Roles of H 2 O to hydrogen bonds, structure and strength of complexes of CH 3 CHS and H 2 O

Six stable geometrical structures of the interaction between CH 3 CHS and H 2 O were observed on potential energy surface at the MP2/ aug‐cc‐pVDZ level of theory. Interaction energies corrected by both ZPE and BSSE for all the complexes at the MP2/aug‐cc‐pVTZ//MP2/aug‐cc‐pVDZ high level of theory range from ‐12.0 to ‐61.4 kJ.mol ‐1 . When adding water molecule to CH 3 CHS, stability of interacting system and cooperative capacity of complexes are increased. In general, the strength of complexes is contributed by O–H∙∙∙O/S and C–H∙∙∙O hydrogen bonds, and their stability decreases in the order of O–H∙∙∙O > O–H∙∙∙S > C–H∙∙∙O. Interestingly, a larger contraction and a stronger increase of stretching frequency of C sp2 –H bond as compared to C sp3 –H bond are observed following complexation although the C sp2 –H∙∙∙O H‐bonds are stronger than the C sp3 –H∙∙∙O counterparts. This detective result is mainly determined by a decrease in the electron density of the σ*(C − H) orbital.