Computational study of the counterion and solvent effect on stereoselectivity in SN2 reactions of cyclic nitrile anions

CHED 967

Lisa N. Morkowchuk, stlnm07@moravian.edu, Department of Chemistry, Moravian College, 1200 Main St., Bethlehem, PA 18018 and Jeffry D. Madura, madura@duq.edu, Department of Chemistry and Biochemistry, Center for Computational Sciences, Duquesne University, 600 Forbes Avenue, Pittsburgh, PA 15282.
Nitrile functional groups see extensive use in organic synthesis due to their electron withdrawing power, low steric interactions, and ability to stabilize cations, anions, and radicals. The stereochemistry of a product involving a nitrile anion is influenced by the presence of specific cations and the use of specific solvent. To determine the role of counterions and solvent on the SN2 reaction of chloromethane with asymmetric cyclic nitrile anions (1-cyano-2-methylcyclohexane anion and 1-cyano-2-methylcyclopentane anion) we performed electronic structure calculations using HF/6-31+G* and MP2/6-31+G* model chemistries. Reactants, transition states, and products were optimized to map the energy pathways of these reactions. We explored how counterion and solvent affect activation energies and stereoselectivity of these systems by studying them in the gas phase, then with a Li+ counterion, and finally with both Li+ counterion and three explicit tetrahydrofuran (THF) solvent molecules.
 

Undergraduate Research Poster Session: Physical Chemistry
2:00 PM-4:00 PM, Monday, April 7, 2008 Morial Convention Center -- Hall A, Poster

Division of Chemical Education

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008