Phenylnitrene fluoro-substituted singlets

Table 8 Kinetic parameters of fluoro-substituted singlet phenylnitrenes.

Table 5.13 Kinetic Parameters of Fluoro-Substituted Singlet Phenylnitrenes...

Figure 11.6. Relative energies (in kcal/mol) of species involved in the ring expansions of singlet fluoro-substituted phenylnitrenes calculated at the CASPT2/cc-pVDZ//CASSCF(8,8)/ 6-3IG level, (a) Difluorinated phenylnitrenes. (b) Monofluorinated phenylnitrenes. [Reproduced with permission from N. R Gritsan, A. D. Gudmundsdottir, D. Tigelaar, Z. Zhu, W. L. Kamey, C. M. Hadad, and M. S. Platz, J. Am. Chem. Soc. 2001, J23, 1951. Copyright 2001 American Chemical Society.]...

Fig. 14 Relative energies (in kcal/mol) of species involved in the ring expansions of singlet fluoro-substituted phenylnitrenes calculated at the CASPT2/cc-pVDZ// CASSCF(8,8)/6-31G level, (a) Difluorinated phenylnitrenes. (b) Monofluorinated phenylnitrenes.

In 1997 the electronic absorption spectra of phenylnitrene" and its perfluorosubstituted analogues " were detected. Recently the kinetics of bimolecular reactions of the singlet fluoro-substituted arylnitrenes were studied using direct spectroscopic methods. The absolute rate constants of reaction of singlet perfluoroarylnitrene 16f and 16g with amines, pyridine and dimethylsulfoxide are presented in Table 11. 

Values of kisc for singlet para-substituted phenylnitrenes are given in Table 11.2. The ISC rate constant for singlet p-bromo phenylnitrene is about seven times larger than that of parent 33s and the p-fluoro and p-chloro analogues. This difference is easily attributable to a small heavy atom effect. The heavy atom effect of iodine is even larger than that of bromine, as expected, and raises the ISC rate by more than a factor of 20, relative to parent 33s. 

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