The calorimetric study of some guanidine derivatives involved in living bodies nitrogen metabolism

The energies of combustion of creatine (anhydrous and monohydrate), creatinine, and arginine were measured in a static bomb adiabatic calorimeter, in pure oxygen at 3,040 kPa. The derived standard enthalpies of formation in solid state of the above-mentioned compounds are, respectively, −520.4 ± 4.3, −809.7 ± 1.3, −204.2 ± 7.0, and −634.8 ± 2.3 kJ mol⁻¹ . The data of enthalpy of formation are compared with literature values and with estimated values by means of group additivity. The dehydration of creatine monohydrate and the processes occurring in the three guanidine derivatives at temperatures exceeding 200 °C were investigated by means of DSC.