bluuebunny/crossref_metadata_2025 huggingface dataset:
The Polarographic Behaviour of 2,4‐Dinitrophenol in Aqueous and non Aqueous Methanolic Media
Authors: Taha Fouad , El Shayeb H. A. , Abd El Gaber A. A. , El Roudi A. M.
Published: September 2010

2,4‐Dinitrophenol (DNP) is polarographically reduced in aqueous buffered solutions along two or three diffusion‐controlled waves depending on the pH. The height of the first‐wave is practically independent of pH. Each of the two nitro‐groups is reduced independently to the hydroxylamine stage. Within the pH range 4.6–9.1 the reduction process exhibits only two steps which manifest the presence of bonded and non bonded states, hence the reduction of DNP is stopped with the formation of two different intermediates.

DNP in non aqueous methanolic media is reduced along three irreversible waves due to the dissociated and anionic forms of the depolarizer. The addition of proton donors causes the reduction of DNP to form the diamine product when 12 equivalents of acid/equivalent depolarizer are present. In the presence of one mole of alkali, the first wave is completely eliminated.

The effect of surfactants on the electroreduction waves of DNP was examined. Additives influence the reduction waves in two distinct ways. The kinetics and mechanism of the reduction process are discussed.
Première Synthèse Totale de L'Alliodorine. Préparation D'Aldéhydes Isopréniques E À Partir des Méthyl‐2 Oxo‐6 Hexène‐2 (E+Z) Carbonitriles‐1
Authors: Tortajada J. , Morizur J‐P.
Published: September 2010

The first synthesis of alliodorine 4EE, a constituent isolated from the duramen of a tropical tree: Cordia alliodora is reported.

A mixture of E and Z isomers of 2‐methyl‐6‐oxo‐2‐heptenenitrile 3 easily accessible by U.V. irradiation of 1‐methyl‐2‐oxo‐cyclopentanecarbonitrile 2 is used as starting material. E/Z isomerism is suppressed during a step of the synthesis reduction of the α,β‐unsaturated nitrile function (E+Z) in the α,β‐unsaturated aldehyde E (the Z→E isomerisation occurs during the hydrolysis of the intermediate imine).

The synthesis was conducted in six steps with an overall yield of 12,5% from 1‐methyl‐2‐oxocyclopentanecarbonitrile 2.
24(R), 25‐Dihydroxycholesterol; An Attempt for Side‐Chain Stereocontrol Via Iodolactonization
Authors: van Der Eycken J. , van Wabeeke L. , Vandewalle M.
Published: September 2010

Stereocontrolled formation of the side‐chain of 24(R), 25‐dihydroxycholesterol (1) via an iodolactonization process, involving a C‐10 carboxylic function and a 24, 25 double bond, has been studied. Low stereoselectivity was observed.
Determination of Tellurium in Cast Iron by Instrumental and Radiochemical Neutron Activation Analysis
Authors: Dams R. , Helsen M.
Published: September 2010

A procedure for the determination of tellurium in cast iron by neutron activation analysis is developed. In a number of samples the 131 I activity (T1/2=8.04 d) produced can be measured purely instrumentally. When the molybdenum/tellurium ratio exceeds 25, a radiochemical separation is required. The pure 131 I activity can then be measured interference‐free. The tellurium content of 7 NBS‐reference cast irons with concentrations varying from 50 to 750 ppm is measured. The reproducibility is generally better than 6% and the accuracy is good.
Analysis of High‐Purity Indium by Spark Source Mass Spectrometry
Authors: Liu X. D. , Verlinden J. , Adams F. , Adriaenssens E.
Published: September 2010

High purity indium samples were analysed by spark source mass spectrometry, using electrical and photoplate detection. Cooling of the samples was applied to obtain stable sparking conditions. For the calibration of the differences in elemental sensitivity, standard samples were prepared in which 9 impurities were determined by graphite furnace atomic absorption spectrometry. In this manner accuracies of less than 40% were obtained for selected elements. About 40 elements could be determined with detection limits of 10 to 30 ppb.
A Study on the Mechanisms Involved in Peritoneal Transfer of CR
Authors: Wallaeys B. , Cornelis R. , Sabbioni E. , Belpaire F. , Lameire N.
Published: September 2010

Pathways were investigated for the Cr transfer from the dialysate into the bloodstream as observed during continuous ambulatory peritoneal dialysis (CAPD). As the presence of Cr(VI) in the dialysate can be ruled out, due to reduction by lactate, a common compound of dialysate, all experiments were aimed at studying the behaviour of Cr(III). The ability of Cr(III) to penetrate across membranes at physiological pH was investigated. The characteristics during ‘in vitro’ dialysis were compared to the behaviour during acute ‘in vivo’ peritoneal dialysis in anesthetized rabbits. It appeared that lactate plays an important role in the mobility and the subsequent peritoneal Cr transfer.
Structural Analysis of Organic Compounds by Laser Microprobe Mass Spectrometry (LAMMA)
Authors: van Vaeck L. , Claereboudt J. , Veldeman E. , Vermeulen M. , Gijbels R.
Published: September 2010

The possibilities of the laser microprobe mass analyser (LAMMA) for the mass spectrometric (MS) characterisation of organic compounds have been explored systematically.

Specific methods of procedure are proposed to overcome the drawbacks of the actual instrumentation for organic applications. Energy selective ionisation and transmission can be used to discriminate inorganic clusters from organic ions.

In general, the microprobe mass spectra are complex and an approach, allowing to extract and rationalise the structurally relevant information, has been developed. The issued model for interpretation and different aspects of laser microbeam induced desorption and ionisation mechanisms are discussed.

