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https://hdl.handle.net/10316/18066
Título: | 1H NMR Spectroscopic and Quantum Chemical Studies on a Poly(ester amide) Model Compound: Nα-Benzoyl-l-Argininate Ethyl Ester Chloride. Structural Preferences for the Isolated Molecule and in Solution | Autor: | Fonseca, A. C. Jarmelo, S. Carvalho, R. A. Fausto, R. Gil, M. H. Simões, P. N. |
Data: | Abr-2010 | Editora: | American Chemical Society | Título da revista, periódico, livro ou evento: | J. Phys. Chem. B, | Volume: | 114 | Resumo: | The molecular structure of the l-arginine derivative, Nα-benzoyl-l-argininate ethyl ester chloride (BAEEH+·Cl−), was characterized by combining quantum chemical methods and 1H NMR spectroscopy. A conformational search on the potential energy surfaces of the three lowest-energy tautomers of BAEEH+ [A: R−N+H═(NH2)2; B: R−NH−C(═NH)N+H3; C: R−N+H2−C(═NH)NH2; R = C6H5C(═O)NH−CH(COOCH2CH3)CH2CH2CH2−] was carried out using the semiempirical PM3 method. The lowest-energy conformations obtained using this method were then optimized at the DFT(B3LYP)/6-31++G(d,p) level of theory. For all tautomers, it was found that all low-energy conformers present folded structures, in which a H-bond interaction between the guanidinium group and the amide carbonyl oxygen atom appears to be the most relevant stabilizing factor. 1H NMR spectra of BAEEH+·Cl− in DMF-D7 were acquired in the temperature range [−55 to 75 °C], providing information about the rotational motions in the guanidinium group and showing that the tautomeric form of BAEEH+ that exists in solution is tautomer A. The interpretation of the experimental findings was supported by 1H NMR chemical shifts obtained theoretically at the DFT(B3LYP)/6-31++G(d,p) level of approximation, using both the polarized continuum model and a BAEEH+−water complex model. | URI: | https://hdl.handle.net/10316/18066 | DOI: | 10.1021/jp9114749 | Direitos: | openAccess |
Aparece nas coleções: | FCTUC Química - Artigos em Revistas Internacionais |
Ficheiros deste registo:
Ficheiro | Descrição | Tamanho | Formato | |
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J.Physical Chemistry B, 114 (2010) 6156.pdf | 279.6 kB | Adobe PDF | Ver/Abrir |
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