Rosa M. Claramunt, Dionisia Sanz, Ibon Alkorta, José Elguero
The reactivity of imidazole, pyrazole, 1,2,4-triazole, 1,2,3-triazole, and tetrazole with acetone (propan-2-one) has been studied by 1H and 13C NMR using acetone-d6 as solvent at temperatures ranging from 173 to 300 K at 10 K intervals. Simultaneously, the reaction has been theoretically calculated at the B3LYP/6-311++G(d,p) level, and experimental and theoretical results have been compared. The equilibrium constants between azoles and adducts α,α-dimethyl-azole-methanol were analyzed, assuming that the straight part of the plots –R ln Ke vs. 1/T can be used to determine ΔH and ΔS. Calculated and experimental data are related, but the theoretical values are proportionally higher. The tautomerism of triazoles and tetrazole has been considered in order to discuss the reactions.
以丙酮-d6 为溶剂,在 173 至 300 K 的温度范围内,以 10 K 为间隔,通过 1H 和 13C NMR 研究了咪唑、吡唑、1,2,4-三唑、1,2,3-三唑和四唑与丙酮(丙-2-酮)的反应性。同时,在 B3LYP/6-311++G(d,p) 水平上对该反应进行了理论计算,并对实验结果和理论结果进行了比较。分析了偶氮和加合物 α,α-二甲基偶氮唑-甲醇之间的平衡常数,假定 -R ln Ke vs. 1/T 图的直线部分可以用来确定 ΔH 和 ΔS。计算数据和实验数据是相关的,但理论值按比例来说更高。为了讨论这些反应,我们考虑了三唑和四唑的同分异构现象。
{"title":"Addition reaction of azoles to acetone-d6: NMR and computational studies","authors":"Rosa M. Claramunt, Dionisia Sanz, Ibon Alkorta, José Elguero","doi":"10.1002/poc.4612","DOIUrl":"10.1002/poc.4612","url":null,"abstract":"<p>The reactivity of imidazole, pyrazole, 1,2,4-triazole, 1,2,3-triazole, and tetrazole with acetone (propan-2-one) has been studied by <sup>1</sup>H and <sup>13</sup>C NMR using acetone-<i>d</i><sub><i>6</i></sub> as solvent at temperatures ranging from 173 to 300 K at 10 K intervals. Simultaneously, the reaction has been theoretically calculated at the B3LYP/6-311++G(d,p) level, and experimental and theoretical results have been compared. The equilibrium constants between azoles and adducts α,α-dimethyl-azole-methanol were analyzed, assuming that the straight part of the plots –R ln <i>K</i><sub>e</sub> vs. 1/T can be used to determine Δ<i>H</i> and Δ<i>S</i>. Calculated and experimental data are related, but the theoretical values are proportionally higher. The tautomerism of triazoles and tetrazole has been considered in order to discuss the reactions.</p>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/poc.4612","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141110710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Bagrat A. Shainyan, Alexey V. Eroshin, Sergey A. Shlykov
6-Iodo-3-(triflamidomethyl)-4-triflyl-1,4,2,7-oxazadisilepane 1 and the product of its cyclization, 2,2,4,4-tetramethyl-6,8-bis (triflyl)-3-oxa-6,8-diaza-2,4-disilabicyclo[3.2.2]nonane 2, have been studied by gas-phase electron diffraction and DFT calculations. The conformational equilibrium in the gas phase was shown to include three and two conformers for 1 and 2, respectively, in contrast to only one conformer determined by single crystal X-ray diffraction. The structural analysis of the conformers was performed and the pathways of the conformational transitions were analyzed.
