Title page for ETD etd-06102009-063106
|Type of Document
||Hulvey, Glenn A.
||Internal pressure's role in the selectivity of the bromine radical
||Master of Science
|Tanko, James M.
|Marand, Hervé L.
|Merola, Joseph S.
|Date of Defense
The results of our studies demonstrate a link between selectivity in free radical
brominations and the internal pressure of solvent. The study encompassed l8 solvents
and/or mixtures over which the rate constant ratio for SH2 ring opening of
cyclopropylbenzene (kC) vs hydrogen abstraction from toluene (kH) by bromine atom
was found to vary by nearly a factor of twenty as a function of solvent. The observed rate
constant ratios correlate with the cohesive energy density of the solvent, which is
approximately equal to the internal pressure (kC/kH is found to increase with increasing
solvent pressure) for the solvents used in this study. A similar competition pitting
cyclopropylbenzene against p-chlorotoluene shows the same solvent effect. It is
suggested that the observed variation in selectivity "with solvent pressure occurs because
the volume of activation with kC is more negative than for kH by about 20 cm3/mol.
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