35Cl NQR and structural studies of N-(2,6-dichlorophenyl)-amides, 2,6-Cl2C6H3-NHCO-R (R = H or CH3-yXy and X = CH3 or Cl; y=0, 1, 2 or 3)

The effect of side chain substitution on the Cl-35 NQR and crystal structure of amides of the type N-(2,6-dichlorophenyl)-amides, 2,6-Cl2C6H3-NHCO-R (R = H or CH3-yXy where X = CH3 or Cl and y = 0, 1, 2 or 3), has been studied by measuring the Cl-35 NQR spectra and determining the crystal structures of the compounds N-(2,6-dichlorophenyl)-formamide, 2,6-Cl2C6H3-NHCO-H (DCPFA); N-(2,6-dichlorophenyl)-2-methylacetamide 2,6-Cl2C6H3-NHCO-CH2CH3 (DCPMA); N-(2,6-dichlorophenyl)-2,2-dimethylaceta 2,6-Cl2C6H3-NHCO-CH(CH3)(2) (DCPDMA) and N-(2,6-dichlorophenyl)-2,2,2-trimethylacetamide (neopentylamide), 2,6-Cl2C6H3-NHCO-C(CH3)(3) (DCPTMA), and by analysing the present data along with the Cl-35 NQR spectra and / or crystal structures of the compounds, 2,6-dichloroaniline, 2,6-Cl2C6H3-NH2 (DCA), N-(2,6-dichlorophenyl)-acetamide, 2,6-Cl2C6H3-NHCO-CH3 (DCPA), N-(2,6-dichlorophenyl)-2-chloroacetamide 2,6-Cl2C6H3-NHCO-CH2Cl (DCPCA), N-(2,6-dichlorophenyl)-2,2-dichloroacetamide 2,6-Cl2C6H3-NHCO-CHCl2 (DCPDCA) and N-(2,6-dichlorophenyl)-2,2,2-trichloroacetamide, 2,6-Cl2C6H3-NHCO-CCl3 (DCPTCA). The crystal type, space group, formula units and lattice constants in Angstrom of the new structures are;DCPFA: orthorhombic, Pbca, Z= 8, a = 8.593(3), b = 12.728(4), c = 14.376(4); DCPMA: orthorhombic, P2(1)2(1)2(1), Z = 4, a = 4.774(2), b = 10.961(5), c = 19.562(8); DCPDMA: monoclinic, P2(1)/c, Z = 4, a = 9.901(4), b = 13.785(5), c = 9.060(3), beta = 103.58(2)degrees and DCPTMA: monoclinic, P2(1)/n, Z = 8, a = 16.047(5), b = 9.882(3), c = 16.270(5) beta = 102.12(1)degrees. The compound, DCPTMA shows two molecules in its asymmetric unit. This is in agreement with the multiple lines observed in the Cl-35 NQR spectra of the compound. The conversion of DCA (monoclinic) into it's various acid amides DCPFA, DCPA, DCPMA, DCPDMA, DCPTMA, DCPCA and DCPTCA affects it's crystal symmetry. The replacement of the side chain CH3 in DCPA by the H atom or substitution of either a CH3 group or a Cl atom for one of the H atoms in the side chain CH3 or replacement of the two ring Cl atoms by the H atoms changes it's crystal symmetry from monoclinic to orthorhombic, while the substitution of 2 or all the 3 H atoms in the CH3 group of DCPA by 2 or 3 CH3 groups or CI atoms restores it's crystal symmetry back to the monoclinic type. The bond lengths and bond angles are normal except for some deviations.