A variety of polyfunctional molecules has been investigated. Examples are selected to illustrate the potential and limitations of LAMMA in organic mass spectrometry.
Regression Methods in Analytical Chemistry: A Comparison of Three Regression Methods on Simulated Data
Authors: Tierens B. , Michotte Y. , Massart D. L.
Published: September 2010

Three regression methods, namely least sum of squares, orthogonal regression and least median of squares are applied on data simulating calibration lines and method comparison studies, with and without outliers.
Degradation of the Desoxycholic Acid Side Chain. Double Bond Isomerization in the Unsaturated Side Chain of Steroids
Authors: Biesemans M. , van de Woude G. , van Hove L.
Published: September 2010

5β‐androstan‐12‐one 1 and 17β‐methyl‐5β‐androstan‐12‐one 2 are efficient way from 12α‐hydroxy‐5β‐cholan‐24‐oic acid 3a. The key steps in this conversion are photochemical degradation or decarboxylation with lead tetraacetate followed by double bond isomerization of the resulting olefins.
Utilisation de la Synthèse Atrolactique Pour L'Évaluation de L'Efficacité D'Inducteurs de Synthèse Asymétrique
Authors: Ben Hassine B. , Gorsane M. , Geerts‐Evrard F. , Pecher J. , Martin R. H. , Castelet D.
Published: September 2010

Atrolactic syntheses have been carried out to evaluate the potentiality, in asymmetric syntheses, of chiral inducers. The (dl)‐hydroxyhelicenes 1, 2, the (dl) sec. alcohols 3–12 and the (dl) phenolic binaphtyl compound 15 have been used as inducers. The d.e. are collected in table I (6–100%). The atrolactic asymmetric synthesis has also been carried out using three optically active inducers, namely: (‐)‐quinine 13, (‐)‐10, 11‐dihydroquinine 14, and R(‐)‐2, 2, 2‐trifluoro‐1‐(9‐anthryl) ethanol 6. Diastereomeric and enantiomeric excesses equal or greater than 88% have been obtained in six cases out of sixteen: (dl)‐2‐hydroxyheptahelicene 1 (d.e=100%±2), (1‐naphtyl)‐(9‐anthryl) methanol 3 (d.e=90%); 2, 2, 2‐trichloro‐1‐(9‐anthryl) ethanol 7 (d.e=100%±2), 2, 2, 2‐tribromo‐1‐(9‐anthryl) ethanol 8 (d.e=100%±2), (‐)‐quinine 13 (e.e=95.5%), and (‐)‐2, 2, 2‐trifluoro‐1‐(9‐anthryl) ethanol 6 (e.e=88%).
Study of the Influencing Factors on the Reaction of α‐halogenated Ketimines with Cyanide Ion
Authors: Kimpe Norbert De , Sulmon Paul , Schamp Niceas
Published: September 2010

The reaction of α‐halogenated ketimines with cyanide ion in various solvents leads to α‐cyanoaziridines. The scope and limitations of this reaction have been studied by investigating reaction parameters such as the nitrogen substituent, the solvent, the source of cyanide, the carbon skeleton and the nature of the α‐halogen. Several side reactions have been observed, including Favorskii‐type rearrangements, solvolyses, nucleophilic substitutions, 1,2‐de‐hydrohalogenation and production of heterocycles. The utility of α‐cyanoaziridines has been exemplified by 1,3‐dipolar cycloadditions of intermediate azo‐methine ylides. The addition of organolithium reagents to α‐cyanoaziridines produced α‐imidoylaziridines, which can be converted into pyrroles via rearrangement of thermally generated azomethine ylides.
Étude Comparative De La Réactivité De Composés β‐Dicarbonyles Et Des Analogues Enaminocarbonyles Vis‐À‐Vis D'Amines Hétérocycliques
Authors: Maquestiau A. , Vanden Eynde J.‐J.
Published: September 2010

Reactions between five β‐dicarbonyl compounds (1–5) or their enaminocarbonyl analogues (6–10) and three heterocyclic amines (12–14) are studied. The two types of carbonyl derivatives give rise to the formation of the same final products.

Kinetic data are established, by1H NMR spectroscopy, in order to compare, in various solvents, the respective reactivity of the acyclic precursors.
Regioselectivity in the Reaction of Nitroquinoxaline‐N‐Oxides With Phosphoryl Chloride
Authors: Nasielski‐Hinkens R. , Vande Vyver E. , Nasielski J.
Published: September 2010

6‐nitro‐, 2‐methyl‐6‐nitro‐ and 2,3‐dimethyl‐6‐nitroquinoxaline have been transformed into their N‐oxides by MCPBA in chloroform; the nitro group orients the oxygen atom preferentially to nitrogen atom N1, but the N4:N1 selectivity is diminished in the methylated derivatives.

Under the action of POCl3 (the Meisenheimer reaction), the N‐oxides of the unmethylated compounds are transformed into chloro‐nitroquinoxalines having lost the N‐oxide oxygen atom. The orientation of the entering chloride ion is discussed on the basis of electronic effects induced by the N‐oxide and nitro groups, and it is suggested that the last step, the elimination of “HPO2Cl2” is a concerted process.
Synthesis of 2‐Arylindoles via Condensation of ortho‐Aminobenzyl Sulfones With Aromatic Aldehydes
Authors: Wojciechowski Krzysztof , Makosza Mieczysław
Published: September 2010

Ortho‐Aminobenzyl sulfones condensed with aromatic aldehydes to give Schiff bases, which in strong alkaline medium undergo transformations into 2‐arylindoles.
Studies of Australian Soft Corals. XXXX.1 The Natural Products Chemistry of Alcyonacean Soft Corals with Special Reference to the Genus Lobophytum
Authors: Coll John C. , Bowden Bruce F. , König Gabrielle M. , Braslau Rebecca , Price Ian R.
Published: September 2010

The eggs of the alcyonacean soft coral Lobophytum microlobulatum contain the known cembranoid diterpene 3,4‐epoxynephthenol (9). This compound was not detected in the soft coral colony from which the eggs were released, although decaryiol (10), which is derived from (9) by acid treatment, was present in the eggs and coral tissue. The new diterpene decaryiol acetate (11) was a natural product in the eggs and coral. Several new non‐cembranoid diterpenes based on known eudesmane, germacrene and elemene sesquiterpene skeletons were isolated. Investigation of the chemistry of two Lobophytum species afforded diterpenes which are prenylated examples of cubebol and germacrene‐type ses‐quiterpenes (12, 18). In the course of studies of the overgrowth of soft corals by filamentous algae, a new eudesmane‐based diterpene (20) was identified. The related diterpene (19) which co‐occurs with (20), was shown to inhibit the growth of the algae Ceramium codii even at 12.5 ppm. Lobophytum chemistry is of interest because of the frequent co‐occurrence of different diterpene skeletons in the same colony, a relatively infrequent observation in other genera.
Two New C‐20 Substituted Trinervitane Diterpenes from a Neo‐Guinean Nasutitermes SP(1)
Authors: Braekman J. C. , Daloze D. , Pasteels J. M. , Roisin Y.
Published: September 2010

Two new 1 (15), 8 (19)‐trinervitadiene derivatives have been isolated from the frontal secretion of an undescribed species of nasute termite (Nasutitermes sp PNG (F)). They have been identified as 20‐acetoxy‐2β, 3α‐dihydroxy‐1(15), 8 (19)‐trinervitadiene (1) and 9β, 20‐diacetoxy‐2β, 3α‐dihydroxy‐1 (15), 8 (19)‐trinervitadiene (2) on the basis of their spectral properties.
New Reactions of Pyridines and Total Synthesis of the Fungal Toxin Orellanine
Authors: Tiecco Marcello
Published: September 2010

