Theoretical investigation of the molecular structure and vibrational spectra of methylphenidate molecule

In this work, molecular structure and the harmonic and anharmonic vibrational frequencies of methylphenidate which is active material of Ritalin drug were studied by HF and DFT methods with different basis sets. Calculations were performed on linux workstations using the Gaussian 03 suite of programs. The optimized geometry was calculated by HF and B3LYP methods using 6-31G(d,) and 6-311++G(d,p) basis sets and the harmonic and anharmonic vibrational wavenumbers and absolute intensities were calculated by means of the DFT/B3LYP/6-311++G (d,p) method at the corresponding optimized structure. On the basis of the comparison between calculated and experimental results and the comparison with related molecules, assignments of fundamental vibrational modes are examined. The X-ray geometry and experimental frequencies are compared with the results of our theoretical calculations.The conformers have been predicted by the potantial energy surface scan employing the DFT method, B3LYP implementing basis set 6-31++G(d,p).