A DFT study on the mechanism for polymerization of δ-valerolactone initiated by N-heterocyclic carbene (NHC) catalysts

Diniz Lessa, Milena, Fajardo, José Renato D, Delarmelina, Maicon ORCID: https://orcid.org/0000-0002-6414-552X and Carneiro, José Walkimar de M 2021. A DFT study on the mechanism for polymerization of δ-valerolactone initiated by N-heterocyclic carbene (NHC) catalysts. Molecular Catalysis 515 , 111896. 10.1016/j.mcat.2021.111896

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Abstract

Polymerization reactions using renewable raw material as substrate (namely, δ-valerolactone) and N-heterocyclic carbenes (NHC) as organocatalysts to form polyesters were investigated by computational approaches. Two routes were investigated for the reaction, either with the NHC acting as a Brønsted base and activating an alcohol used as co-initiator or by direct nucleophilic attack of the NHC on the carbonyl carbon of the lactone, forming a zwitterionic intermediate. In agreement with previous studies, the lowest energy pathway leading to polymerization is that where the NHC activates the alcohol co-initiator, yielding a partially charged alkoxide that then performs a nucleophilic attack on the lactone. The proton affinity of the NHCs shows a high correlation with the activation enthalpy for the first reaction step. Thus, NHCs with high proton affinity stabilize the first intermediate and make the lactone ring-opening the rate-determining step for the reaction.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Chemistry Cardiff Catalysis Institute (CCI)
Publisher:	Elsevier
ISSN:	2468-8231
Date of First Compliant Deposit:	7 October 2021
Date of Acceptance:	12 September 2021
Last Modified:	03 May 2023 09:05
URI:	https://orca.cardiff.ac.uk/id/eprint/144738

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