Hard to swallow dry: kinetics and mechanism of the anhydrous thermal decomposition of acetylsalicylic acid.

The methods of thermal analysis and mass spectrometry have been used to study the kinetics and mechanism of the anhydrous thermal decomposition of acetylsalicylic acid. Both thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) show that decomposition occurs in two steps. Mass-spectrometric analysis of the residue left after the first decomposition step (approximately equal to 60% mass loss) suggests that in the condensed phase, acetylsalicylic acid decomposes by first forming linear oligomers that are further converted into cyclic oligomers.