Energy difference between the classical and the nonclassical 2-norbornyl cation in solution. A combined ab initio Monte Carlo aqueous solution study

Journal Article · Wed Mar 08 04:00:00 EST 1995 · Journal of the American Chemical Society; (United States)

DOI:https://doi.org/10.1021/ja00114a037· OSTI ID:6765932

Schreiner, P R; Schleyer, P R ^[1]; Severance, D L; Jorgensen, W L ^[2]; Schaefer, III, H F ^[3]

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1. Univ. of Georgia, Athens, GA (United States) Institut fuer Organische Chemie der Universitaet Erlangen-Nuernberg (Germany)
2. Yale Univ., New Haven, CT (United States)
3. Univ. of Georgia, Athens, GA (United States)

The hypothesis that the relative energies of anchimerically assisted solvolysis reactions are very similar in the gas phase and in solution, implying that relative carbocation stabilities are the same in both media, is probed in the present work by including solvent effects in the energy computations. We chose water as our solvent since we expect the difference in solvation energies to be large in highly polar media. Results show that the classical 2-norbornyl cation (2) is not significantly more stabilized in aqueous solution than the nonclassical ion (1). Thus both the gas phase ab initio computations and Monte Carlo solution simulation come to the same result. In less polar solvents, the solvation energies are expected to be even more similar. Our results confirm that the nonclassical form 1 of the 2-norbornyl cation is the only stable form in the gas phase and in solution. The classical form 2 is unlikely to be involved in solvolysis reactions. As a consequence, the differences in rates of solvolysis for 2-exo and 2-endo norbornyl derivatives can only be explained in terms of the differences in the exo vs endo transition states. 15 refs., 1 fig.

• DOE Contract Number: FG05-94ER14428
• OSTI ID: 6765932
• Journal Information: Journal of the American Chemical Society; (United States), Journal Name: Journal of the American Chemical Society; (United States) Vol. 117:9; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

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AQUEOUS SOLUTIONS
CALCULATION METHODS
CATIONS
CHARGED PARTICLES
DISPERSIONS
ENERGY
FREE ENERGY
HYDRATION
HYDROCARBONS
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MIXTURES
MOLECULAR ORBITAL METHOD
MOLECULAR STRUCTURE
MONTE CARLO METHOD
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
SOLUTIONS
SOLVATION
THERMODYNAMIC PROPERTIES