Abstract
During the Pschorr cyclisation of 2-aroylphenyl radicals, a rearrangement occurs reversibly by 1,5-hydrogen transfer to give 2-benzoylaryl radicals. Rate constants of (1.2 +/-0.2)x10(6) s(-1) at 293 K are estimated for both the forward and back reactions in the equilibrium between 2-(4-methylbenzoyl)phenyl and 2-benzoyl-5-methylphenyl radicals. Assuming an empirical estimate of 1.6x10(-2) dm(3) mol(-1) s(-1) for the hypothetical rate of abstraction of hydrogen from benzene by phenyl radicals, the radical translocation is calculated to occur with a statistically corrected effective molarity of 2.2x10(8) mol dm(-3). By contrast, the competing cyclisation, though occurring at a rate of (8.0 +/-0.9)x10(5) s(-1), exhibits an effective molarity of only 5.3 mol dm(-3). The causes of these differences are analysed in terms of reaction mechanism.
Original language | English |
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Pages (from-to) | 214-228 |
Number of pages | 15 |
Journal | JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2 |
Issue number | 2 |
DOIs | |
Publication status | Published - 2001 |
Keywords
- ABSOLUTE RATE CONSTANTS
- HYDROGEN ABSTRACTIONS
- PHENYL RADICALS
- WATER LIGANDS
- CU-II
- ENERGY
- CYCLIZATION
- ACTIVATION
- BENZENE
- TRANSITIONS