Search for charge-remote reactions of even-electron organic negative ions in the gas phase. Anions derived from disubstituted adamantanes

Abstract

The collision induced decompositions of 3-substituted adamantanecarboxylate anions have been studied with a view to uncover charge-remote fragmentations of the 3-substituent. The 3-substituent is chosen so that it cannot approach the anion site and therefore any fragmentations of that substituent should proceed independently of the charged centre, (i) Charge-remote radical losses are observed from a 3-CH(Et)2 substituent [e.g. Eṫ and ̇CH(Et)2 losses], but the classical Adams-Gross charge remote loss of an ethene plus dihydrogen is not observed, (ii) Charge-remote loss of MeOD is observed from a 3-C(CD3)2(OMe) substituent together with a number of charge-remote radical losses [e.g. Mė, MeȮ and ̇C(CD3)2(OMe)]. (iii) The 3-substituent C(CD3)2 (OCH=O) undergoes charge-remote loss of HCO2D for both the carboxylate anion and its corresponding cation, a neutral reaction analogous to both the McLafferty rearrangement of radical cations and the Norrish II diradical rearrangement of aliphatic ketones. (iv) The charge-remote radical losses of MeȮ and ̇CO2Me occur from a 3-CO2Me substituent.