1571-60-4Relevant academic research and scientific papers
Formation of complex organic molecules in methanol and methanol-carbon monoxide ices exposed to ionizing radiation - A combined FTIR and reflectron time-of-flight mass spectrometry study
Maity, Surajit,Kaiser, Ralf I.,Jones, Brant M.
, p. 3081 - 3114 (2015/02/05)
The radiation induced chemical processing of methanol and methanol-carbon monoxide ices at 5.5 K exposed to ionizing radiation in the form of energetic electrons and subsequent temperature programmed desorption is reported in this study. The endogenous formation of complex organic molecules was monitored online and in situ via infrared spectroscopy in the solid state and post irradiation with temperature programmed desorption (TPD) using highly sensitive reflectron time-of-flight (ReTOF) mass spectrometry coupled with single photoionization at 10.49 eV. Infrared spectroscopic analysis of the processed ice systems resulted in the identification of simple molecules including the hydroxymethyl radical (CH2OH), formyl radical (HCO), methane (CH4), formaldehyde (H2CO), carbon dioxide (CO2), ethylene glycol (HOCH2CH2OH), glycolaldehyde (HOCH2CHO), methyl formate (HCOOCH3), and ketene (H2CCO). In addition, ReTOF mass spectrometry of subliming molecules following temperature programmed desorption definitely identified several closed shell C/H/O bearing organics including ketene (H2CCO), acetaldehyde (CH3COH), ethanol (C2H5OH), dimethyl ether (CH3OCH3), glyoxal (HCOCOH), glycolaldehyde (HOCH2CHO), ethene-1,2-diol (HOCHCHOH), ethylene glycol (HOCH2CH2OH), methoxy methanol (CH3OCH2OH) and glycerol (CH2OHCHOHCH2OH) in the processed ice systems. Additionally, an abundant amount of molecules yet to be specifically identified were observed sublimating from the irradiated ices including isomers with the formula C3H(x=4,6,8)O, C4H(x=8,10)O, C3H(x=4,6,8)O2, C4H(x=6,8)O2, C3H(x=4,6)O3, C4H8O3, C4H(x=4,6,8)O4, C5H(x=6,8)O4 and C5H(x=6,8)O5. The last group of molecules containing four to five oxygen atoms observed sublimating from the processed ice samples include an astrobiologically important class of sugars relevant to RNA, phospholipids and energy storage. Experiments are currently being designed to elucidate their chemical structure. In addition, several reaction pathways were identified in the irradiated ices of mixed isotopes based upon the results of both in situ FTIR analysis and TPD ReTOF gas phase analysis. In general, the results of this study provide crucial information on the formation of a variety of classes of organics including alcohols, ketones, aldehydes, esters, ethers, and sugars within the bulk ices upon exposure to ionizing radiation that are relevant to the molecular clouds within the interstellar medium.
Energy Barriers to the Diels-Alder Cycloadditions and Cycloreversions of Cation-radicals in the Gas Phase
Turecek, Frantisek,Havlas, Zdenek
, p. 1011 - 1014 (2007/10/02)
The mechanism of the retro-Diels-Alder reaction of substituted bicyclohept-2-ene cation-radicals can be related to the energetics of the fragmentation.Concerted synchronous or asynchronous mechanisms are operative in reactions which occur at their thermochemical thresholds.The reverse process, the Diels-Alder reaction of a cation-radical with a molecule, has a negligible activation energy for symmetrical and slightly unsymmetrical systems, +* + cyclopentadiene, +* + vinyl alcohol, +* + cyclopentadiene, and +* + cyclopentadiene.The retro-Diels-Alder decomposition of the highly unsymmetrical 2-vinylbicyclohept-5-en-2-ol cation-radical proceeds in two steps and overcomes a barrier of 58-67 kJ mol-1 above the thermochemical threshold.The effect of bond-dissociation energies on the reaction mechanism is discussed.
