Hydrogen bonds. Part II. The ethynyl-H ⋯ O interaction in crystals of triethylprop-2-ynylammonium p-bromobenzenesulphonate

Abstract

The C–H stretching frequency of the ethynyl group of triethylprop-2-ynylammonium p-bromobenzenesulphonate is at 3304 cm.^–1 when the salt is in dilute solution in chloroform, but is displaced to 3180 cm.^–1 when dimethyl sulphoxide is used as solvent. A frequency shift of this magnitude is characteristic of a hydrogen-bonded interaction. In the crystalline salt the ethynyl C–H stretch appears at 3191 cm.^–1, and the crystal structure contains an H(ethynyl)⋯ O(sulphonate) contact of 2·38 Å with C–H ⋯ O angle of 154°. The crystals are orthorhombic, of space group Pca2₁, with Z= 4 in a unit cell of dimensions a= 14·63, b= 8·43, c= 14·02 Å. The atomic co-ordinates were determined by Fourier and least-squares methods, and the final discrepancy R over 1398 independent reflections is 0·073.