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A series of fluorinated aryl azides and fluorinated azidobenzoates were studied by laser flash photolysis techniques. Using the pyridine ylide probe method it was possible to determine whether a singlet nitrene or ring-expanded ketenimine ylide is the trappable intermediate that is generated at ambient temperature. It was determined that two fluorine substituents, ortho and ortho' substituted relative to the azide group, are required to retard ring expansion and allow bimolecular capture of the singlet nitrene. LFP of ortho, ortho' difluorinated aryl azides in methanol produces the ground triplet state of the nitrene. The results are consistent with chemical analysis of reaction mixtures. The implications of this data for the design of photoaffinity labeling reagents are discussed.

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Arylaminyl Radicals Studied by Laser Flash Presence of Arylamines that case.5,8,9 Because N2(A) metastables serve to carry these chains, species capable of quenching these metastables (e.g., NO) may well act to stabilize gaseous samples of the halogen azides.Acknowledgment. We are grateful to Professor J. Anderson of Harvard University for kindly loaning to us the computer program used for the calculations described above. This work was supported by the U.S. Air Force Weapons Laboratory under Contract No.