Polymerizations of ethylenic monomers initiated by superacids—I: Model study of initiation by trifluoromethanesulphonic acid

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

• Publisher: Elsevier Science
• Year: 1980
• Tongue: English
• Weight: 362 KB
• Volume: 16
• Category: Article
• ISSN: 0014-3057
• DOI: 10.1016/0014-3057(80)90116-0

✦ Synopsis

The reaction of some diaryl-substituted olefins [l,l-diphenylethylene (DPE), 1,1,3,3-tetraphenyl 1-butene (TPB) and 3-phenylindene (PI)] with trifluoromethanesulphonic acid has been studied in dichloromethane by means of u.v. and IH NMR spectroscopies. All carbocations are stable at temperatures below -30 °. In the case of DPE at -70 °, the carbocation initially formed is dimeric but is slowly transformed into a monomeric cation. The initiation step is too fast to be studied by conventional means except for TPB where a first order rate with respect to the olefin has been observed.

For DPE and TPB, when the ratio olefin/acid is high, a 33~o yield in carbocations with respect to CF3SO3H is obtained for the whole range of acid concentration investigated (10-4-1 moi I-1). In the case of PI, the yield is 50~. IH NMR spectra clearly show that some acid remains unreacted in the presence of olefin. The large downfield shift of unconsumed acid is consistent with the existence of complex anions CF3SO~, (HOSO2CF3)2 and CF3SO 3, HOSO2CF3 resulting from strong hydrogen bonds between the triflate anion and its conjugate acid.