bluuebunny/crossref_metadata_2025 huggingface dataset:
Metal complexes as antioxidants. 8. A kinetic and product study of the reaction of tertiary alkylperoxy radicals with cobalt(II) acetylacetonate
Authors: Howard J. A. , Tong S. B.
Published: May 2006

tert-Butylperoxy radicals react rapidly with Co(acac)2 in non-polar solvents and rate constants measured by kinetic electron spin resonance spectroscopy obey the Arrhenius equation log (nk/M−1 s−1) = (8.9 ± 0.7) − (4.7 ± 1.5)/θ, where θ = 2.303RT kcal mol−1 and n is ~ 0.1. Cumylperoxy radicals react with Co(acac)2 to give mainly α-cumyl alcohol and acetophenone. There is no evidence for the formation of "long-lived" alkylperoxy radicals co-ordinated to cobalt (III) or a stable alkylperoxo cobalt(III) complex in these systems.
The iron(III)-catalyzed oxidation of EDTA in aqueous solution
Authors: Motekaitis Ramunas J. , Martell Arthur E. , Hayes David , Frenier Wayne W.
Published: May 2006

At temperatures above 100 °C iron(III) oxidizes coordinated EDTA to ethylenediaminetriacetic acid in aqueous solution in the absence of molecular oxygen. The reaction proceeds with an activation energy of 28.6 kcal/mol, and its rate is directly proportional to the concentration of Fe(III) and inversely proportional to pH. At 125 °C, the halflife of Fe(III) in the presence of excess EDTA is about 3 h at pH 9.3, but increases to >70 h at pH 5.4. The reaction is stoichiometric and no other reaction products or by-products were detected by nmr, gc, and gc – mass spectroscopy. In the presence of oxygen iron catalyzes quantitative oxidation of ethylenediamine-N,N,N′,N′-tetraacetic acid (EDTA) to ethylenediaminetriacetic acid. The copper(II)–EDTA chelate undergoes a similar reaction but higher temperatures [Formula: see text] are required. Iron(III) also oxidizes nitrilotriacetic acid (NTA) to iminodiacetic acid (IDA) and glycine. The hydrolyzed species Fe(OH)EDTA is shown to be the reactive intermediate, and the well-known (Fe–EDTA)2O4− μ-oxo dimer is shown not to exist at elevated temperatures (above 100 °C). Probable mechanisms are proposed for these reactions and comparisons are made with earlier work.
Solvolysis of specifically C-6 deuterated 7-halonorbornyl brosylates; stereoselectivity of proton loss for "E1-like" 1,3-elimination in locked bicyclo[2.2.1]heptyl Systems
Authors: Werstiuk Nick Henry , Cappelli Frank Peter , Timmins George
Published: May 2006

We have solvolyzed the syn-7-chloro-endo-6-d, anti-7-chloro-endo-6-d, syn-7-chloro-exo,exo-5,6-d2, anti-7-chloro-exo,exo-5,6-d2, syn-7-bromo-endo-6-d, and anti-7-bromo-endo-6-d norbornyl brosylates 1c, 2c, 1d, 2d, 1e, and 2e in 80:20 ethanol–water buffered with NaOAc, isolated the 3-halonortricyclenes, the products of 1,3-elimination, and assayed for deuterium mass spectrometrically. Analysis of the deuterium-loss data established that there is a 10:1 to 15:1 preference for loss of an endo-6-proton for formation of the 7-halonortricyclenes from the 7-halonorbornyl cations. The isotope effects for "E1-like" 1,3-elimination are 1.78, 1.71, 1.53, and 1.52 for 1c, 2c, 1e, and 2e, respectively. That there is an increase in the degree of 1,3-elimination in the solvolysis of anti-7-chloro-exo-2-norbornyl brosylate-exo-3-d (3) relative to the non-deuterated brosylate indicates that the destabilizing effect of the β-deuterium at C-3 leads to an increase in the degree of 1,3-elimination from C-6.
Photolyse du butyne-2 dans la région de l'uv sous vide
Authors: Deschênes Jovette , Deslauriers Hélène , Collin Guy J.
Published: May 2006

The vacuum uv photolysis of gaseous 2-butyne has been studied at 147, 163, and 174 nm. The use of hydrogen iodide as radical scavenger shows the importance of methyl radical formation in the fragmentation of the photoexcited molecule. It is concluded that the principal fragmentation of the photoexcited molecule involves the cleavage of a C—CH3 bond: [Formula: see text] and [Formula: see text]. Unfortunately, it was not possible to scavenge the corresponding C3H3 radicals. From the fast decrease of the transparency of the window it is concluded that an important radical polymerization takes place, even in the presence of oxygen or nitric oxide. Finally, from the pressure effect, it is shown that propyne results from the fragmentation of the vibrationally excited butenyl radical and vinylacetylene arises from the fragmentation of an excited C4H5 radical.
On the evaluation of the nuclear electric quadrupole moment of vanadium-50
Authors: Habayeb Mahmoud Adam , Hileman Jr. O. E.
Published: May 2006

50V- and 51V-nmr relaxation spectra were recorded for neat VOCl3 at 298 K. In addition, the line width at half-height (W1/2) of each resonance was measured. The average Q(50V)/Q(51V) ratio was calculated to be |3.55|. A quadrupole moment, |Q|, of 50V was estimated using these data along with the reported Q values of 51V. The magnetic moments, μ, of both isotopes were also evaluated from the ratio of their Larmor frequencies.
Pyrones. VI. The total synthesis of phacidin
Authors: Poulton Gerald Arthur , Cyr Terry Donald
Published: May 2006

Phacidin (4-methoxy-6-nonanoyl-2H-pyran-2-one-3-carboxaldehyde) is synthesized from triacetic acid lactone in four steps.
Studies of silyl and germyl Group VI species. Part IV. Dimethyl- and tetramethyl-disilyl chalcogenides and related species
Authors: Drake John E. , Glavinčevski Boris M. , Hemmings Raymond T.
Published: May 2006

