bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence of alarm pheromones in the venom ofPolistes dominulusworkers (Hymenoptera: Vespidae)
Authors: BRUSCHINI CLAUDIA , CERVO RITA , TURILLAZZI STEFANO
Published: May 2006

AbstractThe active and coordinating capacity of defending the nest is a key feature of social insects. The present study investigates the presence of alarm pheromones in the venom of workers of the social wasp,Polistes dominulus. Laboratory experiments were performed with caged colonies ofP. dominulususing a wind tunnel apparatus to test the behavioural response of workers to venom released by other workers and to venom extracts. Contrary to that previously reported for European paper wasps, the present results show that the venom is the source of alarm pheromones. Field experiments combining a visual (black target) and a chemical stimulus (venom extract) were performed to test the effect of the venom on the reaction of colonies. Wasps leave the nest, land on the visual target and attack the target significantly more once exposed to venom extract plus target than to solvent plus target. This work shows that the venom ofP. dominulusworkers elicits an alarm response, reduces the threshold for attack and acts as an attractant on targets. These results usingP. dominulusindicate that, in both American and European species, colony defence is based on the same features, suggesting that chemical alarm is a widespread trait in the genusPolistes.
Characterizing luminous efficiency functions for a simulated mesopic night driving task based on reaction time
Authors: Szalmas Attila , Bodrogi Peter , Sik‐Lanyi Cecilia
Published: May 2006

The objective of this study is to test the luminous efficiency functions V(λ), V′(λ), V10(λ) and their linear combinations on the basis of a data set gained from a simulated mesopic night‐time driving experiment. Another aim is to provide ‘real‐world’ data for the ‘X framework’ or ‘linear combination model’, and to find out its limits in a practical situation. Human performance was measured by the reaction time method. Results show that the single parameter of the linear combination of photopic and scotopic luminous efficiency functions can be determined analytically with little variation for a given mesopic background luminance level and a given visual target colour, but the computation leads to considerable deviations comparing all three target colours (red, green and blue) used in the experiment. The conclusion for the given experimental conditions is that the single parameter of the linear combination model has an increasing deviation for lower background luminance levels.
Child Support Reform: Some Analysis of the 1999 White Paper
Authors: PAULL GILLIAN , WALKER IAN , ZHU YU
Published: May 2006

This paper uses a sample of lone mothers (and former lone mothers who are now repartnered) drawn from the 1997 Family Resources Survey to analyse the potential effects of reforming the UK system of child support. The main deficiency of the data is that non‐resident fathers cannot be matched to the mothers in the data, and this is overcome by exploiting information from another dataset which gives the joint distribution of the characteristics of separated parents. The effects of reforming the child support system are simulated for the amount of maintenance liabilities, the amount paid and the net incomes of households containing mothers‐with‐care and of households containing non‐resident fathers. The likely effects of the reform are simulated at various levels of compliance. The analysis highlights the need for further research into the incentive effects of child support on individual behaviour.
Delivery of the Malaria Virulence Protein PfEMP1 to the Erythrocyte Surface Requires Cholesterol-Rich Domains
Authors: Frankland Sarah , Adisa Akinola , Horrocks Paul , Taraschi Theodore F. , Schneider Timothy , Elliott Salenna R. , Rogerson Stephen J. , Knuepfer Ellen , Cowman Alan F. , Newbold Chris I. , Tilley Leann
Published: May 2006

The particular virulence of the human malaria parasitePlasmodium falciparumderives from export of parasite-encoded proteins to the surface of the mature erythrocytes in which it resides. The mechanisms and machinery for the export of proteins to the erythrocyte membrane are largely unknown. In other eukaryotic cells, cholesterol-rich membrane microdomains or “rafts” have been shown to play an important role in the export of proteins to the cell surface. Our data suggest that depletion of cholesterol from the erythrocyte membrane with methyl-β-cyclodextrin significantly inhibits the delivery of the major virulence factorP. falciparumerythrocyte membrane protein 1 (PfEMP1). The trafficking defect appears to lie at the level of transfer of PfEMP1 from parasite-derived membranous structures within the infected erythrocyte cytoplasm, known as the Maurer's clefts, to the erythrocyte membrane. Thus our data suggest that delivery of this key cytoadherence-mediating protein to the host erythrocyte membrane involves insertion of PfEMP1 at cholesterol-rich microdomains. GTP-dependent vesicle budding and fusion events are also involved in many trafficking processes. To determine whether GTP-dependent events are involved in PfEMP1 trafficking, we have incorporated non-membrane-permeating GTP analogs inside resealed erythrocytes. Although these nonhydrolyzable GTP analogs reduced erythrocyte invasion efficiency and partially retarded growth of the intracellular parasite, they appeared to have little direct effect on PfEMP1 trafficking.
Carbamates and 2-oxazolidinones from tertiary alcohols and isocyanates
Authors: Francis Thomas , Thorne Melanie P.
Published: May 2006

Organo-tin catalysts have been used to prepare a large number of new carbamates of tertiary alcohols. Cyclization of carbamates of unsaturated tertiary alcohols leads to the formation of 2-oxazolidinones, and provides a new synthetic route for some of these compounds.
Spectroscopic studies of benzoxazole-2-thione complexes. Derivatives of cobalt(II) and nickel(II) halides
Authors: Preti Carlo , Tosi Giuseppe
Published: May 2006

The preparation of some complexes of benzoxazole-2-thione with halides of cobalt(II) and nickel(II) is reported. The complexes of cobalt(II) and nickel(II) are tetrahedral of the type ML2X2 with the exception of NiLBr2. The complexes have been studied by means of magnetic susceptibility measurements, infrared and far ir spectra, electronic spectra, and conductivity measurements. The ligand behaves as monodentate N-bonded. The various ligand field parameters, Dq, B′, and β show about 60 and 80% of covalency in the cobalt(II) and nickel(II) complexes respectively and suggest a medium strong ligand field. The spectroscopy parameters of cobalt and nickel derivatives confirm the presence of CoN2X2 and NiN2X2 chromophores.
Mercury(I) chemistry. Part I. Complexes of the mercurous ion with some arenes
Authors: Dean Philip A. W. , Ibbott David G. , Stothers J. B.
Published: May 2006

