Abstract
Gas phase equilibria of ion-molecule clustering reactions between (C2H2)m+ ions and N2 were investigated by high-pressure mass spectrometry in N2-C2H2 mixtures irradiated by a-particles. Free energy values of clustering, DG0n-1, n, were obtained for reactions (C2H2)m+.(n-1)N2 + N2 <img border=0 width=32 height=32 src="../../../../../../img/revistas/jbchs/v8n3/a12img01.gif">(C2H2)m+.nN2, for different values of m and n. For m = 2, i.e., for the "core ion" (C2H2)2+, the values found for DG0n-1, n at T = 129 K are 0.87 ± 0.20 kcal/mol for (n-1, n) = (2,3) and 0.88 ± 0.20 kcal/mol for (n-1, n) = (3,4). For m = 3 ("core ion" (C2H2)3+), the free energy changes were found to be 0.91 ± 0.30 kcal/mol for (n-1, n) = (2,3), 0.73 ± 0.30 kcal/mol for (n-1, n) = (3,4); 0.65 ± 0.30 kcal/mol for (n-1, n) = (4,5), and 0.58 ± 0.30 for (n-1, n) = (5,6).
Highlights
The atmosphere of Titan is mainly composed[1,2] of nitrogen, with a few percent of methane, and acetylene as one of its minor components
Ion-molecule reactions pertinent to the ion chemistry of Titan’s atmosphere. Information of this type is fundamental to an understanding of the complex chemistry associated with planetary atmospheres for the following reasons, among others: (1) ions represent efficient nucleating agents, resulting in the formation of large cluster buildup and eventually droplet formation; (2) clustering modifies the chemistry associated with ion neutralization because the ligands can act both as heat “sinks” for energy released in the neutralization as well as nearest-neighbor partners in chemical reactions; (3) planetary atmospheres contain both
The formation of (C2H2)2+ was investigated by Rakshit and Warneck[15], using CO2 as a third body. They studied the formation of the clusters (C2H2)3+ and C2H2+.CO2, as well as the association of C2H2 with C4H2+ and C4H3+, with CO2 as a third body
Summary
The atmosphere of Titan is mainly composed[1,2] of nitrogen, with a few percent of methane, and acetylene as one of its minor components. In the present study only reactions corresponding to equilibrium (1) were investigated.
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