The search for charge-remote reactions of even-electron anions derived from 1,3-disubstituted adamantanes in the gas phase. Retro Diels-Alder and Norrish II processes

The collision induced decompositions of 3-substituted adamantane carboxylat e anions have been studied with a view to uncovering charge-remote fragment ations of the 3-substituent. The 3-substituent is chosen so that it cannot approach the anion site, and so any fragmentations of that substituent shou ld proceed independently of the charged centre, viz. charge-remote reaction s. The following systems have been studied (i) the 3-cyclohexenyl system sh ows no charge-remote retro Diels-Alder fragmentation (DeltaH = +157 kJ mol( -1)), instead, charge-remote loss of the cyclohexenyl radical is noted, (ii ) the 3-isobutyl ketone system shows no Norrish II cleavage (loss Of C3H6, DeltaH = +18 kJ mol(-1)), instead, the competitive losses Of CO2 from the c harged carboxyl centre, together with charge-remote radical loss of the 3-s ubstituent are observed, and (iii) the corresponding 3-isopropyl ester does show the 'Norrish II' loss Of C3H6, together with competitive losses Of CO 2 and the 3-substituent. It is concluded for cases (ii) and (iii), that an adamantane carboxylate anion system with a carbonyl group directly attached at the 3-position is not a suitable model system for studying charge-remot e reactions. Copyright (C) 2001 John Wiley & Sons, Ltd.