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Rapid Fixation of Methylene Chloride By a Macrocyclic Amine

Published

Author(s)

J C. Lee, Keith J. Stanger, Bruce C. Noll, Carlos A. Gonzalez, M Marquez, Bradley D. Smith

Abstract

A simple macrocyclic amine is alkylated by methylene chloride to give a quaternary ammonium chloride salt. When methylene chloride is the solvent, the reaction exhibits pseudo first order kinetics, and the reaction half-life at 25.0 C is 2.0 minutes. The reaction half-life for a structurally related, acyclic amine is approximately 50,000 times longer. Detailed calculations favor a mechanism where the methylene chloride associates with the macrocycle to form an activated pre-reaction complex. The macrocyclic nitrogen subsequently attacks the methylene chloride with a classic SN2 trajectory, and although the carbon-chlorine bond breaks, the chloride leaving group does not separate from the newly formed cationic macrocycle, such that the product is a tightly associated ion-pair. X-ray crystal structures of the starting amine and the product salt, as well as kinetic data, support this mechanism.
Citation
Journal of the American Chemical Society
Volume
127
Issue
No. 12

Keywords

Ab initio molecular orbitals, C-CI activation, halide removal, macrocycles, Menschutkin reaction, supermolecule

Citation

Lee, J. , Stanger, K. , Noll, B. , Gonzalez, C. , Marquez, M. and Smith, B. (2005), Rapid Fixation of Methylene Chloride By a Macrocyclic Amine, Journal of the American Chemical Society (Accessed December 3, 2022)
Created February 28, 2005, Updated October 12, 2021