{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,18]],"date-time":"2026-01-18T21:27:57Z","timestamp":1768771677909,"version":"3.49.0"},"reference-count":77,"publisher":"American Chemical Society (ACS)","issue":"16","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J. Org. Chem."],"published-print":{"date-parts":[[2008,8,1]]},"DOI":"10.1021\/jo800690m","type":"journal-article","created":{"date-parts":[[2008,7,24]],"date-time":"2008-07-24T08:02:03Z","timestamp":1216886523000},"page":"6213-6223","source":"Crossref","is-referenced-by-count":30,"title":["Energetic Differences between the Five- and Six-Membered Ring Hydrocarbons: Strain Energies in the Parent and Radical Molecules"],"prefix":"10.1021","volume":"73","author":[{"given":"Filipe","family":"Agapito","sequence":"first","affiliation":[{"name":"Centro de Qu\u00edmica e Bioqu\u00edmica, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal, Grupo de F\u00edsica Matem\u00e1tica da Universidade de Lisboa, Av. Professor Gama Pinto 2, 1649-003 Lisboa, Portugal, Instituto de Tecnologia Qu\u00edmica e Biol\u00f3gica, Universidade Nova de Lisboa, Av. da Rep\u00fablica, 2780-157 Oeiras, Portugal, and Institute for Biotechnology and Bioengineering Centro de Biomedicina Molecular e Estrutural, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal"}]},{"given":"Paulo M.","family":"Nunes","sequence":"additional","affiliation":[{"name":"Centro de Qu\u00edmica e Bioqu\u00edmica, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal, Grupo de F\u00edsica Matem\u00e1tica da Universidade de Lisboa, Av. Professor Gama Pinto 2, 1649-003 Lisboa, Portugal, Instituto de Tecnologia Qu\u00edmica e Biol\u00f3gica, Universidade Nova de Lisboa, Av. da Rep\u00fablica, 2780-157 Oeiras, Portugal, and Institute for Biotechnology and Bioengineering Centro de Biomedicina Molecular e Estrutural, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal"}]},{"given":"Benedito J.","family":"Costa Cabral","sequence":"additional","affiliation":[{"name":"Centro de Qu\u00edmica e Bioqu\u00edmica, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal, Grupo de F\u00edsica Matem\u00e1tica da Universidade de Lisboa, Av. Professor Gama Pinto 2, 1649-003 Lisboa, Portugal, Instituto de Tecnologia Qu\u00edmica e Biol\u00f3gica, Universidade Nova de Lisboa, Av. da Rep\u00fablica, 2780-157 Oeiras, Portugal, and Institute for Biotechnology and Bioengineering Centro de Biomedicina Molecular e Estrutural, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal"}]},{"given":"Rui M.","family":"Borges dos Santos","sequence":"additional","affiliation":[{"name":"Centro de Qu\u00edmica e Bioqu\u00edmica, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal, Grupo de F\u00edsica Matem\u00e1tica da Universidade de Lisboa, Av. Professor Gama Pinto 2, 1649-003 Lisboa, Portugal, Instituto de Tecnologia Qu\u00edmica e Biol\u00f3gica, Universidade Nova de Lisboa, Av. da Rep\u00fablica, 2780-157 Oeiras, Portugal, and Institute for Biotechnology and Bioengineering Centro de Biomedicina Molecular e Estrutural, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal"}]},{"given":"Jos\u00e9 A.","family":"Martinho Sim\u00f5es","sequence":"additional","affiliation":[{"name":"Centro de Qu\u00edmica e Bioqu\u00edmica, Faculdade de Ci\u00eancias, Universidade de Lisboa, 1749-016 Lisboa, Portugal, Grupo de F\u00edsica Matem\u00e1tica da Universidade de Lisboa, Av. Professor Gama Pinto 2, 1649-003 Lisboa, Portugal, Instituto de Tecnologia Qu\u00edmica e Biol\u00f3gica, Universidade Nova de Lisboa, Av. da Rep\u00fablica, 2780-157 Oeiras, Portugal, and Institute for Biotechnology and Bioengineering Centro de Biomedicina Molecular e Estrutural, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal"}]}],"member":"316","published-online":{"date-parts":[[2008,7,24]]},"reference":[{"key":"ref1\/cit1","doi-asserted-by":"crossref","first-page":"167","DOI":"10.1016\/S0308-8146(99)00247-2","volume":"69","author":"Ruberto G.","year":"2000","journal-title":"Food Chem."},{"key":"ref2\/cit2","doi-asserted-by":"crossref","first-page":"2758","DOI":"10.1021\/jf020993f","volume":"51","author":"Foti M. C.","year":"2003","journal-title":"J. Agric. Food Chem."