bluuebunny/crossref_metadata_2025 huggingface dataset:
Les Complexes Par Transfert De Charge En Chimie Organique. VIII. Etude Thermodynamique Et Spectroscopique Des Complexes De L'anhydride Tetrachlorophtalique
Authors: Nagy J. B. , Nagy O. B. , Bruylants A.
Published: September 2010

The thermodynamic and spectroscopic properties of the charge‐transfer complexes formed by tetrachlorophtalic anhydride with various π electron donors were examined in 1, 2‐dichloroethane. In all cases only one complex of composition 1: 1 was detected. Several theoretical predictions were verified and it was shown that the entropy factor is neither constant nor proportionnaly varying with the enthalpy factor.

The reliability of recently determined ionisation potential values for a large number of donors was also established.

The charge‐transfer transition energies were found to satisfy the LCDA MO theory.
Potentiometric And Polarographic Determination Of The Stability Constants Of Bivalent Metal‐Itaconate Complexes
Authors: Robbrecht R. , Thun H. , Verbeek F.
Published: September 2010

The complexation between bivalent metal ions and itaconate was investigated potentiometrically at unit ionic strength in NaClO4 at 25.00±0.01°C in the pH region 2‐4.5. The complexes ML, ML2, MHL, MHL2 and MH2L2 can be identified and their stability constants calculated by both a graphical and a computer method. The results are in a good agreement with those obtained from polarographic measurements.
Preparative separation and isolation of three. Epimeric 2‐methylcycloalkanols by counter current distribution
Authors: Lemière G. L. , Dierckens J. J. , Alderweireldt F. C.
Published: September 2010

Diastereoisomeric mixtures of 2‐methylcyclopentanol (I), 2‐methylcyclohexanol (II) and 2‐methylcycloheptanol (III) can be separated in very good yields into the cis and trans isomers by counter current distribution. A suitable method for isolation is also given.
Perturbation Theory and Stereoisomerization Modes
Authors: Brocas J. , Willem R.
Published: September 2010

It has been shown previously that the ratio of relaxation times is a characteristic of the modes of stereoisomerization for trigonal bipyramidal complexes. This result has been obtained under the assumption that all the rate constants for a given mode are the same. This equality is no longer true when the differences in chemical nature of the ligands are taken into account.

In this paper, we describe a method, based on perturbation theory, in which this situation is studied. We show that, in the case where there are two ligands of type 1 and three of type 2, the situation where ligand 1 is more electronegative than 2 preserves the possibility of distinguishing the modes, by comparing the relaxation times.
Kinetics of Sulphonic Acid Catalyzed Acylations with Carboxylic Acid Anhydrides: Mixed Anhydrides as Intermediates
Authors: Joly L. , Hoornaert G.
Published: September 2010

From a comparison of the kinetic behaviour in the sulphonic acid catalyzed acylation of anisole with carboxylic anhydrides and synthesized mixed anhydrides of them and the catalyst, the intervention of a mixed anhydride in the acylation with anhydrides has been proved.

From a proposed reaction scheme a rate expression has been derived which is in agreement with all observations especially the pecularities observed for the kinetic behaviour of the anhydride and anisole.
Topological Graphical Representations Of The Intramolecular Rearrangements Of Octahedral Complexes
Authors: Gielen M. , Willem R. , Brocas J.
Published: September 2010

Graphical topological representations are described for isomerization modes of octahedral complexes. Their group theoretical properties are discussed.
Les Chlorures Basiques Mixtes de Zinc et de Cobalt
Authors: Mannoorettonijil M. , Glibert J.
Published: September 2010

By the addition of soda to a solution of ZnCl2 or CoCl2, the following compounds are precipitated: 4 Zn(OH)2. ZnCl2. I H2O (20 and 75°C), 4 Co(OH)2. Co(OH)0,6(Cl)I,4.4 H2O (20°C) and Co2(OH)3, 2(Cl)O,8.O,7 H2O (75°C). At 20°C, the two salts are isomorphous.

In the mixed solution ZnCl2‐CoCl2, at 20°C, a continuous solid solution is formed characterized by a progressive variation of the basicity index between 33 and 63% Co. at. The distribution factor shows an important retention of zinc in the cobalt salt. At 75°C, the solubility of cobalt in the zinc tetrabasic chloride rises to 67% Co. at. A zone of demixtion separates the latter from the compound of cobalt which contains a maximum of 6,5% Zn. at.
Spectrométrie de Masse de Pyrazoline‐5‐Ones N1 Substituées. 1. 5‐AlkoXypyrazoles et 3‐Pyrazoline‐5‐Ones A Structures Fixes
Authors: Maquestiau A. , van Haverbeke Y. , Bruyere A.
Published: September 2010

The mass spectra of fixed pyrazolin‐5‐ones (5‐alkoxypyrazoles and 3‐pyrazolin‐5‐ones) are reported and discussed. Mass spectrometry allows characterization of these two isomeric structures.
Charge‐transfer complexes in organic chemistry. X. Solvent effects on spectroscopic and thermo‐dynamic properties of the complex acenaphtene‐tetrachlorophthalic anhydride
Authors: Nagy O. B. , Nagy J. B. , Bruylants A.
Published: September 2010

Thermodynamic and spectroscopic properties of the charge‐transfer complex acenaphtene‐tetrachlorophtalic anhydride were studied in different solvents. The corresponding thermodynamic and spectroscopic parameters were corrected for solvent competition. Only in this case were correlations obtained in agreement with theory. The solvents were divided into several classes such as aromatic, aromatic with one functional group, halogen containing and n‐donor solvents. The role of general and specific solvent effects is emphasized.
Nouvelles Données Structurales et Spectre Vibrationnel de Composés AB(XO4)2 Dérivant du Type Scheelite
Authors: Paques‐Ledent Marie‐Thérèse
Published: September 2010

Une série de tungstates et molybdates doubles de formule AIBIII(XO4)2 appartiennent au type de la scheelite CaWO4.

