Investigation of the gas phase reactivity of the 1-adamantyl radical using a distonic radical anion approach

The gas phase reactions of the bridgehead 3-carboxylato-1-adamantyl radical anion were observed with a series of neutral reagents using a modified electrospray ionisation linear ion trap mass spectrometer. This distonic radical anion was observed to undergo processes suggestive of radical reactivity including radical-radical combination reactions, substitution reactions and addition to carbon-carbon double bonds. The rate constants for reactions of the 3-carboxylato-1-adamantyl radical anion with the following reagents were measured (in units 10−12 cm3 molecule−1 s−1): 18O2 (85 ± 4), NO (38.4 ± 0.4), I2 (50 ± 50), Br2 (8 ± 2), CH3SSCH3 (12 ± 2), styrene (1.20 ± 0.03), CHCl3 (H abstraction 0.41 ± 0.06, Cl abstraction 0.65 ± 0.1), CDCl3 (D abstraction 0.035 ± 0.01, Cl abstraction 0.723 ± 0.005), allyl bromide (Br abstraction 0.53 ± 0.04, allylation 0.25 ± 0.01). Collision rates were calculated and reaction efficiencies are also reported. This study represents the first quantitative measurement of the gas phase reactivity of a bridgehead radical and suggests that distonic radical anions are good models for the study of their elusive uncharged analogues.