Publication Date:
2013-04-02
Description:
The thermal and light-induced O − O bond breaking of 2-ethyl-4-nitro-1(2H)-isoquinolinium hydroperoxide (IQOOH) were studied using 1 H NMR, steady-state UV/vis spectroscopy, femtosecond UV/vis transient absorption (fs TA) and time-dependent density functional theory (TD DFT) calculations. Thermal O − O bond breaking occurs at room temperature to generate water and the corresponding amide. The rate of this reaction, k = 5.4 · 10 −6 s −1 , is higher than the analogous rates of simple alkyl and aryl hydroperoxides; however, the rate significantly decreases in the presence of small amounts of methanol. The calculated structure of the transition state suggests that the thermolysis is facilitated by a 1,2 proton shift. The photochemical process yields the same products, as confirmed using NMR and UV/vis spectroscopy. However, the quantum yield for the photolysis is low (Φ = 0.7%). Fs TA studies provide additional detail of the photochemical process and suggest that the S 1 state of IQOOH undergoes fast internal conversion to the ground state, and this process competes with the excited-state O − O bond breaking. This result was supported by the fact that the model compound IQOH exhibits similar excited-state decay lifetimes as IQOOH, which is assigned to the S 1 → S 0 internal conversion. Copyright © 2013 John Wiley & Sons, Ltd. Thermal O–O bond breeding isoquinolinium hydroperoxide (IQOOH) occurs at room temperature to generate water and the corresponding amide. The rate of this reaction is significantly decreases in the presence of small amounts of methanol. These results are interpreted in terms of an unusual transition state during IQOOH decomposition process. The photochemical process yields the same products, as confirmed using NMR and UV/vis spectroscopy.
Print ISSN:
0894-3230
Electronic ISSN:
1099-1395
Topics:
Chemistry and Pharmacology
,
Physics
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