De nouvelles données obtenues parallèlement par diffraction X et par spectrométrie vibrationnelle pour un grand nombre de ces composés, indiquent que la symétrie des groupes tétraédriques XO4 est plus basse dans ces composés doubles que dans les scheelites simples. D'autre part, le spectre vibrationnel dans le domaine des vibrations relatives aux groupes XO4, ne peut être interprété sur base d'une maille élémentaire de symétrie C4h.
Complexes par Transfert de Charge en Chimie Organique. XIV. La quaternation des Amines Tertiaires par les Anhydrides Phtaliques
Authors: Mukana D. , Nagy J. B. , Nagy O. B. , Bruylants A.
Published: September 2010

The quaternisation of tertiary amines (triethylamine, pyridine and 1, 4‐diaza‐[2, 2, 2] bicyclooctane) by cyclic anhydrides (phthalic, 4‐nitro, 3‐nitro‐, 3, 5‐dinitro, 3, 6‐dichloro‐and tetrachlorophthalic, naphthalic anhydride) is studied in aprotic media. It appears that the reaction is strongly dependent on substituent and solvent effects. In every case a charge‐transfer complex is formed between the two reactants. This complex is a real intermediate on the reaction path. The activation parameters favour the resulting complex mechanism.
Quantitative investigation of the acid‐catalysed hydrolysis of glyceryl nitrates
Authors: Rosseel M. T. , Bogaert M. G. , De Keukeleire D.
Published: September 2010

The hydrolysis of glyceryl trinitrate, glyceryl‐1,3‐dinitrate, glyceryl‐1,2‐dinitrate and glyceryl‐1‐mononitrate was studied in HCl 4 N, 3 N, 2 N and 1 N, at 37°C. Densitometry was used for the quantitative determination of the four nitrate esters on thin‐layer chromatograms. The data obtained indicate that glyceryl‐1,2‐dinitrate and glyceryl‐1‐mononitrate hydrolyse at the same rate, while the hydrolysis rate is much enhanced for glyceryl trinitrate and somewhat diminished for glyceryl‐1,3‐dinitrate. In each case there is a linear relationship between log k1 and ‐Ho.
A statistical dipolar method for the determination of the structure of complexes in solution
Authors: Huyskens Pierre L.
Published: September 2010

When several structures are possible for an ab complex in solution, the most probable of them can be found using a statistical dipolar method. For a given structure it is possible to calculate from the experimental values of the dipole moment of the complex μab and of the separate molecules μa and μb a value of the dipole increment Δμ resulting from the formation of the complex. The most probable structure is that one where in a given family of complexes, whose structure must be similar, one obtains the most coherent evolution of the calculated dipole increment with characteristics of the complexes, like the complexation enthalpy, or of the partners, like their pKa. In this work the theory is derived on the basis of the Fröhlich equation. It is applied to the case of the complexes between phenols and pyridines.
Oxidation products of hop bitter acids. Part IX. Six‐membered ring products from the oxidation of colupulone
Authors: van Den Bossche R. , Anteunis M. , Verzele M.
Published: September 2010

Air oxidation of colupulone in iso‐octane solution produces a comples mixture, separation of which by Counter‐Current‐Distribution with the two phase system iso‐octane/buffer pH : 7.00 gives four 1,2‐dioxolane peroxides (III, IV, V and VI of figure 1).
Trans‐2‐isopropyl‐1,3‐dithiane‐l‐oxide; a conformationally fixed isopropylgroup
Authors: Anteunis M. , van Acker L. , Danneels D.
Published: September 2010

It is found by 1H n. m. r. spectroscopy that in trans‐2‐isopropyl‐1,3‐dithiane‐1‐oxide an S‐O : C‐Me synaxial type of interaction is relatively disfavoured, having its impact in the rotameric behaviour of the isopropylgroup.
Three new classes of configurationally stable organotin compounds
Authors: Gielen M. , Simon S. , Tondeur Y. , van De Steen M. , Hoogzand C.
Published: September 2010

Methylneophylphenyltin hydride (I), (methylneophylphenylstannyl) cyclopentadienyl molybdenum tricarbonyl(II) and dimethylphenylstannylmethyl‐α‐naphthyl‐phenylgermanium (III) are configurationally stable within the NMR time scale, even in the presence of strong nucleophiles.
An intrinsic non‐equivalence in organotin chemistry
Authors: Gielen M. , Close V. , De Poorter B.
Published: September 2010

α‐Methoxybenzyltribenzyltin shows anisochronous diastereotopic methylene protons. This intrinsic chemical shift nonequivalence is equal to 0.066 ppm.

α‐Methoxybenzyldimethylphenyltin does not show anisochronous methyl protons even at 270 MHz.
Studies in organic mass spectrometry. XIX The fragmentation of the trimethylsilyl derivatives of some 2,3‐dialkyl‐1,4‐cyclopentanediols
Authors: Maenhaut‐Claeys M. , Vandewalle M.
Published: September 2010

The mass spectra of the TMS‐ethers of the isomeric 2,3‐dialkyl‐1,4‐cyclopentanediols are discussed. These compounds exhibit fragmentations, characteristic for the TMS‐1,3‐cyclopentanediol‐system. The dimethyl substituted compounds display differences in the ion abundances for a number of ions, depending upon the stereochemistry of the trimethylsiloxy groups, while for longer alkyl groups only differences in the intensity of a rearrangement ion at m/e 147 are found. A considerable change in the mass spectral behaviour is found for the compounds with an 1′, 2′‐unsaturated alkyl substituent.
NMR experiments on acetals. part 54. Rotameric behaviour of geminal 4‐, and 5‐phenylgroups in 1,3‐dioxanes
Authors: Bernaert E. , Anteunis M. , Tavernier D.
Published: September 2010

The 1H‐NMR spectra were studied of a series of 2‐Me‐5‐R‐5‐ø1,3‐dioxanes (5) (R = H, Me, Et, i.Pr; ø of 2‐Me‐spiro(1,3‐dioxane‐5,9′‐fluorene) (14), of 5‐R‐4,4‐diø‐1,3‐dioxanes (14) (R = Me, Et, n.Pr, i.Pr and i.Bu) and of 5‐R‐spiro(1,3‐dioxane‐4,2′‐adamantane) (7) (R = Me, Et, n.Pr, i.Pr, ø). From a comparative shift study, the preferential orientation of the phenylgroups in the ø‐substituted 1,3‐dioxanes were ascertained. In (10) and (10) the 5‐ø‐axial groups are bisectional (14). The 5‐ø‐equatorial groups are bisectional in the 5‐R‐5‐ø‐derivatives with R = H and Me, but flatsided with the larger substituents R = Et, i.Pr, ø. (See Chart I). For the 4,4‐diø‐derivatives, both aromatic rings are flatsided (10). In order to reach this conclusion comparison between (10) and (14), where the 5‐R‐groups occupy the axial positions, was essential. A rational explanation for the behaviour of the non‐spherical phenyl groups is offered.
Comparative Study of Various Equations for the Determination of Dipole Moments of Complexes
Authors: Pauwels Herman , Huyskens Pierre
Published: September 2010

