Spectroscopie RMN du Carbone‐13 de Thiocétones Aliphatiques: Propanethione et Dérivés, Thiocétones Bicycliques et α Cyclopropaniques

Abstract

Carbon-13 N M R spectra of various aliphatic ketones and tbioketones were determined and interpreted. As shown by the relation between OC chemical sbifts in C=A groups, the C=S is more sensitive to the substituents than the C=O group. Conjugative effects are more pronounced in a-cyclopropyl thioketones than in a-cydopropyl ketones. Compte tenu des remarques suivantes nous avons tent6 de relier So, S, et o, en restant conscient de ce que, en skrie cktonique, les variations AE ont une part non nkgligeable dans les variations de 6 , : RESULTATS ET DISCUSSIONS S6rie aliphatique(1) Pour A fixe (0 ou S) le terme Q, peut Ctre relik h la somme des constantes a, de Taft des substituants X et l'on peut admettre en premikre approximation que ? L a prtsence de radicaux alcoyles au voisinage du groupe carbonyle entraine un kger dtplacement bathochrome de la transition m* + n (Rtf. 5); on peut d'ailleurs relier le dkplacement chimique 6, des cktones aliphatique avec la valeur A,(a* + n) (Rkfs. 6-8). Il n'y a pas de relation directe dans le cas des thiocktones: la position du A,, ne vane pas lintairement avec le nombre de substituants en a (cf. Rtf. 9). Par contre elle varie beaucoup quand on passe d'une &tone la thiodtone homologue. On ne pourra donc pas relier les valeurs SI3C(=0) et 6I3C(=S) en terme de densitt de charge uniquement (cf. Rtf. 2).

Comparative study of the 13C nuclear magnetic resonance shifts of carbonyl and thiocarbonyl compounds

“…Statistical analysis of all the compounds of Group I1 yields Eqn (5) (correlation coefficient 0.9925 and standard error 3.8), which can be compared with Eqn (2). 6(C=S) = 1.53 6(C=O) -63.2 (5) The C=O vs C=S shifts of the ureas and thioureas 2426 ( Table 1) would be expected to be linearly related, in view of Kalinowski's and Kessler's work,3 which interpreted this correlation mainly in terms of the mean excitation energy in the paramagnetic screening term.3…”

Isolation of a Novel Antibacterial Phenyl Thioketone from the Seagrass, Cymodocea serrulata

“…Andreiu et al . () identified a variety of chemical shifts on carbon‐13 NMR spectra for an array of aliphatic ketones and thioketones and assigned thioketone values to be in the range of 35–41 ppm that well falls in line with the present datum (37.5 ppm). It is an established fact that alkanes resonate well between 11 and 25 ppm on the basis of differences in substitutions and the present investigation proves a characteristic alkane signal at 20.1 ppm.…”

Aromatic Versus Heteroradialene Character in Extended Thiophloroglucinol Ligands and their Trinuclear Nickel(II) Complexes

“…[94] Even though the free thiosalen ligand is not accessible, Bergman et al were able to crystalize and characterize the methyl ketimine analog. However, it has also been reported that the influence of substituents on this resonance is more pronounced [96] and that the C Ar S resonance is a rather bad probe for the evaluation of electronic structures. The even larger low-field shift of this signal in H 3 S 3 can therefore be interpreted as an even stronger contribution of the thione-enamine resonance structure VIII in H 3 S 3 .…”

“…The even larger low-field shift of this signal in H 3 S 3 can therefore be interpreted as an even stronger contribution of the thione-enamine resonance structure VIII in H 3 S 3 . However, it has also been reported that the influence of substituents on this resonance is more pronounced [96] and that the C Ar S resonance is a rather bad probe for the evaluation of electronic structures.…”