Vibrational Overtone Spectroscopy, Energy Levels, and Intensities of (CH3)3C—C≡C—H

The vibrational overtone spectra of the acetylenic (Δυ = 4, 5) and methyl (Δυ = 5, 6) C–H stretch transitions of tert-butyl acetylene [(CH3)3C–C≡C–H] were obtained using the phase shift cavity ring down (PS-CRD) technique at 295 K. The C–H stretch fundamental and overtone absorptions of the acetylenic (Δυ = 2 and 3) and methyl (Δυ = 2–4) C–H bonds have been obtained using a Fourier transform infrared and near-infrared spectrophotometer. Harmonic frequency ω(ν1) and anharmonicities x(ν1) and x(ν1, ν24) are reported for the acetylenic C–H bond. Molecular orbital calculations of geometry and vibrational frequencies were performed. A harmonically coupled anharmonic oscillator (HCAO) model was used to determine the overtone energy levels and assign the absorption bands to vibrational transitions of methyl C–H bonds. Band strength values were obtained experimentally and compared with intensities calculated in terms of the HCAO model where only the C–H modes are considered. No adjustable parameters were used to ...