HEATS OF HYDROGENATION AND FORMATION OF LINEAR ALKYNES AND A MOLECULAR MECHANICS INTERPRETATION

The heats of hydrogenation of all of the isomeric linear alkynes containing from six to ten carbons have been measured in hexane solution at room temperature. They were found to be systematically larger by about 4 kcal when the triple bond is at the end of the chain. For the remaining isomers, the heat of hydrogenation decreases further slightly and monotonically as the triple bond moves from the 2 position toward the center of the chain. This result is interpreted in terms of the conformational mixture present with the aid of molecular mechanics calculations. © 1979, American Chemical Society. All rights reserved.