A wide range of arene complexes of the mercurous ion has been prepared from mercurous hexafluoroarsenate and the appropriate arene in liquid sulfur dioxide. Raman spectroscopy confirmed the integrity of the dimeric Hg22+ cation in these complexes. 13C nuclear magnetic resonance spectroscopy showed that Hg22+–arene complexes exist in sulfur dioxide solution. The 13C data allowed the estimation of formation constants for the hexamethylbenzene, p-xylene, and p-dichlorobenzene complexes together with the 13C chemical shifts for the bound substrates in these cases. The 13C chemical shift changes (relative to the free substrate) on addition of Hg22+ to SO2 solutions of various methylated benzenes are compared with those occurring on complexation of the same arenes by the argentous ion and the Cr(CO)3 moiety. In mercurous ion–arene complexes, it is concluded that the cation is involved in a localized interaction with the arene and that there are preferred binding sites. These sites may be identified by the complexation shifts for the Ag+– and Hg22+–arene complexes.
Revised structure for the γ-lactone derived from acid treatment of dihydroisopimaric acid
Authors: ApSimon John W. , Holmes Andrew M. , Beierbeck Helmut , Saunders John K.
Published: May 2006

The γ-lactone obtained from acid treatment of dihydroisopimaric acid was found to have a cis-A/B ring fusion. This structure revision was based on 13C nmr chemical shift data and spin–lattice relaxation time (T1) measurements. Using the same methods, the δ-lactone derived from the same acid was shown to have the previously proposed structure.
Ring C substituted 14-hydroxymorphinans and isomorphinans as narcotic antagonists
Authors: Menard Marcel , Rivest Pierre , Belleau Bernard , Daris Jean-Paul , Perron Yvon G.
Published: May 2006

The synthesis of morphinans incorporating a hydroxyl group at position 14 as well as an appropriate alkyl substitution in ring C is described. It is shown that the spatial area around ring C plays an important role at the analgesic receptor level. A novel morphine structure with ring C frozen in a boat conformation is also described.
Studies of p-nitrobenzoic acid and the p-nitrobenzoate ion in the electrical double layer of oriented cationic and anionic nematic phases
Authors: Lee Yunko , Reeves Leonard W.
Published: May 2006

The p-nitrobenzoate ion and its conjugale acid have been oriented in both cationic and anionic detergent based lyomesophases. In the cationic phase there is no marked change in the order of the C2 axis as the hydrogen ion concentration of the water region of the phase is varied. The degree of order along the C2 axis is decreased considerably in passing to the anionic detergent based phase and in this phase the degree of order of the ion does increase in the expected manner on protonation. The orientation of the larger organic counter ion and its acid is probably complicated by insertion into the hydrophobic region and use of the —NO2, —CO2−, or —COOH moieties as head groups.
An inequality formulation of conformational energy differences
Authors: Colpa Johannes Pieter , Schlegel H. Bernhard , Wolfe Saul
Published: May 2006

A theoretical analysis has been performed of the effects of geometry optimization upon computed barriers to rotation and pyramidal inversion. It is shown that, where ΔE is the true energy difference between the energy minimum and the transition state for a particular conformational process, (barrier using the optimized geometry of the lower state) > ΔE > (barrier using the optimized geometry of the higher state). Some numerical tests of this inequality are discussed. These reveal certain limitations upon the assumption that an optimized geometry is transferable from one basis set to another.
Arylsulfonyltetrazoles as highly efficient condensing reagents for polynucleotide synthesis
Authors: Stawinski J. , Hozumi T. , Narang S. A.
Published: May 2006

Various arylsulfonyltetrazoles have been investigated to build the phosphotriester bond between appropriately protected oligonucleotides. These reagents have been found to be highly effective with respect to the time of reaction and yields.
Esters chromiques dérivés d'alcools tertiaires
Authors: Richer Jean-Claude , Hachey Jean-Marie
Published: May 2006

not available
Synthetic morphinans and hasubanans. VI. Total synthesis of 3-hydroxyisomorphinans, 3-hydroxyhasubanans, and 3,9-dihydroxyhasubanans
Authors: Monković Ivo , Wong Henry
Published: May 2006

A new total synthesis of racemic 3-hydroxyisomorphinans (3), 3-hydroxyhasubanans (9), 3,9α-dihydroxyhasubanans (5), and 3,9β-dihydroxyhasubanans (7), via 4a-(2-aminoethyl)-1,2,3,4,4a,9-hexahydro-6-methoxyphenanthrene (1a) is described.
Free radicals by mass spectrometry, XLVII. lonization potentials and ionic heats of formation of C5–C7 alkyl radicals
Authors: Lossing F. P. , Maccoll Allan
Published: May 2006

Using an energy-resolved electron beam, ionization potentials have been measured for a number of C5–C7 isomeric alkyl radicals, produced by pyrolysis of nitrite intermediates. Values for primary radicals, which could not be produced in sufficient yield, are estimated by extrapolation from lower members of the series. Ionic heats of formation and hydride ion affinities are reported.
Metastable ion studies. VI. The identification of C2H5N+• ion structures from their characteristic kinetic energy releases
Authors: Holmes John L. , Terlouw Johan K.
Published: May 2006

