Mirta G. Mondino

CONFORMATIONAL AND ELECTRONIC INTERACTION STUDIES OF SOME (ALKYLTHIO)-SUBSTITUTED PROPANONES AND THEIR MONO- AND DI-OXIDATED DERIVATIVES

Abstract The analysis of the carbonyl frequency shifts hyperconjugative parameters (ΔV H) along with the Non-Additivity Effect of the α-methylene carbon chemical shifts for the ethylthio- (1), ethylsulfinyl-(2) and ethylsulfonyl- (3) propanones indicated the occurrence of both π∗ CO/σ C-SOn and πCO/σ∗C -SOn interaction in the ground state of their gauche conformers. The bathochromicaly shifted n → π∗CO transition of the title compounds in relation to the parent compound indicated the existence of the π∗CO/σ∗C-SOn interaction in the excited state of their gauche rotamers.

Experimental and theoretical study of the intramolecular interactions determining the conformation of β-carbonyl sulfoxides

Information on the geometrical and electronic structures of α-methylsulfinylacetophenone, C6H5C(O)CH2S(O)CH3 2, have been obtained from X-ray diffraction analysis, UV photoelectron spectroscopy and ab initio 6-31G** calculations. A comparison of the results with those obtained from the spectra and the computations on α-methylthioacetophenone, C6H5C(O)CH2SCH3 1 and α-methylsulfonylacetophenone, C6H5C(O)CH2SO2CH3 3, together with previous results on β-keto sulfides and β-keto sulfones indicates that the CH2–S(O) bond in 2 is quasi-cis to the carbonyl group in the gas and solid phase, at variance with the other β-carbonyl thioderivatives which adopt a gauche conformation. Eigenvector analysis, electron charge distribution at various atoms and/or groups and geometric parameters indicate that the cis conformation of 2 is stabilized by a strong non-bonded interaction between the negatively charged carbonyl oxygen and the positively charged sulfur atom from which it is separated by a distance (2.8–2.9 A) much shorter than the sum of the van der Waals radii. The predominant charge transfer interaction in 3 and related sulfones occurs in the opposite direction (OSO2→ CCO). The inversion of the direction of the charge transfer (and the change of the cis/gauche orientation of the thio group) from sulfone to sulfoxide is associated with an increase of electron affinity of the thio group in the latter, and could explain its smaller thermal stability. Ab initio 3-21G* calculations on several conformations of the bis-thioderivatives C6H5C(O)CH(SCH3)S(O)CH3 4, C6H5C(O)CH(SR)SO2R (R = Me 5 and Ph 6) and C6H5C(O)CH(SOCH3)SO2CH3 7, together with X-ray diffraction (4, 6 and 7) and photoelectron spectroscopy (4) analyses confirmed the cis(SOR) and gauche(SR and SO2R) preferred orientation of the thio groups with respect to the carbonyl group as observed in the monosubstituted derivatives. In 4 and 7 the SSO atom is about 30° out of the cis plane [O(1)–C(2)–C(3)].

Preferred conformations of methylthio-acetone and -acetophenone, methylsulphonyl-acetone and -acetophenone, from molecular-mechanics and dipole-moment techniques

Abstract Preferred conformations for the title compounds are determined from calculated molecular-mechanics energies in the gaseous phase and analysis of the dipole moments measured in solvents of low dielectric permittivity, In all cases, the gauche conformer having the MeS bond situated far away from the Me(C) (or Ph(C)) group, and nearly bisecting one of the C(O)CH valleys, is predominant.

Conformational and Electronic Interaction Studies of Some β-Ketosulfoxides

ABSTRACT. The analysis of the carbonyl I.R. band and the U.V. phoelectron spectroscopic data along with the ab-initio calculations and X-ray diffraction of α-(methylsulfinyl)- and α-(phenylsulfinyl)-acetophenones indicated the predominance of the cis rotamers over the qauche ones.

Electronic interactions in 2-(ethylsulphonyl) ketones studied by ultraviolet photoelectron spectroscopy

The bands present in the low ionization energy region (Ei⩽ 12 eV) of the (He I and He II) photoelectron spectra of some aromatic (R = NO2C6H4, 4; C6H5, 5; MeOC6H4, 6; n= 1) and aliphatic (R = Me, and n= 1, 2; or 2, 3) ethylsulphonyl ketones, RC(O)(CH2)nSO2Et, have been assigned to the corresponding molecular orbitals by comparison with the assignments reported for simpler related molecules. The comparison has been assisted by the determination of the geometric structure of 6. (by X-ray diffraction) and of the model compounds HC(O)CH2SO2H and p-C6H4C(O)CH2SO2CH3(by semiempirical calculations). Oppositely charged atoms of the carbonyl and ethanesulphonyl groups are separated by distances shorter than the sum of the van der Waals radii, allowing crossed charge-transfer interactions. Low symmetry allows a deep through-space and through-bond mixing among the various group orbitals, as indicated by experimental Ei values and theoretical calculations.

Complete assignment of 1H and 13C NMR spectra of α-phenylsulfinyl-N-methoxy- N-methylpropionamide and some p-substituted derivatives

The complete assignment of the 1H and 13C NMR spectra of the diastereomeric pairs of some α‐arylsulfinyl‐substituted N‐methoxy‐N‐methylpropionamides with the substituents methoxy, methyl, chloro, nitro is reported. Copyright

Spectroscopic and theoretical studies on the conformation of some α-sulfinylacetophenones

Paulo R. Olivato,* Mirta G. Mondino, Marcelo H. Yreijo, Blanka Wladislaw, Marcelo B. Bjorklund, Liliana Marzorati, Giuseppe Distefano, Maurizio Dal Colle, Gabriella Bombieri c and Antonio Del Pra c a Instituto de Quimica, Universidade de Sao Paulo, Caixa Postal 26.077, CEP. 05599-970, Sao Paulo, SP Brazil b Dipartimento di Chimica, Universita di Ferrara, Via Borsari 46, 44100 Ferrara, Italy c Istituto di Chimica Farmaceutica, Universita di Milano, Viale Abruzzi 42, 2013 Milano, Italy