Infrared Multiple-photon Decomposition of Perfluorodimethyl Ether

Abstract

Infrared multiple-photon decomposition (IRMPD) of perfluorodimethyl ether, (CF₃)₂O, induced by a pulsed CO₂ laser has been studied as functions of pulse number, laser wavenumber, laser fluence, and reactant pressure. The decomposition gave carbonyl fluoride (54%), carbon monoxide (24%), hexafluoroethane (37%) and carbon tetrafluoride (5%) as main products, and tetrafluoroethylene (<1%) and difluoroacetylene (<1%), where the numbers in parentheses show the product yields relative to the (CF₃)₂O decomposition yie ld. The product distribution and the (CF₃)₂O decomposition yields changed depending on experimental parameters. The observed results are explained on the basis of the unimolecular decomposition of highly vibrationally excited (CF₃)₂O produced in the IRMP absorption process. The overall mechanism involves homolytic cleavage of the C-O bond to form trifluoromethyl and trifluoromethoxyl radicals, subsequent radical-radical reactions, and fragmentation of hot radicals or products.
The ₁₈O separation in the IRMPD of (CF₃)₂O has been extensively studied under various experimental conditions. The measurements of the isotope ₁₈O/₁₆O in CO were carried out using GC-MS system. The separation selectivity showed a maximum value of 2.5 in the irradiation of 3.5 Torr (CF₃)₂O with laser pulses at 940.55 cm^-1 and 15 J. cm^-2, where the conversion was 1.4%. However, the selectivity decreased with increasing pulse number, fluence, and pressure. t IR Photoc hemistry of Organic Compounds. I.