Polymorphism, Intermolecular Interactions, and Properties of Primary Amines at High Pressure

High Resolution Image Download MS PowerPoint Slide A homologous series of the simplest primary amines, ethylamine (EA), propylamine (PA), butylamine (BA), and pentylamine (PEA), has been studied at high pressure by single-crystal X-ray diffraction. The structures of these compounds have been determined, at ambient temperature, from their freezing pressures up to ca. 5 GPa. Ethylamine at high pressure crystallizes in phase II of space group P 2 1 / c, already found at ambient pressure and low temperature. For other amines, six new polymorphs have been found: two of propylamine (phases II and III, both of space group P 2 1 / c ), two of butylamine (phases II and III, both of space group Pbc 2 1 ), and two of pentylamine (phases II and III, space groups Pbc 2 1 and P 2 1 cn, respectively). The competition between NH···N and CH···N intermolecular interactions has been studied for the polymorphic forms of all amines. The properties of investigated compounds have been correlated with the number of carbon atoms in their aliphatic chains.