Preparation, properties, and reactions of carbonyl oxides

Oligomer formation during gas-phase ozonolysis of small alkenes and enol ethers: new evidence for the central role of the Criegee Intermediate as oligomer chain unit

“…Addition of a CI to the double bond of the initial alkene, leading to formation of an 1,2-dioxolane, represents another reaction pathway of CI known from liquid-phase alkene ozonolysis (Bunnelle, 1991), in particular for vinyl ethers (Keul et al, 1985). A similar mechanism as a minor reaction pathway of stabilized CI has been attributed to products identified in the oleic acid/ozone and methyl oleate/ozone reaction systems (Mochida et al, 2006;Zahardis et al, 2006).…”

“…Moreover, these oligomeric products were found by Barton et al (2004) to be thermally stable when extracted and refluxed in methanol for a few hours, a behaviour that agrees with their observed stability in methanol used as solvent for the filter extraction in our work. Furthermore, Barton et al (2004) observed a strong competition among the described formation of oligoperoxides consisting of CI-like units and well known liquid-phase reactions of the CI with compounds carrying hydroxylic functionalities to form small hydroperoxides (see above; Bunnelle, 1991 take place only in non-prononated solvents, such as pentane, while in methanol, the corresponding hydroperoxide, 2-methoxy-2-propyl hydroperoxide, was formed instead through reaction of the CI, (CH 3 ) 2 COO (iso-C 3 -CI), with MeOH. These observations of liquid-phase chemistry are in analogy to the suppression of SOA and oligomer formation during gas-phase enol ether ozonolysis in the presence of excess HCOOH or H 2 O, as described in our previous work (Sadezky et al, 2006).…”

“…CI formed from the ozonolysis of small simple alkenes in the gas phase and stabilized by collision with inert gas molecules have been shown to undergo a variety of reactions similar to those known for a long time from liquid-phase chemistry (Calvert et al, 2000, and references therein;Bunnelle, 1991). Reactions of the stabilized C 1 -CI and C 2 -CI have been thoroughly investigated for gas-phase ozonolysis of alkyl vinyl ethers (AVE) and ethyl propenyl ether (EPE) (Sadezky, 2005), ethene (Neeb et al, 1998, 2-butene and propene (Neeb et al, 1996).…”

“…Oleic acidozone reactions in these studies take place in the condensed phase either in bulk solution with high reactant concentrations or in liquid submicron aerosol droplets after diffusion of ozone into the particles (Zahardis and Petrucci, 2007;Zahardis et al, 2005). Moreover, 1,2,4,5-tetroxanes are known as common crystalline byproducts of many bulk liquid-phase ozonolysis reactions (Bunnelle, 1991). Formation of linear CI dimers in the liquid phase is mentioned by March (1992), these compounds are however reported to be unstable and to directly decompose into two carbonyl compounds and O 2 .…”

Acidity enhances the formation of a persistent ozonide at aqueous ascorbate/ozone gas interfaces

“…In contrast with reaction 1, the ozonolysis of unsaturated neutral species, such as undissociated AH 2 , in nonaqueous media ultimately produces stable (Criegee or secondary) 1,2,4-trioxolane ozonides (19,20). In water, however, the dominant products are ␣-hydroxyalkyl hydroperoxides rather than ozonides (21,22). Significantly, the O 2 ( 1 ⌬ g ) yields and rates of the AH 2 , GSH, and UA reactions with O 3 (g) measured at the air-water interface are markedly different from those reported in bulk solution (23).…”