Three equations are considered for the determination of the dipole moment μ of complexes, derived respectively from the theory of Onsager and from that of Fröhlich and differing with respect to the role of the internal refractive indexes. In each case either no correction is made for the atomic polarization or this is put equal to 15% of the molar refraction corresponding to the Na D line. The equations are tested for some sixty complexes between compounds with a carbonyl group and phenols. Systematic differences appear between the values of μ computed by means of the three equations which are of the order of 2 a 3 Z. Taking into account the atomic polarization lowers the values of μ of some 5%. Differences in the shape of complexes belonging to the same family seem not to affect the computed values of μab, to a greater extent than the systematic errors.
Influence D'Une Faible Déformation sur le Spectre Vibrationnel de “Perovskites” Complexes A2IIBIIBVIO6
Authors: Liegeois‐Duyckaerts M.
Published: September 2010

Complex ordered perovskites A2BIIBVIO6 are ideally cubic, but the structure may be more or less distorted by the presence of large BII cations. A comparison between the vibrational spectra of cubic and slightly distorted perovskites show that the IR spectrum remains insensitive to small deformations of the structure. However, such deformations have a non‐negligible influence on the Raman spectrum, the most evident feature being a broadening or a splitting of the band corresponding to the T2g bending mode of the BVIO6 octahedron.
NMR Experiments on Acetals. Part 55. Conformational Equilibria in 5‐Ethenyl‐, 5‐Ethynyl‐ and 5‐Cyclopropyl‐ 1,3‐Dioxane
Authors: Anteunis M. , Camerlynck R. , De Waele R.
Published: September 2010

Quantitative conformational data are reported for the title compounds (Table I), as obtained from an extensive 1H‐NMR study at several temperatures. Identification of the Me‐5 signals (axial or equatorial) at T < TC could be achieved by spectral comparison with the corresponding anancomerized 2‐Me‐derivatives. The latter were finally related by chemical means to either r‐2‐Me‐cis‐5‐Me‐5‐Et‐1,3‐dioxane or r‐2‐Me‐trans‐5‐Me‐5‐Et‐1,3‐dioxane. The configurations of the latter two compounds were ascertained by specific long range study, established by nmdr.

The conformational results show that in typical apolar solvents the unsaturated substituents slightly prefer the equatorial position with respect to Me, but the axial position in freon‐21. This may be the result of counteracting electrostatic (or dipolar) and steric contributions, but special solvent effects of undisclosed nature govern the conformational picture.
NMR Experiments on Acetals. Part 53. On the Origin of the Low Barrier to Ring Topomerization in DI i. Propyl‐1,3‐Dioxane
Authors: Tavernier D. , Anteunis M. , Bernaert E.
Published: September 2010

The free energy barrier to ring reversal in 5,5‐dii. Pr‐, and 5,5‐dic. Pe‐1,3‐dioxane is measured to be 7.3 (153 K) and 6.6 (137 K) kcal/mole, respectively. An explanation for this exceptionally low barrier is offered; it invokes the existence of rotamers having a carbon atom situated above the 1,3‐dioxane ring and situated along the most favoured reaction path for ring reversal. The explanation is consistent with and predicts the “normal” barriers on the contrary found for 5,5‐dic. Pr‐,4,4‐dii. Pr‐, and 5,5‐diMe‐2,2‐dii. Pr‐1,3‐dioxane. Experimental barriers to ring reversal of some model spiro compounds and of 4,4‐, and 5,5‐diø‐1,3‐dioxanes (9.5 and 10.7 kcal/mole at 172 and 221 K respectively) are reported.
Organometallic Compounds. 42. Organotin Chelates, Synthesis, Spectroscopic Properties and Stereochemical Won Rigidity
Authors: Gielen M. , Topart J.
Published: September 2010

Di‐and triorganotin acetylacetonates and dipivaloylraethanates, and the adducts of some diorganotindihalides with bipyridyl and ortho‐phenanthroline have been synthesized. Their spectroscopic properties (MS, IR, NMR, Mössbauer) are described and discussed. In the light of NMR and literature results, one may conclude that organotin‐β‐diketonates are stereochemically non rigid.
German I ‐ Étude De La Décomposition En Phase Liquide De L'hydroperoxy‐2 Méthyl‐2 Proprionate De T. Butyle
Authors: Rafii Par E. , Lena L. , Metzger J.
Published: September 2010

L'étude de la décomposition thermique de l'hydroperoxy‐2 méthyl‐2 propionate de t.butyle 1 (0,1 à 0,5 mole.1−1), à différentes températures dans cinq solvants, a été envisagée. La faible énergie d'activation de la réaction de décomposition de l'hydroperoxyde 1 dans les solvants polaires (22 à 24 kcal. mole−1 respectivement dans le nitrométhane et le t.butanol) permet d'envisager que, dans ces solvants, la décomposition est induite par les radicaux dérives de l'hydroperoxyde.

Par contre, l'hydroperoxyde‐1 est très stable dans le benzène à une température inférieure à 100° C. Ce qui nous a permis d'envisager l'étude de sa décomposition radicalairement induite par les initiateurs dans ce solvant, Les résultats obtenus montrent que la rupture de la liaison (ROO‐H) par attaque d'un radical alkyle ou aleoxy est négligeagle vis‐à‐vis de la rupture de la liaison (RO‐OH).
Some Carbene Reactions on Myrcene
Authors: De Smet A. , Anteunis M. , Tavernier D.
Published: September 2010

We have ascertained the structure of the adducts of myrcene and the following carbenes: (i) dichlorocarbene (ii) carbethoxycarbene and (iii) methylene (Simmons‐Smith procedure). With dichlorocarbene, the diadduct (2', 2'‐dichloro‐3 ', 3'‐dimethyl)‐(1”‐ethenyl‐2”,2”‐dichloro)‐1, 2‐dicyclopropylethane is obtained in 42% yield. With carbethoxycarbene a mixture of two monoadducts is isolated: l‐ethenyl‐2‐(3'‐isohexenyl)‐carbethoxycyclopropane and 2‐(1'‐methylideen‐4'‐isoheptenyl)‐carbethoxycyclopropane. Both the cis‐and the trans‐isomers of these products are formed. Their configurational assignment was established by 1H‐NMR spectroscopy. By the Simmons‐Smith reaction a complex mixture of myrcene‐related compounds is obtained, containing one, two or three cyclopropane rings.
The Anodic Behaviour of Lead in Acid Sulphate Solutions. Influence of Manganese Ions and Electrochemical Oxidation of Manganese Ions at Lead Anodes
Authors: Ravindran Kanechamkandy , Heerman L. , van Simaeys L.
Published: September 2010

Results concerning the influence of manganous ions, either singly or in combination with cobalt ions, on the anodic corrosion of lead in acid sulphate solutions are reported. The corrosion of lead is much less when it is compared to media containing only copper and cobalt ions. This fact has been corroborated by results obtained by the potentiokinetic method. Some results on the electrochemical oxidation of manganous ions at lead anodes in presence of cobalt ions are also described.
Ion‐Association Extraction Combined With Low Temperature Ashing for the Determination of Cadmium in Foodstuffs
Authors: Dewit A. , Duwijn R. , Smeyers‐Verbeke J. , Massart D. L.
Published: September 2010

A method for the determination of Cd by AAS in foodstuffs is presented. The determination is carried out after low temperature ashing and extraction with a high molecular weight amine.

