Journal of Physical Organic Chemistry最新文献

{"title":"Influence of Homoring Competition Effect of Substituents on the NMR Chemical Shifts in Resonance-Assisted Hydrogen Bond for 2-Hydroxyl Diaryl Schiff Bases","authors":"Chao-Tun Cao,&nbsp;Tinghua Kuang,&nbsp;Lanyu Zhang,&nbsp;Chenzhong Cao","doi":"10.1002/poc.70107","DOIUrl":"https://doi.org/10.1002/poc.70107","url":null,"abstract":"<div>\u0000 \u0000 <p>In multi-substituent organic compounds, the interaction mechanism among groups is of great significance for understanding and predicting the properties of compounds. The homoring competition effect remains largely unexplored. This work rigorously investigates how this effect influences the chemical shift (<i>δ</i>_H(OH)) of hydrogen atom in resonance-assisted hydrogen bond (RAHB). Forty-four 2-hydroxyl diaryl Schiff bases (2-OH-XArCH=NArY, abbreviated as 2-OH-XBAY) bearing diverse substituents X and Y were selected as model molecules, and their ¹H NMR and ¹³C NMR spectra were measured. The results show the following: (1) Using the OH and CH=N groups of RAHB as references, a clear homoring competition effect of substituent X exists in 2-OH-XBAY compounds. (2) For <i>δ</i>_H(OH) of H in OH, the effects of <i>σ</i>_m(X) and <i>σ</i>_p(X) are not additive. The homoring competition effect of substituent X is pronounced: The influence of X on <i>δ</i>_H(OH) is transmitted primarily via path <i>b</i> (Figure 1), with its conjugation effect dominating over its inductive effect. (3) The effect of X on <i>δ</i>_C(C=N) is dominated mainly by <i>σ</i>_F(X), with <i>σ</i>_R(X) contributing negligibly. The cross-interaction effect Δ<i>σ</i>_m² does influence <i>δ</i>_C(C=N), whereas the effect of Δ<i>σ</i>_p² on <i>δ</i>_C(C=N) is negligible. These findings offer a powerful new perspective for deeply understanding substituent effects in diaryl Schiff bases.</p>\u0000 </div>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":"39 10","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148943546","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}

{"title":"Phenylnitrene is not Phenylcarbene: A Special Issue in Honor of Matthew S. Platz","authors":"Anthony W. Czarnik","doi":"10.1002/poc.70106","DOIUrl":"https://doi.org/10.1002/poc.70106","url":null,"abstract":"<p>Matt Platz is a great guy and an even better chemist. This special issue of the <i>Journal of Physical Organic Chemistry</i> celebrates his 75th birthday.</p>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":"39 10","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/poc.70106","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148943028","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}

{"title":"The Activation Entropy of Chemical Exchange Driven by Internal Rotation: A Computational Approach","authors":"Henry J. Castejon","doi":"10.1002/poc.70103","DOIUrl":"https://doi.org/10.1002/poc.70103","url":null,"abstract":"<div>\u0000 \u0000 <p>The activation entropy (<span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>Δ</mi>\u0000 <msup>\u0000 <mrow>\u0000 <mi>S</mi>\u0000 </mrow>\u0000 <mrow>\u0000 <mi>‡</mi>\u0000 </mrow>\u0000 </msup>\u0000 </mrow>\u0000 <annotation>$$ Delta {S}^{ddagger } $$</annotation>\u0000 </semantics></math>) of chemical exchange processes is usually determined using Nuclear Magnetic Resonance (NMR) bandshape analysis. However, the procedure is plagued with problems that render the results unreliable as demonstrated by the large uncertainties of the reported values. A computational approach to calculate <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>Δ</mi>\u0000 <msup>\u0000 <mrow>\u0000 <mi>S</mi>\u0000 </mrow>\u0000 <mrow>\u0000 <mi>‡</mi>\u0000 </mrow>\u0000 </msup>\u0000 </mrow>\u0000 <annotation>$$ Delta {S}^{ddagger } $$</annotation>\u0000 </semantics></math> using third-law gas-phase statistical entropies is presented here. The proposed approach is demonstrated by calculating the activation entropy <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>Δ</mi>\u0000 <msup>\u0000 <mrow>\u0000 <mi>S</mi>\u0000 </mrow>\u0000 <mrow>\u0000 <mi>‡</mi>\u0000 </mrow>\u0000 </msup>\u0000 </mrow>\u0000 <annotation>$$ Delta {S}^{ddagger } $$</annotation>\u0000 </semantics></math> of the chemical exchange driven by internal rotation in a series of amide compounds. The potential parameters were obtained using high level ab initio Molecular Orbital Theory, whereas the rotational eigenstates for the individual conformers were calculated with a suitable Hamiltonian for the internal rotation process. The gas-phase values obtained for <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>Δ</mi>\u0000 <msup>\u0000 <mrow>\u0000 <mi>S</mi>\u0000 </mrow>\u0000 <mrow>\u0000 <mi>‡</mi>\u0000 </mrow>\u0000 </msup>\u0000 </mrow>\u0000 <annotation>$$ Delta {S}^{ddagger } $$</annotation>\u0000 </semantics></math> reproduce well previously reported experimental results for the compounds studied. The proposed method provides a complementary technique to the NMR bandshape analysis to determine the activation entropy of chemical exchange processes driven by internal rotation.</p>\u0000 </div>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":"39 10","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148943225","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}