Metastable peaks for the fragmentation C2H5N+• → C2H4N+ + H• have been studied in the first field-free region of a double focussing mass spectrometer. Isomeric structures of C2H5N+• ions derived from a variety of precursor molecules were characterised by their metastable peak shape and kinetic energy release. The identifications were aided by appropriate deuterium labelling experiments. Four isomeric ionsr [Formula: see text]were shown to retain their structural identity within the ion energy and lifetime ranges observable in these experiments. Ion (a), generated from aziridine was found to be indistinguishable from its open chain isomer [Formula: see text]The results closely parallel those previously found for the isoelectronic C2H5N+• ions, but the differences in characteristic kinetic energy release are smaller. A simple deuterium exchange labelling experiment may be necessary for the unequivocal identification of C2H5N+• ion structures.
13C nuclear magnetic resonance studies. 55. A comparison of the stereochemical dependence of γ- and δ-substituent effects on 13C shieldings in several norbornanols and norbornenols
Authors: Stothers J. B. , Tan C. T. , Teo K. C.
Published: May 2006

The 13C nmr spectra of a series of 50 methyl substituted norbornanols have been determined to gain further insight into the nature of stereochemical effects on the shieldings of carbons having closely neighboring substituents. The relatively rigid norbornyl skeleton permits examination of a variety of orientations of substituents separated by three and four bonds, the γ and δ interactions, respectively. While methyl carbons close to γ substituents exhibit upfield shifts, as is well established, methyl carbons close to δ substituents are significantly deshielded. Even more striking shifts are found for the carbons bearing these closely lying groups. The penultimate carbons in a fragment having a δ interaction between terminal groups show deviations of up to +11 ppm from the shieldings predicted by simple additivity. For fragments having a corresponding γ interaction, the penultimate carbons absorb as much as −10 ppm from the values expected by additivity. These deviations have considerable potential for stereochemical assignments and offer a challenge for theoretical interpretation.Some norbornenols and the acetates of several of the norbornanols were also included in this series and the latter shieldings are compared briefly with those observed for the parent alcohols.
The effect of alkene structure upon the rates and product composition of addition of 4-chlorobenzenesulfenyl chloride
Authors: Schmid George H. , Dean Coleen L. , Garratt Dennis G.
Published: May 2006

The rates and products of addition of 4-chlorobenzenesulfenyl chloride to 30 mono- and disubstituted alkenes have been determined in 1,1,2,2-tetrachloroethane at 25 °C. The rates of addition span a range of 106. No correlation with the extended Taft equation was found with the rates of all 30 compounds. The rate ratio kc/kt for addition to nine pairs of isomeric cis-trans alkenes ranges from a low of 3.1 for the 2-butenes to a high of 1.57 × 105 for the 2,2,5,5-tetramethyl-3-hexenes. The rate ratio kc/kt does not always increase regularly with the increasing size of the substituents which suggests that relief of ground state strain is not important in the rate determining transition state. Greater steric hindrance between the electrophile and the trans alkene compared to the cis isomer is proposed to account for the results.
Synthetic application of α-hydroxydiazene systems. II. Uncatalyzed and phenol catalyzed radical chain hydro-tert-butylation of unsaturated compounds with tert-butylazodiphenylcarbinol
Authors: Yeung Dominic W. K. , Warkentin John
Published: May 2006

tert-Butylazodiphenylcarbinol 1 decomposes in benzene solution by a chain mechanism involving tert-butyl radicals. Many olefinic compounds and azobenzene act as radical traps and are hydro-tert-butylated by 1. The regiochemistry of hydro-tert-butylation of unsymmetric alkenes is that expected for a mechanism which involves addition of tert-butyl radical so as to form the most stable radical adduct, which subsequently abstracts hydrogen from 1.In some cases phenol acts as a catalyst for the hydroalkylation process. The novel catalytic effect of phenol in a radical chain process is attributed to the favourable thermochemistry for induced, concerted decomposition of 1 by radical attack at hydroxyl hydrogen.
Enthalpies of formation of Cr3+(aq) and the inner sphere complexes CrF2+(aq), CrCl2+(aq), CrBr2+(aq), and CrSO4+(aq)
Authors: Dellien Ingemar , Hepler Loren G.
Published: May 2006

We have carried out calorimetric measurements leading to ΔHf0 = −60 kcal mol−1 for Cr3+(aq). Further calorimetric measurements have led to enthalpies of reaction of Cr3+(aq) with HF(aq), Cl−(aq), Br−(aq), and SO42−(aq) to form the 'inner sphere' complexes CrF2+(aq), CrCl2+(aq), CrBr2+(aq), and CrSO4+(aq). Results of our measurements lead to ΔHf0 = (−60.0 ± 1.5) kcal mol−1 for Cr3+(aq), ΔHf0 = −136.8 kcal mol−1 for CrF2+(aq), ΔHf0 = −93.7 kcal mol−1 for CrCl2+(aq), ΔHf0 = −80.1 kcal mol−1 for CrBr2+(aq), and ΔHf0 = −269.7 kcal mol−1 for CrSO4+(aq).
Geometry and rotational barriers in 1,3,5-triphenylpentadienyllithium by 1H and 13C nuclear magnetic resonance
Authors: Hunter D. H. , Klinck R. E. , Steiner R. P. , Stothers J. B.
Published: May 2006

Variable temperature studies of 1H and 13C spectra have been employed to establish the geometry of 1,3,5-triphenylpentadienyllithium in tetrahydrofuran solution. These data show that the anion exists in both W and S forms, which are of comparable energy, and interconversion between the two S forms is more rapid than [Formula: see text] This represents one of the few reported measurements of the barrier to rotation about an internal bond in a delocalized carbanion.
Solubilities of the silver halides in benzonitrile and trichloroacetonitrile mixtures with propylene carbonate
Authors: Salomon Mark
Published: May 2006

The complex solubilities of the silver halides, AgCl, AgBr, and AgI, have been determined in benzonitrile and trichloroacetonitrile mixtures with propylene carbonate. The results are compared with previous work in acetonitrile and propionitrile and are discussed in relation to the solvent effect on ion solvation.
Utilisation de la méthode de Wittig pour la synthèse de vinyl-2 aziridines N-substituées
Authors: Borel Daniel , Gelas-Mialhe Yvonne , Vessière Roger
Published: May 2006