Dihalogenated pyridines react easily with sulphur nucleophiles, in dipolar aprotic solvents (DMF), to afford the products of mono‐ or of bis‐substitution depending on the experimental conditions. On the contrary, with oxygen nucleophiles the bis‐substituted products can be obtained only with some particular substrates. A new and efficient procedure to effect the homo‐coupling of halogenoarenes will be presented. This reaction, which occurs under the influence of low‐valent nickel complexes, allowed us to effect the total synthesis of Orellanine, the lethal toxin of Cortinarius orellanus mushroom, as well as the syntheses of its decomposition products Orellinine and Orelline. The chemical properties of these three products and their behaviour towards UV irradiation will be presented and discussed.
Homolytic Substitution in Trialkyltin Iodides by Photochemically Generated Iodine Atoms. V Mixed Dimethylalkyltin Iodides, Me2R'SnI
Authors: De Ryck P. H. , Verdonck L. , van Hooste H. , van Der Kelen G. P.
Published: September 2010

Mixed trialkyltin iodides form EDA complexes with iodine. The λCTdata suggest an electron transfer from the iodide lone pairs. Rate constants for the reaction under photochemical conditions are determined by kinetic measurements. The selectivity parameter derived from the rate constants and from mass spectrometric measurements prove the presence of a fragmentation step in the reaction process.
Charge‐Transfer Complexes of Isoindolines with 1, 4‐Benzoquinones
Authors: Mourad Aboul‐Fetouh E. , Nour‐El‐Din Ahmed M. , Hassan Alaa A. , Döpp Dietrich
Published: September 2010

Charge‐transfer (CT) complexes of various N‐arylisoindolines as donors with 1, 4‐benzoquinones [2, 3‐dichloro‐5, 6‐dicyanobenzoquinone (DDQ), chloranil (CHL) and bromanil (BRL)] as π‐acceptors have been studied spectrophotometrically. Effects of substituents on CT complexation has been discussed in terms of a Hammett correlation and the wavelengths of the CT absorption maxima. Isoindolines with ortho‐substituted N‐aryl groups have been proven to be more basic than the other para‐and meta‐isomers. The nature of CT interactions in the CT complexes is reported. A linear correlation between the constants of formation and the position of maximum absorption wavelengths of the CT complexes has been observed.
Reactions of Organic Anions. CXVII1. Cleavage of the Dithiin Ring of Thioquinantrene with Some Carbanions
Authors: Jonczyk Andrzej , Pluta Krystian
Published: September 2010

It has been found that the C4‐S bond in 1,4‐dithiinodiquinoline 1 is cleaved by carbanions of some C‐H acids (2‐phenylalkanenitriles, ketones, sulfones) generated in DMSO by means of solid NaOH or dimsyl sodium, to give 3‐arylthio‐4‐substituted quinolines 5a‐h. Phenylacetonitrile carbanion or methoxide cleave the C4‐S bond in product 5al, giving the expected products 6 and 3‐methylthio‐4‐methoxyquinoline respectively as well as ketone 7.
Synthèse de Pyridinobenzotetraazapentalenes
Authors: Maquestiau A. , Biemans R. , Flammang‐Barbieux M. , Vilain E.
Published: September 2010

Four new heteroaromatic pentalenes have been synthetised by reductive cyclisation with triethylphosphite of the appropriate nitropyridylbenzotriazoles or nitrophenyltriazolo [4,5‐b] pyridines: the [2,3‐b] pyridino [4,5] benzo‐1,3a,6,6a‐tetraazapentalene 2; [3,2‐c] pyridino [4,5] benzo‐1,3a,6,6a‐tetraazapentalene 3; [3,2‐b] and [2,3‐b] pyridino [5,6] benzo‐1,3a,4, 6a‐tetraazapentalene 5,6. The spectral properties of these new compounds are described.
A Note on the Synthesis of Methacrylate‐Derived Mercapturic Acid Methyl Esters
Authors: Kopecký Jan , Šmejkal Jaroslav , Linhart Igor , Hanuš Vladimir , Heyrovský J. , Pech Pavel
Published: September 2010

The synthesis, TLC data and spectral characteristics of mercapturic acid methyl esters derived from five industrially important methacrylates and methacrylamide are described.
Platinum(II) and Palladium(II) Complexes of Vitamin B1
Authors: Adeyemo Adegboye , Oderinde Rotimi , Turner Anne , Shamim Abdullah
Published: September 2010

Reaction of vitamin B1 and its derivatives with Pt(II) and Pd(II) salts (4:1 molar ratio) in aqueous medium, employing acetate catalyzed method2 conveniently afforded complexes of the general formula M(Th)X3, where M = Pt(II) or Pd(II) and X = Cl−, Br− or I−. These complexes have been characterized by elemental analyses, conductivity measurements, infrared and nuclear magnetic resonance spectra. Results show that coordination is via N(l) of the pyrimidine moiety in agreement with previous studies2‐9. The mechanism for the acetate catalyzed metal ion incorporation into thiamine and the possible mechanisms for the anticancer activities of these complexes are briefly discussed in terms of their interactions with DNA.
Structural Study in Relation with Captodative Substituent Effect IV. X‐Ray Study of P, P′‐Substituted 2,3‐Disethyl‐2,3‐Diphenyl‐1,4‐Butanedinitrile with Phenylogous Captodative or Dicapto‐Substitution
Authors: Parfonry A. , Tinant B. , Declercq J.‐P. , van Meerssche M. , Klein J. , Merényl R. , Viehe H. G.
Published: September 2010

In order to compare captodative (cd) and dicapto (cc) ‐ substitution effects on molecular geometry, we have determined by X‐ray diffractometry the structures of the four p, p′‐substituted (methylthio, dimethylamino, methoxy‐carbonyl and cyano) 2,3‐dimethy 1‐2, 3‐diphenyl‐1,4‐butanedinitrile (2a‐d). The meso isomers are found to be of centrosymmetric conformation and within experimental error the geometry of each of the four molecules is the same. No significant difference on the central C‐C bond length is observed for phenylogous cd (2a, b) and cc (2c, d)‐substitution. The mean value of the C‐C central distance is 1.602 (2)Å and much longer than expected from force‐field calculations.
Structure of 2′‐METHOXY‐4′,5′‐METHYLENEDIOXY‐2,3‐DIHYDROFURO [3″,2″‐6,7] ISOFLAVONE, NEOTENONE
Authors: Declercq J. P. , van Puyvelde L. , De Kimpe N. , Schamp N.
Published: September 2010

