Temperature dependence sulfone reaction

Oh et al. [16] have demonstrated that a microemulsion based on a nonionic surfactant is an efficient reaction system for the synthesis of decyl sulfonate from decyl bromide and sodium sulfite (Scheme 1 of Fig. 2). Whereas at room temperature almost no reaction occurred in a two-phase system without surfactant added, the reaction proceeded smoothly in a micro emulsion. A range of microemulsions was tested with the oil-to-water ratio varying between 9 1 and 1 1 and with approximately constant surfactant concentration. NMR self-diffusion measurements showed that the 9 1 ratio gave a water-in-oil microemulsion and the 1 1 ratio a bicontinuous structure. No substantial difference in reaction rate could be seen between the different types of micro emulsions, indicating that the curvature of the oil-water interface was not decisive for the reaction kinetics. More recent studies on the kinetics of hydrolysis reactions in different types of microemulsions showed a considerable dependence of the reaction rate on the oil-water curvature of the micro emulsion, however [17]. This was interpreted as being due to differences in hydrolysis mechanisms for different types of microemulsions. 

Lequeux and Chevrie were the first to use a-monofluori-nated BT sulfones to prepare fluoroalkenes. " On their side, Ghosh and Z c " " have used fluorinated PT sulfones as well as BT sulfones to genCTate all kinds of fluoroalkenes. The ( ) versus (Z)-stereoselectivity again depends on reaction conditions. Low-temperature potassium 1,1,1,3,3,3-hexamethyldisilazide (KHMDS)-mediated condensations... 

The basic method of aryl sulfonation of polyphenylene ethers has been described in the literature [1-3,6,9,12,17]. Essentially, PPO is dissolved in chloroform and a chlorosulfonic acid diluted in chloroform, is added dropwise to the stirred polymer solution. The reaction of PPO with chlorosulfonic acid is exothermic, but when the acid solution is added dropwise, overheating is not a problem, and the reaction may be run at room temperature. As the reaction proceeds, the initially gold liquid becomes red and then brown. As the degree of sulfonation increases, a polymer-rich phase separates and eventually the polymer precipitates from the chloroform solution. The degree of sulfonation at which the sulfonated polymer precipitates from the chloroform solution depends on MW of PPO. For similar initial concentrations of polymer in chloroform (approximately 5 wt%), in case of LMW PPO the precipitation occurs when DS approaches 47% [3], while in case of HMW PPO the precipitation occurs when DS approaches 18% [17]. After precipitation of the sulfonated polymer from the chloroform solution, further sulfonation is restricted to the interface between the solution and the precipitated polymer. Consequently, the LMW PPO can be sulfonated to a considerably higher DS than the HMW PPO. The highest DS of SPPO reported in the literature is 70.5% for the polymer of MW equal to 31,000 [2]. 

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