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

Abstract

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.