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Structural Transition of the 2‐Nitropropane Organic Compound at Low Temperature
Author(s) -
Gbabode Gabin,
Lambert Sébastien,
Guillet François,
Hebert Philippe
Publication year - 2010
Publication title -
propellants, explosives, pyrotechnics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.56
H-Index - 65
eISSN - 1521-4087
pISSN - 0721-3115
DOI - 10.1002/prep.200800108
Subject(s) - triclinic crystal system , crystallography , zigzag , molecule , crystal structure , chemistry , phase (matter) , phase transition , diffraction , crystal (programming language) , nitro , alternation (linguistics) , symmetry (geometry) , stereochemistry , materials science , physics , condensed matter physics , geometry , optics , mathematics , programming language , organic chemistry , computer science , alkyl , linguistics , philosophy
Structural investigation of the crystallized 2‐nitropropane compound (C 3 H 7 NO 2 ) 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 T t =172 K, a structural transition is observed which brings to another phase, called phase β (above T t ). This one contains four molecules per unit cell and shows a Pc 2 1 n 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 NO 2 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 C 3 H 7 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.