{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,15]],"date-time":"2026-10-15T12:51:37Z","timestamp":1792068697013,"version":"4.4.0"},"reference-count":40,"publisher":"American Chemical Society (ACS)","issue":"41","license":[{"start":{"date-parts":[[2026,10,5]],"date-time":"2026-10-05T00:00:00Z","timestamp":1791158400000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-029"},{"start":{"date-parts":[[2026,10,5]],"date-time":"2026-10-05T00:00:00Z","timestamp":1791158400000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-037"},{"start":{"date-parts":[[2026,10,5]],"date-time":"2026-10-05T00:00:00Z","timestamp":1791158400000},"content-version":"stm-asf","delay-in-days":0,"URL":"https:\/\/doi.org\/10.15223\/policy-045"}],"funder":[{"DOI":"10.13039\/na","name":"National Research Foundation (NRF) of Korea","doi-asserted-by":"publisher","award":["RS-2024-00396026"],"award-info":[{"award-number":["RS-2024-00396026"]}],"id":[{"id":"10.13039\/na","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"published-print":{"date-parts":[[2026,10,15]]},"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>Temperature-dependent Fourier-transform infrared (FTIR) and two-dimensional infrared (2D IR) spectroscopic measurements are performed on CH3COOH dissolved in CH3CN over the temperature range of 4\u201362 \u00b0C. CH3COOH exists as two conformers, the syn- and anti-isomers, whose relative populations vary with temperature. At each temperature, their relative populations are determined by FTIR and 2D IR spectroscopy, supported by numerical simulations of the corresponding spectra. Accurate determination of the temperature-dependent populations enables the enthalpy difference (\u0394H) and entropy difference (\u0394S) between the two isomers to be obtained from a van \u2019t Hoff analysis. The resulting thermodynamic parameters for the syn \u21c4 anti isomerization are \u0394H = 6.34 \u00b1 0.27 kJ\u00b7mol\u20131 and \u0394S = \u22120.64 \u00b1 0.88 J\u00b7mol\u20131\u00b7K\u20131, indicating that the conformational equilibrium is dominated by the enthalpic contribution.<\/jats:p>","DOI":"10.1021\/acs.jpcb.6c05878","type":"journal-article","created":{"date-parts":[[2026,10,5]],"date-time":"2026-10-05T23:01:16Z","timestamp":1791241276000},"page":"10978-10983","source":"Crossref","is-referenced-by-count":0,"title":["Determination of\n\u0394\n                    <i>H<\/i>\n                    and \u0394\n                    <i>S<\/i>\n                    between\n                    <i>syn<\/i>\n                    - and\n                    <i>anti<\/i>\n                    -Isomers of CH3COOH in CH3CN by a Temperature-Dependent\n2D IR Study"],"prefix":"10.1021","volume":"130","author":[{"ORCID":"https:\/\/orcid.org\/0009-0009-2492-2441","authenticated-orcid":true,"given":"Inwoo","family":"Lee","sequence":"first","affiliation":[{"name":"Ulsan National Institute of Science and Technology (UNIST) , , 50 UNIST-gil , ,","place":["Ulsan, Korea, 44919"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0003-7800-1433","authenticated-orcid":true,"given":"Jin Gyu","family":"Seol","sequence":"additional","affiliation":[{"name":"Ulsan National Institute of Science and Technology (UNIST) , , 50 UNIST-gil , ,","place":["Ulsan, Korea, 44919"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6306-7438","authenticated-orcid":true,"given":"Yung Sam","family":"Kim","sequence":"additional","affiliation":[{"name":"Ulsan National Institute of Science and Technology (UNIST) , , 50 UNIST-gil , ,","place":["Ulsan, Korea, 44919"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2026,10,5]]},"reference":[{"issue":"23","key":"2026101508071440700_cit1","doi-asserted-by":"publisher","first-page":"3481","DOI":"10.1021\/acs.accounts.2c00607","article-title":"Carboxylic\nacids as adaptive functional groups in metallaphotoredox catalysis","volume":"55","author":"Beil","year":"2022","journal-title":"Acc. Chem. Res."