A microwave spectroscopic and ab initio study of keto–enol tautomerism and isomerism in the cyclohexanone–water complex†,Physical Chemistry Chemical Physics

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A microwave spectroscopic and ab initio study of keto–enol tautomerism and isomerism in the cyclohexanone–water complex†
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2019-06-03 00:00:00 , DOI: 10.1039/c9cp01999e
Jiao Gao _{1,

2,

3,

4} , Nathan A. Seifert _{1,

2,

3,

4} , Wolfgang Jäger _{1,

2,

3,

4}

Affiliation

Cyclohexanone and water are two important components of secondary organic aerosol (SOA), and understanding the intermolecular interactions between these two species can provide insight to the initial formation mechanism of SOA particles. In this work, we have investigated the keto–enol tautomeric and conformational changes of the cyclohexanone monomer and its monohydrate by Fourier-transform microwave spectroscopy and ab initio calculations. Chirped-pulse and cavity-based FTMW spectrometers in the region of 7–14 GHz were used to measure rotational spectra of the most stable species prepared in a cold molecular beam. The experimental and theoretical results suggest that the chair conformer of the keto tautomer is the most stable structure. We have measured and assigned rotational spectra of ten isotopologues, including all six single ¹³C substitutions observed in natural abundance and four different isotopic species of water (H₂O, D₂O, DOH and HOD). The experimental structure of cyclohexanone–water was determined directly using this isotopic information. The analysis reveals the existence of both canonical and secondary hydrogen bonding, which we confirm using QTAIM analyses. To further elucidate the hydrogen bonding characteristics in ketone–water clusters, cyclohexanone–water is compared to a variety of other hydrated ketones, namely formaldehyde, acetone, cyclobutanone, and cyclopentanone, through utilization of the symmetry adapted perturbation theory (SAPT) energy decomposition method. The results of this study shed light on the effects of water on keto–enol tautomerization, and the role of hydrogen bonding in ketone monohydrates and the formation of related SOA particles.

中文翻译：

微波光谱法和从头算研究环己酮-水络合物中的酮-烯醇互变异构和异构现象†

环己酮和水是二次有机气溶胶（SOA）的两个重要组成部分，了解这两个物种之间的分子间相互作用可以为SOA颗粒的初始形成机理提供见识。在这项工作中，我们通过傅立叶变换微波光谱法和从头算研究了环己酮单体及其一水合物的酮-烯醇互变异构和构象变化。计算。7脉冲和基于腔的FTMW光谱仪在7–14 GHz范围内用于测量在冷分子束中制备的最稳定物质的旋转光谱。实验和理论结果表明，酮互变异构体的椅子构象异构体是最稳定的结构。我们已经测量并分配了十个同位素同位素的旋转光谱，包括在自然丰度中观察到的所有六个单个¹³ C取代物以及四种不同的同位素水（H ₂ O，D ₂O，DOH和HOD）。使用该同位素信息直接确定了环己酮-水的实验结构。该分析揭示了规范氢键和次级氢键的存在，我们使用QTAIM分析证实了这一点。为了进一步阐明酮-水团簇中的氢键特征，通过利用对称适应扰动理论（SAPT）能量分解方法，将环己酮-水与甲醛，丙酮，环丁酮和环戊酮等多种其他水合酮进行了比较。。这项研究的结果揭示了水对酮-烯醇互变异构的影响，以及氢键在一水合酮中的作用以及相关SOA颗粒的形成。

更新日期：2019-06-03

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