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Updated: Feb 4, 2026

Non-equilibrium Microwave Plasma for Efficient High Temperature Chemistry
Published on: August 1, 2017
Conformational effect on the almost free internal rotation in 4-hexyn-3-ol studied by microwave spectroscopy and
Konrad Eibl1, Wolfgang Stahl1, Isabelle Kleiner2
1Institute of Physical Chemistry, RWTH Aachen University, Landoltweg 2, D-52074 Aachen, Germany.
Abstract:
The microwave spectrum of 4-hexyn-3-ol, CH3-C≡C-CH(OH)-CH2CH3, was recorded in the frequency range of 2-26.5 GHz by molecular jet Fourier transform microwave spectroscopy. The conformational analysis based on quantum chemical calculations yielded nine conformers exhibiting C1 symmetry, of which three could be assigned in the experimental spectrum. The propynyl methyl group CH -C≡C- experiences internal rotation with a very low barrier due to the presence of the cylindrically symmetric -C≡C- group serving as a spacer to the rest of the molecule, which is 7.161 012(7) cm-1, 4.236 5(26) cm-1, and 7.901 6(39) cm-1 for the three assigned conformers, respectively. The spectrum was analyzed with the program XIAM using the combined axis method and the program BELGI-C using the rho axis method and a very flexible Hamiltonian which yields fits with root-mean-square deviations within the measurement accuracy.
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