Of the several extractions investigated, Aliquat 336 3% and Alamine 336 3% in Methylisobutylketone allowed the best results. The former was chosen. The analysis of international standards shows that the method yields accurate results.
General Theoretical Study of the Stepwise Coupling Methods
Authors: Alix Alain J. P. , van Der Veken Benjamin J.
Published: September 2010

In this second part, the authors study the convergence of the iterative procedures based on the stepwise coupling methods in the second order case: especially the Eigenvector Method of H. J. BECHER and R. MATTES and the Matrix Polynomial Expansion Method of A. ALIX. It is shown that under some simple conditions on the number m0 of iterative cycles and on the function which defines the stepwise introduction of the kinematic coupling, that the limit obtained is unique. The expression of that limit and its properties are discussed in detail.
A Self‐Consistent Field Molecular Orbital Theory With “Intermediate Neglect of Differential Overlap”, Based on the Atomic Valence State Concept
Authors: Figeys H. P. , Geerlings P. , van Alsenoy C.
Published: September 2010

Summary. A new INDO method is developped, in which the semi‐empirical evaluation of one‐center integrals is based upon the energy expression of an atom in a valence state, according to Slater, Mulliken, Hinze and Jaffé. The values of these integrals for the first and second row elements are reported. The diatomic bonding parameters were calibrated against experimental molecular valence electronic energies (VEE). The computed VEE‐values for a series of various aliphatic and unsaturated molecules are in fair agreement with experiment.
Constituents of Peppers. Part VI. The Oxygenated Fraction of Pepper Essential Oil
Authors: Debrauwere J. , Verzele M.
Published: September 2010

The oxygen containing part of the essential oil of black pepper was resolved into twenty‐five fractions by preparative gas chromatography. Separation of the major compounds of these fractions was carried out by preparative open tubular column gas chromatography. The compounds were characterized by infrared, nuclear magnetic resonance, mass and ultraviolet spectroscopic studies. Trace constituents were investigated by combined gas chromatography‐mass spectrometry. Thirty‐three compounds were identified, of which only six have been reported previously as occurring in black pepper oil. Nine compounds have to our knowledge never been found in natural products.
Effect of Minor Components on the Surface Tension of Micellar Dodecyl Sulfate Solutions
Authors: Joos P. , Deelstra H.
Published: September 2010

A theory is developed to predict the effect of a minor component on the surface tension variation of micellar surfactant solutions. The approach is similar as this of Lucassen‐Reynders and van den Tempel. The theory was tested for sodium dodecylsulfate solutions containing higher alcohols (hexadecanol, octanol, decanol, dodecanol and tetradecanol). Fair agreement between theory and experiments was achieved except for octanol and hexanol.
Synthesis of the First Optically Active Tetraorganotin Compound in Which the Tin Atom Is The Only Chiral Center
Authors: Gielen M. , Mokhtar‐Jamai H.
Published: September 2010

The synthesis of optically active p‐anisyl‐(3‐hydroxy‐3‐methylbutyl)methyl‐α‐naphthyl tin (IV) is described. The spectroscopic properties of this compound and of the products used as synthesis intermediates are given. The two diastereoisomers of (‐)‐menthyl‐β‐(methylnaphthyl‐phenylstannyl)‐propionate (V) could not be separated.
Cyclopentanones. XII. An Alternative Synthesis of Prostaglandins Involving Catalytic Hydrogenation of 2, 3‐Dialkyl‐4‐Dihydroxy‐2‐Cyclopentenones
Authors: Coen R. , De Clercq P. , van Haver D. , Vandewalle M.
Published: September 2010

A novel approach to Corey's aldehyde is described. A suitable substituted all cis 2, 3‐dialkyl‐l, 4‐cyclopentanediol system is obtained by catalytic reduction of 2, 3‐dialkyl‐4‐hydroxy‐2‐cyclopentenones. Epimerisation to the prostaglandin configuration occurs spontaneously when later on the Horner reaction is carried out.
The Conformational Equilibrium in CIS‐2‐Methoxy‐CIS‐Decalane
Authors: Tavernier D. , De Pessemier F. , Anteunis M.
Published: September 2010

The chair‐chair equilibrium in cis‐2‐methoxy‐cis‐decalane has been studied by 1H‐NMR spectroscopy; the conformer featuring the equatorial methoxyl is the more stable one; ΔG°198 = 1.2 ± 0.1 and ΔG°291 = 1.4 ± 0.2 kcal.mole−1.
Conformational Preferences of Alkyl Substituents in 5‐Me‐5‐R‐1, 2, 3‐Trithianes
Authors: Goor G. , Anteunis M.
Published: September 2010

Variable temperature 1H‐NMR‐study of 5‐Me‐5‐R‐1,2,3‐trithianes shows an axial preference for linear and α‐branched groups; this preference is disfavoured by β‐substitution. The Ph‐group takes exclusively the equatorial position.
Alkylation of Some Potential 2‐Oxoesters
Authors: Kolind‐Andersen H. , Dyrnesli R. , Lawesson S.‐O.
Published: September 2010

On reaction with R‐Hal, salts of ethyl phenylcyanopyruvate, dialkyl oxalacetate and their derivatives undergo 0‐alkylation in almost all cases. Also mono‐ and disubstitutions on carbon are observed. The structure of the product from alkylation of the sodium salt of diethyl oxalacetate with diethyl chlorooxalacetate has been determined. The effect of solvent as well as the influence of the structure of the alkylating agent and the substrate on the 0/c‐ratio of substitution are discussed.
Nucleophilic Substitution of Brominated Isophorone Compounds Via Zwitterionic Intermediates
Authors: Verhé R. , Schamp N. , De Buyck L. , Vanloocke R.
Published: September 2010

The reaction of brominated isophorone compounds with sodium methoxide in methanol has been investigated and mechanisms for these reactions are discussed. 4‐Bromoisophorone gave exclusively 2‐methoxyisophorone, while 2,4,6‐tribromo‐ and 2,4,6,6‐tetrabromo‐3‐bromomethyl‐2‐cyclohexenone afforded 2,4‐cyclohexadienone compounds.

