Ion/molecule reactions of ?bare? FeO+ with linear and branched aliphatic alcohols have been examined by Fourier-transform ion-cyclotron resonance mass spectrometry. Depending on the chain length of the alcohol, three different types of reactions can be distinguished: (i) Oxidation of the alcohols in the ?-positions, to yield the corresponding carbonyl-Fe+ complexes, involves an initial O&bond;H bond activation of the alcohol resulting in the formation of RO&bond;Fe+&bond;OH as the central intermediate. (ii) The formation of Fe(OH)2+, concomitant by loss of the corresponding neutral alkenes, competes with the generation of neutral OFeOH and a carbocation R+. These couples point to the existence of an intracomplex acid-base equilibrium and are connected with each other by a proton transfer from either acid to the other, e.g. i-C3H7+ + OFeOH&rlarr2;C3H6 + Fe(OH)2+. The process is driven by the Lewis acidity of FeO+ and starts with the abstraction of a hydroxide anion from the alcohol. (iii) For longer alcohols, e.g. pentanol, functionalization of non-activated C&bond;H bonds which are remote from the O functionality is observed. Here, the OH group of the alcohol serves as an anchor, which directs the reactive metal-oxide cation toward a particular site of the hydrocarbon chain.