Gas-Phase and Solution-Phase Homolytic Bond Dissociation Energies of H−N+ Bonds in the Conjugate Acids of Nitrogen Bases
- 1 January 1996
- journal article
- research article
- Published by American Chemical Society (ACS) in The Journal of Organic Chemistry
- Vol. 61 (14) , 4778-4783
- https://doi.org/10.1021/jo950933r
Abstract
The oxidation potentials of 19 nitrogen bases (abbreviated as B: six primary amines, five secondary amines, two tertiary amines, three anilines, pyridine, quinuclidine, and 1,4-diazabicyclo[2,2,2]octane), i.e., Eox(B) values in dimethyl sulfoxide (DMSO) and/or acetonitrile (AN), have been measured. Combination of these Eox(B) values with the acidity values of the corresponding acids (pKHB+) in DMSO and/or AN using the equation: BDEHB+ = 1.37pKHB+ + 23.1 Eox(B) + C (C equals 59.5 kcal/mol in AN and 73.3 kcal/mol in DMSO) gave estimates of solution phase homolytic bond dissociation energies of H−B+ bonds. Gas-phase BDE values of H−B+ bonds were estimated from updated proton affinities (PA) and adiabatic ionization potentials (aIP) using the equation, BDE(HB+)g = PA + aIP − 314 kcal/mol. The BDEHB+ values estimated in AN were found to be 5−11 kcal/mol higher than the corresponding gas phase BDE(HB+)g values. These bond-strengthening effects in solution are interpreted as being due to the greater solvation energy of the HB+ cation than that of the B+• radical cation.Keywords
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