However, the reaction of 2,4,6‐ and 2,6,6‐tribromo‐3‐dibromomethyl‐5,5‐dimethyl‐2‐cyclohexenone took a total different way with formation of resp. a bicyclo compound and Favorskii rearrangement products.

These results were rationalized in terms of zwitterionic species instead of the classical nucleophilic substitution.
A 300 MHz Study of Melibiose, Lactose and 3‐Keto‐Lactose in D2O
Authors: De Bruyn A. , Anteunis M. , van Beeumen J. , Verhegge G.
Published: September 2010

The 300 MHz 1H‐n.m.r. spectra of β‐D‐allose (1), α‐D‐galactopyranosyl‐(1 → 6)‐D‐glucopyranose (melibiose) (2), β‐D‐galactopyranosyl‐(l → 4)‐D‐glucopyranose (lactose) (3) and O‐β‐D‐xylo‐hexopyranosyl‐3‐ulose‐(1 → 4)‐D‐glucopyranose (3‐keto‐lactose) (4) are discussed. From comparative considerations of shift increments caused by several substitutions (e.g. downfield shift of 0.1‐0.2 p.p.m. of an axial proton by the presence of a synaxial and a vicinal axial OH, but an absence of any effect on the equatorial proton) it is corroborated that 3‐keto‐lactose occurs in the hydrated form in D2O.
Laplace Transformation Trial Basis Functions for the1Σ Ground State of Two‐Electron Diatomic Molecules
Authors: Leclerc Jean‐Claude
Published: September 2010

The one‐dimensional Laplace transform of the exponential exp(‐rx) was used to generate functions which could be useful as basis sets for molecular calculations. In a particular case, they reduce to the Hulthén approximation. These 2‐ to 4‐ parameter orbitals were applied to the calculation of the ground state energy of H2, He2++, Li24+ and Be26+, using CI definition for the wave function.
Comportement Polarographique et Solvatation de Quelques Lanthanides Dans le Melange Binaire Dimethylsulfoxyde ‐ Carbonate de Propylene
Authors: Massaux J. , Duyckaerts G.
Published: September 2010

Nous avons étudié le comportement polarographique des trois ions Eu3+, Yb3+, Sm3+ dans lea solvants binaires DMSO‐CP. Lee vagues polarographiques sont toutes contrǒlées par la diffusion et dans tous les cas le passage du CP au DMSO est énergiquement favorable. L'application aux vagues irréversibles des méthodes de HALE et PARSONS ou de BOND nous a permis d'accéder aux constantes de dissociation et à la stoechiométrie des complexes de Eu3+, Eu2+, Yb3+ et Yb2+ avec la DMSO dans le CP.

La connaissance de ces constantes d'équilibre nous a permis de déduire les variations d'enthalpie libre associées au passage de ces ions du CP à toutes les compositions du solvant binaire; les valeurs obtenues concordent de façon satisfaisante avec celles obtenues par polarographie sur la base de l'hypothèse de STREHLOW de l'invariance du potentiel normal du couple cobaltocène‐ion cobalticinium.
Extraction par Solvant a l'aide de la Thiothenoyltripluoroacetone et de β‐Dicetones Fluorees en Vue du Dosage de Traces Metalliques Dans les Eaux par Spectrophotometrie d'Absorption Atomique
Authors: Jauniaux M. , De Meyer M. , Lejeune W. , Levert J. M.
Published: September 2010

L'article décrit un procédé de dosage de plusieurs éléments métalliques: aluminium, cadmium, cuivre, fer, plomb et zinc à l'état de traces dans les eaux. Les éléments sont extraits sous forme de chélates métalliques de β‐dicétones fluorées (trifluoroacétyl‐acétone, thénoyltrifluoroacétone) ou de la thiothénoyltrifluoroacétone au moyen de propionate d'éthyle. Ils sont ensuite dosés par spectrophotométrie d'absorption atomique de l'extrait organique. Les courbes d' étalonnage sont linéaires de 0 à 100 μg/l au moins; les sensibilités varient du ppb à la dizaine de ppb selon les métaux. Le procédé peut être étendu à de nombreux autres éléments.
Reactivity of α,α‐Dihalogenated Imino Compounds. Part IX Rearrangement of N‐2‐ (1, 1‐Dichloroalkylidene) Anilines with Lithium Aluminium Hydride
Authors: De Kimpe Norbert , Verhé Roland , Schamp Niceas
Published: September 2010

The lithium aluminium hydride reduction of N‐2‐(1,1‐dichloroalkylidene)‐anilines 3 afforded mainly the rearranged secondary amines 4 next to the normally expected secondary amines 5. The formation of the rearranged secondary amines 4 is explained by an aziridine intermediate. The highly branched derivative 3d gave the aziridine 6d in good yield, besides the secondary amine 5d.
Structure de Bases de Schiff Derivees de 4‐Acylpyrazoline‐5‐Ones et 5‐Thiones
Authors: Maquestiau A. , van Haverbeke Y. , Vanovervelt J. C.
Published: September 2010

The structure of 21 1‐phenyl‐3‐R‐4,1′‐alkyl (aryl)aminoalkyl(aryl)idenepyrazolin‐5‐ones or 5‐thiones is examined.