Several 2-vinylaziridines were prepared by treating N-substituted 2-acylaziridines with phosphoranes. The stereochemistry of the ring and the double bond of the products was established from a study of their nmr spectra. The geometry of the starting material 2-acylaziridine is conserved in the 2-vinylaziridine formed. [Journal translation]
Isomérisation thermique de vinyl-2 aziridines N-substituées
Authors: Borel Daniel , Gelas-Mialhe Yvonne , Vessière Roger
Published: May 2006

The thermal isomerization of 2-vinylaziridines, variously substituted on the ring and the double bond, has been studied. The nature of the products formed depends on the nature of the substituents in positions 1 and 3. If the ring carbon-3 carries a phenyl substituent, the thermolysis yields, in most cases, a Δ-2-pyrroline. With unsubstituted or 3-alkylaziridines the reaction proceeds, depending on the nature of the substituent on the nitrogen, either to an ethylene imine or to a mixture of Δ-2- and Δ-3-pyrrolines. Mechanisms to interpret the experimental results are proposed. [Journal translation]
Moments dipolaires théoriques des dérivés de Mo(CO)6
Authors: Barbeau Claude , Turcotte Jacques
Published: May 2006

It is demonstrated that it is possible to calculate, a priori, the dipole moments of the cis-derivatives of Mo(CO)6−nLn. The partial moment Mo—CO in Mo(CO)6 can be obtained from the measured dipole moments of ArMo(CO)3. Attempts are made to explain the differences observed between the measured and calculated dipole moments. [Journal translation]
Les réactions de Friedel et Crafts d'acylation des hydrocarbures aromatiques polycycliques. IX. L'acétylation de l'anthracène et de ses homologues méso-méthylés
Authors: Perin François , Croisy-Delcey Martine , Jacquignon Pierre
Published: May 2006

A study of the influence of various reaction parameters (solvent, temperature, nature and quantity of the catalyst and of the acylating agent) on the yield and isomeric orientation of the acetylation of 9-methyl- and 9,10-dimethylanthracene relative to that of anthracene itself. reveals the importance of the rearrangement of the meso-substitution product vis à vis that of products substituted in other positions. Analysis of the conditions necessary for reversibility indicates that an excess of the catalyst is the main factor responsible. The experimental results allow one to propose a mechanism for this rearrangement which does not involve the prior dissociation of the acylating agent during acylations by acid anhydrides.
Influence du substituant tertiobutyl-4 sur les constantes d'acidité du cation cyclohexylammonium et de l'acide cyclohexane carboxylique dans les milieux mixtes eau–DMSO et méthanol–DMSO
Authors: Edward John T. , Farrell Patrick G. , Kirchnerova Jitka , Halle Jean-Claude , Schaal Robert
Published: May 2006

Acid dissociation constants for the compounds 1–6 in water–DMSO and methanol–DMSO of varying composition have been determined by a potentiometric method. In all solvents the equatorial group ionized more easily, by gain or loss of a proton, than the axial group, but in the more aqueous solvents the presence of a tert-butyl group across the cyclohexane ring inhibited this ionization slightly. An explanation based on displacement of solvent molecules from the outer solvation sphere is advanced.
The oxidation of cyclobutanol by ruthenium tetroxide and sodium ruthenate
Authors: Lee Donald G. , Spitzer Udo A. , Cleland James , Olson Merle E.
Published: May 2006

The only detectable product obtained from the oxidation of cyclobutanol by ruthenium tetroxide or sodium ruthenate is cyclobutanone. This indicates that both of these reagents act as two-electron transfer oxidants and that the oxidation of alcohols by ruthenium tetroxide likely proceeds via a mechanism that involves a pair of successive two-electron transfer steps.
Préparation et étude des isothiocyanatoboranes halogènes
Authors: Dazord J. , Mongeot H. , Atchekzai H. , Tuchagues J. P.
Published: May 2006

The mixed halide–pseudohalides BXn(NCS)3−n (n = 1 or 2) have been obtained except for X = F. Mixtures of these compounds with boron trihalide and boron triisothiocyanate are prepared by the reaction of BX3 either with metal isothiocyanates or with boron triisothiocyanate. Mass spectrometry, infrared, Raman, and 11B nmr data are reported. Rapid redistribution reactions prevent the isolation of the mixed species. Vibration spectrometry shows that boron is bonded to the nitrogen of the NCS group and not to the sulfur.
Mécanisme d'inhibition par des alcools de la photo-oxydation de l'heptanal en phase liquide
Authors: André J. C. , Lemaire J.
Published: May 2006

The photooxidation of heptaldehyde n-C6H13CHO can be inhibited by primary and secondary alcohols; this inhibition occurs through reaction between the peroxy radical C6H13CO3• and the alcohol, leading to less reactive species disappearing by recombination processes. Moreover, the reactivity of free radicals is modified by alcohols which solvate these radicals by hydrogen bonding. A kinetic scheme is proposed which accounts for the experimental results.
Hydrogen abstraction by perfluoroethyl radicals from methylfluorosilanes
Authors: Bell Thomas N. , Yokota Toshitsugu , Sherwood Alden G.
Published: May 2006

Arrhenius parameters have been measured for hydrogen abstraction by C2F5 radicals (produced from the photolysis of perfluoropropionic anhydride) from methylfluorosilanes and tetramethylsilane.[Formula: see text]The results are discussed in relation to those of similar reactions involving the CF3 and the CH3 radical, and interpreted in terms of polar effects.
Some synthetic routes to 2,3,6-trideoxy-hex-2-enopyranosides and -hex-2-enopyranosid-4-uloses
Authors: Yunker Mark Bernard , Tam Steve Yik-Kai , Hicks D. R. , Fraser-Reid B.
Published: May 2006

