Monothiophosphoric acid

Additionally, they observed a second pathway, hydrolysis through dealkylation leading to a secondary ester of phosphoric acid which still contains the p-nitrophenyl moiety, i.e., de-ethyl Parathion (O-clhyl-O-p-nilrophenyl-monothiophosphoric acid) ... 

Kabachnik and co-workers have determined the pKa s of a number of dithio- and monothio-organophosphorus acids and considered the thiol-thione tautomeric equiUbria of monothiophosphoric acids. For most monothio acids the tautomeric equlibrium is shifted toward the thione form. There are slight changes in the pKa s of O, O -dialkyldithiophosphoric acids with substituent variation. Other data U4,29i) indicates that the pKavalues are rather substituent dependent, e.g., Ref. gives pKa values of -1.10 and +0.22 for HSP(S)(OC2Hs h... 

Thio acids have already been defined (Chap. 18) as acids related to their parent oxyacids by replacement of one or more oxygen atoms by sulfur. Most thio acids themselves are unstable, but their salts are stable and some (particularly the thiosulfates and thiocyanates) are quite familiar. Organic derivatives of monothiophosphoric acid, (HO)3PS, have recently found application as insecticides. 

Mohammed S.A., Inoue K., and Yoshizuka K., Kinetics of palladium extraction with his(2-e-ethylhexyl)monothiophosphoric acid in a hollow fiber membrane extractor. Ind. Eng. Chem. Res. 34, 3899, 1996. 

Ho, W.S. and Wang, B., Inventors Commodore Separation Technologies Inc., Assinee. Combined supported liquid membrane/stripping dispersion process for removal and recovery of metals Dialkyl monothiophosphoric acids and their use as extractants, US Patent... 

Chlorination of acidic dithiophosphoric-0,0-dimethyl- or diethylesters results in the splitting off of sulfurdichloride and the formation of the ester chloride of monothiophosphoric acid ... 

The thio derivatives of orthophosphoric acid—tetrathiophos-phoric acid, trithiophosphoric acid, dithiophosphoric acid and monothiophosphoric acid—are imstable in aqueous media, forming HgS and H3PO4 by hydrolysis ... 

Of the four acids, however, monothiophosphoric acid is sufficiently stable that Klement obtained an 83% solution by reacting barium dithiophosphate with the stoichiometric quantity of H3SO4, followed by hydrolysis of the resulting dithiophosphoric acid to monothiophosphoric acid. 

If the concentrated acid is stored in a refrigerator at —2°C, with exclusion of air, it remains clear. Introduction of air causes turbidity because of the precipitation of S due to oxidation of the H3S which results from the gradual hydrolysis of monothiophosphoric acid. Heating the concentrated acid to 50 C, results in vigorous liberation of H3S The acid is a vitreous solid at —60°C. 

Barium dithlophosphate, required in the preparation of free monothiophosphoric acid, is produced in accordance with the Kubierschky method by precipitation from NasPOsSs solution with BaCls.-... 

Simple salts of all the ortho ions (9.375) are known and in the absence of any restricting conditions, resonance of the double bond is assumed to occur with all four linkages. The successive introduction of the S atom leads to an increasing hydrolytic instability (9.376), and acids or salts with these anions are generally not easy to prepare. Phosphoromonothioic (monothiophosphoric) acid is the most stable, and phosphorotetrathioic (tetrathiophosphoric) acid is the least Solutions of the acids in Equation 9.376 can be prepared by acidification of heavy metal salts. The latter are prepared by precipitation from solutions of their sodium salts with the appropriate metal salt. 

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