The symmetrically substituted disilyl chalcogenides (MenH3−nSi)2E where E = O, S, Se, Te; n = 0 → 3, have been prepared and characterized spectroscopically and by cleavage reactions. The synthetic routes include reactions of halogenosilanes with water, mercury(II) sulfide, lithium telluride, and complex thio- and seleno-aluminates. The spectroscopic properties of the(MeH2Si)2E and (Me2HSi)2E species, which have not been reported previously, are discussed in some detail.
Synthesis of ring A of ambruticin and proof of its absolute stereochemistry
Authors: Just George , Potvin Pierre
Published: May 2006

Appropriately derivatized ambruticin was converted by reductive ozonolysis to tetrahydropyran 9c and cyclopropane 12a, which were synthesized from L-arabinose and (R)-Feist's acid in an unambiguous manner.
Aminomethylation of N-propargylphosphoramides. Synthesis of unsymmetrical acetylenic diamines
Authors: Corbel Bernard , Paugam Jean-Paul , Sturtz Georges
Published: May 2006

The preparation of N-alkyl-N-(4-dialkylamino-2-butynyl)phosphoramides 3 using the Mannich reaction is described. The acidic hydrolysis of those phosphoramides leads to unsymmetrical acetylenic diamines 4.
Complexes of dithiobenzoic acids. III.1H and 13C nuclear magnetic reonance studies of a series of tetrakis(dithiobenzoato)molybdenum(IV) complexes
Authors: Roberie T. , Bhacca N. S. , Lankin D. , Selbin J.
Published: May 2006

A series of dithiocarboxalato (X-dtb) complexes of molybdenum(IV), Mo(X-dtb)4, where the para substituent X = H, CH3, CH3O, F, C6H5, CHO, C6H5CO, or (n-C4H9)2N, the parent acids and tetraalkylammonium salts were studied by 1H and 13C nmr in order to monitor the expected charge density shifts as a function of the group X. Analysis of the 13C nmr data unexpectedly revealed an absence of delocalization of electron density either from molybdenum to ligand or from ligand to molybdenum.
Conformation and crystalline structure of (2→1)-β-D-fructofuranan (inulin)
Authors: Marchessault R. H. , Bleha T. , Deslandes Yves , Revol J.-F.
Published: May 2006

The crystalline conformation of inulin a (2→1)-β-D-fructofuranan has been determined based on conformational analysis coupled with X-ray and electron diffraction data. The energy contour maps as a function of three torsional angles [Formula: see text], ψ, ω in the backbone were calculated taking into account van der Waals, torsional, and electrostatic interactions. Although several minima were observed, only two models are possible when one considers the information obtained from the diffraction data. The two models correspond to five-fold helices, one 54 (left-handed) and the other 51 (right-handed) with an advance per monomer of 2.16 Å, but with different conformational angles: ω = 60° and 180° respectively. Compared to the crystalline state torsion angles of polyethylene oxide analogs of inulin, large differences are noted. Steric interactions of the substituents and the exoanomeric effect are believed responsible for the observed conformational differences.
The total synthesis of (±)hinesol and (±)epihinesol
Authors: Lafontaine Jacques , Mongrain Marcel , Sergent-Guay Mireille , Ruest Luc , Deslongchamps Pierre
Published: May 2006

The tricyclic ketal ketones 15a and 15b have been obtained in an isomeric ratio of 9:1 (4 → 5 → 6 → 7 → 8 → 9 → 10 → 11 → 12 → 13 → 14 → 15a + 15b). Compound 15a was converted in seven (or eight) steps to (±)epihinesol (3) (15a → 29 → 32 → 48 → 49 → 47 (or 32 → 39 → 38 → 44 → 47) → 50 → 3) and compound 38 was transformed into (±)hinesol (2) in rive steps (38 → 76 → 77 → 62 → 63 → 2). The identity of epihinesol and agarospirol was confirmed by formation of a common epoxide.
Photochemistry of N-nitroso-N-alkyl amino acids: a facile oxidative decarboxylation
Authors: Chow Yuan L. , Horning Douglas P. , Polo Joël
Published: May 2006

Several N-alkyl or N-phenyl-N-nitroso α-amino acids were synthesized and were shown to photolytically rearrange to amidoximes with concurrent decarboxylation in solution or solid states without the presence of externally added acids. In contrast, N-nitrosonipecotinic acid, a N-nitroso β-amino acid, as well as N-nitrosopiperidine in the presence of acetic acid were not photolabile. The photolability of N-nitroso α-amino acids was ascribed to the presence of an intramolecular association between the nitrosamino and carboxyl groups through hydrogen bonding. The species having the hydrogen bonding through the nitroso oxygen in the Z-configuration was believed to be photolabile and decomposed to alkylideneimines as the primary product. The mechanism of the oxidative photorearrangement was discussed.
Regioselectivity of metal hydride reductions of unsymmetrically substituted cyclic anhydrides. systems where "steric hindrance along the preferred reaction path" rationalization is not applicable
Authors: Kayser Margaret M. , Morand Peter
Published: May 2006

Metal hydride reductions of planar cyclic anhydrides such as methylmaleic or 3-substituted phthalic anhydrides occur preferentially at the sterically more hindered carbonyl function. This regioselectivity cannot be rationalized in terms of "the most favourable pathway for non-perpendicular attack by a nucleophile" since both carbonyl groups present are equally accessible to non-perpendicular approach. A study which takes into account the alkaline cation and inductive, mesomeric, and steric effects has been conducted for the reduction of several conjugated and aromatic anhydrides. A qualitative interprétation for the regioselectivities observed in these reductions (as well as in reductions already reported in the literature) is suggested. An early transition state for the catalyzed versus late transition state for the non-catalyzed process is proposed.
Stereoelectronic control in acetal formation
Authors: Beaulieu Normand , Dickinson Robert A. , Deslongchamps Pierre
Published: May 2006

