A theoretical DFT study on benzamide and benzoic acid dimers in the gas phase and encapsulated in two cages of different size has been carried out in order to explain experimental observations regarding the % distributions of the different dimers formed in these cages. The results show that the % distribution of encapsulated dimers in the larger cage is similar to the gas-phase distribution. In the smaller cage interaction of amide with the cage leads to lower dimerization energy and a reduced % fraction of the corresponding encapsulated dimers, compared to the large cage % distribution, in agreement with experiment. (C) 2012 Elsevier B. V. All rights reserved.