Alain Massat

Infrared study of indolecarboxylic acids associations with lanthanide acetates

Abstract IR spectra of three indole-carboxylic acids, including 2-indolecarboxylic acid, 5-indolecarboxylic acid and 3-indoleacetic acid have been investigated in their crystalline form (KBr pellets) and in DMSO solution, in the presence and the absence of lanthanide (Dy3+, Er3+, Eu3+, Nd3+ and Yb3+) acetates. This study demonstrates that complexes are formed between indole carboxylates and Ln3+ ions, providing evidence for proton transfer processes between indolecarboxylic acids and lanthanide acetate ions. Monodentate and bidentate structures are proposed for these complexes.

Influence of the structure of ketones and acidity of phenols upon their complexation processes: Part 2. n- vs. π-complex competition depending on ketone branching and phenol acidity☆

Abstract For phenol-alkylketone associations, lineshape analysis of the associated ν OH band allows for the separation of two different complexes attributed either to π or n (lone-pair) carbonyl electrons. Using an original methodology, individual constants K n and K π have been evaluated and their evolution according to the structure of the two partners (ketone and phenol) characterized by a factor analysis treatment. For n -complexes, reduced ketone characteristics K nc are proportional to the number of branches alpha to the carbonyl, K π being insensitive to the structure of the ketone. Both K n and K π are linearly related to the phenol acidity, but with different sensitivities. This induces striking differences in the relative weight of the n - and π-complexes depending on the ketone-phenol pair investigated. For ortho -halogenophenols, the influence of intramolecular hydrogen bonding is discussed.

Equilibre entre conformation a double liaison CO ou CC eclipsee et conformation a double liaison decalee de ⋍ 60° par rapport a l'eclipse: etude comparative par spectroscopie ir d'un carbure, d'un amide, d'un aldehyde et d'une cetone

Abstract The infrared vCO band of the ketone MeCOCH2C(Me)3 displays a splitting with two maxima whose components are attributed to two rotamers. The geometries of these rotamers are calculated by an a priori vibrational analysis.

Influence de la structure des cetones et de l'acidite des phenols sur leur mode de complexation: Partie I. Comportement global et échelles d'acidité et de basicité

Abstract Associations between methyl or halogenated phenols and saturated aliphatic ketones of varied hindrance in positions α or β to the carbonyl group are studied with regard to the search for behavioral similarities and determination of the influence of phenol chelation or steric hindrance of one of the association partners. From a statistical treatment by Principal Component Analysis on 147 couples of ketone-phenol dimers it can be inferred that overall the association constants K pc and the associated OH bandwidth (Δν 1 2 ) OH can be factorized into a product of reduced characteristics, which expresses the association aptitude of each phenol or ketone. Thus phenol donor characteristics K p (Δν 1 2 ) p are linearly related to their p K a values at least in the absence of bisubstitution at ortho positions. For ortho substituted phenols, reduced bandwidths (Δν 1 2 ) p do not depend on intramolecular auto association, and so allow for determination of actual ketone-phenol association constants (and estimation of chelation constants). Comparison of ketone reduced characteristics with the usual basicity scales (association constant with parafluorophenol or iodine, solvation parameters, ν CO frequencies) assess the scope of our proportionality model. The specific behavior of saturated aliphatic ketones when compared to other carbonyl derivatives is interpreted through conformational effects acting differently on accessibility or stretching frequency ν CO of the carbonyl.

Etude infrarouge des effets de structure et de solvant sur la frequence itvC=O de cetones aliphatiques saturees. Relation frequence- topologie-milieu

Abstract The sensitivity of saturated aliphatic ketone stretching frequencies, vCO to structure and solvent effects is expressed by a four-term equation vco = 1740 + I(XXX) -0.24 G + 2.10−3 G ·I(XXX) The four terms represent: the frequency of the base element (acetone) calculated in the absence of intermolecular interactions; the contribution of intramolecular environment E given by structure parameter I(itXXX) previously established in gas phase; that of the intermolecular environment related to the Allerhand and Schleyer G parameter; that of solvent-solute interactions. This equation covers an experimental range of 78 cm−1 for 192 measurements in four highly diverse solvents (C6H14, CC14, CH3CN, CHBr3) with a standard deviation of 1.6 cm−1; it expresses an overall statistical behavior, but masks individual behaviors. The latter are determined by comparing two characteristic parameters of ketones, a topological parameter I(XXX), and p expressing solvent sensitivity [slope of straight lines ν = f(G)]; they are Interpreted in terms of geometrical effect, variation of valency angles and of conformations.

Conformational identity change of 3-methylbutanone from gaseous phase to solutions: An IR vibrational spectroscopy study

Infrared vibrational spectroscopy of 3-methylbutanone [Me(CO)iPr] leads to two conclusions: (1) The conformational identity is different in the gas phase and in various solvents. (2) In the gas phase, type B rovibrational structures are observed. Thus, the molecular symmetry isC5. The following interpretation is based upon a model which implicitly takes the solvent into account in the framework of an empirical calculation. The solvent increases the interconversion barrier between two enantiomers. As a consequence, the molecule changes conformation, moving from the stable conformation with bisected carbonyl seen in the gas phase, to a conformation with an eclipsed carbonyl in solutions.

IR studies of iron complexes with pyridoxal isonicotinoyl hydrazone and three other similar chelating agents

Abstract Infrared studies of pyridoxal isonicotinoyl hydrazone and of three similar chelating agents in solid state brings out, after complexation with iron (III), the deprotonation of phenol for all the compounds; for those which possess the pyridoxal group, a deprotonation of hydrazine leads to a transformation of the linkage between the rings and for the others, the drastic shift of the carbonyl band proves its engagement in the association with iron.

The υCY doublet in the IR spectra of neopentyl (CH3)3CCH2C(Y)Z compounds. evidence for the existence of a conformational equilibrium for (CH33CCH2COCH3 in solution.

Abstract The associative behavior of neoPe-CO-Me and the solvent sensitivity of the neoPe-CO-R ketones provide evidence supporting the hypothesis of a conformational equilibrium accounting for the splitting of the υ CY band of the title compounds.

Associations phenols alkyl cetones: analyse du massif νOH et compétition entre associations n et π

Abstract n vs π competition in phenols-alkyl ketones association is assesed as a function of phenols acidity and of a branching to the carbonyl group ; inversion of the association ratio π/n is demonstrated.