The cyclization under acidic conditions of bicyclic and monocyclic hydroxypropyl methoxytetrahydropyrans 1 and 4 is reported. At room température, compound 1 gives only cis tricyclic acetal 2. At reflux, compound 2 equilibrates to yield a mixture of cis and trans tricyclic acetals 2 (45%) and 3 (55%). Compound 4 gives directly the equilibrium mixture of cis and trans bicyclic acetals 5 (55%) and 6 (45%) at room température. The specific formation of 2 from 1 constitutes strong experimental evidence that acetal formation is controlled by stereoelectronic effects. The anomeric effect can be estimated [Formula: see text] from the equilibrium study of 2 and 3. This value confirms the result previously obtained by Descotes (9).
A mild, general preparation of N-acyl aziridines and 2-substituted 4(S)-benzyloxazolines
Authors: Bates Gordon S. , Varelas Michael A.
Published: May 2006

The conversion of a wide range of carboxylic acids into their acyl imidazolides with subsequent addition of an aziridine rapidly gives a quantitative yield of the corresponding N-acyl aziridines.Iodide (or bromide) ion catalysed rearrangement of N-acyl 2(S)-benzylaziridines 1 to oxazolines 6 proceeds quantitatively.
A synthesis of (+) and (–) methyl nonactate from a derivative of D-ribose
Authors: Sun King Mo , Fraser-Reid Bert
Published: May 2006

C-Glycofuranosides with an activated methylene group at C1 of the glycosyl residue are amenable to epimerisation via a retro-Michael–Michael addition sequence. Advantage is taken of this phenomenon by converting methyl 2,3-O-isopropylidene-β,D-ribo-octofuranosid-6-ulose (8) into the corresponding α,L-lyxo isomer (15) by treatment with base. Both 8 and 15 are then converted into the (−) and (+) enantiomers of methyl nonactate (14) respectively, in ~45 percent yield.
Substituent effects in some autoxidation and hydrogen abstraction reactions in terms of their field (F) and resonance (R) components inclusive of unique positional weighting factors
Authors: Patnaik Lalit N. , Mallick Nigamananda , Rout M. K. , Rout Swoyam P.
Published: May 2006

Substituent effects in some autoxidation and hydrogen abstraction reactions have been studied in terms of the field (Fk) and resonance (Rk) components proposed by Swain and Lupton and the unique positional weighting factors fj and rj incorporated by Williams and Norrington with the aid of the following equation:[Formula: see text]where Pi's are the rate parameters, Pi0 being that for a standard reference compound. The correlations are found to be quite satisfactory, showing the general validity of the above equation for the types of reactions considered. From the information obtained from the present correlation studies, an attempt has been made to resolve the conflict with regard to the nature of the transition state involved in the hydrogen abstraction reactions – that is, whether or not there is charge separation in the transition state. The results of the present studies seem to suggest that both the differences in the resonance stabilization energies of the ring-substituted benzyl radical and the contribution of polar structures to the transition state are to be invoked to explain the observed data.
A regiospecific synthesis of protoberberine alkaloids
Authors: Kiparissides Zinovia , Fichtner Robert H. , Poplawski Janusz , Nalliah Bala C. , MacLean David B.
Published: May 2006

The protoberberine skeleton has been prepared in two steps from N-benzyl-3,4-dihydroisoquinolinium salts. Treatment of the salts with the anion of methyl methylthiomethylsulfoxide yields mixtures of diastereomeric adducts that cyclize on heating with concentrated hydrochloric acid to dihydroprotoberberines. The latter compounds may be reduced to their tetrahydro analogues with sodium borohydride, oxidized to protoberberinium salts with iodine, or converted to 13-methyltetrahydroprotoberberines by treatment with formaldehyde according to an established procedure. The method has been applied successfully to the synthesis of (±)-tetrahydropalmatine, palmatine iodide, (±)-xylopinine, (±)-sinactine, and (±)-corydaline. N-Benzylisoquinolinium salts may be used in place of their dihydro analogues as starting materials in this synthesis, thereby extending the range of substitution patterns potentially available.
The reactions of ethyl-, vinyl-, and ethynyl(trichloromethyl)carbinols with aqueous and methanolic potassium hydroxide, thiourea, and cyanamide
Authors: Reeve Wilkins , Steckel Thomas F.
Published: May 2006

The reactions of ethyl(trichloromethyl)carbinol, dimethyl(trichloromethyl)carbinol, (trichloromethyl)vinylcarbinol, ethynyl (trichloromethyl)carbinol, and 1,1,1,-triehloro-3-nonyn-2-ol have been studied with the following reagents. Methanolicpotassiumhydroxide: α-methoxy acids are formed in 70 and 79% yields with the ethyl- and vinylcarbinols respectively. Double bond migration to the conjugated position was observed with the vinylcarbinol. Thiourea: substituted 2-imino-4-thiazolidinones are formed in 27 to 66% yield with the first three carbinols with double bond migration in the case of the vinylcarbinol. Cyanamide: the saturated carbinols were converted to substituted ethy] 2-imino-4-oxo-1-imidazolidinecarboximidates in 30 to 60% yield. Aqueouspotassiumhydroxide: α-chloro acids were formed from the ethyl- and vinylcarbinols in 23 and 24% yields respectively, again with double bond migration in the case of the vinylcarbinol.The results are discussed in terms of the known parallel reactions with phenyl (trichloromethyl)carbinol, and provide information which illustrates the usefulness and defines the limits of certain known synthetic reactions when applied to the alkyl, alkenyl, and alkynyl trichloromethylcarbinols.
Absolute rate constants for hydrocarbon autoxidation. 29. Rate constants for abstraction of primary aliphatic hydrogens from 2,2-dimethylbutane by the tert-butylperoxy radical
Authors: Howard J. A. , Chenier J. H. B.
Published: May 2006

