Microwave Study of Triflic Acid Hydrates: Evidence for the Transition from Hydrogen-Bonded Clusters to a Microsolvated Ion Pair
Microwave Study of Triflic Acid Hydrates: Evidence for the Transition from Hydrogen-Bonded Clusters to a Microsolvated Ion Pair
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三氟甲磺酸水合物的微波研究：从氢键簇转变为微溶剂化离子对的证据
DOI：
10.1021/acs.jpca.1c06815
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Leopold, Kenneth R.
中科院分区：
文献类型：
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作者：
Huff, Anna K.;Love, Nathan;Leopold, Kenneth R.
本文用脉冲喷嘴傅里叶变换微波光谱法记录了三氟甲磺酸（CF_3SO_3H···（H_2O）_n=1-3）的一、二、三水合物的转动光谱，并将所得光谱常数与理论计算值进行了比较。实验结果与这里和其他地方提出的理论预测一致，表明只有一个或两个水分子，三氟甲磺酸在冷分子复合物中保持非电离状态。实验进一步与理论预测一致，即加入第三个水分子将系统转化为最好被视为水合氢三氟甲磺酸盐离子对的物质。因此，只需要三个水分子就可以在冷分子簇中诱导三氟甲磺酸的电离。与其他简单的质子酸相比，这个数字有点低，可能反映了三氟甲磺酸的超强酸性。简单的能量论证可以用来合理化这一结果。
Rotational spectra of the mono-, di-, and trihydrates of triflic acid, CF3SO3H···(H2O)n=1–3, have been recorded by pulsed nozzle Fourier transform microwave spectroscopy and spectroscopic constants obtained have been compared with values calculated at several levels of theory. The experimental results are consistent with the theoretical predictions presented here and elsewhere, indicating that with only one or two water molecules, triflic acid remains un-ionized in a cold molecular complex. The experiments further concur with theoretical predictions that the addition of a third water molecule transforms the system into what is best regarded as a hydrated hydronium triflate ion pair. Thus, only three water molecules are needed to induce ionization of triflic acid in a cold molecular cluster. This number is somewhat low compared with that for other simple protic acids and likely reflects the superacidity of triflic acid. Simple energetic arguments can be used to rationalize this result.