Title of article :
Modeling chemical growth processes in Titanʹs atmosphere 2. Theoretical study of reactions between C2H and ethene, propene, 1-butene, 2-butene, isobutene, trimethylethene, and tetramethylethene
Author/Authors :
Woon، نويسنده , , David E. and Park، نويسنده , , Jin-Young، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2009
Pages :
14
From page :
642
To page :
655
Abstract :
Barrierless reactions between unsaturated hydrocarbons and the ethynyl radical (C2H) can contribute to the growth of organic particulates in the haze-forming regions of Titanʹs atmosphere as well as in the gas giants and in the interstellar medium. We employed a combination of quantum chemistry and statistical rate theories to characterize reactions between ground state C2H and seven alkenes of the general structure R 1 R 2 C ′ C ″ R 3 R 4 containing up to six carbons. The alkenes included ethene (C2H4); propene (C3H6); 1-butene, 2-butene, and isobutene (C4H8); trimethylethene (C5H10); and tetramethylethene (C6H12). Density functional theory calculations at the B3LYP/6-31 + G∗∗ level were used to characterize the adducts, isomers, products, and the intervening transition states for the addition–elimination reactions of all seven species. A multiple-well treatment was then employed to determine the outcome distributions for the range of temperatures and pressures relevant to Titanʹs atmosphere, the interstellar medium, and the outer atmospheres of the gas giants. Finally, trajectory calculations using an ROMP2 potential energy surface were used to calculate kinetic rates for the ethene + C2H reaction, where the agreement between the computed and measured values is very good. At low pressure and temperature, vinyl acetylene is a dominant product of several of the reactions, and all of the reactions yield at least one dominant product with both a double and a triple CC bond.
Keywords :
Titan , organic chemistry , Atmospheresevolution , Atmospherescomposition , Atmosphereschemistry
Journal title :
Icarus
Serial Year :
2009
Journal title :
Icarus
Record number :
2376958
Link To Document :
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