O. Sorkhabi et al., The ultraviolet photochemistry of phenylacetylene and the enthalpy of formation of 1,3,5-hexatriyne, J AM CHEM S, 123(4), 2001, pp. 671-676
The ultraviolet photochemistry of phenylacetylene was studied in a molecula
r beam at 193 nm. The only primary photofragments observed were HCCH (acety
lene) and C6H4 Some of the C6H4 molecules were found to decompose to 1,3,5-
hexatriyne and molecular hydrogen. An enthalpy of formation of DeltaH(f) le
ss than or equal to 160 +/- 4 kcal mol(-1) wad determined for 1,3,5-hexatri
yne from the energetic threshold for this process, This experimentally dete
rmined value agrees well with our ab initio calculations performed at the G
2 level of theory. Angular distribution measurements for the HCCH + C6H4 ch
annel yielded an isotropic distribution and were attributed to a long-lived
intermediate and ground-state dissociation. An exhaustive search yielded n
o evidence for the phenyl + ethynyl, dr the atomic hydrogen elimination cha
nnels even though these:were observed in the pyrolytic studies of phenylace
tylene [Hofmann,J.; Zimmermann, G.; Guthier; K.; Hebgen, P.; Homann, K. ii.
Liebigs Ann. 1995, 631, 1995, Guthier, K.; Hebgen, P.; Hofmann, K. H.; Zim
mermann, G. Liebigs Ann. 1995, 637, 1995].