C19H14O6, Mr = 338.32, monoclinic, P21, a = 10.151(4), b = 15.209(4), c = 4.959(1)Å, β = 98.54(2)°, V = 757.1(4)Å3, Z = 2, Dx = 1.48 gcm−3, Mokα, λ = 0.71069 Å, μ = 1.2 cm−1, F(000) = 352, T = 291K, R = 0.026 for 1087 observed reflections.
Trimethylsilyl Cyanide, a Reagent and (Co)Solvent “par Excellence” for Homogeneous Peptide Synthesis. A Strategy Circumventing Classical Drawbacks?
Authors: Anteunis M. J. O. , Becu Chr.
Published: September 2010

Attention is called for a superb strategy of peptide synthesis in solution, making use of (per) silylated amino acid fragments. This old methodology may thus present renewed interest if the classical silylation is substituted by silyl cyanides during coupling. Thus, trimethylsilyl cyanide, by its pronounced silylating power affording only gaseous following‐(by) products and by its excellent solubilizing properties in organic solvents, overcomes the difficulties and drawbacks that were encountered in previously described strategies that made use of extempore prepared (per) silylated amino acid residues.
Oxidation of Hydrazines with Nitrosoarenes
Authors: Kano Kunio , Koga Masahiro , Anselme Jean‐Pierre
Published: September 2010

Nitrosoarenes react with 1,1‐disubstituted hydrazines to yield products of direct oxidation and the thermally stable triazene N‐oxides. The triazene N‐oxides undergo photoinduced fragmentation to yield products which may be rationalized through the intermediacy of diazenes.
13C‐Hyperfine Couplings of Carbonate Radicals in Carbonated Calciumapatites Synthesized at High Temperature
Authors: Callens F. J. , Verbeeck R. M. H. , Matthys P. F. A. , Martens L. C. , Boesman E. R.
Published: September 2010

The effect of the substitution mechanism of carbonate ions in calciumapatites synthesized at high temperature on the Electron Spin Resonance (ESR) spectrum is studied. Two pairs of 13C hyperfine lines were detected in the spectrum of all X‐irradiated B‐type carbonate apatites studied. This gives further evidence to the presence of two related CO33‐radicals in B‐type carbonated calciumapatite. For A‐type carbonate apatite no 13C satellites could be found so far. Arguments are presented to assign one of the ESR‐components to a CO3‐3 radical on a phosphate site.
Structure de la Zanhine et de la Medicagine, Deux Prosapogenines Nouvelles Isolées de Zanha Golungensis Hiern
Authors: Dimbi Makoso Zeza , Warin Roger , Delaude Clément , Huls Robert
Published: September 2010

From the perchloric hydrolysis of the root bark saponin of Zanha golungensis Hiern. We have isolated two novel prosapogenins : 3β‐0‐(4‐deoxy‐β‐D‐hex‐4‐enopyranosyluronic acid), 2β‐hydoxy‐olean‐12‐en‐23,28‐dioic acid (medicagin) and 3β‐0‐(4‐deoxy‐β‐D‐hex‐4‐enopyranosyluronic acid), 2β, 16α‐dihydroxy‐olean‐12‐en‐23,28‐dioic acid (zanhin). The structures have been established by spectroscopic data. A two‐dimensional NMR of Zanhin is described.
Catalytic Reactivity of Phosphates with 1‐Butanol, Pure and in a Mixture with Acetone, Ethanol, Acetic Acid and Water
Authors: Ruwet M. , Berteau P. , Ceckiewicz S.
Published: September 2010

Phosphate catalytic systems (B‐PO4, Al‐PO4, Ca‐Ni‐PO4) were tested in transformation of 1‐butanol, pure, and in a mixture typical of acetonobutylic fermentation feed, and compared with γ‐Al2O3 dehydration catalyst. The phosphates were characterized by infrared spectroscopy and temperature programmed desorption methods. Various 1‐butanol reactions can occur, all engaging acidic and basic sites. B‐PO4 has the convenient proportion between those sites to dehydrate pure 1‐butanol to butenes, with a good activity and selectivity, like γ‐Al2O3. Whereas Ca‐Ni‐PO4 dehydrogenates selectively 1‐butanol into butyraldehyde. With the multicomponent mixture, a drop of catalytic activities is observed for phosphates and γ‐Al2O3, due, probably, to the great amount of water in the substrate. B‐PO4 dehydration activity is much better in that case than γ‐Al2O3 one.
Generation and Reactions of Carbanions from Dialkylamino (Methylthio) Acetonitriles
Authors: Jonczyk Andrzej , Owczarczyk Zbysław , Makosza MieczysŁaw , Winiarski Jerzy
Published: September 2010

Dialkylamino (methylthio) acetonitriles 1 have been prepared by two independent pathways. The carbanions generated from 1 in various base/solvent systems reacted with alkyl halides or electrophilic alkenes to give unstable products 2 and 5 respectively. These products were transformed into amides 3 or acids 4 and 6. On the other hand, carbanions from 1 with ethyl maleinate or ω‐nitrostyrene afforded products of aliphatic vicarious nucleophilic substitution 7 while with 1‐nitronaphthalene, the product of aromatic vicarious nucleophilic substitution 8.
Enantioselective Catalysis, 341) Phosphines with (s)‐2‐Methylbutyl. Substituents and Their Ph Complexes ‐ use in Enantioselective Catalysis
Authors: Brunner H. , Leyerer H.
Published: September 2010

(S)‐2‐methylbutyl Grignard, prepared from (S)‐(‐)‐2‐methylbutan‐1‐ol via (S)‐(+)‐2‐methylbutyl‐1‐bromide, was used for the synthesis of phosphines 1‐4, containing (S)‐2‐methylbutyl substituents. In the reaction with [Rh(cod)Cl]2, phosphines 1 and 2 give the neutral complexes 5 and 6 of the type Rh(cod)(L)Cl, whereas phosphines 3 and 4 give the salts 7 and 8 of the type [Rh(cod)L2]PF6. The isolated complexes 5‐8 and the in situ systems [Rh(cod)Cl]2/1‐4 lead to optical inductions of up to 15 a ce in the anantioselective hydrogenation of (Z)‐α‐N‐acetamidocinnamic acid and of up to 4.5% in the enantioselective hydrosilylation of acetophenons with diphenylsilane.
Bipositive Metal Complexes of N1 ‐(4‐Chlorophenyl)‐N4‐(3,5‐Dinitrobenzoyl) Thiosemicarbazide
Authors: Dwivedi D. K. , Agarwala B. V. , Dey A. K.
Published: September 2010

