Discovery and recovery of delta p-aminobenzoic acid

Martin R. Ward, Shatha Younis, Aurora J. Cruz-Cabeza, Craig L. Bull, Nicholas P. Funnell, Iain D. H. Oswald

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)
41 Downloads (Pure)


We explore the polymorphism of p-aminobenzoic acid (pABA) under high-pressure conditions. We have been able to isolate a new high-pressure form (δ-pABA) at pressures exceeding 0.3 GPa from three different pressure-transmitting media, water, water:ethanol and pure ethanol. We explore the compression behaviour of α-pABA in each of these media using neutron powder diffraction and observe that the transition is kinetically hindered using the aqueous ethanol and ethanol solutions compared with the pure aqueous medium. δ-pABA is sufficiently stable to be recovered to ambient pressure to enable its characterisation via X-ray powder diffraction and differential scanning calorimetry. At ambient pressure we have observed that δ-pABA converts into α-pABA on heating beyond 70 °C.
Original languageEnglish
Pages (from-to)2058-2066
Number of pages9
Issue number13
Early online date21 Jan 2019
Publication statusPublished - 7 Apr 2019


  • p-aminobenzoic acid
  • neutron powder diffraction
  • high pressure
  • recovery


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