Rate constants for abstraction of primary and secondary hydrogens from 2,2-dimethylbutane by the tert-butylperoxy radical at temperatures from 323 to 353 K have been determined from autoxidations and co-autoxidations in the presence of tert-butyl hydroperoxide. At 333 K the rate constant for abstraction of a secondary hydrogen is ~1.5 × 10−3 M−1 s−1 and the rate constants for abstraction of a primary hydrogen from the tert-butyl and methyl groups of 2,2-dimethylbutane are ~4 × 10−5 and ~6 × 10−5 M−5 s−1 respectively.
Rate processes and nuclear magnetic resonance spectra of amine•SO2 complexes + H2O in liquid SO2
Authors: Wu Konrad T. , Yencha Andrew J.
Published: May 2006

A 1H dnmr study has been performed on a series of addition compounds formed from the gaseous reactions of di- and trimethyl amine and triethyl amine with sulfur dioxide in the presence of a small amount of water in a liquid sulfur dioxide solvent. The dynamic system involves an equilibrium of the general form: amine• [Formula: see text] The activation parameters for the exchange process were calculated. Large positive entropies of activation were found in the present systems that strongly suggest the formation of an ion pair in the transition state in which the activation process is controlled largely by solvation effects.
Photo-oxidation of formic, acetic, and propionic acids with aqueous hydrogen peroxide
Authors: Ogata Yoshiro , Tomizawa Kohtaro , Takagi Kaoru
Published: May 2006

Photolytic oxidation of aliphatic acids with aqueous H2O2 has been studied. Formic acid gives CO2 and H2O. Acetic acid gives products containing CO2, methane, formic, glycolic, and tartaric acids. Propionic acid gives CO2, methane, ethane, acetic, formic, lactic, β-hydroxypropionic, malonic, and glycolic acids. A mechanism involving an initial H-atom abstraction by HO•formed via photo-dissociation of H2O2 is postulated and discussed.
Synthesis of tris(aminomethyl)phosphine oxide and its carbon dioxide adduct from tetrakis(hydroxymethyl)phosphonium salts via their methyl carbamate derivatives
Authors: Frank Arlen W.
Published: May 2006

Tris(aminomethyl)phosphine oxide (6) can be synthesized from octakis(hydroxymethyl)diphosphonium sulfate (1b) in an overall yield of 54.6% via the methyl carbamate derivatives 2b, 3, and 4. On a preparative scale, the last step is complicated by the formation of a cyclic by-product 8 in amounts up to 20% of the total. The triamine 6 forms a 1:1 adduct (11) with carbon dioxide, whose structure, established by 1H and 13C nmr, consists of equimolar amounts of carbamate A and dicarbamate BC. The components A, B, and C can be separated by ion exchange. Thermolysis of 11 regenerates 6 smoothly, providing a convenient method for purifying the triamine.
The alkaloids of Podopetalum ormondii
Authors: McLean Stewart , Misra Renuka , Kumar Vijaya , Lamberton John A.
Published: May 2006

The major alkaloids of Podopetalum ormondii have been shown to be (−)-podopetaline, (−)-ormosanine, and 6-epipodopetaline. A constant-melting substance, mp 160–161 °C, isolated from the extract proved to be a quasiracemate of (−)-podopetaline and (−)-ormosanine; the absolute configuration of (−)-ormosanine consequently followed from the established absolute configuration of (−)-podopetaline. Both (−)-6-epipodopetaline, mp 118–119 °C, and its racemic form, mp 174–175 °C, were isolated from the extract. A constant-melting ternary mixture, mp 178–179 °C, of the three major alkaloids has also been isolated.
The retroaldol reaction of 3-penten-2-one: equilibrium constant for hydration and rate constants for the hydration and retroaldol reactions in base
Authors: Guthrie J. Peter
Published: May 2006

In aqueous sodium hydroxide solutions at 25 °C, 3-penten-2-one undergoes retroaldol cleavage to acetone and acetaldehyde. The kinetics can be followed spectrophotometrically, and show two exponential phases with rather different rate constants. By a new analysis of the mathematical solution to this system we have been able to derive an improved method for calculating the microscopic rate constants. These rate constants are khyd = 2.89 × 10−3 M−1 s−1, kdehyd = 4.04 × 10−4 M−1 s−1, and kretro = 3.36 × 10−4 M−1 s−1. The equilibrium constant for hydration of 3-penten-2-one (standard state for water is the pure liquid) is 7.13.
Photolysis of heptamethylbenzenonium cation in aqueous acids. Preparation of pentamethylcyclopentadiene
Authors: Childs Ronald F. , Zeya Maung , Dain Robert P.
Published: May 2006

Irradiation of heptamethylbenzenium ion in a variety of aqueous acids using light of wavelength greater than 350 nm leads to the formation of pentamethylcyclopentadiene and acetone. In 50% HBF4 and 70% HClO4 this photolysis is very clean and can be used as a convenient preparation of pentamethylcyclopentadiene. A mechanism is proposed for the reaction.
Biosynthesis of the quinolizidine alkaloids. Incorporation of Δ1-piperideine into matrine
Authors: Leeper Finian J. , Grue-Sørensen Gunnar , Spenser Ian D.
Published: May 2006

Label from [6-14C]-Δ1-piperideine is incorporated nonrandomly into the carbon skeleton of the quinolizidine alkaloid, matrine, in Sophora tetraptera and S. microphylla. The distribution of radioactivity was determined by a new chemical degradation sequence. On the basis of the results, one of two previously postulated biogenetic schemes must be discarded. A modified biogenetic scheme is presented which is consistent with the present results and also leads to the correct stereochemistry of matrine.
An electron spin resonance and CIDEP study of the primary processes in the photoreductions of furaldehyde, furyl methyl ketone, and acetylthiophene by phenols
Authors: Chen Kuang S. , Wan Jeffrey K. S.
Published: May 2006

