Thermochemistry of hexamethylenetetramine pentaborate

The crystalline hexamethylenetetramine pentaborate [(CH2)6N4H][B5O6(OH)4]·0.5H2O has been prepared and identified by XRD, FT-IR, DTA-TG, elemental analysis and chemical analysis. The molar enthalpy of solution of [(CH2)6N4H][B5O6(OH)4]·0.5H2O in (HCl·54.554H2O) and of (CH2)6N4 in (HCl + H3BO3)(aq) were determined. With the incorporation of the enthalpies of solution of H3BO3 in HCl(aq), and the standard molar enthalpies of formation of (CH2)6N4(s), H3BO3(s), and H2O(l), the standard molar enthalpy of formation of −(4042.7 ± 4.1) kJ mol−1 of [(CH2)6N4H][B5O6(OH)4]·0.5H2O was obtained.