Whereas the chelated NH exo Z form exists always in the pyrazolin‐5‐thiones compounds, this type of tautomer is only observed, for the pyrazolinones derivatives, when one or two steric interactions between substituents (R3‐R1′, and/or R1′‐R2′,) occur.
Chemical Studies of Marine Invertebrates ‐ XIII 2 ‐ Hydroxynephtenol, a Novel Cembrane Diterpene from the Soft Coral Litophyton Viridis (Coelenterata, Octocorallia, Alcyonacea)
Authors: Tursch B. , Braekman J. C. , Daloze D.
Published: September 2010

The soft coral Litophyton viridis contains the already known nephtenol and a novel cembrane diterpene whose structure has been established as 2‐hydroxynephtenol. The absolute configuration of (‐)‐nephtenol has been demonstrated.
O‐Alkyl‐O‐Aryl‐Phenylphosphonothioates
Authors: Steurbaut W. , De Kimpe N. , Schreyen L. , Dejonckheere W.
Published: September 2010

A series of 27 O‐alkyl‐O‐aryl‐phenylphosphonothioates was prepared and studied by I. R.‐ and N. M. R.‐spectroscopy. The I. R.‐spectra gave typical vibrations: P‐O‐alkyl, P‐Carom and P‐O‐Carom. Shifts in stretching frequencies were related with electronic properties of the substituents.
1H‐N. M. R Study of Some D‐Aldohexapyranosyl‐D‐Fructos(id)es in D2O
Authors: De Bruyn Andrè , van Beeumen J. , Anteunis M. , Verhegge G.
Published: September 2010

We report on the analysis of the 300 MHz 1H‐n.m.r spectra obtained in D2O of SUCROSE (α‐D‐glucopyranosyl‐(1 → 2)‐β‐D‐fructofuranoside), PALATINOSE (α‐D‐glucopyranosyl‐(1 → 6)‐D‐fructose), LEUCROSE (α‐D‐glucopyranosyl‐(1 → 5)‐D‐fructose), TURANOSE (α‐D‐glucopyranosyl‐(1 → 3)‐D‐fructose) and LACTULOSE (β‐D‐galactopyranosyl‐(1 → 4)‐D‐fructose). It was possible to identify most of the resonances of the major isomers using the homo‐INDOR technique. The extracted chemical shifts are compared with those of the corresponding mono‐oses and increment rules are suggested.
Shift Increment Studies in L‐Arabinopyranoses and β‐D‐Fructopyranose
Authors: De Bruyn A. , Anteunis M.
Published: September 2010

We report on the complete analysis of the 1H‐n.m.r. spectrum at 300 MHz of α‐, and β‐L‐arabinopyranose in D2O. Increment rules as derived previously for aldohexapyranoses and 2‐deoxy‐aldopyranoses are extended to aldopentapyranoses and β‐D‐ketohexapyranoses.
U. V. and I. R. Spectroscopic Studies of 4‐Aryl‐3,5‐Diethoxy‐Carbonyl‐2,6‐Dimethyl‐1, 4‐Dihydropyridines (Hantzsch Esters)
Authors: Dommisse R. A. , Lepoivre J. A. , Alderweireldt F. C.
Published: September 2010

The U.V. and I.R. spectral data of 4‐aryl‐3,5‐diethoxycarbonyl‐2,6‐dimethyl‐1,4‐dihydropyridines with different aryl substituents are discussed. The λmax values of the long‐wavelength absorption band in the U.V. spectra show a similar solvent dependence for all the compounds. (The results indicate a more polar state of the chromophore in the excited state). The variations induced by different 4‐aryl substituents are correlated with the electronic effects of these substituents. The I.R. stretching vibrations of the bonds in the chromophoric system are not influenced by the 4‐R‐substituents.
A Comparative Study of the Radiolysis of 1‐Chloropropane at 77 K and 300 K
Authors: De Jonge D. , Ceulemans J.
Published: September 2010

A study was made of the radiolysis of 1‐chloropropane at 77 K and 300 K. The observed differences between the yields, extrapolated to zero absorbed dose, at these temperatures may be explained by cage and temperature effects on the different radical reactions.
On the Dipole Moments of some Hydrogen‐Bonded Complexes and the Second Electron Affinity of Phenols
Authors: van Hooydonk G.
Published: September 2010

A formula expressing bond dipole moments of donor‐acceptor bonds is derived from the ionic bonding approximation. Only the characteristics ionization energy and electron affinity are thereby used and reasonable agreement is obtained with recently reported experimental data. A rough estimate can be obtained for the second electron affinity of neutral species, defined as the enthalpy of the reaction A− + e → A–.
Structure Electronique de l'oxepine, de l'azepine, de l'oxyde et de l'aziridine de benzene
Authors: Colot G. , Krief A. , André J‐M.
Published: September 2010

Non‐empirical calcutations of the electronic structure of azepine, oxepine, benzene oxide and benzene aziridine are presented. Calculations are found to be in good agreement with available experimental data on relative stabilities and intuitive repartition of electronic charges in the above molecules.
Optically Active Transition Metal Complexes, XXXIV (+)579‐ and (‐)579‐(‐C5H5)Mo(CO) (NO)[P(C6H5)2N(CH3)CH(CH3)(C6H5)]
Authors: Brunner H. , Doppelberger J.
Published: September 2010

In the reaction of C5H5Mo(CO)2NO +) with (+)579 n‐(C6H5)2PN(CH3)CH(CH3) (C6H5), abbreviated with PØ2R*, the pair of diastereoisomers (+)579‐ and (‐)579‐ C5H5Mo (CO) (NO)PØ2R* (+)I and (‐)I is formed. The two diastereoisomers can be separated by preparative liquid chromatography; the less soluble isomer can also be obtained optically pure by several fractional crystallisations. The asymmetric induction of the group R* on the substitution of the enantiotopic CO ligands is only small; the two diastereoisomeric complexes (+)I and (‐)I are obtained in nearly equimolar amounts. The compounds are configurationally stable in solution even in the presence of nucleophiles like triphenylphosphine and isonitriles.

The amino phosphine ligand in C5H5Mo(CO) (NO)PØ2R* can be transformed into the methoxy phosphine ligand P(C6H5)2OCH3 by reaction with HCl followed by addition of CH3OH.
Recherche dans la Serie Des 1, 2, 4‐Triazoles. Micropréparation et étude physico‐chimique du 3‐nitro‐1, 2, 4‐triazole
Authors: Closset J‐L. , Copin A. , Drèze Ph. , Alderweireldt F. , Durant F. , Evrard G. , Michel A.
Published: September 2010

A method is described for isolating and purifying microquantities of 3‐nitro‐1, 2, 4‐triazole obtained by reaction of nitrous acid with 3‐amino‐1, 2, 4‐triazole (A.T.A.) a well known herbicide.

The physico‐chemical properties of that compound are studied by N. M. R., mass, infrared spectrometries and R. X diffraction.

The reaction is discussed in terms of the caracterised formed product.
Zinn ‐ Chalkogen ‐ Heterocyclen. I. 2.4.6‐Hexamethyl‐1.3.5‐triselena‐2.4.6‐tristannacyclohexan, Massen‐ und Schwingungsspektren
Authors: Mathiasch B. , Blecher A.
Published: September 2010

The mass spectrum of the title compound exhibits very similar fragmentation patterns compared with the sulfur analogon. The high stability of triply coordinated organotin cations is remarkable. There is no evidence for any stabilisation effects by pπ‐dπ bonding concerning the ring bonds.

