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Validation of Enthalpy–Entropy Compensation Mechanism in Partial Amide Bond Rotation

[Image: see text] The concept of enthalpy–entropy compensation (EEC) is one of the highly debated areas of thermodynamics. The conformational change due to restricted double-bond rotation shows a classic two-site chemical exchange phenomenon and has been extensively studied. Fifty-four analogs of N,...

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Autores principales: Guerra, Jacob, Bajwa, Bhvandip, Kumar, Prarthana, Vazquez, Salvador, Krishnan, Viswanathan V., Maitra, Santanu
Formato: Online Artículo Texto
Lenguaje:English
Publicado: American Chemical Society 2020
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7191833/
https://www.ncbi.nlm.nih.gov/pubmed/32363286
http://dx.doi.org/10.1021/acsomega.0c00332
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author Guerra, Jacob
Bajwa, Bhvandip
Kumar, Prarthana
Vazquez, Salvador
Krishnan, Viswanathan V.
Maitra, Santanu
author_facet Guerra, Jacob
Bajwa, Bhvandip
Kumar, Prarthana
Vazquez, Salvador
Krishnan, Viswanathan V.
Maitra, Santanu
author_sort Guerra, Jacob
collection PubMed
description [Image: see text] The concept of enthalpy–entropy compensation (EEC) is one of the highly debated areas of thermodynamics. The conformational change due to restricted double-bond rotation shows a classic two-site chemical exchange phenomenon and has been extensively studied. Fifty-four analogs of N,N-diethyl-m-toluamide (DEET) as a model system were synthesized to study the thermodynamics of the partial amide bond character using nuclear magnetic resonance (NMR) spectroscopy. Line-shape analysis as a function of temperature is used to estimate the chemical exchange. Eyring analysis was then used to convert the chemical exchange rates to determine the transition state enthalpy and entropy of the molecules. The experimental design follows selective variations that perturb one aspect of the molecular system and its influence on the observed thermodynamic effect. The results of the study demonstrate that amide bond resonance in analogs of DEET follows an EEC mechanism. Simple modifications made to DEET’s structural motif alter both the enthalpy and entropy of the system and were limited overall to a temperature compensation factor, T(β) = 292.20 K, 95% CI [290.66, 293.73]. We suggest EEC as a model to describe the kinetic compensation seen in chemical exchange phenomena in analogs of DEET.
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spelling pubmed-71918332020-05-01 Validation of Enthalpy–Entropy Compensation Mechanism in Partial Amide Bond Rotation Guerra, Jacob Bajwa, Bhvandip Kumar, Prarthana Vazquez, Salvador Krishnan, Viswanathan V. Maitra, Santanu ACS Omega [Image: see text] The concept of enthalpy–entropy compensation (EEC) is one of the highly debated areas of thermodynamics. The conformational change due to restricted double-bond rotation shows a classic two-site chemical exchange phenomenon and has been extensively studied. Fifty-four analogs of N,N-diethyl-m-toluamide (DEET) as a model system were synthesized to study the thermodynamics of the partial amide bond character using nuclear magnetic resonance (NMR) spectroscopy. Line-shape analysis as a function of temperature is used to estimate the chemical exchange. Eyring analysis was then used to convert the chemical exchange rates to determine the transition state enthalpy and entropy of the molecules. The experimental design follows selective variations that perturb one aspect of the molecular system and its influence on the observed thermodynamic effect. The results of the study demonstrate that amide bond resonance in analogs of DEET follows an EEC mechanism. Simple modifications made to DEET’s structural motif alter both the enthalpy and entropy of the system and were limited overall to a temperature compensation factor, T(β) = 292.20 K, 95% CI [290.66, 293.73]. We suggest EEC as a model to describe the kinetic compensation seen in chemical exchange phenomena in analogs of DEET. American Chemical Society 2020-04-13 /pmc/articles/PMC7191833/ /pubmed/32363286 http://dx.doi.org/10.1021/acsomega.0c00332 Text en Copyright © 2020 American Chemical Society This is an open access article published under an ACS AuthorChoice License (http://pubs.acs.org/page/policy/authorchoice_termsofuse.html) , which permits copying and redistribution of the article or any adaptations for non-commercial purposes.
spellingShingle Guerra, Jacob
Bajwa, Bhvandip
Kumar, Prarthana
Vazquez, Salvador
Krishnan, Viswanathan V.
Maitra, Santanu
Validation of Enthalpy–Entropy Compensation Mechanism in Partial Amide Bond Rotation
title Validation of Enthalpy–Entropy Compensation Mechanism in Partial Amide Bond Rotation
title_full Validation of Enthalpy–Entropy Compensation Mechanism in Partial Amide Bond Rotation
title_fullStr Validation of Enthalpy–Entropy Compensation Mechanism in Partial Amide Bond Rotation
title_full_unstemmed Validation of Enthalpy–Entropy Compensation Mechanism in Partial Amide Bond Rotation
title_short Validation of Enthalpy–Entropy Compensation Mechanism in Partial Amide Bond Rotation
title_sort validation of enthalpy–entropy compensation mechanism in partial amide bond rotation
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7191833/
https://www.ncbi.nlm.nih.gov/pubmed/32363286
http://dx.doi.org/10.1021/acsomega.0c00332
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