Photo-initiated oxygen-atom transfer reaction from nitrogen dioxide to acetylene and methyl acetylene under matrix isolation conditions

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1991

OSTI ID:5600942

Harrison, J A

The study of the photo-initiated reaction of nitrogen dioxide (NO[sub 2]) with acetylene, and with methyl acetylene is reported. Fourier transform infrared spectroscopy is utilized to monitor the laser photochemistry of alkyne [center dot] NO[sub 2] reactive pairs. The reactive pairs are isolated in cryogenic (12 K) rare-gas matrices. Photooxidation of both acetylene [center dot] NO[sub 2] and methyl acetylene [center dot] NO[sub 2] is observed at photon energies far below the NO[sub 2] gas-phase dissociation threshold (71.9 kcal mol[sup [minus]1], 398 nm). The threshold for methyl acetylene + NO[sub 2] is 46.7 [+-] 0.3 kcal mol[sup [minus]1] (613 [+-] 3 nm) and the corresponding threshold for acetylene + NO[sub 2] is at 55.0 [+-] 5.3 kcal mol[sup [minus]1] (520 [+-] 50 nm). The sole photochemical product observed in the acetylene + NO[sub 2] reaction is ketene. Heavy isotope ([sup 15]N and [sup 18]O) substitution of product ketenes showed the constitution of the intermediate to be that of an iminoxy radical. The iminoxy radical is presumably formed by the reaction of a transient ketocarbene with in-cage nitric oxide coproduct. Deuterium substitution revealed that the iminoxy radical contains an aldehyde group, confirming that the methyl acetylene + NO[sub 2] reaction is regioselective (at wavelengths longer than 520 nm). Wavelength selective photolysis of the aldehyde iminoxy radical allowed the observed multiplets to be assigned to four conformers. In addition, the inimoxy radical isomers are found to photolyze at [lambda] [le] 625 nm into propynol, methyl ketene, and a third secondary photoproduct.

• Research Organization: California Univ., Berkeley, CA (United States)
• OSTI ID: 5600942
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400500* -- Photochemistry
ABSORPTION SPECTROSCOPY
ACETYLENE
ALKYNES
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
DEUTERIUM
ELECTROMAGNETIC RADIATION
EVEN-EVEN NUCLEI
FOURIER ANALYSIS
HYDROCARBONS
HYDROGEN ISOTOPES
ISOMERS
ISOTOPES
KETENES
KETONES
LASER RADIATION
LIGHT NUCLEI
MATRIX ISOLATION
NITRIC OXIDE
NITROGEN 15
NITROGEN COMPOUNDS
NITROGEN DIOXIDE
NITROGEN ISOTOPES
NITROGEN OXIDES
NUCLEI
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
OXIDES
OXYGEN 18
OXYGEN COMPOUNDS
OXYGEN ISOTOPES
PHOTOCHEMICAL REACTIONS
PHOTOCHEMISTRY
PHOTOLYSIS
PROPYNE
RADIATIONS
RADICALS
REACTION INTERMEDIATES
SPECTROSCOPY
STABLE ISOTOPES