium constants, rate constants, primary deuterium isotope effects, and activation parameters have been measured for the proton transfer reactions in acetonitrile solvent of 4-nitrophenylphenylcyanomethane and 2-methyl-4-nitrophenylphenyl-cyanomethane with tetramethylguanidine base and for the reactions of 2-methyl-4-nitrophenylphenylcyanomethane and 2,6-di-methyl-4-nitrophenylphenylcyanomethane with 1,5-diazabicyclo[5.4.0]undec-7-ene base. Introduction of the ortho-methyl groups in the substrate molecule caused significant reductions in the equilibrium and rate constants. The expected rise in the kinetic primary deuterium isotope effect was not observed when the first ortho-methyl group was introduced, but a 20% increase did accompany the introduction of the second ortho-methyl group. Enthalpy of activation measurements indicated that there was no increase in the proton tunnelling contribution to the isotope effect when the amount of steric hindrance is increased with ortho-methyl groups.
La photochimie de l'isoprène gazeux dans la région de l'ultraviolet très lointain
Authors: Deslauriers Hélène , Dufour Sylvain , Collin Guy J.
Published: April 2011

Yields of various products have been measured in the photolysis of isoprene at 184.9, 213.8, and 228.8 nm and at pressures between 1 and 400 Torr. At each wavelength, the major process is the rupture of a C—CH3 bond, which leads to the formation of methyl and CH2=C=CHCH2. The quantum yield for this process is 0.83 ± 0.08 at 213.8 nm. The lifetime of the intermediate involved in this process is 20 ns at 184.9 nm. Similar quantities of ethylene and C3H4[Formula: see text] and propene and acetylene [Formula: see text] are measured. All the measured yields decrease with an increase in the pressure. In addition to these fragmentation processes, isomerization reactions are also observed, particularly at 228.8 nm. They lead to the formation of 1,3- and 1,4-pentadiene as well as 3-methyl-1,2-butadiene. The Stern–Volmer plot for each isomer is different and each plot shows a strong negative curvature, indicating the complexity of the reaction process. The lifetime of each intermediate is 2 ns or less.
Excess molar volumes of methyl alkanoate with n-alkanols at 298.15 K
Authors: Ortega J. , Garcia J. D.
Published: April 2011

This work reports on the excess molar volumes at 298.15 K of fifteen binary systems formed by {xCmH2m+1CO2CH3 (m = 1, 2, 3) + (1 − x)CnH2n+1(OH) (n = 6, 7, 8, 9, 10)}. The [Formula: see text] values were calculated using densities obtained in a vibrating-tube densimeter, the excess molar volumes being positive for all these systems. A qualitative interpretation of the results is presented on the basis of the appearance of specific interactions between the —CO—O— groups of the ester and the —OH of the n-alkanol.
Kinetics of crystal growth of calcium sulfate dihydrate. The influence of polymer composition, molecular weight, and solution pH
Authors: Amjad Zahid
Published: April 2011

A seeded crystal growth technique has been used to study the influence of solution pH and temperature ranging from 25 to 50 °C on the performance of polymers of varying functional groups as calcium sulfate dihydrate (CaSO4•2H2O, gypsum) crystal growth inhibitors. Results indicate that at constant temperature and at a constant solution pH, crystallization in the presence of polyacrylic acids is preceded by an initial slow growth reaction, hereafter called induction period, following which crystal growth of gypsum proceeds with a rate close to that in pure supersaturated solution. Results suggest that at a constant pH, polyacrylic acid concentration, molecular weight, and temperature greatly affect the duration of induction period. Kinetic data collected as a function of solution pH in the range 2.5 to 9.0 suggest that solution pH has a marked effect on the induction period. The observed dependence of induction period on solution pH may be explained in terms of the degree of ionization of polyacrylic acid. Among the polymers of varying functional groups studied, i.e. carboxyl, sulfonate, acrylamide, dimethyldiallylammonium, etc., only those polymers having carboxyl group showed marked inhibitory activity for the growth of gypsum crystals.
NMR study of π–σ* stereoelectronic interactions in 3-substituted benzocycloheptene derivatives
Authors: Aubin Y. , St-Jacques M.
Published: April 2011

Dynamic NMR methods are used to study 3-substituted benzocycloheptene derivatives, useful models for investigating the conformational effect of the stereoelectronic π–σ* orbital interaction. The 11 compounds studied are divided in two subgroups, the first one containing mainly halogenated derivatives (F, Cl, Br, and OCH3) and the second consisting of oxy derivatives (OCH3, OCH2CH3, OCH=CH2, OAc, p-OPh-R, where R = H, OCH3, and NO2). The results for the first series show the presence of two chair conformations (Ca and Ce) characterized by a decreasing Ca population with increasing electronegativity of the substituent. This trend suggests the presence of a dominant π–σ* interaction for Cl and Br stabilizing the Ca form. The larger Ce population observed for F suggests that a strong attractive interaction with the aromatic peri hydrogen is present in this compound. Finally, in the oxy-substituent series, the populations trend does not correspond to that predicted from the π–σ* orbital interaction, but the individual population perturbations appear to be caused primarily by electrostatic interactions involving the nonsymmetrical polar substituents. Keywords: low temperature NMR, conformational analysis, seven-membered rings, orbital interactions, benzocycloheptene derivatives.
Oxidation products of 5-ethenyl-4-methyl-3-pyridinecarbonitrile and 2- and 4-methylpyridines
Authors: Jahangir  , Wang Jian , Smith Richard W. , MacLean David B. , Holland Herbert L.
Published: April 2011

