Organic chemistry

Ring (chemistry)

Stereochemistry

Crystallography

Chemistry

Moiety

Photodissociation

Photochemistry

Proceedings of the National Academy of Sciences

The recent observation [Wentworth, P., Jones, L. H., Wentworth, A. D., Zhu, X. Y., Larsen, N. A., Wilson, I. A., Xu, X., Goddard, W. A., Janda, K. D., Eschenmoser, A. &amp; Lerner, R. A. (2001) Science 293, 1806–1811] that antibodies form H 2 O 2 from 1 O 2 plus H 2 O was explained in terms of the formation of the H 2 O 3 species that in the antibody reacts with a second H 2 O 3 to form H 2 O 2 . There have been few reports of the chemistry for forming H 2 O 3 , but recently Engdahl and Nelander [Engdahl, A. &amp; Nelander, B. (2002) Science 295, 482–483] reported that photolysis of the ozone–hydrogen peroxide complex in argon matrices leads to significant concentrations of H 2 O 3 . We report here the chemical mechanism for this process, determined by using first-principles quantum mechanics. We show that in an argon matrix it is favorable (3.5 kcal/mol barrier) for H 2 O 2 and O 3 to form a [(HO 2 )(HO 3 )] hydrogen-bonded complex [head-to-tail seven-membered ring (7r)]. In this complex, the barrier for forming H 2 O 3 plus 3 O 2 is only 4.8 kcal/mol, which should be observable by means of thermal processes (not yet reported). Irradiation of the [(HO 2 )(HO 3 )-7r] complex should break the HO–OO bond of the HO 3 moiety, eliminating 3 O 2 and leading to [(HO 2 )(HO)]. This [(HO 2 )(HO)] confined in the matrix cage is expected to rearrange to also form H 2 O 3 (observed experimentally). We show that these two processes can be distinguished isotopically. These results (including the predicted vibrational frequencies) suggest strategies for synthesizing H 2 O 3 and characterizing its chemistry. We suggest that the [(HO 2 )(HO 3 )-7r] complex and H 2 O 3 are involved in biological, atmospheric, and environmental oxidative processes.

Peroxone chemistry: Formation of H 2 O 3 and ring-(HO 2 )(HO 3 ) from O 3 /H 2 O 2