The primary processes in the photoreduction of 2-furaldehyde, 2-furyl methyl ketone, and 2-acetylthiophene by phenol, 2,6-di-tert-butylphenol, and pentachlorophenol, respectively, were studied by esr and time-resolved CIDEP techniques. These furan derivatives, in their excited triplet states, can abstract a hydrogen atom from phenol via either the carbonyl group or the carbon–carbon double bond. The present results suggest that they all behave in the primary processes predominantly as carbonyl compounds. The spin–lattice relaxation times of all transient and polarized radicals observed in these photochemical systems were estimated by the CIDEP technique. The photoreductions of furaldehyde and furyl methyl ketone were also examined by high-field CIDNP. The nuclear polarization is mainly due to the cage products and the results are consistent with triplet carbonyl abstraction mechanism. Secondary radical addition to the carbon–carbon double bond of the furan ring was also observed in the furaldehyde–phenol system.
Conformational analysis and photochemical behavior of sulfoxides in the naphtho[1,2-b]thiopyran and naphtho[2,1-b]thiopyran series
Authors: Still Ian W. J. , Arora Parkash C. , Hasan S. Khaqan , Kutney Gerald W. , Lo Lawrence Y. T. , Turnbull Kenneth
Published: May 2006

The sulfoxides derived from 2,3-dihydro-4H-naphtho[1,2-b]thiopyran and its 4-phenyl and 4-oxo derivatives, as well as the analogous sulfoxides in the 2,3-dihydro-1H-naphtho[2,1-b]thiopyran series, have been synthesized and their structures established by spectroscopic methods, especially 1H and 13C nmr. On photolysis these sulfoxides have been found to react by a rather inefficient photochemical deoxygenation pathway.
The addition of simple aromatic hydrocarbons to condensed aromatic thiophenes promoted by aluminum chloride. Part I. Naphtho[2,1-b]thiophene
Authors: Clark Peter David , McKinnon David M.
Published: May 2006

Naphtho[2,1-b]thiophene undergoes addition of aromatic hydrocarbons across the 1,2-bond in the presence of aluminum chloride. At 20 °C 1-aryl-1,2-dihydronaphtho[2,1-b]thiophenes are the major products and at higher temperatures 2-arylnaphtho[2,1-b]thiophenes result. 1-Arylnaphtho[2,1-b]thiophenes may be prepared by treatment of the dihydro-addition products with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone thus giving a new synthesis of 1- and 2-arylnaphtho[2,1-b]thiophenes from the parent heterocycle.
Stereoselective syntheses of O- and S-nitrophenyl glycosides. Part III. Syntheses in the α-D-galactopyranose and α-maltose series
Authors: Apparu Marcel , Blanc-Muesser Michèle , Defaye Jacques , Driguez Hugues
Published: May 2006

The action of p-nitrophenol on penta-O-acetyl-β-D-galactopyranose in dichloromethane, in the presence of stannic tetrachloride, gave p-nitrophenyl α-D-galactoside in fair yield. This technique failed when o-nitrophenol was used. Tetra-O-acetyl-β-D-galactopyranosyl and hepta-O-acetyl-β-maltosyl chlorides were converted to p- or o-nitrophenyl α-D-glycosides and p-nitrophenyl α-D-1-thioglycosides in good yield using hexamethylphosphoramide as a solvent and the sodium salt of the phenols as nucleophiles. The galactosides have been functionalized for further condensation at the C-4 position by selective benzoylation.
Conformational analysis in carbohydrate chemistry. V. Formation of glycosidic anhydrides from heptoses
Authors: Angyal Stephen John , Tran Trung Quang
Published: May 2006

The position of the equilibrium between aldoheptoses and their glycosidic anhydrides depends crucially on the configuration of the heptose. Depending on that configuration, the 1,6-anhydropyranose, the 1,7-anhydropyranose, or the 1,6-anhydrofuranose is the major product, its proportion varying from 99% to less than 1%. The position of the equilibrium is predictable from conformational considerations. 1,7-Anhydrofuranoses have not been encountered. The 1,3-dioxane ring of the 1,7-anhydropyranoses was found to assume a skew form.
The absorption spectrum of trans-diimide (N2H2) in the vacuum ultraviolet region
Authors: Neudorfl P. S. , Back R. A. , Douglas A. E.
Published: May 2006

The vacuum ultraviolet absorption spectrum of trans-diimide (N2H2) in the gas phase has been re-examined between 1800 and 1300 Å, using diimide prepared by the thermal decomposition of sodium tosylhydrazide. Two band systems were observed, designated [Formula: see text] and [Formula: see text], with origins at 1727 and 1473 Å, which have been assigned to the Rydberg transitions 3pπ(bu) ← n+ and 4pπ(bu) ← n+ respectively. Both systems show long progressions in v2′, the N—N—H symmetric bending frequency, and short progressions in v3′, the symmetric N—N stretching frequency.The [Formula: see text] system has well-resolved rotational J type structure in some bands, and the rotational analysis showed that the ground state is a totally symmetric singlet state of C2h symmetry (planar trans-N2H2 isomer), and that the system arises from a 1Bu ← 1Ag transition. Rotational constants obtained for the 0–0 band of the [Formula: see text]-state were A = 15.63, B = 1.32, and C = 1.22 cm−1, and the values of rH−N = 1.028 Å, rH−N = 1.167 Å, and [Formula: see text] were estimated from them assuming a planar trans conformation.
Thiotungstate isopolyanions: an electrometric study
Authors: Prasad Shiva
Published: May 2006

The stoichiometry of the various polyanions formed during the reaction between sodium thiotungstate and sulphuric acid has been investigated by pH and conductance measurements, which have revealed the formation of different polymerized species, viz. (W4SI5)6−, (W2S7)2−, and possibly (W4S13)2− in the vicinity of pH 6.2, 4.4, and 2.7 respectively. The formation of (W4S13)2− is, however, not evidenced by the pH investigations. It was observed that at higher hydrogen ion concentration (pH < 2.4), thiotungstate decomposes into hydrated tungsten trisulphide.
Structure of condensation products between isonicotinylhydrazine and reducing sugars by 13C nmr spectroscopy
Authors: Bailey Keith , Butterfield Andrew G.
Published: May 2006

