We have studied if and how it is possible to use quantum mechanical terms to describe the interaction between reacting molecules and the electromagnetic field in a microwave-assisted reaction. A model of an S(N)2 reaction was studied by DFT and HF methods. By adding solvent molecules in the form of water, it was computationally shown that several of the models of solvated. reaction complexes have vibrational modes whose frequencies are close to the normally used microwave frequency of 2.45 GHz. We thus find it likely that there may exist vibrational motion in the form of hindered rotation which overlaps with this normal microwave heating frequency in turn suggesting that microwave photons may excite these vibrational modes.