Anhydrous 1-methylhexamethylenetetramine (also referred to as N-methylurotropinium or methylhexaminium) fluoride was prepared by either halogen exchange between the corresponding iodide and AgF or by a single-step, one-pot, self-assembling synthesis from aqueous CH3NH2, HF, formaldehyde, and NH3. It was characterized by NMR and vibrational spectroscopy. Its hydrate undergoes at 70 degrees C a Sommelet-type ring opening and coupling reaction to form a potential cryptand system consisting of two bicyclic triazine groups that are connected through a methylene bridge and contain eight ternary nitrogen atoms. The compound was characterized by multinuclear NMR and vibrational spectroscopy, and its structure was determined from single-crystal X-ray diffraction data.