Polymeric coordination complexes of the type (ML.2H2O)n, where M(II) ‐ Mn, Fe, Ni, Cu or Zn and L = N1 ‐(4‐chlorophenyl)‐N4‐(3,5‐dinitrobenzoyl)thiosemicarbazide have been synthesised and characterised by microanalytical, I. R., magnetic, D. R. S. and thermal analysis. The IR spectra indicate tetradentate ligand coordination through the enolic oxygen, thioenolic sulphur and the nitrogen atom of the CN group. The metal ion is the bridging unit between the donor sites of the ligand molecule, and it is likely that a polymeric chain grows through consecutive ligand‐metal links.
Crystal Structure and Conformation of Short Linear Peptides. Part V. N‐Benzyloxycarbonyl‐Glycyl‐Glycyl‐L‐Proline
Authors: Wu S. , Tinant B. , Declercq J. P. , van Meerssche M.
Published: September 2010

C17H21N3O6, Mr = 363.37, monoclinic, P21, a = 17.774(6), b = 10.105(3), c = 4.963(1)Å, β = 92.30(2)°, V = 890.7(5)Å1, Z = 2, Dx = 1.36 g. cm−3, MoKα, λ = 0.71069 Å, μ = 1.12 cm−1, F(000) = 384, T = 291K, R = 0.056 for 717 observed reflections. The (φ, Ψ) values of (81°, 35°), (‐174°, 169°) and (‐79°, 164°) define a left‐handed α‐helix conformation at Gly(1), an extended form at Gly(2) and a collagen‐like conformation at terminal Pro respectively. The pyrrolidine ring has a C8‐Cβ‐exo conformation.
Evidence for a Presumed Mechanism of the Reaction of 2‐Benzoyl 1, 2‐Dihydro Isoquinaldonitrile Hydrofluoroborate on Methyl Methacrylate
Authors: Schmitt Gerard , Fathi Toufik , Cerutti Ernest , Laude Bernard
Published: September 2010

The previously suggested mechanism of the condensation‐rearrangement reaction of Reissert compound hydrofluoroborate salts with reactive olefins was reexamined in the case of methyl methacrylate. Addition of triethylamine to the reaction medium leads to isolate a presumed intermediate.
Synthesis and Spectroscopic Study of a Series of Diarylacetylene Dicobalt Hexacarbonyl Complexes. AOSC ‐TW
Authors: Pepermans Henri , Willem Rudolph , Hoogzand Cornelis
Published: September 2010

A series of methyl, methoxy and trimethylsilyl substituted diphenylacetylenes was reacted with Co2(CO)8, giving the corresponding (diarylacetylene) Co2(CO)6 complexes. The predominance of the steric effect of the substituents in these reactions was established. The complexes were studied by IR, MS, 13C NMR, 1H NMR and UV‐visible spectroscopy.
Synthesis and Thermolysis of Some N‐Hydroximoyl ‐ and N‐Hydrazonoylazoles
Authors: Plenkiewicz Jan , Zdrojewski Tadeusz
Published: September 2010

The reactions of nitrile oxides or nitrile imines with pyrazole, imidazole, 1,2,3‐ and 1,2,4‐triazole or tetrazole derivatives yield the appropriate N‐hydroximoyl‐ or N‐hydrazonoylazoles. Thermolysis of 1‐hydroximoyltetrazoles, depending on the nature of the substituents in the tetrazole ring, yields 1,2,4‐oxadiazoles or 5‐amino‐l,2,4‐oxadiazoles upon hydrazoic acid or nitrogen evolution. Under similar conditions, 1‐hydazonoyltetrazoles give 1,2,4‐triazoles or 5‐amino‐1,2,4‐triazoles while 2‐hydrazonoyltetrazoles decompose to the dihydro‐1,2,4,5‐tetrazine derivatives.
Tungsten Carbonyl Precursors in Catalyzed Olefin Metathesis I. Photochemically Induced Olefin Metathesis by the W(CO)6/TiX4 Catalytic System
Authors: Vanwijnsberghe F. M. G. , Vanderyse L. , Bossuyt A. R. , Verdonck L. , van Der Kelen G. P. , Gent Rijksuniversiteit
Published: September 2010

The catalytic and spectroscopic properties of the photochemically activated metathesis catalyst system W(CO)6/TiX4/hx∼︁ (X = Cl, Br, I) have been studied. All evidence indicates a high resemblance with the chemically activated W(CO)6‐XLX/RAlCl2/O2 systems. Irradiation of the W(CO)6/TiX4 precursor solution causes loss of CO ligands and has the same promoting effect as O2 for chemically activated systems.
Crystal Structure of 3‐Tert‐Butylimino‐2,3‐Dihydroimidazo [1, 2‐a]Pyridin‐2‐One
Authors: L'abbé Gerrit , Meervelt Luc Van , Brems Patrick , Declercq Jean‐Paul
Published: September 2010

The crystal structure of 3‐tert‐butylimino‐2,3‐dihydroimidazo[1,2‐a]pyridin‐2‐one (C11H13N3O, Mr = 203.25, a = 9.247(1), b = 11.947(1), c = 9.736(1) Å, V = 1075.6(2) Å3, space group P212121, Z = 4, Dx = 1.26 g. cm−3, F(000) = 432) has been determined by single crystal X‐ray diffraction techniques (CuKα, T = 291K) and refined to R = 0.034 for 1867 observed reflections. The exocyclic imino function on the planar imidazo[1,2‐a]pyridine ring adopts the E‐configuration.
Experiences in Z‐Deprotection. Simple Preparations of Z‐His and diz‐His
Authors: Anteunis M. J. O. , Becu Chr. , Becu F. , Reyniers M. ‐F.
Published: September 2010

A systematic investigation about the possibilities of removing benzyloxycarbonyl groupings in some model peptides acids that resist easy deprotection, have led to some interesting and efficient modified procedures. One‐pot synthetic methods for Zα‐His‐OH and Zα, ZIm‐His‐OH are also reported.
A New Version of Hugershoff Synthesis
Authors: Garin Javier , Guillen Carmen , Melendez Enrique , Merchan Francisco L. , Orduna Jesús , Tejero Tomás
Published: September 2010

N‐halosuccinimide/sulfuric acid is a new, highly efficient reagent for the oxidation of cyclic thioureas to the corresponding 2‐aminobenzothiazole derivatives.
Synthèses Asymétriques Potentielles Impliquant la Réaction “Ene”
Authors: Ben Hassine B. , Gorsane M. , Pecher J. , Martin R. H.
Published: September 2010

Racemic “ene” syntheses have been carried out to evaluate the potentiality, in asymmetric syntheses, of the corresponding optically active inducers. The (dl)‐crotonates 5 to 8 were prepared from (dl)‐hydroxyheptahelicene 1 and the sec. alcohols 2, 3 and 4. Chemical yields are shown in table 1 (85–94%).

