PEROXYISOBUTYRYL NITRATE

Peroxyisobutyryl nitrate, (CH3)2CHC(O)OONO2(PiBN), has been synthesized in the liquid phase, measured by electron capture gas chromatography (EC-GC), characterized in a number of decomposition tests, and prepared in-situ in the gas phase by sunlight irradiation of isobutyl nitrite, of isobutanal with NO, and of 3-methyl-1-butene with NO in air. The corresponding reaction mechanisms are outlined. In the liquid phase, PiBN decomposes to isopropylnitrate. In the gas phase, thermal decomposition in the presence of NO yields acetone (91+/-7%). Isobutanal reacts with OH predominantly (greater-than-or-equal-to 98%) by H abstraction from the carbonyl carbon, and 3-methyl-1-butene reacts with OH predominantly (greater-than-or-equal-to 98%) by addition on the C=C bond. Reaction with oxygen predominates (greater-than-or-equal-to 96%) over unimolecular decomposition for the alkoxy radicals (CH3)2CH(O) and (CH3)2CHCH2(O). Emission inventory data for hydrocarbons that are precursors to PiBN indicate that the PiBN-forming potential relative to that of PAN is less-than-or-equal-to 0.10. This ratio also represents an upper limit for the positive bias due to PiBN when measuring ambient PAN by EC-GC with packed columns, on which PiBN and PAN co-elute.