Redox reactions with ferrocene/ferricenium species of radicals derived by H atom abstraction from alcohols and diols

The effect of various alcohols and diols in diminishing the extent of the photo-oxidation of 4-ferrocenylbutanoate ion in the presence of N2O has been investigated. Where the hydroxyl radical generated in the photo-initiated electron transfer reacts with an alcohol by H atom abstraction at the α-position, the resulting radical is capable of reducing the ferricenium zwitterion to the ferrocenyl anion. Abstraction at other positions produces radicals that are essentially inert in this system and rate constants are derived for the reaction of OH with some such compounds. Non-vicinal diols behave similarly to the corresponding alcohols. With vicinal diols, a dehydration process, which occurs the more slowly the more highly substituted the diol, converts the radical -CR(OH)Ċ(OH)- into -ĊRCO-, which is an oxidizing species. The behaviour of pinacol was found to be anomalous. Key words: radical reactions, redox behaviour, alcohols.