},{"key":"ref3\/cit3","doi-asserted-by":"crossref","first-page":"255","DOI":"10.1021\/ar020230d","volume":"36","author":"Blanksby S. J.","year":"2003","journal-title":"Acc. Chem. 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Chem."},{"key":"ref14\/cit14","unstructured":"The final uncertainty of the TR-PAC determination ofDH\u00b0(C\u2212H) (eq7) is equal to the uncertainty ofDHsln\u00b0(C\u2212H) (eq6), since the error in \u0394slnH\u00b0(H\u2022,g) cancels out and the error in \u0394slnH\u00b0(RH,g) \u2212 \u0394slnH\u00b0(R\u2022,g) is negligible, see e.g., ref12."},{"key":"ref15\/cit15","doi-asserted-by":"crossref","DOI":"10.1021\/bk-1998-0677","volume-title":"Computational Thermochemistry. Prediction and Estimation of Molecular Thermodynamics","author":"Irikura K. K.","year":"1998"},{"key":"ref16\/cit16","doi-asserted-by":"crossref","first-page":"93","DOI":"10.1002\/kin.550020203","volume":"2","author":"Furuyama S.","year":"1970","journal-title":"Int. J. Chem. Kinet."},{"key":"ref17\/cit17","doi-asserted-by":"crossref","first-page":"5130","DOI":"10.1021\/jp060325n","volume":"110","author":"Nunes P. M.","year":"2006","journal-title":"J. Phys. Chem. 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The values for these molecules, which are not relevant for the discussion except in this regard, are given inSupporting Information."},{"key":"ref39\/cit39","unstructured":"Stability is a precise thermodynamic concept, measured for instance by the enthalpy of formation of a molecule, as in the definition ofEstrin eq12. As such, it is meaningless in comparing molecules with a different number of atoms. We are not discussing the stability of, for instance, propane versus cyclopentane. The words \u201cstabilization\u201d and \u201cdestabilization\u201d refer to the effect of strain in each individual molecule, which is defined in relation to the hypothetical unstrained molecule, modeled in this case by propane or its radical."},{"key":"ref40\/cit40","unstructured":"Note that theEstr(R\u2022) values calculated with eq18used experimentally definedEstr(RH) values from Table3and \u0394DH\u00b0(C\u2212H) results from Table2(selected from computational and experimental results). In this sense, they can be called \u201cexperimental\u201d strain energies."},{"key":"ref41\/cit41","unstructured":"Cyclopentane planarity would correspond to C\u2212C\u2212C angles of 108\u00b0, close to the 109\u00b0 of a sp3hybridization."},{"key":"ref42\/cit42","volume-title":"March\u2019s Advanced Organic Chemistry: Reactions, Mechanisms, and Structure","author":"Smith M. B.","year":"2001","edition":"5"},{"key":"ref43\/cit43","doi-asserted-by":"crossref","first-page":"4855","DOI":"10.1063\/1.1348275","volume":"114","author":"Applegate B. E.","year":"2001","journal-title":"J. Chem. Phys."},{"key":"ref44\/cit44","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1016\/S0166-1280(98)00536-3","volume":"464","author":"Cunha C.","year":"1999","journal-title":"THEOCHEM"},{"key":"ref45\/cit45","doi-asserted-by":"crossref","first-page":"10683","DOI":"10.1021\/ja026304y","volume":"124","author":"Zilberg S.","year":"2002","journal-title":"J. Am. Chem. 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Soc."},{"key":"ref49\/cit49","unstructured":"At our theory level for structure optimization (B3LYP\/cc-pVTZ), vibrational frequency analysis shows that the dienyl-like structure (2B1) is not a minimum on the potential energy surface but is essentially isoenergetic with the allylic structure (the energy difference is only ca. 3 J mol\u22121), in agreement with the previous computations."},{"key":"ref50\/cit50","unstructured":"When designing these equations, note that apparently different structures are in fact the same radical, such as 1,3-pentadien-5-yl, 1,4-pentadien-3-yl or simply pentadienyl, and 1-methylallyl or 2-buten-1-yl."},{"key":"ref51\/cit51","doi-asserted-by":"crossref","first-page":"686","DOI":"10.1039\/b707559f","volume":"37","author":"Walsh R.","year":"2008","journal-title":"Chem. Soc. Rev."},{"key":"ref52\/cit52","doi-asserted-by":"crossref","first-page":"597","DOI":"10.1006\/jcht.1995.0061","volume":"27","author":"Diogo H. P.","year":"1995","journal-title":"J. Chem. 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