Joseph J. Zupancic

The reactions of fluorenylidene with heteroatomic nucleophiles

Abstract The reaction of fluorenylidene with heteroatomic nucleophiles gives good yields of addition products. The rates of these reactions were determined using laser spectrophotometric techniques Kinetic and product isotope effects were measured. The results of this investigation show that the reaction of the carbene with the nucleophile is not a one-step process. The implication of these conclusions to the spin selective reactions of carbenes and their utility as photoaffinity labels is discussed.

Additions and Corrections - Chemical and Physical Properties of 2,3-Benzofluorenylidene. Closing the Gap between Singlet and Triplet Carbenes.

Irradiation of 2,3-benzo-ll-diazofluorene generates the carbene 2,3-benzo-ll-fluorenylidene. This carbene was detected in frozen media by EPR and optical spectroscopy and shown to have a triplet ground state. The carbene was detected in fluid solution at room temperature by nanosecond and picosecond laser spectroscopy. The reactions of the carbene with methyl alcohol, cyclohexane, and a-methylstyrene were examined. Direct photolysis, triplet sensitization, and analysis of the reaction kinetics all show that the singlet state of the carbene is present in equilibrium with the triplet in significant concentration. The energy gap between the ground-state triplet and the first singlet state (AGsT) is estimated to be less than or equal to 1.0 kcal/mol. The properties of this carbene are compared with those of fluorenylidene, and a correlation of carbene structure and reactivity is suggested.