Polymorph II of hydroxyurea 150 years after its first synthesis

A new polymorph of hydroxyurea (HU) was crystallized 150 years after its first synthesis. Due to its medicinal use in neoplastic diseases and sickle cell anemia, a high throughput screen of HU binary cocrystals was attempted. Instead of a cocrystal, an isoenergetic form II crystallized concomitantly with urea in methanol.

Automated summary

A new polymorph of hydroxyurea (HU) was discovered 150 years later, and it crystallized concurrently with urea in methanol. Despite attempting a high throughput screen of HU binary cocrystals, an isoenergetic form II was obtained instead.