6-Carbonyl-2,4-cyclohexadien-l-one (1.1) has been generated from a number of precursors and a small dichotomy regarding IR spectral assignment has been resolved. Matrix photochemistry of 1.1 has been further extended to show carbon monoxide extrusion to 5-carbonylcyclopenta-1,3-diene (1.4). Generation of 1.1 from 1-13C methyl salicylate followed by the trapping of 1.1 with methanol to recover methyl salicylate showed complete scrambling of the 13C label between the 1 and 3 positions.
Cyclohexyne has been generated from three precursors by pyrolytic methods. Cyclohexyne was not directly trapped but was observed to fragment to butatriene and ethylene as previously described by Shevlen et al. FVP-MS studies conducted on the three precursors clearly demonstrated that only in one case would it be possible to isolate cyclohexyne.
In an attempt to generate CN radicals by the FVP of cyanogen chloride a photoinitiated gas phase reaction of cyanogen chloride to isocyanogen was found. Isocyanogen was found to react with metallic copper to produce a radical species which could be CN. However, this could not be confirmed by UV spectroscopy.
Triplet cycloheptatrienylidene has now been unambiguously identified by ESR spectrosocopy. In order to clarify the earlier discrepancy a number of matrix trapping experiments were conducted. This work clearly demonstrated that the earlier report by Kuzaj, Luerssen and Wentrup was correct.
Finally the thermal and photochemical rearrangements of 2-(trifluoromethyl) phenylcarbene (5.2) were investigated. Thermally 5.2 was seen to undergo ring expansion and ring contraction reactions which were known for phenylcarbene. Two other products formed showed the carbene centre reacting with the trifluoromethyl group. The generation of 5.2 in an argon matrix by photolysis of 3-phcnyl-3-( trifluoromethyl)-3H-diazirinc (5.1) or 2,2,2-trifluoro-1-phenyldiazoethane gave two triplet carbenes as observed by ESR spectroscopy.