The assignment of the vibration spectra leads to the conclusion that the molecule of triselenastanninane possesses a boat conformation.
Structure de Paires d'ions du Sodium dans les Solvants Oxygènes
Authors: Detellier Christian , Laszlo Pierre
Published: September 2010

Au moyen de la rmn du sodium‐23, on étudie la séparation par les glymes des paires d'ions formées par l'iodure de sodium. Le degré d'agrégation de la paire d'ions serrée présente dans le THF correspond principalement à une dimérisation. L'alcool tétrahydro furfurylique est au moins aussi efficace que le triglyme pour séparer les paires d'ions.
Contribution a L'Étude des Sulfures Mixtes ZnSCo1‐xS, ZnSFe1‐x et ZnSMnS
Authors: Blaton Norbert , Glibert Jacques
Published: September 2010

A distribution curve for the systems ZnSCo1‐xS, ZnSFe1‐x and ZnSMnS is established by precipitation at 25°C and pH 5 with a deficient quantity of Na2S in mixed ZnSO4CoSO4, ZnSO4FeSO4, and ZnSO4MnSO4. solutions. The distribution reaction between the solid and liquid phase leads to the formation of mixed sulphides. The saturation limits for the different solid solutions can be derived from the slope changes in the respective distribution curves.
Etude de L'Equilibre Azido → Tetrazole Dans la Serie du Thiazolo [2,3‐e] Tetrazole I. Effets de Solvant
Authors: Elguero J. , Faure R. , Galy J. P. , Vincent E. J.
Published: September 2010

The influence of solvent on the azido‐tetrazole equilibrium in thiazole series has been investigated by means of proton NMR spectroscopy. We made a hypothesis about the structure of the cation of azidothiazoles and we proposed that there is a rough parallelism between azido‐tetrazole isomerism and prototropic tautomerism.
Benzo‐ and indoloquinolizine derivatives ‐ VII The dehydrogenation of enamines in the synthesis of benzo[c]substituted quinolizidines
Authors: van Binst G. , Baert R. , Biesemans M. , Mortelmans C. , Salsmans R.
Published: September 2010

During the synthesis of benzo[c]quinolizidine derivatives, the dehydrogenation of enamines with palladium on charcoal in the presence of a hydrogen acceptor has been studied. The reaction conditions are rather drastic. The best results are obtained when the enamine is stabilised by conjugation with a keto‐group.
Approche theorique du problème de la tautomérie des triades HX‐Y=Z⇆X=Y‐ZH. I. Équilibre Amine‐Imine (Y=CH, Z=NH)
Authors: Teysseyre J. , Arriau J. , Dargelos A. , Elguero J. , Katritzky A. R.
Published: September 2010

The imino→amino tautomerism of four classes of related compounds, enamines, amidines, amides and thioamides, has been examined by means of the CNDO/2 method with complete geometry optimization. The calculated energy differences between the two tautomers agrees with the experiment in the case of oxygen and nitrogen derivatives, but in the case of thioamides the real situation lies between the sp and spd approximation. To understand the origin of the differences between the equilibrium constants an analysis of the bicentric partition of the total energy has been done.
A New substituent constant E(R) derived from carbonyl intensities of simple R′R″CO molecules — II Chloroform
Authors: Seth‐Paul W. A. , van Hoeyland P.
Published: September 2010

The carbonyl intensities E (l.Mole−1 cm−2) of simple R′R″CO molecules measured in dilute chloroform solutions can be estimated by means of the relation: E=ϵ(R') · ϵ(R″) where ϵ(R') and ϵ(R″) are factors dependent upon the nature of the R′ and R″ substituents. The contribution of each substituent to the carbonyl frequency or intensity change on passing from carbon tetrachloride to chloroform solutions can be determined Combinations of the following substituents: OH, OMe, Me, Et, nPr, iPr, CH2Ph, (CH2)2Cl, CHCl2 and CCl3 which form stable compounds are expected to have log10 E values which correlate with ΣEs, Σσ1, ΣσoR(R) and ΣX(R) in carbon tetrachloride, and with ΣσoR(R) and ΣX(R) in chloroform solutions.
The Kerr constants of 4‐and 5‐phenyl‐1,3‐dioxanes and the conformations of their phenyl groups
Authors: Kataev V. E. , Vul'fson S. G. , Vereshchagin A. N. , Anteunis Marc , Tavernier Dirk , Hosten Noël
Published: September 2010

The molar Kerr constants and the dipole moments of r‐2‐cis‐5‐dimethyl‐trans‐5‐ø‐1,3‐dioxane (1), r;‐2‐trans‐5‐dimethyl‐cis‐5‐ø‐1,3‐dioxane (2), 2‐methyl‐5,5‐di‐ø‐1,3‐dioxane (3), cis‐2‐methyl‐4‐ø‐1,3‐dioxane (4)‐2‐cis‐6‐dimethyl‐cis‐4‐ø‐1,3‐dioxane (5), r‐2‐cis‐6‐dimethyl‐trans‐4‐ø‐1,3‐dioxane (6) have been obtained in CCl4 at 20°C. The molecular anisotropy of 3, evaluated from the light‐scattered measurements, has also been obtained. The rotation angles of the phenyl groups with respect to the Csp2‐C‐H plane or the Csp2‐C‐CH3 plane have been determined by the comparison of the observed molar Kerr constants with those calculated for various conformations; these values emerge as (2): 60°; (3): ø‐eq. 70°, ø‐ax. 15° or ø‐eq.80°, ø‐ax.−10°; (4) and (5): 25°; (6): 60° (turning towards the oxygen atom of the dioxane cycle).
Hydrogen bond propensity of a thyroid hormone model
Authors: Herwats Luc , Laszlo Pierre , Wiertz Jean
Published: September 2010

Despite steric hindrance by the bulky iodines, the terminal OH group of thyroxine appears to be a good hydrogen‐bond donor as found from a study of the proton chemical shifts of 2, 6‐di‐iodohydroquinone in acetone and dimethyl sulfoxide.
Base‐catalyzed dimerization of ethyl‐2‐(dicyanomethylene) propanoate
Authors: Cornelis André , Failon Albert , Laszlo Pierre
Published: September 2010

