Ring-opening polymerization of ε-caprolactone catalyzed by sulfonic acids: computational evidence for bifunctional activation.
The mechanism of ring-opening of ε-caprolactone by methanol catalyzed by trifluoromethane and methane sulfonic acids has been studied computationally at the DFT level of theory. For both elementary steps, the sulfonic acid was predicted to behave as a bifunctional catalyst. The nucleophilic addition proceeds via activation of both the monomer and the alcohol. The ring-opening involves the cleavage of the endo C-O bond of the tetrahedral intermediate with concomitant proton transfer. In both cases, the sulfonic acid acts as a proton shuttle via its acidic hydrogen atom and basic oxygen atoms. The computed activation barriers are consistent with the relatively fast polymerizations observed experimentally at room temperature with both catalysts.
Susperregui
Nicolas
N
University of Toulouse, INSA, UPS, LPCNO, 135 Avenue de Rangueil, F-31077 Toulouse, France.
Delcroix
Damien
D
Martin-Vaca
Blanca
B
Bourissou
Didier
D
Maron
Laurent
L
D002384:Catalysis; D005617:Chlorofluorocarbons, Methane / Q000737:chemistry; D003198:Computer Simulation; D006860:Hydrogen Bonding; D000432:Methanol / Q000737:chemistry; D015394:Molecular Structure; D011091:Polyesters / Q000138:chemical synthesis* / Q000737:chemistry; D013451:Sulfonic Acids / Q000737:chemistry*
D005617:Chlorofluorocarbons, Methane; D011091:Polyesters; D013451:Sulfonic Acids; C016240:polycaprolactone; D000432:Methanol; C009554:fluoroform