The formation and reactions of 9,10-phenanthryne and related arynes by pyrolytic reactions in the vapor phase

Article abstract of DOI:10.1016/S0040-4020(01)93699-3

The formation of 9,10-phenanthryne (5), 4-methyl-9,10-phenanthryne (7) and 9,10-benz(c)phenanthryne (9) by the thermal degradation of appropriate arenedicarboxylic acid anhydrides has been investigated by a combination of VLPP and mass spectrometry and by a co-pyrolysis of the anhydrides with benzene, hexadeuterobenzene and 1,3-butadiene. Compounds 5,7 and especially 9 are formed easily by VLPP at 700-900° from the anhydrides. The results indicate that 7 and 9 are less reactive by H-addition to the aryne bond than 5, benzyne or naphthalyne, respectively. The results of the co-pyrolysis experiments show that 5 and 9 react with benzene and 1,3-butadiene by H-abstraction and addition reactions, similar to 1,2-benzyne and 2,3-naphthalyne. However, the reactivity of the aryne in the H-abstraction reaction decreases and the selectivity for the addition reaction increases in the series 1,2-benzyne, 2,3-naphthalyne, 9,10-phenanthryne and 9,10benz(c)phenanthryne.