Relative Polarity of 1,3-Dioxane and 1,4-Dioxane Studied by the Reaction Field theory and via Computer Simulation

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Etude de l'équilibre conformationnel du bromocyclohexane-D4. Données thermodynamiques et cinétiques.

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Solution Thermodynamic Studies. 7. A Thermodynamic Study of Solvent Effects on the Relative Stability of cis- and trans-Dichloroethylene: Importance of the Quadrupolar and Octupolar Electric Moments in the Reaction Field Model

Calorimetric measurements of heats of solution on the title compounds clearly show a similar solvent effect on both isomers even though the cis isomer is a dipolar molecule and the trans isomer a quadrupolar molecule. Interaction energies of both isomers with various solvents can be described by a reaction field model in which higher moments than the dipole moment are taken into account. The quadrupolar contribution is as important for the trans isomer as for the cis, and even the octupolar contribution to the interaction energy is not negligible in the case of the cis isomer. © 1982, American Chemical Society. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Importance of High Order Multipoles in the Reaction Field Model

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Etude de l'influence des groupes alkyles en position 4 sur les glissements chimiques des groupes méthyles en position 1 dans les sels de pipéridinium

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A new method for the determination of the dipole moment of an electronic excited state: The π of cyclohexanone and the 1La of indole

In this work, a new method for the determination of a Franck‐Condon excited state moment in solution is described. This method is based both on the study of the solvatochromic effect and on the use of Onsager reaction field theory. The method we propose requires (1) calorimetric measurements of the heat of transfer from solvent S1 to solvent S2 for the solute in its ground state and for a homomorph; (2) the absorption frequencies of the solute in the two solvents and (3) experimental determination of the solute and homomorph ground state dipole moments. It is easy to show that a very simple relationship exists between these various experimental quantities if the two solvents are such that the reaction field theory can be applied to describe the dipolar part of the solvent solute interactions. The use of the homomorph method permits one to take into account the variation of the cavity term from solvent to solvent and the variation of the solute solvent dispersive energy term with the nature of the solvent. Moreover, the method does not requires neither the estimation of the cavity radius nor the dangerous assumption that the dipole is centred in the cavity. This new method, which compared to older methods, must give more reliable results, is applied to the π* state of cyclohexanone and to the 1La state of indole. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA, WeinheimSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Calorimetric studies in solution solvent effect on the carbonyl n → π transition in relation with solvation of the ground and excited states: --

The relative solvation of the ground and the excited states corresponding to the n → πSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Study of NMR Relaxation of Xenon- 131 in Quadrupolar Solvents

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Solution thermodynamic studies. 5. A thermodynamic study of solvent effects on the relative stability of diastereoisomers. The trans-1,2-dibromo-4-tert-butylcyclohexane, trans-2,3-dibromodecalin, and 1-bromo-4-tert-butylcyclohexane systems

Calorimetric measurements of transfer enthalpies associated with activity-coefficient determinations lead us to a precise description of the solvent influence on the relative stability of the stereoisomers of the title compounds. This solvent influence is important since it is higher than 1 kcal/mol in solvents like C6H6 or acetone with respect to cyclohexane (in terms of enthalpy contribution). The antagonist entropy contribution does not cancel out the enthalpy contribution. The solvent effect, therefore, remains very effective at the ΔG° level. © 1980 American Chemical Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Analyse conformationnelle par RMN-VII. Derives piperidiniques

A conformational free-energy différence of -2 kcal/mole for a C4CH3 group in the N,N-dimethyl-4-methylpiperidinium salt has been derived from application of Eliel's NMR method. The attribution of the N-methyl absorptions was based on the high stereospecific dependence of the long range coupling constants 4J. Long range 4-alkyl substituent effects on the chemical shifts of the N-methyl groups were also considered. The free energy differences between the equatorial and axial conformers of 4-hydroxy-4-chloro- and 4-acetoxypiperidine have been obtained by studies on the C4-proton band-width. The ΔG° values of the dree derivatives are respectively -0·55, -0·34 and -0·56 kcal/mole while the ΔG° values for the corresponding piperidinium compounds are +0·03, +0·67 and +0·43 kcal/mole. An electrostatic attraction between the electronegative 4-substituent, carrying a partial negative charge, and the positive nitrogen atom can justify the observed variation of δG°. © 1971.SCOPUS: ar.jinfo:eu-repo/semantics/publishe