The anion of 5-ethenyl-4-methyl-3-pyridinecarbonitrile 1 undergoes oxidative coupling on treatment with dibenzoyl peroxide affording 1,2-bis-(5′-ethenyl-3′-cyano-4′-pyridyl)-ethane, 2. It is also shown that the anions of 2- and 4-methylpyridine undergo oxidative coupling. In the latter case, however, the coupling reaction is accompanied by addition to the carbonyl group of dibenzoyl peroxide. The addition products have been identified as phenacyl pyridines and dipicolyl phenyl carbinols. The ethenyl side chain of 1 has been hydrated by way of the oxymercuration–reduction process and the secondary alcohol oxidized to a ketone. Both the alcohol and ketone in protected form are potentially useful intermediates in alkaloid synthesis. Keywords: oxidative coupling, 2- and 4-methylpyridines, dibenzoyl peroxide, oxymercuration–reduction.
Electron spin resonance detection of heterogeneous reactions of Pigment Red 122
Authors: Walzak Mary Jane , Harbour John R.
Published: April 2011

Electron spin resonance spectroscopy (ESR) has been used to investigate the electrochemical and photolytic behaviour of particulate C.I. Pigment Red 122. Heterogeneous electrochemical reduction and oxidation of the pigment resulted in different reversible ESR signals with the radical cation giving a signal of ΔHpp = 2.3 G and g-factor of 2.0033 and the radical anion giving ΔHpp = 3.2 G and g-factor 2.0039. On exposure to light the inherent ESR signal, which was determined to be a two-component signal, increased in intensity by a factor of 2.4 but did not change in linewidth or g-factor. This light-induced signal was reversible and decayed to initial levels in the dark. The mechanism of these reactions is discussed. Keywords: ESR, pigment, electrochemistry, photo effects.
Synthesis of (±)-15-thia-15-deoxy-PGE1 methyl ester
Authors: Holland Herbert L. , Ratemi Elaref S. , Contreras Luis
Published: April 2011

The 15-thia-15-deoxy analogue of prostaglandin E1 methyl ester has been prepared by the zirconocene chloride mediated conjugate addition of an n-pentyl ethynyl sulfide derived anion to an appropriately substituted cyclopentenone. Similar methodology has also been used to prepare other 3-(3′-thia-1′-octenyl)-cyclopentanones.
Nucleoside intermediates in blasticidin S biosynthesis identified by the in vivo use of enzyme inhibitors
Authors: Gould Steven J. , Guo Jincan , Geitmann Anja , Dejesus Karl
Published: April 2011

Intermediates in the biosynthesis of blasticidin S and its nucleoside co-metabolites were detected by altering fermentation conditions. Inhibitors of specific types of biochemical reactions that were expected to be involved in blasticidin biosynthesis were fed to Streptomyces griseochromogenes, in some cases with the inclusion of large quantities of the primary precursors of blasticidin S. The types of reactions and inhibitors used were (1) transaminase (aminooxyacetic acid and 2-methylglutamate), (2) amidotransferase (azaserine and 6-diazo-5-oxo-L-norleucine), (3) arginine biosynthesis (arginine hydroxamate), and (4) methyltransferase (ethionine). These manipulations apparently distorted the pools of precursors and (or) intermediates, and led to substantial accumulations of three known, previously minor, metabolites of S. griseochromogenes, cytosylglucuronic acid, pentopyranine C, and demethylblasticidin S, and of two new ones, pentopyranone and isoblasticidin S. New cytosyl metabolites were detected by HPLC with photodiode array detection. Fermentations to which arginine hydroxamate and cytosine had been added also produced three aberrant metabolites that were derived from pentopyranone and arginine hydroxamate.
The synthesis and some chemical reactions of a 5a-methyl 2H-naphtho[1,8-bc]furan
Authors: Burns Patricia A. , Taylor Nicholas J. , Rodrigo Russell
Published: April 2011

A synthesis of the tricycle 19 has been completed in 14% overall yield from guaiacol. Several chemical transformations of this compound including its reduction to an octahydro naphtho[1,8-bc]furan and conversion to the hitherto unknown azuleno-[8,1-bc]furan ring system are described.
Rearrangements of tricyclic ketones: [3.3.3]propellane formation via a γ-enolate revealed in an approach to the pentalenene skeleton through β-enolization
Authors: Patel Hemant A. , Stothers J. B. , Thomas S. E.
Published: April 2011