{"title":"Revealing Structure–Function Relationships Involving Substituent Position for Isoquinoline Photobases","authors":"Joshua Valdez,&nbsp;Megan Warner,&nbsp;Claudia Ramos,&nbsp;Viktoria Silva,&nbsp;Dara Varasteh,&nbsp;Samantha del Pozo,&nbsp;Stevan Pecic,&nbsp;Jonathan Ryan Hunt,&nbsp;Andrew Scott Petit","doi":"10.1002/poc.70101","DOIUrl":"https://doi.org/10.1002/poc.70101","url":null,"abstract":"<div>\u0000 \u0000 <p>Photobases are molecules that become much stronger bases upon photoexcitation. Previous experimental work has carefully characterized structure–function relationships for 5-substituted quinolines, demonstrating that the thermodynamic driving force for excited-state protonation increases as the substituent becomes more electron-donating. Subsequent computational work examined possible descriptors for photobasicity in this family. However, a detailed analysis of how photobasicity strength is affected by changes in substituent position is lacking in the literature. In this work, we fill this gap by experimentally demonstrating that the ground- and excited-state basicity of bromoisoquinolines is significantly modulated by the position of the bromine atom. Complementary computational work applies descriptors based on intramolecular charge-transfer, excited-state antiaromaticity relief, and energy decomposition analysis to these photobases. Overall, this study provides new insights into structure–function relationships involving <i>N</i>-heterocycle photobases.</p>\u0000 </div>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":"39 10","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148942662","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}

{"title":"The Great Escape? Investigations of Tunneling Contributions to the Valence Tautomerizations of Benzene Chalcogenides and Heteroepins","authors":"Liam Tsou,&nbsp;Muhammad Dilawar Danish,&nbsp;Daniel P. Miller,&nbsp;Tim Schleif","doi":"10.1002/poc.70097","DOIUrl":"https://doi.org/10.1002/poc.70097","url":null,"abstract":"<div>\u0000 \u0000 <p>Valence tautomerizations are prototypical pericyclic rearrangements with broad relevance in (bio)organic chemistry that can exhibit significant contributions from quantum mechanical tunneling (QMT), as demonstrated previously e.g., for the oxepin—benzene oxide equilibrium. Such contributions were evaluated computationally for the valence tautomerizations of heteroepins C₆H₆X (X = S, Se, and Te) and thiepin oxides (X = SO or SO₂). Ring contraction of the heteroepins becomes increasingly exothermic from X = O to X = Te; however, as an exception to the Bell–Evans–Polanyi principle, the associated activation barriers also increase. Analysis of the intrinsic reaction coordinates reveals that the critical C1–C6 distance in the heteroepins strongly widens within this series, resulting in increasingly wider and higher barriers despite the growing thermodynamic driving force. Consequently, estimated tunneling probabilities decrease dramatically across the series, ruling out tunneling as a significant contributor to the experimentally observed instability of thiepin, selenepin, and tellurepin. In contrast, the valence tautomerizations of thiepin-<i>S</i>-oxide and thiepin-<i>S,S</i>-dioxide follow conventional Bell–Evans–Polanyi behavior. The equatorial conformer of thiepin-<i>S</i>-oxide is expected to not exhibit any appreciable tunneling reactivity, while its axial conformer is projected to undergo rapid ring contraction by heavy-atom tunneling. The bicyclic tautomer of C₆H₆SO₂ is predicted to ring-expand to the less strained thiepin-<i>S,S</i>-dioxide with a half-life suitable for matrix isolation spectroscopy experiments. Overall, this study of the potential role of QMT in the valence tautomerizations of heteroepins and thiepin oxides provides broader insights into how characteristic molecular features influence the intrinsic barrier width of a reaction.</p>\u0000 </div>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":"39 10","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148848946","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}

