Kinetics of drug decomposition. Part 73. Kinetics and mechanism of vitamin K3 soluble form thermal decomposition in solid phase.

Kinetics of thermal decomposition of trihydrate of sodium salt of 1,2,3,4-tetrahydro-2-methyl-1,4-dioxo-2-naphthalenesulfonic acid (MDS, vitamin K3 soluble form) in solid state by accelerated aging method at elevated temperature has been studied. It was found that the process occurs according to Prout-Tompkins model and its rate depends on temperature, humidity and particle size of the substance. Thermodynamic parameters of the reaction (Q10(0), EA, delta H not equal to, delta S not equal to, delta G) were determined and theoretically predicted stability of MDS at room temperature is given. The reaction mechanism assumes a preliminary dehydration occurring via the successive elimination of one and a half, two and a half and finally three molecules of water. The obtained anhydrous form decomposes thermally forming free radical intermediates and yielding finally 2-methyl-1,4-naphthoquinone (vitamin K3), SO2 and NaOH.