A Quantum-Chemical Study of the Structure of the Complex of Dibenzo-18-Crown-6 Ether with CaCl2 and Its Reactivity in the Oxidation of Ethylbenzene

Ethylbenzene hydroperoxide (EBOOH) is used as an initiator of polymerization of anaerobic adhesives. It was experimentally established that the complex of dibenzo-18-crown-6 ether with CaCl2 (Ca2+∙DBC) accelerates the ethylbenzene oxidation. Based on quantum-chemical modeling by the PBEPBE-GD3/def2TZVP method, it was revealed that the formation of the catalyst’s intermediate adducts with the reaction system’s components is possible and energetically favorable. The O–O bond strength decreases both in α-EBOOH and in β-EBOOH in the adduct EBOOH∙Ca2+∙DBC. However, the adduct α-EBOOH∙Ca2+∙DBC promotes a more rapid decomposition of ethylbenzene hydroperoxide into radicals.