Abstract
The acyclic o-oxygen benzyl carbocation 1, the 6-membered-ring endocyclic o-oxygen benzyl carbocation 2, and the 5-membered-ring endocyclic o-oxygen benzyl carbocation 3 were used as model compounds to get insights into the general phenomenon for the unusual stability of the 5-membered-ring endocyclic benzyl carbocations in aqueous solution. The hydride-ion affinities of 1, 2, and 3 in gas phase, acetonitrile, and DMSO were calculated and compared by the density functional theory method, and 3 isodesmic reactions were designed to confirm their thermodynamic stability. What we found is that the 5-membered-ring endocyclic o-oxygen stabilizes the benzyl carbocation 3 less than the acyclic o-oxygen stabilizes the benzyl carbocation 1 in gas phase because of ring strain and through-bond induction. However, the high solvation energies of the 5-membered-ring endocyclic o-oxygen benzyl carbocation 3 not only offset the destabilizing effects of ring strain and through-bond induction but also make it even more stable than the acyclic o-oxygen benzyl carbocation 1 in polar solvents like acetonitrile, DMSO, and water.
| Original language | English |
|---|---|
| Article number | e3863 |
| Journal | Journal of Physical Organic Chemistry |
| Volume | 31 |
| Issue number | 10 |
| DOIs | |
| Publication status | Published - 2018 Oct 1 |
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All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Organic Chemistry
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Insights into unusual stability of 5-membered-ring endocyclic benzyl carbocations in aqueous solution. / Sung, Robert; Sung, Kuang-Sen.
In: Journal of Physical Organic Chemistry, Vol. 31, No. 10, e3863, 01.10.2018.Research output: Contribution to journal › Article
TY - JOUR
T1 - Insights into unusual stability of 5-membered-ring endocyclic benzyl carbocations in aqueous solution
AU - Sung, Robert
AU - Sung, Kuang-Sen
PY - 2018/10/1
Y1 - 2018/10/1
N2 - The acyclic o-oxygen benzyl carbocation 1, the 6-membered-ring endocyclic o-oxygen benzyl carbocation 2, and the 5-membered-ring endocyclic o-oxygen benzyl carbocation 3 were used as model compounds to get insights into the general phenomenon for the unusual stability of the 5-membered-ring endocyclic benzyl carbocations in aqueous solution. The hydride-ion affinities of 1, 2, and 3 in gas phase, acetonitrile, and DMSO were calculated and compared by the density functional theory method, and 3 isodesmic reactions were designed to confirm their thermodynamic stability. What we found is that the 5-membered-ring endocyclic o-oxygen stabilizes the benzyl carbocation 3 less than the acyclic o-oxygen stabilizes the benzyl carbocation 1 in gas phase because of ring strain and through-bond induction. However, the high solvation energies of the 5-membered-ring endocyclic o-oxygen benzyl carbocation 3 not only offset the destabilizing effects of ring strain and through-bond induction but also make it even more stable than the acyclic o-oxygen benzyl carbocation 1 in polar solvents like acetonitrile, DMSO, and water.
AB - The acyclic o-oxygen benzyl carbocation 1, the 6-membered-ring endocyclic o-oxygen benzyl carbocation 2, and the 5-membered-ring endocyclic o-oxygen benzyl carbocation 3 were used as model compounds to get insights into the general phenomenon for the unusual stability of the 5-membered-ring endocyclic benzyl carbocations in aqueous solution. The hydride-ion affinities of 1, 2, and 3 in gas phase, acetonitrile, and DMSO were calculated and compared by the density functional theory method, and 3 isodesmic reactions were designed to confirm their thermodynamic stability. What we found is that the 5-membered-ring endocyclic o-oxygen stabilizes the benzyl carbocation 3 less than the acyclic o-oxygen stabilizes the benzyl carbocation 1 in gas phase because of ring strain and through-bond induction. However, the high solvation energies of the 5-membered-ring endocyclic o-oxygen benzyl carbocation 3 not only offset the destabilizing effects of ring strain and through-bond induction but also make it even more stable than the acyclic o-oxygen benzyl carbocation 1 in polar solvents like acetonitrile, DMSO, and water.
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U2 - 10.1002/poc.3863
DO - 10.1002/poc.3863
M3 - Article
VL - 31
JO - Journal of Physical Organic Chemistry
JF - Journal of Physical Organic Chemistry
SN - 0894-3230
IS - 10
M1 - e3863
ER -