Routes to 6-deoxy-hex-2-enopyranosides and the corresponding 4-ulo derivatives have been investigated. The route (Scheme 2) beginning with the readily prepared ethyl 2,3-dideoxy-α-D-erythro-hex-2-enopyranoside is preferred, and the steps involve selective tosylation, iodinolysis, and reduction with Raney nickel. During the iodinolysis step a rearrangement occurs leading to furan derivatives. However, tliis is suppressed completely by the addition of pyridine to the iodinolysis medium. If the 4-ulo derivative is the desired substance, the most direct route (Scheme 3) utilises the well-known 2,3-dideoxy-hex-2-enopyranosid-4-ulose, the primary hydroxyl group being removed in two simple steps.
Study on the preparation of 3α-hydroxy-5α-cholestan-6-one and-7-one by stereoselective catalytic hydrogenation
Authors: Ishige Masayoshi , Shiota Michio , Suzuki Fumiyo
Published: May 2006

The title compounds are conveniently obtained from the corresponding diones by the stereoselective hydrogenation with Urushibara nickel A catalyst in cyclohexane.
Binding energies and stabilities of potassium ion complexes with ethylene diamine and dimethoxyethane (glyme) from measurements of the complexing equilibria in the gas phase
Authors: Davidson W. R. , Kebarle P.
Published: May 2006

The temperature dependence of the gas phase equilibria [Formula: see text] where en = ethylene diamine were measured for n = 1 to n = 3. The equilibrium K+ + dimethoxyethane [Formula: see text] K+(dimethoxyethane) was also determined. The measurements were made with a high ion source pressure mass spectrometer equipped with a thermionic potassium ion emitter. The resulting ΔH0, ΔG0, and ΔS0 values are compared with the corresponding values for monodentate ligands like H2O, NH3, CH3OCH3 etc. determined in earlier work. As expected, the bidentate ligands lead to considerably stronger (0,1) interactions. Dimethoxyethane leads to a stronger complex than ethylene diamine. The third molecule of ethylene diamine leads to much weaker binding than is observed for the first two molecules. Explanation of the observed effects is given on basis of electrostatic and steric arguments.
Organometallic peroxy radicals. Part II. A kinetic electron spin resonance study of some organogermylperoxy radicals
Authors: Howard James Anthony , Tait John Charles
Published: May 2006

Trimethylgermylperoxy and triphenylgermylperoxy have been prepared and their kinetic behaviour investigated by electron spin resonance techniques. At low temperatures (< −50 °C) these radicals exist in equilibrium with the tetroxide. The thermodynamic parameters for this equilibrium (−ΔH0 ≈ 11.5 kcal mol−1 and −ΔS0 ≈ 26.5 cal deg−1 mol−1) are the same, within experimental error, for both radicals. Above −50 °C (CH3)3GeO2 and (C6H5)3GeO2 decay irreversibly by a unimolecular process. (C6H5)3GeO2 is slightly less stable than (CH3)3GeO2 although both radicals appear to fit an Arrhenius equation of the approximate form log (kepr1/s−1) ≈ 5 − 6/θ where θ = 2.303RT kcal mol−1.
Oligoribonucleotide synthesis. X. An improved synthesis of the anticodon loop region of methionine transfer ribonucleic acid from E. coli
Authors: Werstiuk E. S. , Neilson Thomas
Published: May 2006

Nonaribonucleotide, GpCmpUpCpApUpApApC, was synthesized using a block phosphotriester method. Its sequence corresponds to that of the anticodon loop of transfer RNAfMet (E. coli). Protected tetramer, GCmUC and pentamer nucleotides, AUAAC, assembled stepwise from nucleoside derivatives, were joined together to give protected nonamer which on deblocking, gave the free nonaribonucleotide in milligram amounts. The superior internucleotide coupling efficiency of mesitylenesulfonyl triazolide (MST) over triisopropylbenzenesulfonyl chloride (TPS) is demonstrated.
The synthesis and spectroscopic characterization of Indulin 6B tetrasulfonate
Authors: Solodar W. E. , Monahan A. R.
Published: May 2006

An unambiguous synthetic route to pure forms of Indulin 6B base and Indulin 6B tetrasulfonate is described. The visible electronic spectrum of each compound was examined in solution and the solid state. The longest wavelength electronic transition observed for both compounds is a π – π* state possessing a considerable amount of intramolecular charge transfer character. Indulin 6B tetrasulfonate was found to self-associate in water with a dimerization constant of (1.84 ± 0.22)×102M−1. The nature of the intermolecular interactions between Indulin dye molecules in solution and the solid state is discussed.
Molecular weight of lecithin micelles in toluene by osmometry and Brillouin spectroscopy
Authors: Braedley Robert J. , Grant Douglas H. , Reinsborough Vincent C. , Ross Peter A.
Published: May 2006

Number average molecular weights for lecithin micelles in toluene were determined by osmometry at 25 and 40 °C to be 54 000 and 41 900 respectively. The weight average molecular weights were found to be 78 000 and 68 000 for the same two temperatures by Brillouin spectroscopy. This new technique shows promise in determining micelle size.
Dielectric and nuclear magnetic resonance characterization of unstable clathrate hydrates of acetaldehyde and propionaldehyde
Authors: Davidson D. W. , Gough S. R. , Ripmeester J. A.
Published: May 2006

Sub-MHz dielectric absorption at low temperatures is used to demonstrate the formation by acetaldehyde and propionaldehyde of unstable clathrate hydrates, probably of type II. This result is supported by the proton nmr line shapes of propionaldehyde enclathrated in D2O, which also show fast rotational tunnelling of the methyl group at 4 K.
Chromyl chloride oxidations. IV. The oxidations of cyclohexene and 1-methylcyclohexene
Authors: Bachelor Frank William , Cheriyan Ukken Ouseph
Published: May 2006

