Analyse structurale des derives fonctionnels des acides carboxyliques. Partie II. Halogeno et cyanoacetates de methyle

Article abstract of DOI:10.1016/0022-2860(91)80133-O

Methylene bending mode analysis and dipole moment determinations were carried out in solution (CCl4) for some methyl esters ΣCH2CO2Me with Σ =F(I), Cl(II), Br(III), I(IV), CN(V), in order to identify the conformers induced by ΣCH2 group rotating motion and determine their relation amounts.The results are consistent with the existence of two conformations; syn and anti for (I), syn and gauche for (II) and (III).Compounds (IV) and (V) occur almost exclusively in gauche and syn forms respectively.A theoretical study of compounds (I), (II) and (V) by P.C.I.L.O. methods and the Onsager formalism was performed.The collected data show that the conformers have the O-Me bond syn to the carbonyl.The calculated value of ΔE for the equilibrium between the syn and anti rotamers (E_a-E_s =600 cal mol^-1) is in good agreement with ΔH⁰₂₉₈ estimated from the temperature-dependence studies (ΔE =158 cal mol^-1).