2,4,6-trimethoxy-1,3,5-triazine undergoes methyl transfer in few stages, some in the melt and some in the solid-state, to the end product, 2,4,6-trioxo-1,3, 5-trimethylazine. The three possible intermediates have been prepared and their methyl transfer reaction was investigated. The mechanism and the dependence of the reactivity on the packing of the molecules in the crystal lattice have been studied by high temperature X-ray diffraction (HTXRD), by thermal analysis (DSC) and by crystal structure determination.