Molecular structure, vibrational spectra and (13)C and (1)H NMR spectral analysis of 1-methylnaphthalene by ab initio HF and DFT methods.

The Fourier transform infrared (FT-IR) and FT-Raman of 1-methylnaphthalene (1MN) have been recorded and analyzed. The equilibrium geometry, bond lengths, bond angles and harmonic vibrational frequencies have been investigated with the help of density functional theory (DFT) method. Vibrational spectroscopic assignments of 1-methylnaphthalene (1MN) are carried out with the help of quantum chemical calculation. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule are calculated by the Gauge including atomic orbital (GIAO) method. The molecular stability and bond strength have been investigated by using natural bond orbital analysis (NBO). The assignments of vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shift of the molecular is depend only on the structure of the molecule. The calculated HOMO and LUMO energy shows that charge transfer interactions take place within the molecule. Finally, the calculation results are applied to simulate infrared and Raman spectra of the title compound which show good agreement with observed spectra.