The thermodynamics of the reaction R+(g) + RrefOH(g) -> ROH(g) + R-ref(+)(g) involving R-ref = tert-butyl and 21 carbenium ion/alcohol systems has been studied at the MP2/6-311+G(3d, 2p)//MP2/6-311+G(d, p) level. The results have been compared to the experimental data for the same systems in solution. The range of structural effects spans 102 kcal mol(-1) in the gas phase and is the widest ever examined. A physically meaningful correlation has been found. Phenyl-substituted systems are among the most important exceptions. (c) 2006 Elsevier B.V. All rights reserved.