Rapid Fixation of Methylene Chloride By a Macrocyclic Amine
J C. Lee, Keith J. Stanger, Bruce C. Noll, Carlos A. Gonzalez, M Marquez, Bradley D. Smith
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.
Journal of the American Chemical Society
Ab initio molecular orbitals, C-CI activation, halide removal, macrocycles, Menschutkin reaction, supermolecule
, Stanger, K.
, Noll, B.
, Gonzalez, C.
, Marquez, M.
and Smith, B.
Rapid Fixation of Methylene Chloride By a Macrocyclic Amine, Journal of the American Chemical Society
(Accessed December 3, 2022)