Analysis of the Reasons for the Reaction of Chloromethyloxirane and Nucleophiles Mainly Undergo the Nucleophilic Ring Opening and Intramolecular Cyclization
XU Jia-Xi1**, MA Yuan2
1. College of Chemistry, Beijing University of Chemical Technology, Beijing 100029, China; 2. Department of Chemistry, Tsinghua University, Beijing 100084, China
Abstract Nucleophiles and primary haloalkanes generally take place bimolecular nucleophilic substitution. However, the reaction of chloromethyloxirane (epichlorohydrin) and nucleophiles first undergoes a nucleophilic ring opening of its oxirane followed by an intramolecular nucleophilic cyclization, affording final products, rather than nucleophiles directly displace its chlorine atom to give the final products. The reason is that the banana bond for the formation of small ring compounds does not overlap axially. The overlap is not efficient so that the stability of the banana bond is weaker than that of the axially overlapped bond in other compounds. Thus, nucleophiles first attack the weaker C—O σ-bond in oxiranes, the generated alkoxides further undergo an intramolecular nucleophilic cyclization, affording the final products. The reactive differences of chloromethyloxirane and primary haloalkanes are rationally explained through analysis of the forming orbitals and stabilities of the crucial chemical bonds in reactants. It would provide a deeper understanding for students.
XU Jia-Xi, MA Yuan. Analysis of the Reasons for the Reaction of Chloromethyloxirane and Nucleophiles Mainly Undergo the Nucleophilic Ring Opening and Intramolecular Cyclization[J]. Chinese Journal of Chemical Education, 2024, 45(16): 105-107.
