Torsion-rotational spectrum of 2-acetyl-3-methylthiophene determined using microwave spectroscopy – quantum chemistry duet. The anti-conformer, being energetically more stable than the syn-form, is ultimately the only one observed in the experimental spectrum. Internal rotations arising from two inequivalent methyl groups are analyzed to yield highly accurate torsional barriers whose values are strongly influenced by steric effects.

中文翻译：

---

双顶分子的微波光谱：2-Acetyl-3-Methylthiophene

使用微波光谱测定的 2-乙酰基-3-甲基噻吩的扭转-旋转光谱 - 量子化学二重奏。的抗-conformer，是能量上高于所述更稳定的顺式-形式，最终是唯一一个在实验光谱中观察到。分析由两个不等价的甲基引起的内部旋转，以产生高度准确的扭转势垒，其值受空间效应的影响很大。