The kinetics of cyclization of 3-ureidopropionic acid (UPA) to dihydrouracil (DHU) in hydrochloric acid solution has been studied. The reaction was found to be reversible with the equilibrium shifting in favour of UPA with increasing acid strength. It was shown that the failure to cyclize 3-ω-N-phenylureidopropionic acid in HCl is due to an equilibrium under which the extent of cyclization is only 30%. The rate of cyclization of UPA is proportional to ...
