Mass spectroscopic study of halocyanoacetylenes: Appearance energies and thermochemical data

The mass spectra of the cyanoacetylenes X? C?C? C?N, X ? H, F, CI, Br, I, are reported, together with electron impact appearance energies as determined using a modified second derivative method. From these data the enthalpies of formation and the C? X as well as the C?C bond energies are deduced. These bond energies are discussed in comparison with values of corresponding saturated and acetylenic compounds.