Polymerizations of ethylenic monomers initiated by superacids—II: Complexation of some trifluoromethanesulphonates by their conjugate acid

✍ Scribed by D. Souverain; A. Leborgne; G. Sauvet; P. Sigwalt

• Publisher: Elsevier Science
• Year: 1980
• Tongue: English
• Weight: 405 KB
• Volume: 16
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(80)90117-2

✦ Synopsis

A~tract--lonic trifluoromethanesulphonates (triflates) are strongly solvated with their conjugate acid in dichloromethane (Ph3C +, n-Bu,N +, Ag ÷ ) and acetonitrile (Na +, Ag + ). A ~H and t gF NM R study of the chemical shifts of various acid-salt mixtures show that in CH2CI2 three homoconjugates A-' HA, A-. (HA)2 and A-(HA)3 were formed with large formation constants whereas in acetonitrile only the 1:1 homoconjugate was formed with an equilibrium constant KI ~ 4 1. M-I. This result explains why the protonation by CFaSO3H of non-polymerizable olefins such as l,l-diphenylethylene and 3-phenylindene is always incomplete (1/3 and 1/2 respectively) in CH2CI 2. Conditions in which covalent triflates could be obtained have been investigated. As a consequence of homoconjugation, reaction of Ph3COH with triflic anhydride led to Ph3 C+ CFsSO~-' HOSO2CFs. Other tertiary alcohols were dehydrated by triflic anhydride and led to ethylenic compounds (l,l-diphenylethanol) or ethers (2-phenyl 2-propanol). Esters were only observed in the case of benzyltriflate (at -20 °) and in the case of l-phenylethyltriflate which is a model of polystyryltriflate (stable at room temperature).