Ionization Spectroscopy of Conformational Isomers of Propanal: The Origin of the Conformational Preference

Abstract

Two different conformational isomers of propanal, cis and gauche, are investigated by the vacuum-UV mass-analyzed threshold ionization (VUV-MATI) spectroscopy to give accurate adiabatic ionization potentials of 9.9997 +/- 0.0006 eV and 9.9516 +/- 0.0006 eV, respectively. cis-Propanal, which is the more stable conformer in the neutral state, becomes less stable in the cation compared to gauche-propanal. Vibrational structures revealed in the MATI spectra indicate that cis and gauche isomers undergo their unique structural changes upon ionization. The ionization of gauche-propanal induces a geometrical change along the conformational coordinate, suggesting that the steric effect in the ground state is diminished upon ionization. Natural bonding orbital (NBO) calculations provide the extent of hyperconjugation in each conformational isomer of propanal.

REMPI and IR-UV double resonance spectroscopy of 3-aminophenol·(NH3)1 cluster in the gas phase

“…It was reported that collision effect during expansion can result in exclusive formation of the most stable conformer. By changing the buffer gas from helium to argon, enhanced conformational cooling lead to exclusive formation of the cis conformational isomer of propanal over the gauche isomer [28]. The effect was explained with different collision cross-sections of collision gases.…”

The study of ethanethiol structure and vibrational spectra based on Ab initio

“…MW=62.14, on the structure, oxygen atoms in the ethanol is substituted by sulfur atoms, then to obtain the compounds. The schematic structure of ethanethiol is shown in Fig.1, the structural formula is CH 3 CH 2 SH [1]. Ethanethiol is toxic [2] and oily liquid with achromatic color , transparent, volatile.…”

Solvent-assisted conformational isomerization and the conformationally-pure REMPI spectrum of 3-aminophenol

“…[12][13][14][15][16][17] Sometimes a simple change of expansion gas can drastically change the distribution of conformations by relaxing the less stable conformers to the more stable ones. 18 There have been many studies on the relaxation between conformers. Rotational conformers of ethyl formate, ethanol, and isopropanol seeded in inert gases (He, Ne, Ar, and Kr) have been studied and it was found that those conformers with internal rotation barriers less than 400 cm À1 were efficiently relaxed.…”