PROCESS FOR THE PREPARATION OF DISULFIDES FROM THIOLS

Abstract: The process oxidizes thiols to disulfides using elemental selenium as a catalyst. Elemental selenium complexes with the thiol to form the species RSSe- which is rapidly oxidized by molecular oxygen to the disulfide RSSR.

Description: Description Process for the preparation of dlsulfides from thlols The present Invention relates to a process for the preparation of dlsulfides by oxidizing thiols in the presence of a catalyst in aqueous solution. Several catalysts are known to catalyze the oxidation of thiols to dlsulfides according to the equation These catalysts include CuClα,FeCl 3 ,and Na a Se0 3 .The preparation of dlsulfides as a result of the oxidation of alkylthlols with 0^ in the presence of cuprous chloride has been described in an article by D.W. Giles,J.A. Cha and P.K. Lim in Chemical Engineering Science,Vol. 1,No.12,pp.3129-3140,1986. The present invention provides a process for the preparation of dlsulfides in aqueous solution by oxidizing thiols with molecular oxygen in the presence of a catalyst in the temperature range in which water is a liquid. R = H.alkyl group or other organic moieties ) The catalyst is elemental selenium which is solubilized by complexing with sulfides according to the equation RS~+ Se . -RSSe " (3) The thiol containing molecule that was used is mercaptoethanol which was deprotonated using sodium hydroxide solution HOCHaCH^SH + NaOH >H0CH^CH 2 S"Na + + H a O (-4.) The deprotonated mercaptoethanol complexes with selenium according to the equilibrium HOCH 2 .CH 2 .S~ + Se * -=-≥H0CH 2 .CH a SSe * (5) The equilibrium constant for the above equilibrium is given by the equation K = HOCHaCH-iSSe-] (6) LHOCHiCHaS-] The equilibrium constant was found to be O.36. Saturation was achieved after approximately 2 hours of vigorous stirring. If oxygen is passed through the solution containing HOCH j CH^SSe" anlons,the HOCHaCHjjSSe ' anions are rapidly oxidized to the disulfide H0CH 2 CH2.SSCH 2 CH a 0H with a yield exceeding 95%. Selenium catalyzes the oxidation of thiols according to the equations ( RS " + Se ^RSSe " ) 2RS~+ 2H + + -0- 2 . >RSSR + H 2 (7) As the HOCH^CHaSSe " anlons are oxidized,the solubilized selenium precipitates out of solution in the form of grey selenium. Eventually, ll the solubilized selenium precipitates out of solution. Example 0.5g of selenium and 50ml of water was placed in a 250ml flask. 0.5ml of mercaptoethanol was added to the flask. The mercaptoethanol was deprotonated by adding 71.68ml of 0.1N NaOH to the flask. The solution was stirred with a magnetic stirring bar until equilibrium was reached after 2 hours. Oxygen was passed through the solution for 10 minutes using a fritted glass attachment to oxidize mercaptoethanol to the disulfide HOCH^CH^SSCHaCH^OH. THE EMBODIMENT OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED IS DEFINED AS FOLLOWS t 1. A process for preparing dlsulfides in aqueous solution by oxidizing thiols with oxygen in the presence of a catalyst characterized in that the catalyst is elemental selenium. 2. A process according to claim 1 in which the thiols have the formula R-SH wherein R is hydrogen,an alkyl group or other organic moieties. 3. A process according to claim 1 or 2 in which sodium hydroxide is added.

Claims: AMENDED CLAIMS [received by the International Bureau on 26 November 1993 ( 26.11.93 ) ; original claim 2 amended ; other claims unchanged ( 1 page ) ] THE EMBODIMENT OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE IS CLAIMED IS DEFINED AS FOLLOWS t 1. A process for preparing dl sulfides in aqueous solution by oxidizing thiols with oxygen in the presence of a catalyst characterized in that the catalyst i s elemental selenium. 2. A process according to claim 1 in which the thlols have the formula R-SH wherein R i s hydrogen or alkyl . 3. A process according to claim 1 or 2 in which sodium hydroxide i s added.

Inventors: CHAUDHRY OMAR, CHAUDHRY, OMAR
Applicants: CHAUDHRY OMAR, CHAUDHRY, OMAR
Application year: 1993
Main classification: C07C319
IPC codes: B01J27, C07C319, C07C323