Cucurbituril-Mediated Catalytic Hydrolysis: A Kinetic and Computational Study with Neutral and Cationic Dioxolanes in CB7

Autor(es)

Scorsin, Leandro ^[1] ; Roehrs, Juliano A. ^[2] ; Campedelli, Roberta R. ^[1] ; Caramori, Giovanni F. ^[1] ; Ortolan, Alexandre O. ^[1] ; Parreira, Renato L. T. ^[3] ; Fiedler, Haidi D. ^[1] ; Acuna, Angel ^[4] ; Garcia-Rio, Luis ^[4] ; Nome, Faruk ^[1]

Afiliação do(s) autor(es)

^[1] Univ Fed Santa Catarina, Dept Quim, BR-88040900 Florianopolis, SC - Brazil

^[2] Inst Fed Educ Ciencia & Tecnol Sul Rio Grande IFS, BR-96015360 Pelotas, RS - Brazil

^[3] Univ Franca, Nucleo Pesquisa Ciencias Exatas & Tecnol, BR-14404600 Sao Paulo - Brazil

^[4] Univ Santiago, Ctr Singular Invest Quim Biolox & Mat Mol CIQUS, Santiago 15782 - Spain

• Tipo de documento: Artigo Científico
• Fonte: ACS CATALYSIS; v. 8, n. 12, p. 12067-12079, DEC 2018.
• Citações Web of Science: 7

Resumo

Cucurbit{[}7]uril (CB7) catalyzes the acid hydrolysis of alkoxyphenyldioxolanes bearing both neutral and cationic alkoxy groups. The magnitude of the catalytic effect depends on the dioxolane structure, as reflected by both the CB7 binding constants and the catalysis rate constants. However, there is no clear relationship in such a way that increasing the binding affinity (cationic dioxolanes or large alkoxy groups) does not enhance the catalytic effect. The A-1 mechanism for dioxolane hydrolysis involves the protonation and formation of a carbocation by protonated dioxolane ring opening. Supramolecular catalysis takes place through the formation of the ternary complex dioxolane@CB7@H3O+, where the hydronium ion is stabilized by hydrogen bonding with the carbonyl groups of the CB7 portal. The ternary complex evolves to a binary complex by protonation of dioxolane and release of a water molecule. It is important to note that these structures are only stable in the presence of CB7 and not in bulk water. The carbocation is formed by opening the protonated dioxolane group in the rate-determining step. The distance between the carbonyl portal of CB7 and the dioxolane group in the ternary and binary complexes (protonated and carbocation) increases with the alkyl chain length, resulting in the loss of the CB7 stabilizing effect and decrease in catalytic efficiency. The existence of two recognition motifs with cationic dioxolanes results in the formation of both 1:1 and 2:1 complexes with different catalytic properties. (AU)

• Processo FAPESP: 11/07623-8 - Utilização de métodos mecânicos-quânticos para estudo das ligações e interações químicas em sistemas auto-organizados com aplicação em catálise, química medicinal, eletrocromismo, armazenamento e conversão de energia
• Beneficiário: Renato Luis Tame Parreira
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores