Vibrational spectra of N-methylpyrazole: an experimental and theoretical study
The gas-phase infrared spectrum of N-methylpyrazole was measured in the range 5000–500 cm−1 and with a resolution of 0.5 cm−1. Its Raman spectrum was obtained in the condensed-phase in the range 3500–100 cm−1 and with a resolution of 2.7 cm−1. The corresponding depolarization ratios were also measured. Theoretical information on harmonic vibrational frequencies, infrared and Raman intensities and depolarization ratios was obtained by means of ab initio and density functional theory approaches. The former were performed at the MP2/6-31G** level and the latter at the B3LYP/6-31G** level. This information was useful in the assignment of the different fundamentals. In general the agreement theory-experiment was very good, with the only exception of the infrared and Raman intensities of some transitions.