Chemistry Reference
In-Depth Information
have the lowest energy singlet states of a similar nature. All these singlet nitrenes are
cyclic closed-shell species significantly stabilized due to the O
N bonding inter-
action, although only carbonyl nitrenes have singlet ground state. The nitrene esters,
sulfonyl-, phosphinyl-, and phosphorylnitrenes are the triplet ground state species.
Nevertheless, the singlet-triplet splitting for these nitrenes (4-15 kcal/mol) is
significantly smaller than in alkyl nitrenes (
30 kcal/mol).
14,15
As carbonyl nitrenes have a singlet ground state, it was possible to use nanosecond
spectroscopy to directly observe these singlet nitrenes and to study their bimolecular
reactions. Very recently,
36,37,166,170
femtosecond and picosecond time-resolved
spectroscopic techniques have been applied to study primary processes in the
photochemistry of carbonyl, phosphoryl, and sulfonyl azides, as well as selected
reactions of corresponding singlet nitrenes. The combination of theory and ultrafast
time-resolved spectroscopy gave also new insights into the acyl azide excited state
chemistry including the concerted photo-Curtius rearrangement of carbonyl
azides.
36,37,166
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15. Gritsan, N. P.; Platz, M. S. in
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Brase, S.,
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