These (dl)‐crotonates underwent the “ene” reaction with cyclohexene in the presence of SnCl4 to give the corresponding diastereomeric (dl)‐esters 9, 10, 11 and 12, with respectively ∼︁100, 48, 70 and ∼100% diastereomeric excesses.
Diesel Hydrotreating With NiMo/Al2O3 Catalyst
Authors: Galiasso R. , Rodríguez E.
Published: September 2010

The hydrotreatment of two cracked Diesel fractions have been studied using fresh and on “stade state” catalysts at different pressure and operating conditions. The effect of temperature, pressure, type of feedstock on catalyst activity and selectivity were evaluated. Physicochemical analysis of the catalyst was performed in order to investigate the changes in the active phases. It was demonstrated that activity and selectivity change during the initial deactivation of fresh catalyst by coke deposition and active center modification. The hydrogenation activity decreases more than desulfurization which reduces the quality of products obtained. The higher the pressure the lower the loss. It was also observed that more than 70% of accessible metal content in surface is lossed. Additionally, acidity and average pore diameter are increased by operation. Some structural modifications of active phase are postulated.
Studies of Molybdena‐Alumina Catalysts XIII no Adsorption and Sh Content of Sulfided Catalysts
Authors: Miciukiewicz J. , Zmierczak W. , Massoth F. E.
Published: September 2010

A series of Mo/Al2O3 catalysts were prepared containing various levels of Mo, several different Al2O3 supports, and by different solution pH's. Sulfided catalysts were characterized by NO chemisorption, SH content and thiophene HDS activity. Uptake of NO depended on the temperature of adsorption employed, and consequently an absolute number of adsorption sites could not be determined. Also, correction for NO adsorption on the support was needed to obtain values representative of the MoS2 species present. Assuming NO adsorbs at edge sites of the MoS2 slabs, it was found that the size of the MoS2 slabs was affected by the nature of the Al2O3 support but only slightly by the pH of the impregnating solution. Residual SH content roughly correlated with net NO adsorption. HDS activity was roughly proportional to net NO adsorption and to residual SH content. Significant deviations, however, were observed, indicating that catalytic activity is not precisely related to either.
Formation of Promoted Sites From Ni(CO)4 Decomposition on Sulfided Mo/Al2O3 Catalysts. A Comparative Ir Study With Conventional Ni‐Mo/Al2O3 Catalysts, Using CO as a Probe Molecule
Authors: Angulo M. , Maugé F. , Duchet J. C. , Lavalley J. C.
Published: September 2010

IR spectroscopy has been used to characterize samples prepared by decomposition of nickel carbonyl over a MoS2/γ‐Al2O3 based catalyst. IR spectra of adsorbed CO indicates a much higher degree of promotion than for the conventional Ni‐Mo/Al2O3 catalyst. The samples also readily catalyse the in‐situ transformation of piperidine into intermediate species yielding further pyridine. Chemical analysis leads to very low Ni content, indicating a delocalization of the electronic effects of the promoter over the whole MoS2 slab. Results are consistent with the promoted sites pictured as highly reduced sites.
Solvent influence on the dipole moment and charge transfer effect in the 2, 6‐Lutidine. I2 Complex
Authors: Pawelka Z.
Published: September 2010

The dipole moments of the CT complex between 2, 6‐lutidine and I2 have been measured in cyclohexane, CCl4, benzene, trichloroethylene, chloroform and chlorobenzene. The fractions of charge transferred from donor to acceptor have been estimated. It has been stated that the contribution of the dative structure F1 increases with an increase in the solvent activity and varies linearly with the frequency shift Δv/v of the visible iodine absorption band. The solvent influence on F1 and Δv/v has been rationalized in terms of correlations with empirical parameters of the solvent polarity which are related to their polar and electron‐accepting properties.
Enantiomeric quantifications of amino acids through their Na‐Acyl amides by gas chromatography
Authors: Hosten N. , Anteunis M. J. O.
Published: September 2010

Apparent separation factors of 1.1 or higher on Chirasil Val III can be obtained for Na‐acyl N‐alkyl aminoacid amides allowing the use of short capillary gas chromatographic columns. A clean derivatization protocol without racemization is described, proceding through the NCA derivatives that are prepared from “in situ” silylated amino acids with trimethylsilyl cyanide.
Functionalisation of isophorone involving polychlorination part III. Synthesis of hydroxycyclohexadienone aldehydes from a pentachloroisophorone by base‐induced acetolysis
Authors: De Buyck L. , De Pooter H. , Schamp N.
Published: September 2010

The reaction of 2, 6, 6‐trichloro‐3‐dichloromethyl‐5, 5‐dimethyl‐2‐cyclohexenone (1) with triethylamine in acetic acid containing acetic anhydride afforded 2‐acetoxy‐6‐diacetoxymethyl‐3‐chloro‐4, 4‐dimethyl‐2, 5‐cyclohexadienone (2) in 49% yield (47% isolated). As a side reaction the isomeric 2,4‐cyclohexadienone 5 or mixtures of three of its precursors were formed in 30‐46% yield. The formation of an aromatic side product 8 (4‐23%) was suppressed at low initial reaction temperature. Acid catalyzed hydrolysis of 2 and 5 afforded the isomeric hydroxycyclohexadienone aldehydes 4 resp. 6. In aqueous bicarbonate solution 6 was readily converted into a dimer for wich the pentacyclic structure 29 is proposed, containing two different cyclobutanone rings. The reaction mechanisms are discussed in the context of related substitution reactions.
Conclusive evidence against a cyclobutadiene intermediate in the cyclotrimerization of diarylacetylene using the diarylacetylene hexacarbonyl dicobalt complex as catalyst
Authors: Pepermans Henri , Willem Rudolph , Gielen Marcel , Hoogzand Cornelis
Published: September 2010