},{"issue":"2","key":"2026101508071440700_cit2","doi-asserted-by":"publisher","first-page":"225","DOI":"10.1002\/pen.25849","article-title":"A review on\ncarboxylic acid cross-linked polyvinyl alcohol: properties and applications","volume":"62","author":"Gautam","year":"2022","journal-title":"Polym. Eng. Sci."},{"issue":"21","key":"2026101508071440700_cit3","doi-asserted-by":"publisher","DOI":"10.1002\/ejoc.202300166","article-title":"Free carboxylic acids: the trend of radical decarboxylative\nfunctionalization","volume":"26","author":"Li","year":"2023","journal-title":"Eur. J. Org. Chem."},{"issue":"52","key":"2026101508071440700_cit4","doi-asserted-by":"publisher","first-page":"16188","DOI":"10.1021\/ja038341a","article-title":"Rotational\nisomerism in acetic acid: the first experimental observation of the\nhigh-energy conformer","volume":"125","author":"Mac\u0327o\u0302as","year":"2003","journal-title":"J. Am. Chem. Soc."},{"issue":"8","key":"2026101508071440700_cit5","doi-asserted-by":"publisher","first-page":"1912","DOI":"10.1139\/v88-308","article-title":"The complementary\nuse of factor analysis\nand spectral deconvolution in a study of the CD3COOD\u2013D2O system","volume":"66","author":"Ng","year":"1988","journal-title":"Can. J. Chem."},{"key":"2026101508071440700_cit6","doi-asserted-by":"publisher","first-page":"113","DOI":"10.1016\/S0166-1280(98)00436-9","article-title":"The syn-\/anti-conformational\nequilibrium of acetic\nacid in water studied by the RISM-SCF\/MCSCF method","volume":"461","author":"Sato","year":"1999","journal-title":"J. Mol. Struct.: THEOCHEM"},{"issue":"14","key":"2026101508071440700_cit7","doi-asserted-by":"publisher","first-page":"3491","DOI":"10.1021\/jp012606v","article-title":"States of molecular associates in\nbinary mixtures of acetic acid\nwith protic and aprotic polar solvents: a Raman spectroscopic study","volume":"106","author":"Nakabayashi","year":"2002","journal-title":"J. Phys. Chem. A"},{"issue":"18","key":"2026101508071440700_cit8","doi-asserted-by":"publisher","first-page":"4170","DOI":"10.1021\/jp076920m","article-title":"Ultrafast dynamics of the carbonyl\nstretching vibration in acetic acid in aqueous solution studied by\nsub-picosecond infrared spectroscopy","volume":"112","author":"Banno","year":"2008","journal-title":"J. Phys.\nChem. A"},{"key":"2026101508071440700_cit9","doi-asserted-by":"publisher","first-page":"59","DOI":"10.1016\/j.comptc.2013.08.017","article-title":"The syn\u2013anti\nequilibrium for the COOH group reinvestigated. Theoretical conformation\nanalysis for acetic acid in the gas phase and in solution","volume":"1022","author":"Nagy","year":"2013","journal-title":"Comp. Theoret. Chem."},{"issue":"5","key":"2026101508071440700_cit10","doi-asserted-by":"publisher","first-page":"503","DOI":"10.1177\/0003702819831325","article-title":"Structural\nand optical characteristics of aqueous solutions of acetic acid","volume":"73","author":"Gofurov","year":"2019","journal-title":"Appl. Spectrosc."},{"issue":"5","key":"2026101508071440700_cit11","doi-asserted-by":"publisher","first-page":"1957","DOI":"10.1021\/acs.jcim.8b00835","article-title":"Assessing the conformational\nequilibrium of carboxylic acid via quantum mechanical and molecular\ndynamics studies on acetic acid","volume":"59","author":"Lim","year":"2019","journal-title":"J. Chem. Inf.