The S(N)1-type hydrolysis reaction of cellobiose in ionic liquids (ILs) was theoretically investigated. First principles and ab initio quantum chemical methods were used in conjunction with the 'reference interaction site model self-consistent field with spatial electron density distribution' (RISM-SCF-SEDD) method. Reaction mechanism pathways are discussed and compared to calculations in gas phase and in aqueous solution. Analysis of solvation effects indicates strong interaction between hydrogen atoms of glucose hydroxyl groups and the anions in ILs, contributing to large stabilization of the reaction product. The calculated activation energy in ILs (24.5 kcal/mol) agrees quantitatively with the experimental value (26.5 kcal/mol). (C) 2014 Elsevier B. V. All rights reserved.