Comparing positively and negatively charged distonic radical ions in phenylperoxyl forming reactions
This data set accompanies the manuscript "Comparing positively and negatively charged distonic radical ions in phenylperoxyl forming reactions" by Peggy E. Williams, David L. Marshall, Berwyck L. J. Poad, Venkateswara R. Narreddula, Benjamin B. Kirk, Adam J. Trevitt, Stephen J. Blanksby.
Abstract: In the gas phase, arylperoxyl forming reactions play a significant role in low temperature combustion and atmospheric processing of volatile organic compounds. We have previously demonstrated the application of charge-tagged phenyl radicals to explore the outcomes of these reactions using ion trap mass spectrometry. Here we present a side-by-side comparison of rates and product distributions from the reaction of positively and negatively charge tagged phenyl radicals with dioxygen. The negatively charged distonic radical ions are found to react with significantly greater efficiency than their positively charged analogues. The product distribution of the anion reactions favors products of phenylperoxyl radical decomposition (e.g., phenoxyl radicals and cyclopentadienone) while the comparable fixed-charge cations yield the stabilized phenylperoxyl radical. Electronic structure calculations rationalise these differences as arising from the influence of the charged moiety on the energetics of rate-determining transition states and reaction intermediates within the phenylperoxyl reaction manifold and predict that this influence could extend to intra-molecular charge-radical separations of up to 14.5 Å. Experimental observations of reactions of the novel 4-(1-carboxylatoadamantyl)phenyl radical anion confirm that the influence of the charge on both rate and product distribution can be modulated by increasing the rigidly imposed separation between charge and radical sites. These findings provide a generalizable framework for predicting the influence of charged groups on polarizable radicals in gas phase distonic radicals ions.
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Mass spectral files acquired using a Thermo LTQ-XL mass spectrometer. Requires Thermo XCalibur to read these files.
Computational log files including optimised structures and transition states from Gaussian09 calculations
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