\nModel."},{"key":"2026101508071440700_cit12","doi-asserted-by":"publisher","first-page":"463","DOI":"10.1016\/j.saa.2018.08.029","article-title":"Study of molecular\nassociation in acetic acid-water binary solution by Raman spectroscopy","volume":"213","author":"Yang","year":"2019","journal-title":"Spectrochim. Acta, Part A"},{"key":"2026101508071440700_cit13","doi-asserted-by":"publisher","first-page":"123135","DOI":"10.1016\/j.saa.2023.123135","article-title":"FTIR spectroscopy and molecular level\ninsight of diluted aqueous solutions of acetic acid","volume":"302","author":"Pem","year":"2023","journal-title":"Spectrochim. Acta, Part A"},{"issue":"23","key":"2026101508071440700_cit14","doi-asserted-by":"publisher","first-page":"6768","DOI":"10.1021\/j100334a054","article-title":"Self-association\nof acetic acid in\nsome organic solvents","volume":"92","author":"Fujii","year":"1988","journal-title":"J. Phys. Chem."},{"issue":"29","key":"2026101508071440700_cit15","doi-asserted-by":"publisher","first-page":"7406","DOI":"10.1021\/acs.jpclett.5c01541","article-title":"syn- and\nanti-Isomers and Fermi Resonance\nof Acetic Acid in Acetonitrile Revealed by 2D IR","volume":"16","author":"Lee","year":"2025","journal-title":"J. Phys. Chem. Lett."},{"issue":"31","key":"2026101508071440700_cit16","doi-asserted-by":"publisher","first-page":"6123","DOI":"10.1021\/jp9813286","article-title":"Structure\nof the amide I band of\npeptides measured by femtosecond nonlinear-infrared spectroscopy","volume":"102","author":"Hamm","year":"1998","journal-title":"J. Phys. Chem. B"},{"issue":"15","key":"2026101508071440700_cit17","doi-asserted-by":"publisher","first-page":"8219","DOI":"10.1073\/pnas.140227997","article-title":"Two-dimensional infrared spectroscopy\nof peptides by phase-controlled femtosecond vibrational photon echoes","volume":"97","author":"Asplund","year":"2000","journal-title":"Proc. Natl. Acad. Sci. U. S. A."},{"issue":"20","key":"2026101508071440700_cit18","doi-asserted-by":"publisher","first-page":"11265","DOI":"10.1073\/pnas.201412998","article-title":"Two-dimensional\nIR spectroscopy can be designed to eliminate the diagonal peaks and\nexpose only the crosspeaks needed for structure determination","volume":"98","author":"Zanni","year":"2001","journal-title":"Proc. Natl. Acad. Sci. U. S. A."},{"issue":"6","key":"2026101508071440700_cit19","doi-asserted-by":"publisher","first-page":"962","DOI":"10.1021\/jp011768o","article-title":"Effects\nof Vibrational Frequency\nCorrelations on Two-Dimensional Infrared Spectra","volume":"106","author":"Ge","year":"2002","journal-title":"J. Phys. Chem. A"},{"issue":"27","key":"2026101508071440700_cit20","doi-asserted-by":"publisher","first-page":"5258","DOI":"10.1021\/jp0219247","article-title":"Coherent 2D IR spectroscopy: Molecular\nstructure and dynamics in solution","volume":"107","author":"Khalil","year":"2003","journal-title":"J. Phys.\nChem. A"},{"issue":"10","key":"2026101508071440700_cit21","doi-asserted-by":"publisher","first-page":"5601","DOI":"10.1073\/pnas.0931292100","article-title":"Dual-frequency 2D-IR spectroscopy\nheterodyned photon echo of the peptide bond","volume":"100","author":"Rubtsov","year":"2003","journal-title":"Proc. Natl. Acad. Sci. U. S. A."},{"issue":"1","key":"2026101508071440700_cit22","doi-asserted-by":"publisher","first-page":"75","DOI":"10.1021\/ar068010d","article-title":"Ultrafast 2D IR vibrational\necho\nspectroscopy","volume":"40","author":"Zheng","year":"2007","journal-title":"Acc. Chem. Res."