{"title":"Assembly and Properties of Donor/Acceptor–Functionalized 2,6-Bisethynylpyridines; Investigations of Through-Bond and Through-Space Charge Transfer Behavior","authors":"Jarod T. Sjoquist,&nbsp;Noah A. Grinde,&nbsp;Maggie A. Schultz,&nbsp;Olivia J. Schwarz,&nbsp;John T. Nabors,&nbsp;Nathaniel P. Litts,&nbsp;Joseph D. Scanlon,&nbsp;Eric Bosch,&nbsp;Nathan P. Bowling","doi":"10.1002/poc.70100","DOIUrl":"https://doi.org/10.1002/poc.70100","url":null,"abstract":"<p>Introduction of Ag(I) cations to 2,6-bisethynylpyridine units decorated with electron-donating (<i>N</i>,<i>N</i>-dimethylaniline) and electron-accepting (1,3-dinitrobenzene) groups yields electronic changes consistent with the formation of distinct metal-organic complexes. Although the formation of these complexes is dynamic—allowing for the possibility of contributors with several different ligand:metal stoichiometries—¹H NMR titration data point to significant contributions from a 2:1 ligand:metal complex. Mutual shielding of the donor and acceptor arms in the 2:1 complex leads to sharp decreases in ¹H NMR chemical shifts of hydrogens on these rings. Though the changes in electronic properties and evidence of mutual shielding infer formation of a complex with a close spatial relationship of donor and acceptor units, the electronic effects that would be expected for through-space charge transfer are not clearly distinguishable from through-bond electronic effects. Protonation of the central pyridines illuminates how through-bond interactions of the <i>N</i>,<i>N</i>-dimethylaniline arms with a positively charged central pyridine tend to dominate the electronic profile of each ligand. X-ray crystallographic studies of an Ag(I) complex of a donor-acceptor system illustrate notable contacts between <i>N</i>,<i>N</i>-dimethylaniline and 1,3-dinitrobenzene units.</p>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":"39 10","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/poc.70100","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148848947","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}

{"title":"Density Functional Theory Insights Into Ruthenium-Catalyzed Alkene–Alkyne Cross-Coupling: Mechanism, Regioselectivity, and Catalyst Effects","authors":"Hongtai Chen,&nbsp;Guixian Liu,&nbsp;Wei Zhou,&nbsp;Xiangtai Meng,&nbsp;Lei Zhang","doi":"10.1002/poc.70102","DOIUrl":"https://doi.org/10.1002/poc.70102","url":null,"abstract":"<div>\u0000 \u0000 <p>Direct cyclometalation of two unsaturated bonds at a transition metal center constitutes a highly efficient strategy for carbon–carbon cross-coupling. In this work, density functional theory calculations were performed to delineate the detailed reaction mechanism of ruthenium-catalyzed direct alkene–alkyne coupling for diene synthesis. Computational results reveal that the reaction proceeds via three elementary steps: concerted cyclometalation, β-hydride elimination, and reductive elimination, with the initial cyclometalation step serving as both the rate-determining and regioselectivity-controlling step. Under standard reaction conditions, the branched diene is the major product, whereas the more stable linear diene is a minor isomer; however, this regioselectivity is significantly modulated by ligand architecture and substrate substituent effects. Calculations demonstrate that replacing the pentamethylcyclopentadienyl ligand with the unsubstituted cyclopentadienyl ligand, or introducing alkyl substituents on the alkene substrate, can invert the selectivity, switching the major product from branched to linear diene. Furthermore, investigations into catalyst structure–reactivity relationships reveal that ligand structure plays a dominant role, because the presence of a cyclooctatetraene ligand results in a substantial reduction in catalytic activity, whereas the formal charge of the Ru center exerts only a secondary influence. The present computational findings not only rationalize existing experimental observations but also provide deeper mechanistic insights into the origins of regioselectivity and reactivity in this class of transformations.</p>\u0000 </div>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":"39 10","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148849170","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}

{"title":"PyQuiverHS: A Web Tool for Computing Isotope Effects","authors":"Gianmarc Grazioli,&nbsp;Andrew Ly,&nbsp;Dianoosh Sabetnejad,&nbsp;Anvitha Mattapalli,&nbsp;Calvin T. Nguyen,&nbsp;Daniel J. O'Leary","doi":"10.1002/poc.70099","DOIUrl":"https://doi.org/10.1002/poc.70099","url":null,"abstract":"<p>Predicting isotope effects using electronic structure calculations is widely done, but current software options can present a barrier for some chemists, depending upon their needs and software/programming proficiency. Building upon existing code bases, we have developed PyQuiverHS as a free web tool (www.isotope-effects.com) to provide ready access to kinetic and equilibrium isotope effect (EIE) calculations employing the Bigeleisen–Mayer (B-M) and enthalpy–entropy (<i>H-S</i>) partition functions. A graphical user interface assists in setting up a configuration file, which contains scaling factor and isotope substitution information. After uploading the configuration file and Gaussian frequency jobs for the unlabeled system, users execute a kinetic isotope effect (KIE) or EIE calculation at a particular temperature or range of temperatures with a defined increment. Wigner and Bell tunneling corrections are provided for KIE calculations. Overall KIEs or EIEs and their contributing B-M and <i>H-S</i> terms are compiled in auto-downloaded comma-separated values (*.csv) and plain text files. Automating the process with PyQuiverHS is a significant gain in efficiency, as previous methods for these types of calculations have relied on spreadsheets, which require time-intensive data manipulation. We demonstrate the utility of PyQuiverHS by calculating temperature-dependent conformational KIEs in 9,10-dihydro-4,5-dimethylphenanthrene (<b>1</b>), a doubly bridged biphenyl derivative (<b>2</b>), [2.2]-metaparacyclophane (<b>3</b>), a secondary KIE for the S_N2 reaction of chloride with methyl bromide (<b>4</b>), and an EIE for the interconversion of chair conformations of 1,1,3,3-tetramethylcyclohexane (<b>6</b>).</p>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":"39 10","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/poc.70099","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148784521","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}

{"title":"A Stable Hemicarceplex With an Encapsulated Cationic Guest","authors":"Casey Lee-Foss,&nbsp;Alex Lovstedt,&nbsp;Lewis Nguyen,&nbsp;Steven R. Kass","doi":"10.1002/poc.70098","DOIUrl":"https://doi.org/10.1002/poc.70098","url":null,"abstract":"<p>A hemicarcerand first reported by Quan and Cram in 1991 was prepared and characterized by X-ray crystallography. It incorporates CoCp₂⁺ PF₆⁻ with an equilibrium constant of ~220 M⁻¹ at 120°C and apparently is indefinitely stable at room temperature. This potential weakly coordinating cation's structure was also determined by X-ray analysis, and the cation is located on the inside and the counteranion on the outside of the cage through one of its four potential openings. Computations model these results and suggest that the imine linker needs to be modified to reduce the electrostatic attraction of the oppositely charged ions by physically separating them further.</p>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":"39 10","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1002/poc.70098","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148784142","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}

{"title":"Solvent Effects on the Reactivity of a Phenolate Betaine: Kinetics and Theoretical Calculations of Transition-State Solvation","authors":"Marcos Caroli Rezende,&nbsp;Carolina Mascayano,&nbsp;Sofia Cornejo,&nbsp;Miroslav Cabadaj","doi":"10.1002/poc.70095","DOIUrl":"https://doi.org/10.1002/poc.70095","url":null,"abstract":"<div>\u0000 \u0000 <p>The kinetics of the reaction of solvatochromic 4-(2,4,6-triphenylpyridinio)phenolate with methyl iodide was followed at 25.0°C in various solvents (chloroform, dichloromethane, acetone, acetonitrile, dimethyl sulfoxide, 2-octanol) and in six binary mixtures of variable composition. Rates in poorly acidic solvents correlated with the medium polarizability and dipolarity. Solvent effects in binary mixtures were rationalized by a non-ideality approach based on the preferential solvation of the transition state in these media. Correlations of reactivities with solvent properties found support with theoretical calculations of the transition state of the reaction in different solvents, simulated by a continuum model and by the explicit solvation of the TS by molecules of a hydroxylic solvent.</p>\u0000 </div>","PeriodicalId":16829,"journal":{"name":"Journal of Physical Organic Chemistry","volume":"39 9","pages":""},"PeriodicalIF":1.9,"publicationDate":"2026-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148616661","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}