Putting the squeeze on mephedrone hydrogen sulfate

Herein we report the characterisation of a novel salt of the "legal high" (+/-)-4'-methylmethcathinone hydrogen sulfate and its polymorphism under ambient and high pressure conditions. Under ambient pressure only one polymorph of the title compound was isolated but when subjected to high pressure a further two polymorphs are observed. The phase transitions at >0.5 GPa and >3.6 GPa are reversible single crystal to single crystal transitions which is possible due to the similarity of the packing in the molecules. It is proposed that these transitions are driven by the pV term of the Gibbs Free Energy equation rather than by the relief of repulsive interactions between molecules.