The structures of the condensation products of isonicotinylhydrazine (isoniazid) with galactose, glucose, lactose, maltose, glycolaldehyde and glyceraldehyde were investigated by examination of their 13C nmr spectra, determined in D2O and DMSO-d6 solution. Spectroscopic data and their interpretation are presented. Spectroscopic and chromatographic (hplc) evidence are combined to show that the products formed with the four sugars exist in solution predominantly as l-(1β-pyranosyl)-2-isonicotinylhydrazines, and to a lesser extent as the analogous 1α-pyranosyl anomers. The products formed with glycolaldehyde and glyceraldehyde are normal hydrazones.
Kinetics of the oxidation of dimethyl sulfoxide with aqueous hydrogen peroxide catalyzed by sodium tungstate
Authors: Ogata Yoshiro , Tanaka Kazushige
Published: May 2006

The oxidation of dimethyl sulfoxide (DMSO) by hydrogen peroxide in the presence of a catalytic amount of sodium tungstate (Na2WO4) has been studied kinetically by means of iodometry of hydrogen peroxide. The reaction is first-order with respect to the substrate and the catalyst, but independent of the concentration of hydrogen peroxide which is present in excess of the catalyst. The polarographic study implies that in solutions two main kinds of peroxytungstic acids (H2WO5 and H2WO8) are formed which contain active oxygen in ratios (active oxygen):(Na2WO4) of 1:1 and 4:1, respectively. The effect of acidity on the oxidation rate and a probable mechanism involving a rate-determining attack of peroxytungstic acids are discussed.
Graphical rules of steady-state reaction systems
Authors: Kuo-Chen Chou , Forsen Sture
Published: May 2006

Four rules to deal with first-order or pseudo-first-order steady-state reaction systems are presented.By means of Rule 1, we can immediately write down the apparent rate constants of consecutive reaction systems. This rule is actually the same as the "Rule of Thumb" proposed by Gilbert, but here its mathematical proof is given.Rule 2 and Rule 3 may serve to derive the apparent rate constants of various complex reaction systems. In comparison with the general algebraic methods, these two rules can simplify laborious calculations that would otherwise be tedious and liable to errors.Rule 4 presents a new schematic method to calculate the concentrations of the reactants. The new method, in simplifying the calculation of complex problems, is extraordinarily efficacious in comparison with the existing schematic methods. For complex mechanisms which are too complicated to be treated with the general manual calculation method, the practical calculations show that we can easily write down the desired results by means of Rule 4.In addition, Rules 2, 3, and 4 include corresponding check formulae, by use of which we can avoid missing subgraphs to be counted. Their advantages will be manifested particularly in dealing with complex mechanisms.The mathematical proofs of these rules are given in the Appendices.
Chemistry of chelocardin. V. Condensation with amino reagents
Authors: Chu Daniel T. W. , Huckin Stuart N. , Bernstein Edith , Garmaise David L. , Egan Richard S. , Stanaszek Ruth S.
Published: May 2006

The nature of the products obtained from the reaction of chelocardin (1) and the model compound 2-acetyldimedone (5) with a variety of amines was investigated. It was observed that amines react with β-triketones having an exocyclic carbonyl side-chain to give exclusively β,β′-diketoenamines with substitution at the side-chain carbonyl.
The preparation of porphyrin S-411 (dehydrocoproporphyrin) and harderoporphyrin from protoporphyrin IX
Authors: Dolphin David , Sivasothy Ramani
Published: May 2006

Protoporphyrin IX dimethyl ester has been converted into the two 2,4-positional isomers bearing hydroxyethyl and methoxycarbonylvinyl side chains. The 4-(2-hydroxyethyl) group was extended to a methoxycarbonylethyl group to give the tetramethyl ester of porphyrin S-411 (2-methoxycarbonylvinyl-4-methoxycarbonylethyldeuteroporphyrin dimethyl ester). On the other hand reduction of the 4-methoxycarbonylvinyl to the corresponding methoxycarbonylethyl group and dehydration of the 2-(2-hydroxyethyl) to a vinyl side chain gave the trimethyl ester of harderoporphyrin (2-vinyl-4-methoxycarbonylethyldeuteroporphyrin dimethyl ester).
Spectroscopic and electrochemical properties of intramolecularly hydrogen-bonded compounds. Ortho-hydroxyazobenzenes
Authors: Millefiori Salvatore , Millefiori Arcangelo
Published: May 2006

The gas-phase uv photoelectron spectra and the half-wave polarographic reduction potentials in acetonitrile solutions of a series of 2-hydroxy-5-methylazobenzene have been determined. The first three IP's and the E1/2 values were linearly correlated with σ+ and σ constants, respectively. E1/2 can also be linearly related to the energy of the lowest unoccupied molecular orbital. Effects of the intramolecular hydrogen bonding on the pe spectra and on the polarographic reduction of the title compounds were evaluated by comparing the experimental findings in 2-hydroxy-5-methylazobenzene, 2-methoxy-5-methylazobenzene, and p-hydroxyazobenzene. On H-bond formation, the antibonding combination of the two nitrogen lone-pairs, n−, and the oxygen lone-pair is ionized at a slightly higher energy and at a lower energy, respectively, than in the non H-bonded compound. The first π-ionization band is slightly lowered in energy in the non H-bonded structure, probably owing to a normal substituent effect. These features are not maintained in the 4'-nitro derivative, where the band encompassing the n− ionization remains at the same potential in both structures, while the first π band in the non H-bonded compound moves toward higher IP. Spectral differences between the bonded and nonbonded structures are the result of a balance of substituent effects, and of both hydrogen bond and orbital interactions. The solution electron affinity of the studied compounds increases on H-bond formation by an amount comparable with the experimental strength of the H-bonding. INDO/S-CI calculations are in qualitative agreement with the experimental results.
Interactions gauches et chemins réactionnels. Etudes conformationnelles d'hydroxyalkyl-4 cyclohexènes contraints
Authors: Bouteiller-Prati Jeanine , Bouteiller Jean-Claude , Aycard Jean-Pierre
Published: May 2006