},{"issue":"4","key":"2026101508071440700_cit23","doi-asserted-by":"publisher","first-page":"1331","DOI":"10.1021\/cr078377b","article-title":"Coherent two-dimensional\noptical spectroscopy","volume":"108","author":"Cho","year":"2008","journal-title":"Chem. Rev."},{"issue":"24","key":"2026101508071440700_cit24","doi-asserted-by":"publisher","first-page":"8231","DOI":"10.1021\/jp8113978","article-title":"Applications\nof 2D IR spectroscopy to peptides, proteins,\nand hydrogen-bond dynamics","volume":"113","author":"Kim","year":"2009","journal-title":"J. Phys. Chem. B"},{"key":"2026101508071440700_cit25","doi-asserted-by":"crossref","DOI":"10.1017\/CBO9780511675935","volume-title":"Concepts\nand Methods of 2D Infrared\nSpectroscopy","author":"Hamm","year":"2011"},{"issue":"10","key":"2026101508071440700_cit26","doi-asserted-by":"publisher","first-page":"1769","DOI":"10.1021\/acs.jpclett.6b00668","article-title":"Differences in the vibrational dynamics\nof H2O and D2O: observation of symmetric and\nantisymmetric stretching vibrations in heavy water","volume":"7","author":"De Marco","year":"2016","journal-title":"J. Phys. Chem. Lett."},{"issue":"1\u20133","key":"2026101508071440700_cit27","doi-asserted-by":"publisher","first-page":"80","DOI":"10.1016\/j.cplett.2009.01.025","article-title":"2D IR photon\necho study of the anharmonic\ncoupling in the OCN region of phenyl cyanate","volume":"470","author":"Tucker","year":"2009","journal-title":"Chem. Phys. Lett."},{"key":"2026101508071440700_cit28","doi-asserted-by":"publisher","first-page":"1036","DOI":"10.1021\/acs.jpcb.4c08307","article-title":"Distinct Fermi Resonance\nPatterns of Weak Coupling\nin 2D-IR Spectra of 5-Cyanoindole Revealed by Isotope Labeling","volume":"129","author":"Wang","year":"2025","journal-title":"J. Phys. Chem. B"},{"issue":"5","key":"2026101508071440700_cit29","doi-asserted-by":"publisher","first-page":"2709","DOI":"10.1063\/1.1586694","article-title":"Two-dimensional vibrational spectroscopy of the amide I band of crystalline\nacetanilide: Fermi resonance, conformational substates, or vibrational\nself-trapping?","volume":"119","author":"Edler","year":"2003","journal-title":"J. Chem. Phys."},{"issue":"18","key":"2026101508071440700_cit30","doi-asserted-by":"publisher","first-page":"4440","DOI":"10.1021\/acs.jpcb.3c06698","article-title":"Perturbation of Fermi Resonance on\nHydrogen-Bonded &gt; C\u2550O: 2D IR Studies of Small Ester Probes","volume":"128","author":"Sakpal","year":"2024","journal-title":"J. Phys. Chem. B"},{"issue":"21","key":"2026101508071440700_cit31","doi-asserted-by":"publisher","first-page":"214303","DOI":"10.1063\/5.0142700","article-title":"Systematic investigation of coupling between symmetric\nand antisymmetric stretches of D2O in CHCl3 by\n2D IR","volume":"158","author":"Kwon","year":"2023","journal-title":"J. Chem. Phys."},{"issue":"20","key":"2026101508071440700_cit32","doi-asserted-by":"publisher","first-page":"5935","DOI":"10.1021\/ja00254a006","article-title":"Barriers to rotation adjacent to double bonds. 3. The\ncarbon-oxygen barrier in formic acid, methyl formate, acetic acid,\nand methyl acetate. The origin of ester and amide resonance","volume":"109","author":"Wiberg","year":"1987","journal-title":"J. Am. Chem. Soc."