Synthesis and characterization of carboxylic acid‐terminated polyisobutylenes

Abstract

tert-Chloride-terminated polyisobutylenes (PIB) (1020 M n 6700 g/mol) were dehydrochlorinated nonregiospecifically using basic alumina, or regiospecifically either via potassium tert-butoxide or in situ quenching of quasiliving PIB. Olefin-terminated PIBs were quantitatively ozonized at À78 8C using hexane/methylene chloride/methanol, 62/31/7 (v/v/v) cosolvents, and an ozone generator, employing pure oxygen as source gas. The primary ozonides were reduced using trimethyl phosphite to yield pure PIB methyl ketone from exo-olefin PIB, and a mixture of PIB methyl ketone and PIB aldehyde from mixed olefin-PIB. PIB methyl ketone was oxidized to carboxylate via the haloform reaction; titration revealed near-quantitative functionalization, but the reaction was slow. Tetrahalomethane oxidation was identified as a preferred alternative method, and was conducted using either CCl 4 as the reaction solvent, THF as the solvent with CCl 4 in reagent amounts, or hexane as the solvent with a phasetransfer catalyst and CCl 4 in reagent amounts. The system using hexane, with tetran-butyl ammonium chloride as phase-transfer catalyst, showed complete conversion in $ 4 h. PIB carboxylic acid was recovered by acidification and isolation. V

End-Quenching of TiCl4-Catalyzed Quasiliving Polyisobutylene with Alkoxybenzenes for Direct Chain End Functionalization

“…6 Such conditions naturally lead to tert-chloride functionality at the chain end, 7 and postpolymerization dehydrochlorination would still be required to synthesize exo-olefin telechelic PIB. [8][9][10] Olefin-terminated PIB has been subjected to numerous postpolymerization transformations, including hydroboration-oxidation, 11 hydroformylation, 12 epoxidation, 13 ozonolysis, 14,15 lithiation, 16 sulfonation, 17 hydrosilylation, 18 and hydrobromination. 19 The terminal unsaturation has also been used as a Friedel-Crafts alkylating agent 20 and a substrate for the free radical addition of thiols.…”

“…Olefin-terminated PIB has been subjected to numerous postpolymerization transformations, including hydroboration−oxidation, hydroformylation, epoxidation, ozonolysis, , lithiation, sulfonation, hydrosilylation, and hydrobromination . The terminal unsaturation has also been used as a Friedel−Crafts alkylating agent and a substrate for the free radical addition of thiols .…”