1H and 13C NMR Studies of Etidocaine Free Base and Hydrochloride Salt. Solvent and Temperature Dependence |
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| Authors: | Laurine A LaPlanche Robert Rothchild Yangdong Xu |
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| Institution: | 1. Department of Chemistry , Northern Illinois University , DeKalb, IL, 60115-2862;2. The City University of New York John Jay College of Criminal Justice, Department of Science Toxicology Research and Training Center , 445 West 59th Street, New York, NY, 10019-1199 |
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| Abstract: | The 1H and 13C NMR spectra of etidocaine free base, 1, and its hydrochloride salt, 2, have been examined at 200 MHz in a variety of solvents. Variable temperature 1H NMR spectra of 2 were measured between 0° and 90°C at 500 MHz. Both 1H and 13C spectra of the salt were strongly dependent on temperature, solvent and spectrometer frequency. Results are interpreted primarily as a consequence of acid-induced chirality at the amine nitrogen, resulting in solvent-dependent diastereoisomerism. Spectral complexity is explained as the result not only of diastereotopic nuclei due to the fixed “natural” chiral center at carbon, but also, in 2, to the presence of diastereomeric racemates resulting from the second chiral center (at nitrogen). |
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| Keywords: | Variable temperature NMR Local anesthetics Diastereotopic nuclei Diastereomers Nitrogen inversion Solventdependent diastereoisomerism Proton transfer Enantiomers NMR solvent effects |
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