3 research outputs found
Photoisomerization and Infrared Spectra of Allene and Propyne Cations in Solid Argon
Allene
and propyne as well as their cationic forms play important
roles in combustion and interstellar chemistry and serve as a model
system for molecular spectroscopic studies. Both cations show Jahn–Teller
(J–T) distortions in their ground states. These J–T
distortions make the theoretical and experimental studies of their
electronic structures difficult. We produced allene cations upon electron
bombardment during matrix deposition of Ar containing a small proportion
of allene. The intensities of the absorption features of the allene
cation decreased after irradiation with UV light, whereas new bands
attributed to propyne cations increased. The observed line wavenumbers,
relative intensities, and deuterium-substituted isotopic ratios of
the isomers of C<sub>3</sub>H<sub>4</sub><sup>+</sup> agree satisfactorily
with those predicted by density functional theory at the B3PW91/aug-cc-pVTZ
level of theory. This method produced the hydrocarbon cations of interest
with few other fragments that enabled the clear identification of
the IR spectra of allene and propyne cations
Study on the Adsorption and Reactions of FCH<sub>2</sub>CH<sub>2</sub>OH and ClCH<sub>2</sub>CH<sub>2</sub>OH on Ni(111): Effects of Halogen and Preadsorbed Oxygen
Temperature-programmed reaction/desorption
(TPR/D), reflection–absorption
infrared spectroscopy (RAIRS), and X-ray photoelectron spectroscopy
(XPS) have been employed to investigate the reactions of FCH<sub>2</sub>CH<sub>2</sub>OH and ClCH<sub>2</sub>CH<sub>2</sub>OH on Ni(111)
and oxygen-precovered Ni(111) (O/Ni(111)). In the chemical process
of FCH<sub>2</sub>CH<sub>2</sub>OH on Ni(111), only FCH<sub>2</sub>CH<sub>2</sub>O- is found to be the stable reaction intermediate,
which starts to appear at ∼190 K. At low coverages, this intermediate
decomposes into H<sub>2</sub> and CO. Additional C<sub>2</sub>H<sub>4</sub> (219 K) is generated at higher exposures. On Ni(111) at 200
K, ClCH<sub>2</sub>CH<sub>2</sub>OH mainly dissociates to form ClCH<sub>2</sub>CH<sub>2</sub>O- and -CH<sub>2</sub>CH<sub>2</sub>O- at lower
exposures, with H<sub>2</sub> and CO as the final products, while
ClCH<sub>2</sub>CH<sub>2</sub>O- becomes predominant at higher exposures
and is responsible for the extra C<sub>2</sub>H<sub>4</sub> channel
of 218 K. C<sub>2</sub>H<sub>4</sub> is also generated at 161 and
174 K as the exposure is increased to render multilayer adsorption.
Due to the competition in the scission of the carbon–halogen
and carbon–hydrogen bonds, ClCH<sub>2</sub>CH<sub>2</sub>OH
has better reactivity toward C<sub>2</sub>H<sub>4</sub> formation
than FCH<sub>2</sub>CH<sub>2</sub>OH. No -CH<sub>2</sub>CH<sub>2</sub>OH is found in the decomposition of FCH<sub>2</sub>CH<sub>2</sub>OH and ClCH<sub>2</sub>CH<sub>2</sub>OH on Ni(111), which is the
intermediate in the reaction of ICH<sub>2</sub>CH<sub>2</sub>OH on
Ni(100) and Pd(111). The presence of preadsorbed oxygen can enhance
the ethylene formation at low coverages of FCH<sub>2</sub>CH<sub>2</sub>OH and ClCH<sub>2</sub>CH<sub>2</sub>OH. At higher coverages, additional
acetaldehyde is formed in the reaction of FCH<sub>2</sub>CH<sub>2</sub>OH, in contrast to the ethylene oxide from ClCH<sub>2</sub>CH<sub>2</sub>OH
Study on the Adsorption and Reactions of FCH<sub>2</sub>CH<sub>2</sub>OH and ClCH<sub>2</sub>CH<sub>2</sub>OH on Ni(111): Effects of Halogen and Preadsorbed Oxygen
Temperature-programmed reaction/desorption
(TPR/D), reflection–absorption
infrared spectroscopy (RAIRS), and X-ray photoelectron spectroscopy
(XPS) have been employed to investigate the reactions of FCH<sub>2</sub>CH<sub>2</sub>OH and ClCH<sub>2</sub>CH<sub>2</sub>OH on Ni(111)
and oxygen-precovered Ni(111) (O/Ni(111)). In the chemical process
of FCH<sub>2</sub>CH<sub>2</sub>OH on Ni(111), only FCH<sub>2</sub>CH<sub>2</sub>O- is found to be the stable reaction intermediate,
which starts to appear at ∼190 K. At low coverages, this intermediate
decomposes into H<sub>2</sub> and CO. Additional C<sub>2</sub>H<sub>4</sub> (219 K) is generated at higher exposures. On Ni(111) at 200
K, ClCH<sub>2</sub>CH<sub>2</sub>OH mainly dissociates to form ClCH<sub>2</sub>CH<sub>2</sub>O- and -CH<sub>2</sub>CH<sub>2</sub>O- at lower
exposures, with H<sub>2</sub> and CO as the final products, while
ClCH<sub>2</sub>CH<sub>2</sub>O- becomes predominant at higher exposures
and is responsible for the extra C<sub>2</sub>H<sub>4</sub> channel
of 218 K. C<sub>2</sub>H<sub>4</sub> is also generated at 161 and
174 K as the exposure is increased to render multilayer adsorption.
Due to the competition in the scission of the carbon–halogen
and carbon–hydrogen bonds, ClCH<sub>2</sub>CH<sub>2</sub>OH
has better reactivity toward C<sub>2</sub>H<sub>4</sub> formation
than FCH<sub>2</sub>CH<sub>2</sub>OH. No -CH<sub>2</sub>CH<sub>2</sub>OH is found in the decomposition of FCH<sub>2</sub>CH<sub>2</sub>OH and ClCH<sub>2</sub>CH<sub>2</sub>OH on Ni(111), which is the
intermediate in the reaction of ICH<sub>2</sub>CH<sub>2</sub>OH on
Ni(100) and Pd(111). The presence of preadsorbed oxygen can enhance
the ethylene formation at low coverages of FCH<sub>2</sub>CH<sub>2</sub>OH and ClCH<sub>2</sub>CH<sub>2</sub>OH. At higher coverages, additional
acetaldehyde is formed in the reaction of FCH<sub>2</sub>CH<sub>2</sub>OH, in contrast to the ethylene oxide from ClCH<sub>2</sub>CH<sub>2</sub>OH