Synthesis Of Functional Alkyl Disulfides And Their Application

Organic compounds bearing S–S bonds are usually called disulfides with a general structure of R-S-S-R. Functional alkyl disulfides can be looked as important intermediates for fine chemicals and have been widely applied in various fields ranging from protein engineering, natural products, organic products, medicine and nanomaterials etc. In this work, we explored the synthesis of several functional alkyl disulfides and further studied the application as modifiers for gold nanoparticles. The main results are as following points:1. Alkyl disulfides were obtained via a phase-transfer catalysis process from alkyl bromide and sodium disulfide which was prepared by sublimated sulfur and sodium sulfide. The content of target disulfide could be controlled by adjusting the molar ratio of sublimated sulfur and sodium sulfide in the first step, and the conversion of alkyl bromide can be enhanced at elevated temperature. All of these surfactants such as didodecyldimethylammonium bromide, hexadecyl trimethyl ammonium bromide, tetrabutyl ammonium bromide and tetraoctylammonium bromide could be used as phase transfer catalyst, while those organic solvents such as chloroform, dichloromethane, trichloroethylene, and carbon tetrachloride could be used as organic solvent phase.2?The optimized reaction condition includes the following items: The ratio of sublimated sulfur and sodium sulfide is 0.633, reaction temperature is 40 oC, the phase transfer catalyst is DDAB, the solvent is chloroform and the reaction time is 12 hours. The found conversion of reactant bromide can reach to 99% with a yield more than 90%. The purity of obtained products are approximately 97% without further purification, which can be considered as great advantage of the simple and environmental friendly phase-transfer catalysis method for direct synthesis of alkyl disulfides.3?The phase-transfer catalysis method were directly used to prepare hydroxyl and bromo-terminated alkyl disulfides, in which the yield of bis(11-hydroxyl undecane) disulfide was 90% with a purity of 97% and that of bis(12-bromo dodecane) disulfide was 43% with a purity of 96%. The azide or alkyne terminated alkane bromides were first prepared from alkane dibromides and sodium azide or sodium alkyne, respectively, and subsequently reacted with sodium disulfide via phase-transfer catalysis process to provide bis(12-azide dodecane) disulfide(N3C12H24SSC12H24N3) or bis(11-alkyne dodecane) disulfide(HC?CC10H22SSC10H22C?CH), with final yield of 32% or 20%.4. The obtained bis(12-azide-dodecane) disulfide was modified onto the surface of gold nanoparticles via Au-S bond, and the usage of poly(ethyl glycol) thiol and 11-Mercapto undecanoic acid could enhance the stability of modified gold nanoparticles which could be well dispersed into H2O-EtOH, H2O-DMF or H2O-CH3 CN mixed solvent. In H2O-DMF(1:4) mixed solvent, the azide groups grafted on gold nanoparticle surface could react with 1,6-heptadiyne based on the click reaction mechanism under the catalysis of copper sulfate and sodium ascorbic acid, which resulted into an aggregation of gold nanoparticles.