Monothioformic acid

An ab initio study of the unimolecular pyrolysis mechanisms of monothioformic acid (363) has yielded activation energies for dehydrogenation and dehydrosulfidation. ... 

Unimolecular pyrolysis of the tautomers of monothioformic acid (two conformers of thiol- and two conformers of thiono-) have been studied by ab initio methods with STO-3G and 6-31 G basis sets. The barrier heights for dehydrogenation (via a four-centre transition state) and dehydrogensulfldation (via a three-centre transition state) of thiol formic acid are 67.47 and 67.09 kcalmol" respectively. Dehydration of 5-cw-HCSOH occurs via a three-centre transition state with an activation energy of 81.18 kcalmoG this is much greater than for dehydration of the s-trans form, which occurs via a four-centre transition state with a barrier of only 68.83 kcalmol" ... 

Insertion of CSj in metal-hydride bonds gives metal dithioformates. Bonding of the ligands to the metal can take place in several ways (a) ionic in alkali and alkaline earth metal compounds (b) symmetric bidentate in most of the transition metal complexes and (c) as a positive symmetrically bonded ligand to (25), in which the HC(S)S has donated two electrons to the two electron-deficient dicarbanonaborane groups.36 Little is known about monothioformic acid and its complexes. 

Formic Acid, Formates, etc. The structure of monothioformic acid has been determined in an analysis of the microwave spectra of isotopically substituted species of HCOSH. Two distinct but similar spectra were observed which could be assigned to a mixture of trans (24) and cis (25) isomers of HCOSH. No evidence for either isomer of HCSOH was obtained. Preliminary values of r(C—S) and OCS were calculated for both isomers. 

Synthesis.— In an attempt to synthesize dithioformic acid by the action of dilute hydrochloric acid on potassium dithioformate (the product of the reaction between chloroform and potassium sulphide ), Gattow and Engler obtained a material consisting mainly of trimeric dithioformic acid. Recently, the same workers have also shown that the polymer of monothioformic acid in aqueous potassium hydroxide may undergo disproportionation, yielding equal amounts of formate and dithioformate anions. 

A theoretical study has been performed on the influence of solvent on the thiol-thione tautomeric equilibrium of monothioformic acid [see (417) (418)], and... 

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