离子-分子缩合反应：电离还原气氛中有机合成的一种机制。

Ion-molecule condensation reactions: a mechanism for organic synthesis in ionized reducing atmospheres.

作者信息

Meot-Ner M

出版信息

Orig Life. 1978 Dec;9(2):115-31. doi: 10.1007/BF00931409.

Abstract

The CH3+ ion, formed in ionized methane, undergoes consecutive eliminative condensation reactions with methane to form the carbonium ions C2H5+, i-C3H7+ and t-C4H9+. At T smaller than 500 degrees K, NCH4 greater than 10(16) cm-3 these ions react with NH3 in competitive condensation -- H+ transfer reactions, e.g. C2H5 + NH3 M leads to C2H5NH3+ leads to NH4+ + C2H4 At particle densities of NCH4 smaller than 10(16) cm-3 proton transfer is the only significant reaction channel. At NCH4 greater than 10(17) cm-3 condensation constitutes 5--20% of the overall reactions. The product of the condensation reaction further associates with CO2 to form C2H5NH3+ . CO2; the atomic composition of this cluster ion is identical with the protonated amino acid alanine. The carbonium ions i-C3H7+ and t-C4H9+ condense also with HCN to yield protonated isocyanides. HCNH% also appears to condense with HCN at T greater than 570 degrees K, and form cluster ions with HCN at lower temperatures. The rate constants of the condensation reactions vary with temperature and pressure in a complex manner. Under conditions similar to those on Titan at an altitude of 100 km (T = 100--150 degrees K, NCH4 approximately 10(18) cm-3), with a methane atmosphere containing 1% H2 and traces of NH3 and H2O, ion-molecule condensation reactions followed by H+ transfer are expected to lead to the atmospheric synthesis of C2H6, C3H8, CH3OH, C2H5OH and the terminal ions NH4+, CH3NH3+ and C2H5NH3+. At higher temperatures (250 degrees K smaller than T smaller than 400 degrees K), the synthesis of i-C4H10, i-C3H7OH and t-C4H9OH and of the ions i-C3H7NH3+ and t-C4H9NH3+ is also expected. Electron recombination of the terminal ions may yield amines, imines and nitriles. Cycles of protonation and dissociative recombination of the alkanes and alcohols produced in condensation reactions will also produce unsaturated hydrocarbons, ketones and aldehydes in the ionized atmosphere.

摘要

在电离的甲烷中形成的CH₃⁺离子与甲烷发生连续的消除缩合反应，生成碳正离子C₂H₅⁺、异-C₃H₇⁺和叔-C₄H₉⁺。在温度T小于500开尔文、甲烷数密度NCH₄大于10¹⁶厘米⁻³时，这些离子与NH₃在竞争性缩合——氢转移反应中发生反应，例如C₂H₅⁺ + NH₃ → C₂H₅NH₃⁺ → NH₄⁺ + C₂H₄。在甲烷数密度NCH₄小于10¹⁶厘米⁻³时，质子转移是唯一重要的反应通道。在NCH₄大于10¹⁷厘米⁻³时，缩合反应占总反应的5% - 20%。缩合反应的产物进一步与CO₂缔合形成C₂H₅NH₃⁺·CO₂；该簇离子的原子组成与质子化氨基酸丙氨酸相同。异-C₃H₇⁺和叔-C₄H₉⁺碳正离子也与HCN缩合生成质子化异腈。HCNH⁺在温度T大于570开尔文时似乎也与HCN缩合，并在较低温度下与HCN形成簇离子。缩合反应的速率常数随温度和压力以复杂的方式变化。在类似于土卫六100千米高度处的条件下（T = 100 - 150开尔文，NCH₄约为10¹⁸厘米⁻³），在含有1% H₂以及痕量NH₃和H₂O的甲烷气氛中，离子 - 分子缩合反应随后的氢转移预计会导致大气中合成C₂H₆、C₃H₈、CH₃OH、C₂H₅OH以及终端离子NH₄⁺、CH₃NH₃⁺和C₂H₅NH₃⁺。在较高温度下（250开尔文小于T小于400开尔文），预计还会合成异-C₄H₁₀、异-C₃H₇OH和叔-C₄H₉OH以及离子异-C₃H₇NH₃⁺和叔-C₄H₉NH₃⁺。终端离子的电子复合可能产生胺、亚胺和腈。缩合反应中产生的烷烃和醇的质子化和解离复合循环也将在电离大气中产生不饱和烃、酮和醛。