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 CH₃—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-C₁ using the rho axis method and a very flexible Hamiltonian which yields fits with root-mean-square deviations within the measurement accuracy.

中文翻译：

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微波光谱和量子化学研究对4-己烯-3-醇几乎自由内旋的构象效应

通过分子射流傅里叶变换微波光谱法，在2–26.5 GHz的频率范围内记录了4-己炔-3-醇CH ₃ -C≡C-CH（OH）-CH ₂ CH _3的微波光谱。基于量子化学计算的构象分析产生了九个具有C ₁对称性的构象异构体，其中三个可以在实验光谱中分配。丙炔基甲基CH _3- C≡C-以非常低的势垒经历内部旋转，这是因为存在圆柱对称的-C≡C-基团作为分子其余部分的间隔基，其为7.161 012（7） ）厘米^-1，4.236 5（26）厘米^-1，和7.901 6（39）厘米^-1分别分配给三个分配的构象体。光谱用的程序分析XIAM使用组合的轴的方法和程序BELGI-C ₁使用RHO轴方法和其产生配合与测量精度范围内根均方偏差非常灵活的哈密顿。