Interactions between Functional Groups. Part I. Crystal Structure of 2-Phenylethynyl-N,N-dimthlaniline at 98 K: A Remarkably Short C?H …︁ C Distance

In the crystal structure of the title compound at 98 K the dimethylamino group has pyramidal geometry. The nitrogenlone pair is not directed towards the triple bond; instead, one N? CH₃ bond lies almost in the plane of the disubstituted ring, directed away from the triple bond, while the other N? CH₃ bond and the lone pair are directed to opposite sides of the plane, nearer to the acetylene. There is a remarkably short intramolecular contact (2.39 Å) between a methyl H- and an acetylenic C-atom. The Taft σ_I parameter of the arylethynyl substituent appears to be similar to that of a carboxylic ester, judging from the bond-angle deformation at the ipso-C-atom.