To decide whether the cyclotrimerization of diarylacetylene with diarylacetylene hexacarbonyl dicobalt as catalyst, proceeds via a cyclobutadiene intermediate, two experiments were performed, both relying on the experimentally verified hypothesis that a 3‐methoxyphenyl ring can be considered as an ideally chemically labelled phenyl ring : (1) the co‐cyclotrimerization of diphenylacetylene with bis(3‐methoxyphenyl)acetylene, and (2) the cyclotrimerization of 1‐(3‐methoxyphenyl)‐2‐phenylacetylene. Analysis of the resulting meta methoxy substituted hexaphenylbenzenes using our chemical shift model, is for both experiments conclusive against the involvement of a cyclobutadiene intermediate.
Validation Par Spectroscopie Rmn1H Des Paramètres Geométriques Du Dimère Phénolique Obtenus Par Calculs Cndo/2
Authors: Moreau Descoings M. C. , Goethals G. , Seguin J. P. , Doucet J. P.
Published: September 2010

Hydroxylic hydrogen chemical shifts of phenol are measured in carbon tetrachloride at different concentrations. We have also calculated by the C NDO/2 method, the electronic populations on the hydroxylic hydrogen and oxygen atom of the phenol dimer and monomer for optimized geometry. From the biparametric relationship relating the chemical shift to both hydroxylic hydrogen and oxygen electronic population, established in a previous work, we have calculated a theoretical shift for the dimer hydroxylic hydrogen. For each concentration, we have compared the experimental chemical shift with the calculated value obtained in using the dimer and monomer concentrations and the theoretical chemical shift for each proton. The good agreement between experimental and calculated value validates the optimized geometry of hydrogen bond complex and the biparametric relationship.
The synthesis of a Nγ‐phthalyl‐Nα‐methyl‐α, γ‐diaminobutyryl congener of virginiamycin S1
Authors: Anteunis M. J. O. , van Der Auwera C. , Vanfleteren L. , Borremans F.
Published: September 2010

A synthesis of Z‐Thr1 ‐D‐Abu2 ‐Pro3 ‐MePhe4 ‐MeA2bu(γPht)5 ‐Phg6 ‐ (A2bu = α, γ‐diaminobutyric acid) is reported using the very efficient coupling agent BOP‐Cl (N, N'‐bis(3‐oxo‐2‐oxazolidinyl)phosphinic chloride) for imino acid peptide bond formation. The total yield is 11% for the 5 coupling steps and one lactonization. The final step was a cyclization between residues 5 and 6, after (i) first t‐Boc acidic deprotection with 85% HCOOH of the linear precursor Z‐Thr (Nα‐Boc‐Phg‐O‐)‐D‐Abu‐Pro‐MePhe‐MeA2bu(γPht)‐OBu followed by (ii) acidic saponification (Tfa) of the t‐Bu ester. This sequence was found to be a prerequisite, in view of the extreme lability of the 4–5 peptide bond under acidic conditions.
Cycloaddition De Quelques Diarylnitrilimines Sur Diverses Arylidene‐2 Indanones‐1. Régio‐ Et Diastéréochimies Des Spiropyrazolines Synthétisées
Authors: Kerbal Abdelali , Tshiamala Kabula , Vebrel Joäl , Lauds Barnard
Published: September 2010

Spiropyrazolines have been synthetized by 1,3‐dipolar cycloaddition of some 2‐arylidene 1‐indanones with diarylnitrilimines. It is shown that ringclosure reaction is regiospecific, yielding stereohomogeneous spiropyrazolines in one step. The relative configuration and stereochemistry of the products have been determined by means of protonic magnetic resonance measurements.
Synthèse Des Premiers Esters Sulfamiques Adamantyles
Authors: Hedayatullah Mir , Beji M.
Published: September 2010

The reaction of 1‐adamantanol with the alkoxy and aroxysulfonyl isocyanates constitute the first high‐yield synthesis of N‐adamantyl sulfamates which are inaccessible by other procedures.
Bop‐Cl mediated cyclization of a linear precursor of virginiamycin S. Contra indication for using HOBt as racemization suppressor
Authors: Anteunis M. J. O. , Sharma N. K.
Published: September 2010

Cyclization of a model linear hexapeptide (VS1, linear peptide, 1) was achieved at moderate temperature (‐15° to r. t.) in ≥80% yields in using BOP‐C1 [N, N'‐bis(2‐oxo‐3‐oxazolidinyl) phosphinic chloride] and BOP‐reagent [benzotriazolyloxy tris (dimethylamino) phosphonium hexafluorophosphate] as coupling reagents in one‐pot procedures. Stereomutation was high (∼︁40%). The addition of N‐hydroxybenzotriazole doubled the degree of epimerization. A rationale is offered in order to explain the enantiomeric induction. High dilution was necessary to avoid side products (dimer/trimer) formation. However, dilution does not effect the rate of cyclization considerably.
Cholest‐6‐EN‐11β, 19‐epoxy‐3β, 5α, 8α, 9α‐tetrol, a novel polyoxygenated steroid from the sponge dysidea tupha
Authors: Braekman J. C. , Daloze D. , Moussiaux B. , Vandevyver G. , Riccio R.
Published: September 2010

Cholest‐6‐en‐11β, 19‐epoxy‐3β, 5α, 8α, 9α‐tetrol(1), a new toxic polyoxygenated steroid, has been isolated from the sponge Dysidea tupha. Its structure has been determined on the basis of its spectral properties.
Tungsten carbonyl precursors in catalyzed olefin metathesis II. Homegeneous olefin Metathesis by the RnX3‐n SnW(CO)3π‐C5H5/iBuAlCl2/O2 System
Authors: Vanderyse L. M. , Verdonck L. , Bossuyt A. R. , van Wijnsberghe F. M. G. , van Der Kelen G. P.
Published: September 2010

RnX3‐nSnW(CO)3Cp (R = Me, Ph; X = Cl) precursors activated by iBuAlCl2 in the presence of oxygen in an optimal 1 October 5 ratio, show high conversion rates and a good selectivity for the 2‐pentene metathesis. The conversion rates follow the sequence Ph3Sn‐ « Me3Sn‐ < Me2ClSn‐ < Cl3Sn‐ but the tin moiety has no significant effect on the stereoselectivity for cis‐2‐pentene. There are several indications for the occurrence of competitive and successive α‐ and β‐H elimination reactions in the generation of the active tungsten carbene species.
Structure Determination of Isoxazolidine Derivatives Obtained from (E)‐Unsaturated 5,10‐Seco‐steroidal Ketones
Authors: Tinant B. , Declercq J. P. , van Meerssche M. , Mihailovic M. Lj. , Lorenć Lj. , Rajković M. , Milovanović A.
Published: September 2010

