Conformations and conformational interconversions of enantholactam

Autor:	Gerd Borgen, Johannes Dale, Frode Rise
Rok vydání:	1993
Předmět:	NMR spectra database Crystallography Geminal Carbon-13 NMR satellite Chemistry Stereochemistry Carbon-13 Proton NMR General Materials Science Pulse sequence General Chemistry Activation energy Carbon-13 NMR
Zdroj:	Magnetic Resonance in Chemistry. 31:855-858
ISSN:	1097-458X 0749-1581
DOI:	10.1002/mrc.1260310912
Popis:	The conformational properties of enantholactam (1-azacyclooctane-2-one) in solution were studied by 1H and 13C NMR at various temperatures. Only the cis-isomer is present and it occurs in two different conformations in the ratio 3:2, as observed by 13C NMR at − 133°C. In the temperature range − 50 to − 140°C, two conformational processes were observed. A low energy process was visible in both the 1H and the 13C NMR spectra with coalescence temperature ca. − 110°C and a free energy of activation of 30 kJ mol−1, identified as interconversion between the two conformations. A higher energy process was visible in the 1H but not in the 13C NMR spectrum with coalescence temperature ca. − 96°C and free energy of activation 35 kJ mol−1. This process was identified as geminal 1H exchange. A conformational interconversion scheme for partial and full site exchange of protons and carbon atoms, explaining the variable-temperature NMR results, is proposed.
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::cbde3d19438e90e7e1d414bb9c4f0877 https://doi.org/10.1002/mrc.1260310912 Zobrazit plný text záznamu Plný text