From J and δ values determined by the nmr study of alcohols obtained by addition of CH3Li and LiAlH4 to the exocyclic carbonyl of cis and trans 3-alkyl 4-carbomethoxy (or acetyl) cyclohexenes (alkyl = H, CH3, C(CH3)3), we have deduced the conformational free energy values (ΔG0X) of the CH(CH3)OH and C(CH3)2OH substituents (0.62 and 2.08 kcal mol−1 respectively) as well as the values for some related conformational equilibria. For transtert-butyl derivatives the stability of the diaxial conformer agrees with a reaction path involving high energy conformers.
Oxydation anodique de β-cétocarboxylates en milieu aqueux ou hydroorganique. Application à la synthèse de γ-dicétones, de cétones éthyléniques et de cétoamides
Authors: Chkir Moncef , Lelandais Daniel , Bacquet Cathy
Published: May 2006

A systematic study of the anodic oxidation of β-ketocarboxylate anions in aqueous or hydroorganic solvents allows to distinguish the factors directing this reaction. Thus, it is possible by the appropriate choice of reaction medium and the structure of the starting ion to synthesize products such as γ diketones, ethylenic ketones and ketoamides.The mode of formation of these last two classes of compound involves an α-ketocarbonium ion which is usually difficult to obtain. [Journal translation]
Hydrogen–deuterium exchange of heteroaromatics in neutral D2O at elevated temperatures
Authors: Werstiuk Nick Henry , Timmins George
Published: May 2006

Pyridine (1), 2-methylpyridine (2), 3-methylpyridine (3), 4-methylpyridine (4), and 1,10-phenanthroline undergo H—D exchange in neutral D2O at elevated temperatures (180–300 °C). With a suitable choice of temperature and reaction time it is possible to prepare selectively deuterated or perdeuterated substrates in good yield.
Mécanisme des réactions du chlorite et du dioxyde de chlore. 1. Stoechiométrie des réactions du chlorite et cinétique en présence d'ortho-tolidine
Authors: Schmitz Guy , Rooze Henri
Published: May 2006

The relative amount of chlorine dioxide produced by the disproportionation of sodium chlorite increases as the concentrations of chlorite and chloride ions increase. It passes through a minimum when the concentration of perchloric acid varies from 2 M to 0.01 M. The fast reaction between chlorite and hypochlorous acid is a part of the mechanism of this disproportionation and its stoichiometry was also investigated. The relative amount of chlorine dioxide produced depends on the method of mixing the reactants and on the acidity. It increases if the concentration of chlorite increases and can exceed the amount predicted by:[Formula: see text]Ortho-tolidine reacts very rapidly with chlorine and with chlorine dioxide but not with chlorous acid. In perchloric acid solutions (pH < 2.5) the product of its oxidation has a considerable absorption with a maximum at 440 nm (ε = 59700 M−1 cm−1). Chlorine reacts more rapidly with ortho-tolidine than with chlorous acid. The kinetic investigation of the disproportionation of chlorous acid is thus simplified by the use of ortho-tolidine. With added chloride ions the rate determining step is HClO2 + Cl− + H+ → 2HClO with a rate constant[Formula: see text]The most reliable values for the free enthalpy of formation of oxychlorine compounds are selected from the literature.
Studies of molecular complexes of some π- and n-donors with iodine by the constant activity method
Authors: Sing Ram Adhar , Bhat Subray N.
Published: May 2006

The iodine complexes of naphthalene, biphenyl, hexamethylbenzene, aniline, and o-toluidine in carbon tetrachloride were studied by using the constant activity method. The association constants and the heats of formation of the complexes were determined and the results are compared with those obtained by using conventional spectral methods. The blue-shifted iodine band maxima were determined directly.
n–π Electron donor–acceptor complexes. I. Aliphatic amines with benzonitrile
Authors: Anunziata J. , Singh J. , Silber J. J.
Published: May 2006

Interaction of diethyl, triethyl, n-butyl, di-n-butyl and tri-n-butyl amines as n-donor with benzonitrile as π-acceptor has been studied in n-hexane. The formation of weak electron donor–acceptor (EDA) complexes is proposed to explain the spectroscopic behavior of the mixtures. An iterative procedure was used to obtain values of stability constants (K) and extinction coefficients (ε). The fact that from the new absorption observed for these systems a value of K and a finite constant value of ε could be determined gives proof of the existence of EDA complexes. This conclusion is further supported by the temperature effect observed. Correlations of the experimental data with amine structure and other types of amine complexes were found.
The thermal and photochemical decomposition of maleic anhydride in the gas phase
Authors: Back R. A. , Parsons J. M.
Published: May 2006

The thermal decomposition of maleic anhydride has been studied in the gas phase in a static system at temperatures from 645 to 760 K and pressures from 0.7 to 20 Torr. The first-order rate constant for the homogeneous unimolecular reaction,[Formula: see text]is described by the Arrhenius parameters log A (s−1) = 14.33 (±0.3), and E = 60.9 (± 1) kcal/mol. The reaction appears to proceed through a concerted mechanism rather than a biradical one.The photochemical decomposition, studied at wavelengths from 220 to 350 nm, yielded the same products. At 300 nm and below, the decomposition was unaffected by pressure, but at longer wavelengths collisional quenching was observed. Weak light emission was observed on excitation between 350 and 380 nm. The absorption spectrum was measured from 250 to 400 nm, and three overlapping transitions, π*←π, π*←n+, and π*←n−, can be distinguished. The mechanism of the photolysis is discussed and it is concluded that it probably proceeds through internal conversion to a vibrationally excited ground state.
Aggregation of a symmetrical metalloporphyrin. Concentration and temperature dependence of the absorption and magnetic circular dichroism spectra of dilute zinc octamethyltetrabenzporphyrin solutions
Authors: Reimer Kenneth J. , Reimer Monica M. , Stillman Martin J.
Published: May 2006