The chromyl chloride oxidations of cyclohexene and 1-methylcyclohexene have been reexamined. The products from cyclohexene were found to be cyclohexanone, cis- and trans-2-chlorocyclohexanols, 2-chlorocyclohexanone, cyclohex-2-enol, cyclohex-2-enone, and cyclohexene oxide. Treatment of cyclohexene oxide with chromyl chloride produced only trans-2-chlorocyclohexanol and 2-chlorocyclohexanone. The products from 1-methylcyclohexene were 2-methylcyclohexanone, 1-methylcyclopentyladehyde, cis- and trans-2-methyl-2-chlorocyclohexanol, 2-methyl-2-chlorocyclohexanone, 2-methylcyclohex-2-enone, and 4-methylcyclohex-2-enone. Treatment of 2-methylcyclohexene oxide with chromyl chloride yielded only 2-methylcyclohexanone and 1-methylcyclopentylaldehyde. The origin of the various products and possible mechanisms for their formation is discussed. A 1,3-cyclic addition reaction is proposed for the formation of the cis-chlorohydrins.
Synthesis of d,l-epiramulosin and the configuration of ramulosin
Authors: Findlay John A. , Matsoukas John M. , Krepinsky Jiri
Published: May 2006

The synthesis of epiramulosin 1b, the epimer of ramulosin, a metabolite of Pestolatia ramulosa, has been achieved via a seven step sequence from butadiene and Δα,β-hexenolactone and the assignment of the relative and absolute configurations of ramulosin is achieved.
Chemistry of amido radicals: Stereochemical controls in II radical reactions
Authors: Joseph T. C. , Tam Josiah N. S. , Kitadani Masayuki , Chow Yuan L.
Published: May 2006

The acyclic amido radicals generated from the corresponding N-bromo-N-tert-alkylamides reacted like N-radicals, rather than O-radicals, and preferentially abstracted a δ-hydrogen of the alkyl chain, rather than a γ-hydrogen of the acyl chain. On the basis that, in these amido radicals, the conformation of the transition state of the hydrogen transfer is a five-membered ring and the stereoelectronic requirement for the transfer demands a colinear arrangement of the radical containing orbital and the C—H bond, the results are satisfactorily rationalized by the II electron configuration of the amido radicals. It is also established that the chain length of these N-bromoamide photodecompositions increases as the intramolecular hydrogen transfer of the corresponding amido radicals becomes easier; the hydrogen abstraction step must be the rate determining step in the chain reaction. The spontaneous formations of γ-iminolactones from γ-bromoamides indicate that the intramolecular nucleophilic displacement by the O-center of the amido group is facilitated since its transition state conformation readily accommodates the stereoelectronic requirements for the nucleophilic substitution. A colinear approach of the p-orbital of the more nucleophilic N-center to the rear side of the γ-C—Br bond is shown to be prohibitively strained.
A pulse Fourier transform equivalent of the homonuclear (proton–proton) INDOR experiment
Authors: Bock Klaus , Burton Roland , Hall Laurence D.
Published: May 2006

A simple, selective pulse sequence has been developed whereby the equivalent of a continuous wave INDOR nmr experiment, can be performed in the pulse Fourier transform mode of operation. The advantages and limitations of this approach for proton nmr studies are demonstrated with four samples, uridine (1), cytidine (2), vinyl acetate (3), and 2,3,4,-tri-O-acetyl-1,6-anhydro-β-D-mannopyranose (4). The observed responses depend upon the flip angle of the monitoring pulse. A small flip angle (20–30°) detects responses only for those transitions having an energy level in common with the perturbed transition, whereas a 90°-flip angle also results in responses from those transitions which have an indirect connectivity relationship.
Hydrazine derivatives. III. A study of alkylation of guanazole
Authors: Fuentes José J. , Lenoir Jacques A.
Published: May 2006

Spectroscopic results from mono- and dibenzylidene derivatives of 1-alkylguanazoles establish that alkylation of 3,5-diamino-1,2,4-triazole (guanazole) with alkyl halides in basic non-aqueous media occurs at position N-1.
Water-soluble lysine-containing polypeptides. III. Sequential lysine-glycine polypeptides. A circular dichroism and electron microscopy study of annealed complexes with DNA, sonicated DNA, and denatured DNA
Authors: Kielland Sandra L. , Williams Ross E.
Published: May 2006

Circular dichroic spectra, turbidity measurements, and electron micrographs have been taken of annealled complexes of native, sonicated, and denatured DNA's in association with several sequential lysine-glycine copolypeptides. The results indicate that: (1) the molecular weight and strandedness of the DNA influences not only the assymmetric organization of the DNA in the complexes but also the size and shape of the complexes formed; (2) the hydrophobic nature (or sequence) of the polypeptide influences the shape of the complexes formed.
Photoisomerization of 1-triphenylmethylcyclopentadiene. Di-π-methane rearrangement to 5,6,6-triphenylbicyclo[3.1.0]hex-2-ene
Authors: Weigl Stefan , Warkentin John
Published: May 2006

Triphenylmethylcyclopentadiene exists as a mixture of isomers, the minor and major components of which are shown to be 1-triphenylmethylcyclopentadiene (1) and 2-triphenylmethyl-cyclopentadiene (2), respectively.Direct irradiation of a mixture of 1 and 2 led to formation of 5,6,6,-triphenylbicyclo[3.1.0]hex-2-ene (3) via rearrangement of 1. Acetophenone-sensitized irradiation of the same mixture gave 3 as well as a two component mixture of photodimers of 1 and/or 2. Results are interpreted in terms of the di-π-methane rearrangement mechanism.
X-Ray structure of tris(acetonitrile)tricarbonylrhenium(I) tetrafluoroborate
Authors: Chan Lillian Y. Y. , Isaacs E. E. , Graham W. A. G.
Published: May 2006

