Vibrational Overtone Spectroscopy of Phenol and Its Deuterated Isotopomers

Abstract

We have measured the OH- and OD-stretching fundamental and overtone spectra of phenol and its deuterated isotopomers under jet-cooled conditions using nonresonant ionization detection spectroscopy and vapor-phase infrared (IR) and near-infrared (NIR) spectra at room temperature using conventional and photoacoustic spectroscopy. The OH- and OD-stretching bands in the jet-cooled spectra are about 1-10 cm(-1) wide and generally show a few Lorentzian shaped peaks. The bands in the room-temperature spectra have widths of 20-30 cm(-1) and display clear rotational profiles. The band profiles in the jet-cooled spectra arise mostly from nonstatistical intramolecular vibrational redistribution (IVR) with specific coupling to "doorway" states, which are likely to involve CH- and CD-stretching vibrations. The transition dipole moment that determines the rotational structure is found to rotate significantly from the fundamental to the third overtone and is not directed along the OH(D) bond. We use these calculated transition dipole moments to simulate the rotational structure. We determine the rotational temperature in the jet-cooled spectra to be about 0.5 K. Anharmonic oscillator local mode calculations of frequencies and intensities of the OH- and OD-stretching transitions are compared with our measured results. The calculated intensities are in good agreement with the absolute intensities obtained from conventional spectroscopy and with the relative intensities obtained from the room-temperature laser spectroscopy.

Calculated Band Profiles of the OH-Stretching Transitions in Water Dimer

“…25,26 The widths of OH-stretching transitions at ambient temperatures are typically 25-40 cm -1 with hydrogen bonded OH-stretching overtone transitions typically wider. [27][28][29][30][31] In addition, a recent cavity ringdown laboratory experiment in this region 32 measured a number of new water lines not included in the HITRAN version used in ref 24. The new water lines lead to an additional absorbance of similar magnitude to the water dimer absorbance reported in ref 24.…”

Vibrational population relaxation of hydrogen-bonded phenol complexes in solution: Investigation by ultrafast infrared pump–probe spectroscopy

“…Hydrogen-bonded complexes of phenol with various bases in non-polar solvents have been intensively studied by steady-state IR spectroscopy over many decades [1,[21][22][23][24]. Furthermore, the electronic and vibrational states of phenol clusters solvated by small molecules have been intensively studied in the gas phase [25][26][27][28][29][30]. By using various bases to act as hydrogen-bond acceptors, we can change the strength of the hydrogen bonds in the complex and thus investigate in detail the influence of hydrogen bonding on vibrational dynamics.…”

Multivariate Analysis of Phenol in Freeze-Dried and Spray-Dried Insulin Formulations by NIR and FTIR

“…The bands found in the region 5,000-4,000 cm −1 are all combination bands mostly assigned to C-H stretching υ(CH) + υ(CH). For phenol, the bands at 4,648, 4,550, 4,300 and 4,046 cm −1 are C-H combination bands (35,36). No apparent O-H stretching band is observed in the solid phenol samples.…”