Thion (RCSOH), Selenon (RCSeOH), and Telluron (RCTeOH) Acids as Predominant Species

Abstract

Thiocarboxylic acids, such as selenocarboxylic acids, exist predominantly in the thioxo form (RCSOH, thion acid) in polar solvents such as tetrahydrofuran (THF) at temperatures below −50 °C. Tellurocarboxylic acids (5) were observed for the first time by acidolysis of the corresponding cesium tellurocarboxylates with hydrogen chloride. The telluroic acids (6) exist predominantly in the telluroxo form (RCTeOH, telluron acid) in THF at temperatures below −70 °C. Telluron acids were reddish to blue violet for the aliphatics (R = alkyl) and dark green for the aromatics (R = aryl) and reacted with aryl isocyanates at −70 °C to give crystalline acyl carbamoyl tellurides in good yields.

Substituent effects on the tautomerism of monochalcogenocarboxylic acids XC(O)YH (X=H, F, NH2, OH, CN, and CH3; Y=S, Se, and Te): A theoretical study

“…In 1994, Kato and co-workers successfully isolated the selenoic acids RC(@O)SeH from RC(@O)SeNa (R = aryl or alkyl), which is the predominant form in the solid state and in nonpolar solvents, while in polar solvents, the tautomeric form RC(@Se)OH presents predominantly [4]. In 1996, the tellurocarboxylic acids RC(@O)TeH were characterized by the same group [5]. They concluded that for the monochalcogenocarboxylic acids, the chalcogenoxo form RC(@E)OH (E = S, Se, and Te; R = aryl or alkyl) is the predominant species in apolar solvents at low temperature, whereas the chalcogenol acid RC(@O)EH is the predominant species in both the solid state and nonpolar solvents.…”

Selenoacetic Acid, CH3C(O)SeH: Preparation, Characterization, and Conformational Properties

“…For the spectra with apodized resolutions of 0. 5 Se NMR spectra, respectively. The samples were held at 243 K, and CD 3 OD was used as an external lock and reference.…”

The hydrogen bond donor and acceptor ability of thioformic acid

“…Theoretical results also suggested the thiol form to be the most stable in the gas phase with its presence in both cis and trans conformers. Kato et al [47] on the other hand deduced that the thione form [RC(=S)OH] to be predominant in polar solvents at very low temperatures on the basis of IR and NMR studies. They rationalized the higher stability of thione form in terms of stronger interactions of O-H bond with the polar solvent molecules.…”