Reaction of [n-Bu4N]2[Re4(CO)16] with AgBF4 in acetonitrile affords the compound [(CH3CN)3Re(CO)3][BF4]. The latter crystallizes in monoclinic space group P21/c with unit cell dimensions a = 11.021(5) Å, b = 11.136(5) Å, c = 12.980(6) Å, β = 96.906(25)°, and four molecules per unit cell. Data were collected by counter methods and the structure was refined using least-squares procedures to give R = 0.041. The rhenium cation is approximately octahedrally coordinated by six facially arranged ligands. The mean rhenium–nitrogen distance is 2.13 Å, and the mean rhenium–nitrogen–carbon angle in the coordinated acetonitrile is 174.7°.
Ozone yields from the Febetron radiolysis of oxygen – rare gas mixtures
Authors: Boyd A. W. , Miller O. A. , Selkirk E. B.
Published: May 2006

Ozone yields have been measured from the Febetron irradiation of mixtures containing 1–50 mol% oxygen and each of the five rare gases. The maximum values of G(O3) calculated using the energy absorbed only in the rare gas are obtained with the addition of less than 10% oxygen and are for: He, 16; Ne, 14; Ar, 11; Kr, 10; Xe, 12; each with an uncertainty of less than ±10%. On the addition of 0.2 mol% SF6 these yields are reduced to 6,5,1,2, and 2.5 respectively.These values are compared with those derived from ion and excited state yields and the contributions of subexcitation electrons.
The reaction of certain α-diazocarbonyl compounds with thiophosgene and ethyl chlorodithioformate
Authors: Demaree Patricia , Doria Marie-Carmen , Muchowski Joseph M.
Published: May 2006

The reaction of thiophosgene with α-diazocarbonyl compounds produced mixtures of 1,2,3-and 1,3,4-thiadiazoles, in which the latter predominated, irrespective of whether the bis(α-diazoacyl)mercury derivatives or the free diazo compounds were used. In contrast, ethyl chlorodithioformate gave exclusively 1,3,4-thiadiazoles with α-diazocarbonyl compounds in the presence of triethylamine and only 1,2,3-thiadiazoles when the bis(α-diazoacyl)mercury derivatives were used.
Milieux hyperbasiques: préparation de carbanions en α d'amides N,N-disubstitués. Synthèse de β- et γ-hydroxyamides et de γ-butyrolactones
Authors: Hullot Pierre , Cuvigny Thérèse , Larchevêque Marc , Normant Henri
Published: May 2006

The α anions of N,N-disubstituted carboxamides can be conveniently prepared by treatment with "activated" lithium dialkylamides in HMPT. They react with aldehydes and ketones and lead to β-hydroxyamides; furthermore the ring opening of epoxides affords γ-hydroxyamides which may be cyclized in situ to γ-butyrolactones
The preparation and the crystal and molecular structure of tetradecamethylcycloheptaphosphazene, (NPMe2)7
Authors: Gallicano Keith D. , Oakley Richard T. , Paddock Norman L. , Rettig Steven J. , Trotter James
Published: May 2006

The preparation of tetradecamethylcycloheptaphosphazene, by the methylation of the corresponding fluorophosphazene (NPF2)7 with methylmagnesium bromide, is reported. Crystals of tetradecamethylcycloheptaphosphazene are monoclinic, a = 13.160(1), b = 11.685(1), c = 18.576(1) Å, (β = 108.333(5)°, Z = 4, space group C2/c. The structure was solved by direct methods and was refined by full-matrix least squares procedures to a final R of 0.046 and Rw of 0.063 for 2568 reflections with I ≥ 3σ(I). The molecule has crystallographic C2 symmetry with mean bond lengths (rms deviations from the mean in parentheses, bonds not involving hydrogen have been corrected for libration) P—N, 1.592(6), P—C, 1.804(11), and C—H, 0.94(7) Å, and mean angles in the 14-membered ring are 132.9° at N and 117.1° at P.
Unusual formation of N-(1-isoquinolinyl)benzamide from 1-o-and 1-m-chlorobenzoylisoquinolines
Authors: Aysola D. Prasad , Gibson Martin S.
Published: May 2006

Syntheses of 1-o- and 1-m-chlorobenzoylisoquinolines are described, (a) from 2-benzoyl-1,2-dihydroisoquinoline-1-carbonitrile and the appropriate chlorobenzaldehyde, and (b) from 2-o- and 2-m-chlorobenzoyl-2-dihydroisoquinoline-1-carbonitrile. Treatment of either ketone with potassamide - potassium tert-butoxide in ammonia gives N-(1-isoquinolinyObenzamide. The mechanism of this reaction is discussed.
Décharge triboélectrique dans les alcanes C1–C5 à basse pression
Authors: Herman Jan A. , Mayrand Gilles , Tarki Hadi
Published: May 2006

The following gases were submitted to a triboelectric discharge: CH4, C2H6, C3H8, n-C4H10, iso-C4H10, and n-C5H12 and their decomposition products were analyzed. The proportion of unsaturated in the products is around 75% of the total. The total yield of decomposition products increases with the number of carbon atoms in the compound submitted to the discharge. The proportion of saturated products formed from methane increases with pressure. Tentative explanations are offered to elucidate the observed behaviour of gases in the tribodischarges.
Kinetic studies on the mechanism of the decomposition of a number of β-substituted tert-butyl α, α -dimethylperpropionates
Authors: Tanner Dennis D. , Yabuuchi H. , Lutzer H.
Published: May 2006

A series of ter-butyl peresters having a general formula corresponding to I were synthesized.[Formula: see text]The thermally initiated rates of decomposition of these peresters were determined at several temperatures and the activation parameters for these thermolyses were calculated.The rates of decomposition were relatively insensitive to the substituents and followed the order I > C2H5 > C6H5S > H > Br > Cl. The activation parameters and product studies were consistent with a simple two bond scission mechanism and no evidence could be found for neighboring group participation in these homolyses.
Synthesis of 6-substituted 5,6,7,12-tetrahydrodibenzo[a,d]cyclooctenes
Authors: Renaud Roger N. , Bovenkamp John W.
Published: May 2006

