Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
J Phys Chem A. 2010 Aug 19;114(32):8337-44. doi: 10.1021/jp105081f.
The water complexes of 4-ethynylbenzonitrile (4EBzN) were investigated with IR-UV double resonance spectroscopy. Water interacts with the pi electron density of the C[triple bond]N group in 4EBzN, leading to the formation of a quasiplanar cyclic complex incorporating C-H...O and O-H...pi hydrogen bonds. The (H(2)O)(2) and (H(2)O)(3) complexes of 4EBzN are characterized by the presence of hydrogen bonding bridges between the hydrogen bond donor (aromatic C-H group) and acceptor (C[triple bond]N group) sites present in 4EBzN. The present structures of the water complexes are similar to the corresponding complexes of benzonitrile but are drastically different from water complexes of phenylacetylene and fluorophenylacetylenes. The infrared spectra in the O-H stretching region indicate that the stability of all the water complexes of 4EBzN is lower than that of the corresponding complexes of benzonitrile, which can be attributed to the mild electron withdrawing ability of the ethynyl group present in the para position relative to the nitrile group. Hierarchally, the C[triple bond]N group has the higher propensity to form hydrogen bonding relative to the acetylenic group and the benzene ring in 4EBzN.
采用红外-紫外双共振光谱法研究了 4-乙炔基苯甲腈（4EBzN）的水合复合物。水与 4EBzN 中的 C≡N 基团的π电子密度相互作用，形成了一个准平面环状复合物，其中包含 C-H…O 和 O-H…π氢键。（H(2)O）(2)和（H(2)O）(3)的 4EBzN 复合物的特征在于氢键供体（芳族 C-H 基团）和受体（C≡N 基团）位点之间存在氢键桥，这些位点存在于 4EBzN 中。目前水合复合物的结构与苯甲腈的相应复合物相似，但与苯乙炔和氟苯乙炔的水合复合物有很大的不同。O-H 伸缩区域的红外光谱表明，所有 4EBzN 的水合复合物的稳定性均低于苯甲腈的相应复合物，这归因于相对于腈基，对位存在的乙炔基的轻微吸电子能力。在 4EBzN 中，相对于乙炔基和苯环，C≡N 基团具有更高的形成氢键的倾向。
