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Structural transition of the 2-nitropropane organic compound at low temperature

par Gbabode, Gabin ;Lambert, Sébastien;Guillet, François;Hebert, Philippe
Référence Propellants, explosives, pyrotechnics, 35, 2, page (136-142)
Publication Publié, 2010-03

Article révisé par les pairs

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Résumé :

Structural investigation of the crystallized 2-nitropropane compound (C3H7NO2) was performed by X-ray powder diffraction at low temperature. A first crystalline phase, called phase α, is observed below 172 K. This form exhibits a triclinic symmetry with P-1 space group (a=1.0313(3) nm, b=0.5873(2) nm, c= 1.6146(4) nm, α=90.17(2)°, β=92.17(2)° and γ=90.09(2)°), and Z=8). At Tt = 172 K, a structural transition is observed which brings to another phase, called phase β (above Tt). This one contains four molecules per unit cell and shows a Pc21n symmetry (a=1.0141(3) nm, b=0.5855(2) nm, and c=0.8319(4) nm). In addition to the doubling of the c-axis, structural networks differ by the different conformations of NO2 nitro groups and by the orientation of the propyl group in the unit cell. Both crystal structures can be described using infinite zigzag chains of C3H7 NO 2 molecules showing a regular alternation along the c-axis. Two orientations of these ribbons, called A and B, are observed. The crystal structures are then built with different distribution of these ribbons within the crystalline network. © 2010 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.