Low barrier methyl rotation in 3-pentyn-1-ol as observed by microwave spectroscopy

Konrad Eibl (1, 2) , Raphaela Kannengiesser (1) , Wolfgang Stahl (1) , Ha Vinh Lam Nguyen (2) , Isabelle Kleiner (2)

1 RWTH - Rheinisch-Westfälische Technische Hochschule Aachen University
2 LISA (UMR_7583) - Laboratoire Interuniversitaire des Systèmes Atmosphériques

The rotational spectrum of 3-pentyn-1-ol, CH3−C≡C−CH2CH2OH, was measured using a molecular beam Fourier transform microwave spectrometer operating in the frequency range from 2 to 26.5 GHz. A two-dimensional potential energy surface was calculated at the MP2/6-311++G(d,p) level of theory for a conformational analysis, yielding five conformers. The most stable conformer exhibits C1 symmetry and was assigned in the spectrum by comparison with the results from quantum chemical calculations. The barrier to internal rotation of the propynyl methyl group CH3−C≡C− was found to be only 9.4552(94) cm−1. Molecular parameters and internal rotation parameters could be accurately determined using the program xiam and belgi-C1. The internal rotation barrier was compared with those of other molecules containing a propynyl methyl group.

Mots clés: propynyl; rotational spectroscopy; internal rotation; large amplitude motion; conformation analysis; potential energy surface

Domaines: Chimie théorique et/ou physique

Konrad Eibl, Raphaela Kannengiesser, Wolfgang Stahl, Ha Vinh Lam Nguyen, Isabelle Kleiner. Low barrier methyl rotation in 3-pentyn-1-ol as observed by microwave spectroscopy. Molecular Physics, 2016, 114 (23), pp.3483-3489. ⟨10.1080/00268976.2016.1239034⟩. ⟨hal-03183104⟩