Effect of Substituent on Crystal Structures

The crystal structures of N-(substitutedphenyl)-2,2,2-trichloroacetamides of the type 2/3/4XC 6H 4 .NHC0.CC1 3 (X = CI, N 0 2 or CH3) , namely, N-(3-nitrophenyl)-2,2,2-trichloroacetamide, 3 N 0 2 C 6 H 4 . N H C 0 . C C l 3 (m-N02PhTCA); N-(4-nitrophenyl)-2,2,2-trichloroacetamide, 4 N 0 2 C 6 H 4 . N H C 0 . C C l 3 (p-N02PhTCA); N-(2-chlorophenyl)-2,2,2-trichloroacetamide, 2-ClC6H4 .NHCO.CCl3 (o-ClPhTCA) and N-(4-chlorophenyl)-2,2,2-trichloroacetamide, 4C1C6H4 .NHC0.CC13 (p-ClPhTCA) have been determined at room temperature. The present data are analysed along with our earlier crystal structures of N-(2-nitrophenyl)-2,2,2-trichloroacetamide, 2 N 0 2 C 6 H 4 . N H C 0 . C C l 3 (o-N02PhTCA); N-(4-methylphenyl)-2,2,2-trichloroacetamide, 4-CH 3 C 6 H 4 . NHC0.CC1 3 (p-CH3PhTCA); N-(phenyl)-2,2,2-trichloroacetamide, C 6 H 5 .NHC0.CC1 3 (PhTCA); N-chloro-N-(phenyl)-2,2,2-trichloroacetamide, C 6 H 5 .NClCO.CCl 3 (NClPhTCA); and finally with N-(phenyl) acetamide, C 6 H 5 .NHCO.CH 3 (PhA). The crystal type, space group, formula units and lattice constants in A of the new structures are; m-NO->PhTCA: triclinic, P I , Z = 4, a = 7.493(3), b = 9.992(3), c = 15.225(5), o = 84.16(2)°, ß = 82.59(2)°, 7 = 84.92(2); p-N02PhTCA: monoclinic, P2, /n, Z = 4, a = 5.807(2), b = 15.354(6), c = 12.475(5), ß = 92.28(2)°; o-ClPhTCA: orthorhombic, P m ^ , Z = 4, a = 8.769(2), b = 12.838(3), c = 9.578(2) and p-ClPhTCA: orthorhombic, Pbca, Z = 8, a = 9.742(4), b = 10.031(4), c = 23.110(9). The compounds, m N 0 2 P h T C A , 0-NO2PI1TCA and P-CH3PI1TCA show two molecules each in their asymmetric units. This is in agreement with the multiple lines observed in the C1 NQR spectra of the latter two compounds. But the presence of two molecules in the asymmetric unit of mNO2PI1TCA indicates that it may undergoe a phase transition below room temperature. The bond lengths and bond angles are normal except for some deviations. The presence of strong electron withdrawing group at the ortho position of the phenyl ring and N-chlorination of the amide will have significant effect on some bond distances and bond angles.