Structural Studies on Substituted N-(phenyl)-2,2-DichIoroacetamides, 2/4-XC₆H₄ NHCO CHCI₂ (X = H, Cl or CH₃)

Abstract

The effect of substitution in the phenyl ring on the crystal systems of amides of the type, 2/4-XC₆H₄-NHCO-CHCl₂ (X = H, Cl or CH₃), has been studied by determining the crystal structures of the compounds, iV-(phenyl)-2,2-dichloroacetamide, C₆H₅-NHCO-CHCl₂ (PhDCA); N-(2-chlorophenyl)-2,2-dichloroacetamide, 2-ClC₆H₄-NHCO-CHCl₂ (o-ClPhDCA), jY-(4-chlorophenyl)-2,2-dichloroacetamide, 4-ClC₆H₄-NHCO-CHCl₂ (p-ClPhDCA) and N -(4-methylphenyl)-2,2-dichloroacetamide, 4-CH₃C₆H₄-NHCO-CHCl₂ (p-CH₃PhDCA) and analysed the data along with our earlier crystal structures of the compounds, N-(phenyl)-2,2,2-trichloro-acetamide (PhTCA), N-(2-chlorophenyl)-2,2,2-trichloroacetamide (o-ClPhTCA), N -(4-chloro-phenyl)-2,2,2-trichloroacetamide (p-ClPhTCA), N-(4-methylphenyl)-2,2,2-trichloroacetamide (p-CH₃PhTCA); N-chloro-N-(phenyl)-2,2-dichloroacetamide (NClPhDCA), N-chloro-N-(phenyl)-2,2,2-trichloroacetamide (NClPhTCA) and N-(phenyl) acetamide (PhA). The crystal type, space group, formula units and lattice constants in A of the new structures are; PhDCA: monoclinic, P 2₁/c, Z = 4, a = 8.785(3), b = 11.139(4), c = 9.521(3), ß = 97.47(2)°; o-CIPhDCA: monoclinic, P 2₁/c, Z = 4, a = 4.711(2), b = 11.234(6), c = 19.191(8), ß = 98.12(2)°; p-CIPhDCA: monoclinic, P 2₁/c, Z = 8, a = 18.627(5), b = 11.533(3), c = 9.583(3), ß = 102.43(2)°, and /?-CH₃PhDCA: orthorhombic, Pbca, Z = 8, a = 9.464(3), b = 9.894(3), c = 21.973(7). The compound p-ClPhDCA shows two molecules in its asymmetric unit. This is in agreement with the multiple lines observed in the ³⁵Cl NQR spectra of the compound. The crystal systems of the chlorosubstituted and methyl substituted chloroacetamides get interchanged on replacement of the side chain -CHCl₂ by -CCl₃. C(i)-C(j) ring distances show no significant variations with the substitution either at the side chain or in the phenyl ring. C(ring)-N and C (0)-N bond distances are also not much affected by either ring or side chain substitution, but are affected by N-chlorination, while the C -0 bond length is slightly shortened by the replacement of the -CH₃ group by -CCl₃, the introduction of electron withdrawing group into the phenyl ring or by N-chlorination. Deviations of C2(ring)-Cl(ring)-N, C6(ring)-Cl(ring)-N and C (ring)-N-C(0) bond angles from 120° narrow down on substitution either in the phenyl ring or in the side chain, but the latter increases on W-chlorination of the compounds.