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首页> 外文期刊>Chemistry: A European journal >Towards the Experimental Decomposition Rate of Carbonic Acid (H_2CO_3) in Aqueous solution
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Towards the Experimental Decomposition Rate of Carbonic Acid (H_2CO_3) in Aqueous solution

机译：水溶液中碳酸（H_2CO_3）的实验分解速率

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Dry carbonic acid has recently been shown to be kinetically stable even at room temperature. Addition of water molecules reduces this stability significantly, and the decomposition (H_2CO_3 + nH_2O -> (m+1)H_2O + CO_2) is extremely accelerated for n = 1, 2, 3. By including two water molecules, a reaction rate that is a factor of 3000 below the experimental one (10 s~(-1)) at room temperature was found. In order to further remove the gap between experiment and theory, we increased the number of water molecules involved to 3 and took into consideration different mechanisms for thorough elucidation of the reaction. A mechanism whereby the reaction proceedes via a six-membered transition state turns out to be the most efficient one over the whole examined reaction rates approach experimental values in aqueous solution reasonably well; most especially, a significant increase in the rates in comparison to the decomposition reaction with fewer water molecules is found. Further agreement with experiment is found in the kinetic isotope effects (KIE) for the deuterated species. For water-free carbonic acid, the KIE (i.e., k_(H_2CO_3)/k_(D_2CO_3)) for the decomposition reaction is predicted to be 220 at 300 K, whereas it amounts to 2.2-3.0 for the investigated mechanisms including three water molecules. This result is therefore reasonably close to the experimental value of 2 (at 300 K).these KIEs are in much better accordance with the experiment than the KIE for decomposition with fewer water entities.
机译：最近已证明，干碳酸即使在室温下也具有动力学稳定性。添加水分子会大大降低这种稳定性，并且在n = 1、2、3时，分解（H_2CO_3 + nH_2O->（m + 1）H_2O + CO_2）会大大加速。通过包含两个水分子，反应速率为发现在室温下比实验值（10 s（-1））低3000倍。为了进一步消除实验和理论之间的鸿沟，我们将涉及的水分子数量增加到3，并考虑了彻底阐明反应的不同机制。结果表明，通过六元过渡态进行反应的机理是在整个检测的反应速率接近水溶液中的实验值时最有效的一种机理。最特别地，发现与具有较少水分子的分解反应相比，速率显着增加。在氘化物种的动力学同位素效应（KIE）中发现了与实验的进一步一致性。对于无水碳酸，分解反应的KIE（即k_（H_2CO_3）/ k_（D_2CO_3））预计在300 K时为220，而对于所研究的机制（包括三个水分子），其KIE（2.2_3.0） 。因此，该结果合理地接近于2的实验值（在300 K时）。这些KIE在实验上要比KIE在分解较少水实体时要好得多。

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