Details

Autor(en) / Beteiligte

• Vansco, Michael F.
• Marchetti, Barbara
• Trongsiriwat, Nisalak
• Bhagde, Trisha
• Wang, Guanghan
• Walsh, Patrick J.
• Klippenstein, Stephen J.
• Lester, Marsha I.

Titel

Synthesis, Electronic Spectroscopy, and Photochemistry of Methacrolein Oxide: A Four-Carbon Unsaturated Criegee Intermediate from Isoprene Ozonolysis

Ist Teil von

• Journal of the American Chemical Society, 2019-08, Vol.141 (38)

Ort / Verlag

United States: American Chemical Society (ACS)

Erscheinungsjahr

2019

Link zum Volltext

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Ozonolysis of isoprene, one of the most abundant volatile organic compounds in the earth’s atmosphere, generates the four-carbon unsaturated methacrolein oxide (MACR-oxide) Criegee intermediate. The first laboratory synthesis and direct detection of MACR-oxide is achieved through reaction of photolytically generated, resonance-stabilized iodoalkene radicals with oxygen. MACR-oxide is characterized on its first π* ← π electronic transition using a ground-state depletion method. MACR-oxide exhibits a broad UV–visible spectrum peaked at 380 nm with weak oscillatory structure at long wavelengths ascribed to vibrational resonances. Complementary theory predicts two strong π* ← π transitions arising from extended conjugation across MACR-oxide with overlapping contributions from its four conformers. Electronic promotion to the 11ππ* state agrees well with experiment, and results in nonadiabatic coupling and prompt release of O 1D products observed as anisotropic velocity-map images. Furthermore, this UV–visible detection scheme will enable study of its unimolecular and bimolecular reactions under thermal conditions of relevance to the atmosphere.