},{"issue":"27","key":"2026101508071440700_cit33","doi-asserted-by":"publisher","first-page":"5240","DOI":"10.1021\/jp9900739","article-title":"Equilibrium constant and enthalpy for the hydrogen\nbonding of acetic acid with tetrahydrofuran in supercritical CO2","volume":"103","author":"Xu","year":"1999","journal-title":"J. Phys. Chem. A"},{"issue":"7","key":"2026101508071440700_cit34","doi-asserted-by":"publisher","first-page":"074325","DOI":"10.1063\/1.2006089","article-title":"Hydrogen-bonding interactions in acetic acid monohydrates and dihydrates\nby density-functional theory calculations","volume":"123","author":"Gao","year":"2005","journal-title":"J.\nChem. Phys."},{"issue":"11","key":"2026101508071440700_cit35","doi-asserted-by":"publisher","first-page":"7477","DOI":"10.1039\/C4CP05684A","article-title":"Standard free\nenergy of the equilibrium between the trans-monomer and the cyclic-dimer\nof acetic acid in the gas phase from infrared spectroscopy","volume":"17","author":"Goubet","year":"2015","journal-title":"Phys. Chem. Chem. Phys."},{"issue":"2","key":"2026101508071440700_cit36","doi-asserted-by":"publisher","first-page":"49","DOI":"10.1007\/s00894-024-05850-2","article-title":"Theoretical study on formation mechanism\nof acetic acid associating configurations and their distributions\nunder saturated conditions","volume":"30","author":"Zhao","year":"2024","journal-title":"J. Mol. Model."},{"issue":"15","key":"2026101508071440700_cit37","doi-asserted-by":"publisher","first-page":"1311","DOI":"10.1080\/00268970110048374","article-title":"Ab initio\ndetermination of the torsional spectra of acetic acid","volume":"99","author":"Senent","year":"2001","journal-title":"Mol. Phys."},{"issue":"5","key":"2026101508071440700_cit38","doi-asserted-by":"publisher","first-page":"1007","DOI":"10.1021\/acs.jpca.6b12713","article-title":"Phase-resolved heterodyne-detected\ntransient grating\nenhances the capabilities of 2D IR echo spectroscopy","volume":"121","author":"Jin","year":"2017","journal-title":"J. Phys. Chem. A"},{"issue":"15","key":"2026101508071440700_cit39","doi-asserted-by":"publisher","first-page":"7511","DOI":"10.1021\/jp044989d","article-title":"Two-dimensional\ninfrared spectroscopy\nof the alanine dipeptide in aqueous solution","volume":"109","author":"Kim","year":"2005","journal-title":"J. Phys. Chem. B"},{"issue":"50","key":"2026101508071440700_cit40","doi-asserted-by":"publisher","first-page":"10837","DOI":"10.1021\/acs.jpca.9b09219","article-title":"Scattering elimination of heterodyne-detected two-dimensional\ninfrared spectra using choppers and shutters","volume":"123","author":"Seol","year":"2019","journal-title":"J. Phys. Chem. A"}],"container-title":["The Journal of Physical\nChemistry B"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/acs.jpcb.6c05878","content-type":"application\/pdf","content-version":"vor","intended-application":"unspecified"},{"URL":"https:\/\/pubs.acs.org\/jpcbfk\/article-pdf\/doi\/10.1021\/acs.jpcb.6c05878\/68750781\/acs.jpcb.6c05878.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/pubs.acs.org\/jpcbfk\/article-pdf\/doi\/10.1021\/acs.jpcb.6c05878\/68750781\/acs.jpcb.6c05878.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,10,15]],"date-time":"2026-10-15T12:20:13Z","timestamp":1792066813000},"score":1,"resource":{"primary":{"URL":"https:\/\/pubs.acs.org\/jpcbfk\/article\/130\/41\/10978\/5444856\/Determination-of-H-and-S-between-syn-and-anti"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,10,5]]},"references-count":40,"journal-issue":{"issue":"41","published-online":{"date-parts":[[2026,10,5]]},"published-print":{"date-parts":[[2026,10,15]]}},"URL":"https:\/\/doi.org\/10.1021\/acs.jpcb.6c05878","relation":{},"ISSN":["1520-6106","1520-5207"],"issn-type":[{"value":"1520-6106","type":"print"},{"value":"1520-5207","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,10,5]]}}}