title: Direct observation of vinyl hydroperoxide.
abstract: Many alkyl-substituted Criegee intermediates are predicted to undergo an intramolecular 1,4-hydrogen transfer to form isomeric vinyl hydroperoxide species (C[double bond, length as m-dash]COOH moiety), which break apart to release OH and vinoxy radicals. We report direct detection of stabilized vinyl hydroperoxides formed via carboxylic acid-catalyzed tautomerization of Criegee intermediates. A doubly hydrogen-bonded interaction between the Criegee intermediate and carboxylic acid facilitates efficient hydrogen transfer through a double hydrogen shift. Deuteration of formic or acetic acid permits migration of a D atom to yield partially deuterated vinyl hydroperoxides, which are distinguished from the CH3CHOO, (CH3)2COO, and CH3CH2CHOO Criegee intermediates by mass. Using 10.5 eV photoionization, three prototypical vinyl hydroperoxides, CH2[double bond, length as m-dash]CHOOD, CH2[double bond, length as m-dash]C(CH3)OOD, and CH3CH[double bond, length as m-dash]CHOOD, are detected directly. Complementary electronic structure calculations reveal several reaction pathways, including the barrierless acid-catalyzed tautomerization reaction predicted previously and a barrierless addition reaction that yields hydroperoxy alkyl formate.
authors.affiliation: Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, USA. milester@sas.upenn.edu.
authors.forename: Fang
authors.initials: F
authors.lastname: Liu
authors.forename: Yi
authors.initials: Y
authors.lastname: Fang
authors.forename: Manoj
authors.initials: M
authors.lastname: Kumar
authors.forename: Ward H
authors.initials: WH
authors.lastname: Thompson
authors.forename: Marsha I
authors.initials: MI
authors.lastname: Lester
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry; D002384:Catalysis; D006861:Hydrogen Peroxide / Q000138:chemical synthesis / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000138:chemical synthesis / Q000737:chemistry; D014753:Vinyl Compounds / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D002264:Carboxylic Acids; D014753:Vinyl Compounds; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide