Vibrational spectra of diacetylene and its deuterated species

Reactions of C6H6 and C6D6 after 193 nm excimer laser irradiation have been studied by the trapping of products into an argon matrix at 14 K. IR spectroscopy was used to identify the product species; most were known species arising from either isomerization or fragmentation. The ratio of isomerization product to fragmentation product was seen to vary as a function of sample concentration. Addition of Cl2 as an electron trap to aid in cation formation led to a number of chlorinated benzene species as well as biphenyl. A set of bands was also observed that could be photobleached by a mercury arc lamp; these bands may be due either to C6H6+ or to the σ complex C6H6Cl+. Parallel experiments with C6D6 were conducted in support of these observations.

193 nm excimer laser photochemistry of benzene in argon matrices

Matrix FTIR study of products of benzene transformations in a pulsed glow discharge at low pressure in highly diluted mixtures of benzene with argon in the presence and absence of small oxygen additions has been carried out. Formation of the following hydrocarbon species has been established: acetylene, butadiyne, fulvene, benzvalene, methane, ethylene, phenyl, ethynyl and butadiynyl radicals. It has been shown that oxygen additions mainly result in deep oxidation of benzene to CO2, CO and H2O, although some products of intermediate oxidation have been detected. Those are formaldehyde, formyl radical, ketene, ketenyl radical, propadiene-1,3-dione, propadien-3-on-1-ilyden and hydroperoxyl radical. At the same time, it has unexpectedly been found that oxygen additions strongly increase the yield of butadiyne. Possible pathways, leading to formation of the listed species have been discussed on the basis of the obtained data and results reported in the literature.

Matrix IR Study of Benzene Transformations in a Pulsed Glow Discharge in the Absence and the Presence of Oxygen

An infrared study of the reaction of acetylene halides : hcccl with o2

Vacuum ultraviolet photochemical experiments have been performed in an argon matrix, at low temperature (− 12 K). It appears that starting from a variety of simple organic molecules photo-products are formed which nearly always show strong light absorption in the 200- 235 nm range. Infrared and ultraviolet spectra indicate that the absorbing species are polyacetylene and cyano-polyacetylene type molecules. Such molecules are found in space. The polyacetylenes and cyano-polyacetylenes have extremely strong light absorption bands in the ultraviolet; in a matrix the shift in band position is quite large. It is suggested that such molecules on grains could give rise to the 216 nm interstellar extinction hump.

Molecular Origin of the 216 nm Interstellar Hump

In the course of an investigation into the reactions of ethynyl radicals with alkynes1, monobromoethyne and certain polyalkynes were synthesized and their infra-red spectra were recorded. Although ...

D. J. Hucknall

Papers

Infra-Red Spectra of Monobromoethyne and Some Polyalkynes