Absorption and magnetic circular dichroism (mcd) spectra of toluene solutions of zinc octamethyltetrabenzporphyrin, Zn(OMBP), exhibit marked concentration and temperature dependence. Monomeric Zn(OMBP), 1, characterized by a 429 nm Soret band, dominates at low concentrations (10−7 M, 300 K) and higher temperatures (10−5M, 320 K) in toluene solution. Decreasing temperatures (320 to 235 K for a 10−5 M solution) and increasing concentrations (10−7 M to 10−4M, 300 K) result in 8–10 nm red shifts in this band. These spectral changes are attributed to the concurrent formation of a species 2 with a low extinction coefficient and another compound, 3, with λmax at 439 nm. At the highest concentrations (10−3 M) and lowest temperatures (225–190K) used, a dramatic blue shift (439 to 422 nm) due to a fourth species (4) is observed. All the spectral changes observed are completely reversible. In addition, and consistent with self-association, species 2, 3, and 4 are formed at higher temperatures as the concentration is increased. Possible aggregate structures are proposed and evidence is presented for a novel Zn—N (pyrrole) intermolecular bond.
Removal of allergens from natural oils by selective binding to polymer supports. II. Application of aminated resins to isoalantolactone and costus oil
Authors: Cheminat Annie , Benezra Claude , Farrall M. Jean , Fréchet Jean M. J.
Published: May 2006

A number of crosslinked polymers containing primary or secondary amine functional groups were prepared by chemical modification of styrene–divinylbenzene or styrene–acrylonitrile–divinylbenzene resins. The polymers were tested in the binding of α-methylene-γ-butyrolactone allergens via Michael addition of their nucleophilic ends with the conjugated system of the lactones. Best results were obtained using 1% crosslinked poly(aminoethylstyrene) in ethanol; polymers with higher crosslinking or other functional groups were somewhat less reactive. This technique for the removal of α,β-unsaturated lactones from solution was applied successfully to the selective removal of the allergenic components of costus oil, a natural oil of plant origin used in the cosmetics industry. After purification of the costus extracts, the allergens which were retained by the polymer could be cleaved by permethylation followed by base treatment, and characterized. The polymer-treated natural oil had lost its allergenic properties while the polymer-retained materials were found to be powerful allergens.
A novel approach to the synthesis of a variety of aminodeoxy-α-D-glycopyranosides
Authors: Lemieux Raymond U. , Georges Fawzy F. Z. , Smiatacz Zygfryd
Published: May 2006

Conditions for the replacement of the 3-acetoxy group of ethyl 3,4,6-tri-O-acetyl-2-deoxy-2-oximino-α-D-arabino-hexopyranoside (1) by nucleophiles including azide, phthalimide, hydride, and thiophenoxide are reported. The reaction was discovered through the formation of dimeric and trimeric derivatives of deacetylated 1 in the course of its alkaline hydrolysis. The possible use of the replacement reaction to achieve precursors for the formation of 3-deoxy-, 3-amino-3-deoxy-, 2-amino-2,3-dideoxy-, 2,3-diamino-2,3-dideoxy-, and 2-amino-2,3,4-trideoxy-α-glycopyranosides is demonstrated.
The determination of copper, cadmium, and lead in sea water by anodic stripping voltammetry with a thin film mercury electrode
Authors: Green D. G. , Green L. W. , Page J. A. , Poland J. S. , Loon G. van
Published: May 2006

The application of anodic stripping voltammetry to the determination of Cu, Pb, and Cd in acidified sea water samples has been examined. The analyses were carried out using a thin film mercury electrode prepared in situ by the method of Florence. The electrode was rotated in the collection step but held stationary in the stripping step. The stripping involved a linear DC potential ramp and background compensation was employed. Resolution of the stripping peaks required "curve fitting" of the baseline.In the acidified sea water electrolyte it was found that the Pb and Cd stripped to Pb(II) and Cd(II) while the Cu stripped to Cu(I). A good correlation was found between the stripping signals and predictions based on the Levich equation for deposition at a rotating disk electrode and the De Vries and Van Dalen equation for stripping from a thin film electrode. The effect of sample acidity was examined and it was concluded that in unpolluted, filtered sea water the total metal was free for analysis at pH 2. Calibration was by the method of standard addition and intercalibration studies showed that the results agreed well with those obtained by other methods.
Basicity of N-substituted anilines and pyridine in dimethylsulfoxide
Authors: Benoit Robert L. , Mackinnon Moyra J. , Bergeron Léon
Published: May 2006

The ionization constants of the conjugated acids BH+ of aniline, N-methyl- and N,N-dimethylaniline, and pyridine have been determined potentiometrically in Me2SO. The heats of neutralization of the amines B and their heats of solution have been obtained by calorimetry. The pK's and enthalpies of ionization of these BH+ ions and alkylammonium ions are linearly related. Comparisons with gas phase data show that the abnormal basicity order of the amines B in Me2SO is mainly due to the decreasing exothermicity of the heat of solution of the BH+ ions with the number of N—H protons available for H-bonding to Me2SO. The large increase in basicity difference between equally substituted aromatic and alkylamines, when passing from the gas phase to Me2SO, is linked to the larger heat of vaporization of the aromatic amines.
Infrared and thermogravimetric studies of the thermal degradation of chrysotile asbestos fibers: evidence for matrix effects
Authors: Jolicoeur Carmel , Duchesne Daniel
Published: May 2006

Thermal decomposition of short chrysotile asbestos fibers under static heating has been studied by infrared spectroscopy and thermogravimetry. The spectral changes were monitored at room temperature for fibers heated (a) in the free state or (b) in KBr matrix. In either case dehydration occurs sharply near 550 °C. However, subsequent transformations of the chrysotile anhydride were found to be markedly different for (a) and (b), suggesting important matrix effects. This provides an explanation for earlier observations in which the thermal decomposition scheme appeared dependent of the size of the chrysotile fibers.
Simulation of electrochemical processes by orthogonal collocation. Spherical electrode geometry
Authors: Pons B. Stanley
Published: May 2006

Discretization formulas for the digital simulation of the diffusional processes associated with a variety of electrochemical processes at a spherical electrode are given. The formulas are based on orthogonal collocation techniques. Several mechanisms are represented, and the technique is demonstrated for chronoamperometry, chronopotentiometry, and cyclic voltammetry.