We prove the structure of an earlier reported(2) dimer of the title compound. It is a six‐membered carbocycle, resulting from a double Michael addition followed by a prototropy.
Thermal cyclisation of an alleneamidine to a dihydropyridine derivative involving a 1,5‐hydrogen shift
Authors: Fuks R. , Merenyi R. , Viehe H. G.
Published: September 2010

The alleneamidins 1 has been shown to cyclise to a dihydropyridine derivative 2 by heating for a 2 hours at 220°. This reaction is assumed to proceed via a (1, 5 a)‐sigmatropic hydrogen shift followed by a 6 π‐electrocyclisation. An attempt has been made to extend this new heterocyclisation.
The stereochemistry of the tetrahydropyranes formed by reacting 4‐methyl‐4‐penten‐2‐ol with acetaldehyde. Evidence for a hemiacetal intermediate
Authors: Tavernier Dirk , Anteunis Marc , Hosten Noël
Published: September 2010

4‐Methyl‐4‐penten‐2‐ol reacts in acidic medium with acetaldehyde to give a mixture of r‐2, cis‐4‐, cis‐6‐, & r‐2, trans‐4, cis‐6‐trimethyl‐4‐tetrahydropyranol (2) and r‐2, cis‐4‐, cis‐6‐, & r‐2, trans‐4, cis‐6‐trimethyl‐4‐(4′‐methylidene‐2′‐pentoxy)‐tetrahydropyrane (3). The third possible isomer, the trans‐2, 6‐dimethyl derivative, could not be detected. This stereochemical outcome strongly suggests a hemiacetal intermediate. The dehydration products of 2, cis‐2,6‐dimethyl‐4‐methylidene‐tetrahydropyrane (5) trans‐and cis‐2, 4, 6‐trimethyl‐5, 6‐dihydro‐2, pyrane (6 and 7) are reported. A half‐chair form for 6 follows from its 1H‐nmr spectrum.
Evaluation par spectromètrie infrarouge des grandeurs thermodynamiques d'association de quelques phosphates, phosphoramides et phosphoramidates propargyliques en solution dans le tetrachlorure de carbone
Authors: Paugam Jean‐Paul , Lauransan Jacques
Published: September 2010

Les constantes thermodynamiques de la complexation de phosphates, de phosphoramidates
et de phosphoramides propargyliques ont été déterminées par spectrométrie infrarouge, d'une part avec le p‐chlorophénol (PCP), d'autre part avec le diméthylsulfoxyde (DMSO).
Nous situons ainsi ces composés comme de très bons accepteurs de proton (380 < K < 4000 1.mole−1) tandis qu'ils ne sont que faiblement donneurs (K < 1 l.mole−1). Dans des cas particuliers, les enthalpies de complexation avec le DMSO et le PCP ont été évaluées ainsi que la constante d'autoassociation.
Contribution à l'étude theorique de la liaison hydrogène II. Les dimères de l'acide sulfhydrique
Authors: Leroy G. , Louterman‐Leloup G. , Ruelle P.
Published: September 2010

L'étude ab initio des dimères de l'acide fluorhydrique est le troisième exemple illustrant notre approche théorique de la liaison hydrogène. Les résultats obtenus confirment les précédents: la structure linéaire est la plus stable; la chaleur de formation de ce complexe vaut‐5.766 kcal m−1; la distance d'équilibre correspondante (1.627 Å) est inférieure à la somme des rayons de Van der Waals du fluor et de l'hydrogène; le transfert de charge est important; le lien hydrogène se forme dans l'axe d'un des centroïdes localisé sur l'atome de fluor ou encore dans le creux de potentiel électrostatique créé par la molécule qui reçoit l'hydrogène.
Biosynthèse de L'Averufine et de la Versicolorine B: Deux Metabolites de L'Aspergillus Versicolor
Authors: Berger Yves , Jadot Joseph
Published: September 2010

The labeling distribution of averufin and versicolorin B produced from (1‐13C) acetate by Aspergillus versicolor was determined by 13C FT NMR. The results support the polyketide hypothesis for averufin and versicolorin B biogenesis. The pattern of versicolorin B indicates a biogenetic relationship with bisfuranoids, sterigmatocystin and aflatoxins.
Chemical studies of marine invertebrates XIX. Glycosidic chain structure of thelothurins A and B, two new saponins from the Indo‐pacific sea cucumber Thelonota ananas Jaeger (Echinodermata)
Authors: Kelecom A. , Tursch B. , Vanhaelen M.
Published: September 2010

The Indo‐pacific sea cucumber Thelonota ananas contains two new triterpene saponins, thelothurins A and B. Both have the same glycosidic chain shown to be 3‐0‐methyl‐β‐D‐glucosyl‐(1→4)‐β‐D‐xylosyl‐(1→4)‐β‐D‐glucosyl‐(1→4)‐2‐0‐X‐3‐0‐methyl‐β‐D‐glucosyl‐(1→3'β‐aglycone A or B) (IA/B), where X is an hitherto unidentified substituent.
L'Utilisation d'orbitales Localisées dans l'Étude Theorique des Molécules III. Les Derivés Heteroatomiques
Authors: Clarisse F. , Leroy G. , Peeters D.
Published: September 2010

L'étude de la transférabilité des orbitales localisées et de leurs propriétés a été étendue aux composés hétéroatomiques. Des composés de référence permettent d'établir une systématique tant au niveau des orbitales de liaison qu'à celui des éléments de matrice qui leur sont associés. La transférabilité des éléments de Fock permet d'élaborer une méthode LCLO‐MO paramétrique applicable aux hydrocarbures saturés, insaturés et composés hétéroatomiques. Quelques applications montrent l'intérêt de la méthode.
Conjugative stabilization in organosilicon reactive intermediates
Authors: Heaton Marie , Rogers Pamela Z. , Davis Dennis D.
Published: September 2010

Molecular orbital theory is used to study the effects of conformation and geometry on the stabilities of β‐SiR3, (R=CH3, H) substituted‐ethyl cations, radicals and carbanions. Both the radical and cation slightly favor a three‐centered cyclic form over a highly distorted, bisected open form (C‐C‐Si < = 75°), while the anion prefers the open form. The distortion is due to strong interaction between the carbon‐pz and the d‐orbitals on silicon (p‐d homoconjugation). A separation of conjugative effects based upon conformational dependence of hyperconjugation suggests that both hyperconjugative and homoconjugative stabilization are of major importance in stabilizing the cation, whereas the latter appears more important in the radical and anion.

Specific‐site solvation of the cation by water shows a large steric effect at silicon and generally responds to charge density at other centers.