Theoretical Study of 13 C Chemical Shifts Structures of Some ortho ‐Substituted 3‐Anilino‐2‐nitrobenzo[ b ]thiophenes and 2‐Anilino‐3‐nitrobenzo[ b ]thiophenes and Comparison with Experimental

13 C NMR chemical shifts have been calculated for structures of some substituted 3‐anilino‐2‐nitrobenzo‐[ b ]thiophenes ( 2 o ) and 2‐anilino‐3‐nitrobenzo[ b ]thiophenes ( 3 o ) derivatives containing OH, NH 2 , OMe, Me, Et, H, F, Cl and Br. The molecular structures were fully optimized using B3LYP/6‐31G(d,p). The calculation of the 13 C shielding tensors employed the GAUSSIAN 03 implementation of the gauge‐including atomic orbital (GIAO) and continuous set of gauge transformations (CSGT) by using 6‐311++G(d,p) basis set at density functional levels of theories (DFT). The isotropic and the anisotropy parameters of chemical shielding for all compounds are calculated. The predicted 13 C chemical shifts are derived from equation δ = δ 0 + δ where δ is the chemical shift, δ is the absolute shielding, and δ 0 is the absolute shielding of the standard TMS. Excellent linear relationships have been observed between experimental and calculated 13 C NMR chemical shifts for all derivatives