{"title":"Molecular structure and conformational properties of triflamide derivatives in the gas phase—Part II: 6-Iodo-3-(triflamidomethyl)-4-triflyl-1,4,2,7-oxaazadisilepane and 2,2,4,4-tetramethyl-6,8-bis (triflyl)-3-oxa-6,8-diaza-2,4-disilabicyclo[3.2.2]nonane by gas-phase electron diffraction and theoretical calculations","authors":"Bagrat A. Shainyan, Alexey V. Eroshin, Sergey A. Shlykov","doi":"10.1002/poc.4613","DOIUrl":"10.1002/poc.4613","url":null,"abstract":"<p>6-Iodo-3-(triflamidomethyl)-4-triflyl-1,4,2,7-oxazadisilepane <b>1</b> and the product of its cyclization, 2,2,4,4-tetramethyl-6,8-bis (triflyl)-3-oxa-6,8-diaza-2,4-disilabicyclo[3.2.2]nonane <b>2</b>, have been studied by gas-phase electron diffraction and DFT calculations. The conformational equilibrium in the gas phase was shown to include three and two conformers for <b>1</b> and <b>2</b>, respectively, in contrast to only one conformer determined by single crystal X-ray diffraction. The structural analysis of the conformers was performed and the pathways of the conformational transitions were analyzed.</p>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-05-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141124574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The potential energy surfaces for the reactions of 1,3-butadiene with 2-hydroxythioacrolein and 2-aminoacrolein exhibit ambimodal transition states leading to both dipolar (4 + 3) and Diels–Alder (4 + 2) cycloaddition products, thereby demonstrating a post transition state bifurcation feature. We have investigated the bifurcation dynamics of these reactions using three molecular dynamics (MD) methods: quasi-classical trajectory, classical MD, and ring-polymer MD simulations. The trajectory calculations were performed with the semiempirical GFN2-xTB method with the element-specific parameters optimized to reproduce the density-functional theory calculations. The effect of water solvation was examined using an implicit solvation model, revealing significant differences in bifurcation dynamic between gas-phase and solution-phase reactions. Nuclear quantum effects were found to play a crucial role in the proton-transfer process from the (4 + 3) intermediate to the (4 + 3) product in the case of the 2-aminoacrolein reaction.
{"title":"Molecular dynamics simulation study of post-transition state bifurcation: A case study on the ambimodal transition state of dipolar/Diels–Alder cycloaddition","authors":"Tatsuhiro Murakami, Yuya Kikuma, Daiki Hayashi, Shunichi Ibuki, Shoto Nakagawa, Hinami Ueno, Toshiyuki Takayanagi","doi":"10.1002/poc.4611","DOIUrl":"10.1002/poc.4611","url":null,"abstract":"<p>The potential energy surfaces for the reactions of 1,3-butadiene with 2-hydroxythioacrolein and 2-aminoacrolein exhibit ambimodal transition states leading to both dipolar (4 + 3) and Diels–Alder (4 + 2) cycloaddition products, thereby demonstrating a post transition state bifurcation feature. We have investigated the bifurcation dynamics of these reactions using three molecular dynamics (MD) methods: quasi-classical trajectory, classical MD, and ring-polymer MD simulations. The trajectory calculations were performed with the semiempirical GFN2-xTB method with the element-specific parameters optimized to reproduce the density-functional theory calculations. The effect of water solvation was examined using an implicit solvation model, revealing significant differences in bifurcation dynamic between gas-phase and solution-phase reactions. Nuclear quantum effects were found to play a crucial role in the proton-transfer process from the (4 + 3) intermediate to the (4 + 3) product in the case of the 2-aminoacrolein reaction.</p>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/poc.4611","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140830524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Eduardo Humeres, Marília Isabel Tarnowski Correia, Nito Angelo Debacher, Regina de F. P. M. Moreira
The desulfurization of carbons modified with SO2 was studied as a dispersion in boiling cyclohexane (81°C) using activated carbon (mAC) and graphene oxide (mGO), modified by SO2. The steady-state species in the carbon matrix after the catalytic reduction of SO2 was considered a trisulfane. For mAC, there was a burst of a sulfur species identified as S2 by UV spectrum with a maximum at 217 nm (εM at 217 nm = 2.56 × 103) that showed a second-order decay of absorbance with