M. Haisa, S. Kashino, Y. Matsuzaki
Aug 15, 1977
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0
Influential Citations
12
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Journal
Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry
Abstract
The crystal structures ofp-aminoacetanilide (PAAA), and the monoclinic [PMAA (M)] and orthorhombic [PMAA (O)1 dimorphs of p-methylacetanilide have been determined from visually estimated Cu Ka data. The unit cells are: Pcab, a = 11.98 (2), b = 17.44 (2), c = 7.37 (1) A, Z = 8 for PAAA; P2,/c, a = 11.74 (2), b = 9.59 (2), c = 7.56 (1) A, fl = 106.0 (2) ° , z = 4 for PMAA (M); and Pna2~, a = 9.899 (5), b = 12.956 (6), c = 6.541 (4) A, Z = 4 for PMAA (O). The structures were refined by block-diagonal leastsquares calculations to R values of 0.084, 0.084 and 0.088 for 1161, 1328 and 767 non-zero reflexions, for PAAA, PMAA (M) and PMAA (O) respectively. In PAAA two kinds of hydrogen bonds 13.088 (4) A, NH 2 donates H to O=C; 3-050 (4) A, NH 2 accepts H from amide NHI form molecular sheets parallel to (001), in a similar manner to that found in the orthorhombic form of p-hydroxyacetanilide. The sheets are stacked along c. In PMAA (M) the molecules related by a twofold screw axis are linked together by the C = O . . . HN hydrogen bond I2.923 (3) A1, while in PMAA (O)those related by an a glide plane are O . . . N [2.904 (8) A[. A disordered structure mirrored by an n-glide plane with an occupancy factor of 0.25 was found in PMAA (O). Torsion angles about the N(amide)-C(ring) bond vary from 8.3 ° for PMAA (O) to 32.2 ° for PAAA.