The known isomerization of the tricyclo[5.3.1.01,5]- to the [6.3.0.01,5]undecane skeleton by β-homoenolization led to examination of 2,9,9-trimethyl-6-methoxymethyltricyclo[5.3.1.01,5]undecanone (6) as a potential precursor for the synthesis of pentalenene, a naturally occurring sesquiterpenoid, utilizing a β-enolate rearrangement as a key step. While the anticipated rearrangement of 6 occurs, it is a minor process. The major rearrangement product arises by generation of a γ-enolate intermediate from a tricyclic enone formed by loss of methanol from 6. This constitutes a new route to [3.3.3]propellanes and provides a third example of γ-enolate rearrangement. Structures of the products were established primarily from their 1H and 13Cmr spectra.
Biosynthesis of tetraponerine-8, a defence alkaloid of the ant Tetraponera sp.
Authors: Renson B. , Merlin P. , Daloze D. , Braekman J. C. , Roisin Y. , Pasteels J. M.
Published: April 2011

The administration of sodium [1-14C] and [2-14C] acetate, L-[U-14C] glutamic acid, &([a-z]+);-amino [U-14C] butyric acid, L-[U-14C] ornithine hydrochloride, and [1,4-14C] putrescine dihydrochloride to Tetraponera sp. ants resulted in the formation, for each feeding experiment, of labelled tetraponerine-8 (2). The distribution of radioactivity into 2 was established by chemical degradation. The results obtained favor the hypothesis that the pyrrolidine ring of tetraponerine-8 is derived from L-glutamic acid via L-ornithine and putrescine, while the 12-carbon chain is derived from the combination of six acetate units.
Synthesis of (2S,4S)- and (2S,4R)-[5,5,5-2H3] leucine from (R)-pulegone
Authors: Hill Richard K. , Abächerli Claudio , Hagishita Sanji
Published: April 2011

Beginning with (R)-pulegone, a CD3 group attached to the stereogenic center containing CH3 has been created by conversion to citronellal-1-d, exchange of the acidic hydrogens at C-2 by deuterium, and decarbonylation with Wilkinson's catalyst. Oxidation to isovaleric acid-d3 and conversion to leucine by standard procedures gave the (2S,4S) and (2R,4S) diastereomers (10 and 12) of [5,5,5-2H3]leucine.
Synthesis, characterization, and enzymic conversion of nonhydrolysable analogues of propionylcoenzyme A
Authors: Zhao Yimin , Michenfelder Martina , Rétey János
Published: April 2011

We describe the synthesis of three novel analogues of propionyl-coenzyme A, in which the sulfur atom has been replaced by methylene, ethylene, and thiomethylene, respectively. All three analogues, propionyl-dethia(carba)-CoA (1), propionyl-dethia(dicarba)-CoA (2), and S-(2-oxobutanyl)-CoA (3) were characterized by 1H and 31P NMR spectroscopy and FAB mass spectrometry. Propionyl-CoA–oxaloacetate transcarboxylase from Propionibacterium shermanii accepted the novel analogues as substrates and carboxylated them to the corresponding methylmalonyl-CoA analogues (4–6). The latter were further converted into the succinyl-CoA analogues by the coenzyme-B12-dependent methylmalonyl-CoA mutase from the same organism. The succinyl-CoA analogues, succinyl-dethia(carba)-CoA (7), succinyl-dethia(dicarba)-CoA (8), and 4-carboxy(2-oxobutanyl)-CoA (9) were obtained on a preparative scale and their Michaelis constants (Km) with methylmalonyl-CoA mutase were determined to be 0.136, 2.20, and 0.132 mM, respectively (Km for succinyl-CoA is 0.025 mM). The Vmax values for 7, 8, and 9 are 1.1, 0.013, and 0.0047 µmol min−1 U−1, respectively (Vmax for succinyl CoA is 1.0). The utility of the novel coenzyme A analogues in enzyme mechanistic studies is discussed.
Lupin alkaloids 6. Stereochemistry of bis-quinolizidine alkaloids with γ-oxo-α,β-enamine system
Authors: Brukwicki Tadeusz , Wysocka Waleria , Nowak-Wydra Barbara
Published: April 2011

1H nmr, 1H,1H and 1H,13C COSY, and 2D J-resolved spectra of multiflorine (1) and 13α-hydroxymultiflorine (2) in CDCl3 were taken. Some erroneously determined chemical shifts in 1 were corrected and for the first time signals in 2 were assigned. Most of the coupling constants in 1 and 2 were established. A coupling constant of H7–H17β and chemical shifts for H17β, C14, and C8 were used to define the conformational equilibrium of boat or chair forms in the C rings, in 1 and 2 in solution. The results obtained confirm the previous findings based on chemical shifts of C12: ca. 75 and 70% of the "boat" conformer in 1 and 2, respectively, at room temperature. Of all the criteria used, the H7–H17β coupling constant seems to be least sensitive to the influence of substituents at rings A and D. From the Haasnoot equation, torsion angles of HCCH in regions of molecular geometry featuring low sensitivity to conformational changes were calculated. The hydroxyl group at position 13α has a slight influence on the geometry of ring D.