Structure and conformation
2-chloro-6-methoxy-3-nitropyridine ( 2, 6, 3-CMNP) has a planar structure of the Cs point group symmetry. The three Cartesian displacements of the 17 atoms provide 45 internal modes. All 45 fundamental vibrations are active in both IR and Raman. For an N-atomic molecule, 2N-3 of all vibration is in plane and N-3 is out of plane. Thus, for 2-chloro-6-methoxy-3-nitropyridine, 31 of all the 45 vibrations are n-plane and 14 are out-of-plane.
The compound 2, 6, 3-CMNP has only one methoxy group at the 6th position; therefore there will be only one O-CH3 stretching mode. In case of HF/6-31+G (d, p) this O-C stretching vibration is observed at 1041 cm-1 and by the DFT calculations observed at 1069 cm-1. Each CH3 or OCH3 group rise to three C-H valance oscillations (2800-3000 cm-1) and three C-H deformations as suggested by Bellamy.
[1] Sharma B, et al. Ab-initio Hartee-Fock and Density functional theory calculations of 2-Chloro-6-methoxy-3-nitropyridine. Arch. Appl. Sci. Res, 2011; 3: 334-344.
