Criegee intermediates have raised much attention in atmospheric chemistry because of their significance in ozonolysis mechanism. The simplest Criegee intermediate, CH 2 OO, and its reactions with acrylic acid including cycloadditions and insertions as main entrance channels have been investigated at CCSD(T)/cc-pVTZ// M06-2X/6-31G(d,p) level. Temperature-and pressure-dependent kinetics were predicted by solving the time-dependent master equations based on Rice−Ramsperger−Kassel−Marcus theory using MESS program, with temperatures from 200 to 500 K and pressures from 0.001 to 1000 atm. Variational transition state theory (VTST) was used for barrierless pathways and conventional transition state theory (CTST) for pathways with distinct barriers. Results indicate that hydroperoxymethyl acrylate is the dominant product under atmospheric conditions. The combination of two reactants will reduce the volatility and makes a possible factor that induces formation of secondary organic aerosols, which suggests CH 2 OO's entangled role in everincreasing air pollution.

The dissociative photoionization of cyclopentanone was investigated by means of a reflectron time-of-flight mass spectrometer (RTOF-MS) with tunable vacuum ultraviolet synchrotron radiation in the photon energy range of 9.0—15.5 eV. The photoionization efficiency (PIE) curves for molecular ion and fragment ions were measured. The ionization energy of cyclopentanone was determined to be 9.23±0.03 eV. Fragment ions from the dissociative photoionization of cyclopentanone were identified as C5H7O+, C4H5O+, C4H8+/C3H4O+, C3H3O+, C4H6+, C2H4O+, C3H6+, C3H5+, C3H4+, C3H3+, C2H5+ and C2H4+. With the aid of the ab initio calculations at the ωB97X-D/6-31+G(d,p) level of theory, the dissociative mechanisms of C5H8O+ are proposed. Ring opening and hydrogen migrations are the predominant processes in most of the fragmentation pathways of cyclopentanone.

No abstract