The microwave rotational spectrum of the gas-phase bimolecular heterodimer formed between cis-1,2-difluoroethylene and acetylene is obtained using Fourier transform microwave spectroscopy from 5.9 to 21.2 GHz. Rotational constants derived from the analysis of the spectra for the normal isotopologue and singly substituted 13C isotopologues, obtained in natural abundance, allow the determination of the structure of the complex, which, in the absence of a fluorine-hydrogen atom pair located cis to each other, adopts a sterically disfavored geometry ("side-binding") in which the acetylene interacts with a geminal fluorine-hydrogen atom pair. Structural details are found to be similar to those of previously studied heterodimers with side-binding of acetylene to fluorine while reflecting the degree of halosubstitution. A detailed comparison with the (Z)-1-chloro-2-fluoroethylene-acetylene complex reveals information regarding the relaxed steric requirements for hydrogen bonding to chlorine as opposed to hydrogen bonding to fluorine.

中文翻译：

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探索乙炔与双链烯烃氢氟原子对的空间不利结合：顺式1,2-二氟乙烯-乙炔的微波光谱和分子结构。

使用5.9至21.2 GHz的傅里叶变换微波光谱法，可得出在顺式1，2-二氟乙烯与乙炔之间形成的气相双分子异二聚体的微波旋转光谱。通过自然丰度获得的正常同位素和单取代13C同位素的光谱分析得出的旋转常数，可以确定配合物的结构，在没有氟-氢原子对的情况下，它们的结构另一方面，乙炔采用空间上不利的几何形状（“侧结合”），其中乙炔与双键氟-氢原子对相互作用。发现结构细节与先前研究的具有乙炔与氟的侧结合的异二聚体相似，同时反映了卤代取代的程度。