The eight-membered ring 6,6-dicyano-5,6,7,12-tetrahydrodibenzo[a,d]cyclooctene was prepared from 2,2′-bis(bromomethyl)diphenylmethane and sodiomalononitrile. From this dicyano derivative a series of mono- and disubstituted cyclooctenes was synthesized.The corresponding 5,7,12-trihydro-6H-dibenzo[a,d]cycloocten-6-one was obtained by the ring enlargement of 5,10-dihydro-11H-dibenzo[a,d]cyclohepten-11-one with diazomethane. The parent compound and its dideuterio derivative were prepared from the eight-membered ring ketone. A Wittig reaction on the ketone gave the methylene derivative.
Use of the scaled-particle theory for the determination of single ion standard free energy of transfer between solvents
Authors: Treiner Claude
Published: May 2006

The tetraphenylboron extrathermodynamic assumption is one of the methods most often used for the evaluation of single ion standard thermodynamic functions of transfer between two solvents. We show in this article that the scaled-particle theory may be useful for discriminating among those solvents for which this extrathermodynamic assumption may be questionable because of strong solute–solvent interactions. Although no general rule is proposed, the tetraphenylboron assumption seems valid in the case of the free energy of transfer between water and solvents like methanol, ethanol, acetonitrile, and formamide; it should not be used in the case of the transfer to solvents like propylene carbonate, dimethylsulfoxide or sulfolane. The scaled-particle theory may also be used to predict within 20% the standard free energy of transfer of the tetraphenylboron ion between water and aqueous mixed solvents; examples are given for water–methanol and water–ethanol mixtures.
Reply to comment: "A problem in extracting structure information from the temperature of maximum density for aqueous solutions"
Authors: MacDonald Digby D.
Published: May 2006

The arguments presented by Kuppers in the preceding paper on the use of the temperature of maximum density parameters Δθ and Δθst for the analysis of the effect of solutes on the structure of water are critically examined. The validity of these arguments is challenged on both theoretical and experimental grounds. In particular, the proper choice of the standard state is stressed, and it is demonstrated that Δθst contains structural information which cannot be extracted from Δθ directly.
Formation of ketenes from carboxylic acids in strong acids. Intermediacy of ketenes in the acid-catalyzed α-chlorination of carboxylic acids
Authors: Ogata Yoshiro , Harada Taira , Sugimoto Toshiyuki
Published: May 2006

Evidence (chemical trapping by aniline, and nmr and laser–Raman spectroscopy) is presented for the presence of ketenes in heated solutions of carboxylic acids in fuming H2SO4. The intermediacy of ketenes in α-chlorination catalyzed by strong acids is suggested.
Cryoscopic and nuclear magnetic resonance studies of interaction between acetylacetone and water in benzene
Authors: Kato Masanao , Watarai Hitoshi , Suzuki Nobuo
Published: May 2006

The interaction between acetylacetone and water in benzene solution has been examined by freezing point depression and nuclear magnetic resonance spectroscopy. The experimental results suggest that a 1:1 associated complex between acetylacetone and water is formed in benzene solution saturated with water, and the association constant is estimated to be 2.4 ± 0.1 (kg solvent/mol). By comparison with the results of methylacetylacetone and dimethylacetylacetone, it is suggested that the enol tautomer of acetylacetone preferentially associates with water.
Structure and conformation of hydroxylubimin, a sesquiterpenoid phytoalexin
Authors: Birnbaum George I.
Published: May 2006

In order to determine the orientation of the isopropenyl group and confirm the stereochemistry at other chiral centers in lubimin (1) and hydroxylubimin (2), two antifungal sesquiterpenes, an X-ray structure analysis of 2 was carried out. Crystals of 2 are orthorhombic, space group P212121, a = 6.190, b = 7.210, c = 63.082 Å, Z = 8. The structure was solved by direct methods and refined to R = 0.045. In both independent molecules the six-membered ring is chair-shaped with all four substituents equatorially oriented. The five-membered ring, attached by a spiro junction, is a half-chair with the isopropenyl substituent in an equatorial position. This side-chain is trans to the methyl-bearing carbon in the six-membered ring.
Intramolecular hydride shifts in 4-hydroxycyclohexanones
Authors: Warnhoff E. W.
Published: May 2006

The two reversible base-catalyzed ketol rearrangements [Formula: see text] and [Formula: see text] have been proved to occur by intramolecular hydrogen (probably hydride) transfer. A combination of evidence including reduction studies, 1Hmr data, and determination of absolute configuration has shown that both ketol pairs have the stereochemistry required for suprafacial hydride migration. In the course of this work, the anomalous sodium–1-propanol reduction of dione 9 has been reinvestigated.
Cationic rhodium(I) sulfoxide complexes. Synthesis and spectroscopic properties
Authors: James Brian R. , Morris Robert H. , Reimer Kenneth J.
Published: May 2006

Displacement of the labile acetone ligand from [Rh(diene)(PPh3)(acetone)]A (diene = 1,5-cyclooctadiene (COD), norbornadiene (NBD); A = PF6−, SbF6−) allows facile coordination of dialkyl or alkyl aryl sulfoxides, and [Rh(diene)(PPh3)(sulfoxide)]+ complexes have been synthesized using dimethyl sulfoxide (DMSO), tetramethylene sulfoxide (TMSO), di-n-propyl sulfoxide (NPSO), (S,S;S,R)-(+)-2-methylbutyl methyl sulfoxide (MBMSO), methyl phenyl sulfoxide (MPSO), (R)-(+)-methyl-p-tolyl sulfoxide (MPTSO), and (R)-t-butyl p-tolyl sulfoxide (TBPTSO).Diaryl sulfoxides appear to coordinate in solution but no solid compounds could be isolated. The upfield shifts of the sulfoxide resonances (1H nmr), reflecting shielding by the adjacent phenyl groups of PPh3, and the decrease in ν(SO) on coordination, are indicative of O-bonding in all cases. Infrared data indicate that the frequency shift of ν(SO) upon O-coordination is roughly proportional to the strength of the metal–oxygen bond for a range of transition metal DMSO and TMSO complexes.