WEAK HYDROGEN-BONDING .2. THE HYDROGEN-BONDING NATURE OF SHORT C-H-CENTER-DOT-CENTER-DOT-CENTER-DOT-PI CONTACTS - CRYSTALLOGRAPHIC, SPECTROSCOPIC AND QUANTUM-MECHANICAL STUDIES OF SOME TERMINAL ALKYNES
T. Steiner et al., WEAK HYDROGEN-BONDING .2. THE HYDROGEN-BONDING NATURE OF SHORT C-H-CENTER-DOT-CENTER-DOT-CENTER-DOT-PI CONTACTS - CRYSTALLOGRAPHIC, SPECTROSCOPIC AND QUANTUM-MECHANICAL STUDIES OF SOME TERMINAL ALKYNES, Perkin transactions. 2, (7), 1995, pp. 1321-1326
In a number of crystalline terminal alkynes, the alkyne C-H groups for
m short intermolecular contacts with other alkyne or with aromatic,moi
eties. A particularly short C-H ... phenyl contact is found in (+/-)-3
-phenylbut-1-yn-3-ol, with an H ... midpoint separation of only 2.51 A
ngstrom. Crystallographic, spectroscopic:and computational evidence is
given to show that these contacts represent hydrogen-bond-type intera
ctions. Quantum chemical calculations indicate hydrogen bond energies
in the range 1-2.2 kcal mol(-1). Interconnected contacts such as C=C-H
... C=C-H ... C=C-H exhibit a pronounced cooperativity effect, with e
nergy increases of similar to 0.5 kcal mol(-1) compared with isolated
contacts. Based on these results, the role of the terminal alkyne grou
p in cooperative hydrogen bond networks is described as topologically
paralleling that of hydroxy groups.