(E)‐Δ1 (10) ‐unsaturated 5‐oxo‐5,10‐seco‐steroids such as 1, react with hydroxylamine and N‐methylhydroxylamine to give stereospecifically isoxazolidine derivatives of type 2 and 3, respectively. The molecular structure of isoxazolidine 3a obtained from (E)‐3β‐acetoxy‐5,10‐seco‐cholest‐1 (10)‐en‐5‐one (la) and N‐methylhydroxylamine has been determined by X‐ray analysis.
Anchoring Substitution in Acyclic Fragments. A Topical Basis for Enhanced Diastereofacial Selection in the Diels‐Alder Reaction to Chiral Acrylates
Authors: De Corte Filip A. J. , De Clercq Pierre J.
Published: September 2010

Chiral acrylates 4a, 4b and 4c, derived from primary alcohols with a single stereogenic centre, were studied for possible diastereoface differentiation in their Lewis acid catalyzed Diels‐Alder reaction with cyclopentadiene. No relevant diastereomeric excess was observed for the tert‐butyl derived 4a. On the other hand, moderate but significant diastereomeric excesses (72‐76 %) resulted when the trityl derived acrylates 4b and 4c were used. The ability of enforcing a 1,3‐parallel orientation between the aryl shielding group and the acrylate moiety by incorporation of a tert‐butyl or trityl anchoring substituent in the connecting chain is qualitatively assessed by 1H NMR.
Convenient Method for the Preparation of 3‐(2‐Pyridyl Dithio) Propionic Acid N‐Hydroxy Succinimid Ester
Authors: Loccufier J. , Schacht E.
Published: September 2010

A new efficient and simple method for the preparation of 3‐(2‐pyridyl dithio) propionic acid N‐hydroxy succinimid ester using diethyl azo dicarboxylate, is described.
Introduction of substituents into 5‐membered aza‐heteroaromatics
Authors: Begtrup Mikael
Published: September 2010

With emphasis on mono‐ and regio‐selectively, methods for introduction of substituents at nitrogen and carbon atoms of 5‐membered aza‐heteroaromatics have been developed. The methods involve application of activation and of assistant groups for direction and protection. Activation has been achieved by the use of quaternary azolium ions and azol‐N‐oxides as reactive intermediates. If necessary, the N‐oxides were further activated by alkylation or acylation.
Tungsten carbonyl precursors in catalyzed olefin metathesis. III. infrared study of RnCl3‐nSnW(CO)3π−C5H5derivatives and their interaction with iBuAlCl2and O2
Authors: Vanderyse L. M. , Haemers T. , Bossuyt A. R. , Verdonck L. , van Der Kelen G. P.
Published: September 2010

The LW(CO)3Cp (L = RnSnCl3‐n, H, Cl) derivatives and their interaction with iBuAlCl2and O2have been studied by i. r. spectroscopy.

Mechanisms for the generation of the active tungsten‐carbene complex in the early stages of reaction are proposed.
A liposoluble cationic complex of Ru(II) based on 1,4,5,8‐tetra‐azaphenanthrene
Authors: Nasielski J. , Garcia Y Abeledo M. ‐L. , Nasielski‐Hinkens R.
Published: September 2010

Reacting 2,2‐dichlorododecanal with 1,2‐diamino‐4‐nitrobenzene in dioxane in the presence of a base gives a 46% yield of 2‐decyl‐6‐nitroquinoxaline, which after amination by hydroxylamine and reduction gave 5,6‐diamino‐2‐decylquinoxaline. This diamine, again with 2,2‐dichlorododecanal in dioxane and base, affords 2,6‐didecyl‐ and 2,7‐didecyl‐1,4,5,8‐tetraazaphenanthrene (2,7ddTAP); the latter ligand gives the hexane‐soluble Ru(2,7ddTAP)3(PF6)2.
Infrared emission spectroscopy in H2/F2 and CH4/F2 premixed flames
Authors: Vandooren J. , Vanpee M.
Published: September 2010

The infrared emission corresponding to the Δ v=1 transitions of the vibrationally excited HF (1 < =v< =3) has been recorded in rich premixed hydrogen‐fluorine and methanefluorine flames burning at various pressure (1.3–9 torr). The initial hydrogen and fluorine element content was identical in both CH4‐and H2‐ fluorine flames.

The rational temperature profiles have been determined as well as in H2/F2 flames than in CH4/F2 ones. The analysis of the experimental data has put forward the occurrence of an equilibrated vibrational population relatively early in the burnt gases region of flames burning at pressures higher than 5 torr. From these evidences, profiles of the relative mole fractions of HF in its vibrationally excited states (1 < =v< =3) have been established in both series of flames. The absolute total concentrations of HF have been deduced by considering the Lewis number equals to one and therefore the absolute mole fraction profiles of the individual vibrationally excited HF (0 < =v< =3) have been determined.

Besides the well‐known mechanism of the HF formation in H2/F2 systems it appears clearly that in CH4/F2 flames the final concentration of fluorocarbon derivatives are close to those of fluorhydric acid. This evidence indicates that in rich methane‐fluorine flames the reaction CH3 + F2 → CH2F + HF and subsequent reactions of CH2F are important in addition of the primary attack of methane CH4 + F → CH3 + HF and CH4 + F → CH3F + H.
Fundamental questions about entropy III. A kind of mobile order in liquids : preferential contacts between molecular groups
Authors: Huyskens P. L. , Siegel G. G.
Published: September 2010

At 25°C, in liquid alcohols and in water an O‐H proton follows an oxygen atom of a neighbouring molecule in its peregrinations during a fraction (1‐γ) of the time (more than 95% for the lower alcohols). During this time the proton can be found only in a part Vo of the standardized domain  of the molecule. Neither Vo not  are fixed. The highly preferential contacts create in the liquid a kind of mobile order that does not exist in crystalline substances. As a consequence of the mobile order the standardized possibilities  of one molecule A of the liquid are reduced by a factor  = γ−γ (1‐γ)γ‐1 (Vo/  1‐γ. This factor is smaller than one. In the case of water there are two such factors, one for the first and the other for the second proton. The mobile order provokes a change in the molar entropy ΔSA mobile order = R In  that is therefore negative.  is the volume of the solution divided by the number of A molecules. In the series of the normal alcohols, up to hexanol, the changes of γ can be neglected. Vo and the effects of H‐bonding on the vibrations can also be considered as constant. As a consequence in this series one expects an increase of the negative value of the entropy of mobile order according to d(−ΔSA mobile order) = R d ln VA. This is confirmed by the differences between the standard entropies of the alcohols and of their homomorphous hydrocarbons. In the vapour phase where H‐bonding is negligible, the differences are positive and practically constant: 13.8 ± 0.7 JK−1 mole−1. For the liquids the differences are negative and increase with the molecular weight.