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O F T H E A M E R I C A N CHEMICAL S O C I E T Y Registered in U S . Parent Oflice. 0 Copyright, 1977, bj' the American ChemicalSociety
 

Summary: TOURNALJ
O F T H E A M E R I C A N CHEMICAL S O C I E T Y
Registered in U S . Parent Oflice. 0 Copyright, 1977, bj' the American ChemicalSociety
VOLUME 99, NUMBER5 MARCH2, 1977
Molecular Orbital Theory of the Electronic Structure of
Molecules. 33. The Effect of a-Electropositive
Substituents on the Stabilitiesof Carbenium Ions
Yitzhak Apeloig,la Paul v. R. Schleyer,*lband J. A. Poplelc
Contributionfrom the Departments of Chemistry, Princeton University,
Princeton, New Jersey 08540, Carnegie-Mellon University,
Pittsburgh, Pennsylvania 15213, and the Institut fur Organische Chemie der
UniversitatErlangen-Niirnberg,8520 Erlangen, West Germany.
Received February 3, I976
Abstract: The effect of substituents, X, on the stabilitiesof a-substituted methyl, ethyl, and vinyl cations is studied by standard
ab initio procedures. X is varied systematically along the whole series of the first short period substituents, Li, BeH, BH2, CH3,
NH2, OH, and F. SiH3 was included because of the availability of experimental evidence. It is found that electropositive sub-
stituents can be extremely effective in stabilizing carbenium ions. Lithium stabilizes the ethyl and vinyl cations even better
than the best ?r donor, the amino group; BeH, BH2, and SiH3 are roughly as effective as CH3. The methyl cation is the most
sensitive to ?r donors, while the vinyl cation is the most sensitive to u donors. Consequently,the a-lithiovinyl cation is more sta-
ble than the a-lithioethyl cation, and BeH is more effective than OH for the stabilization of thevinyl cation. The binding ener-

  

Source: Apeloig, Yitzhak - Department of Chemistry, Technion, Israel Institute of Technology

 

Collections: Chemistry