Nuclear Magnetic Resonance Spectral Studies of Amides PDF Download

Author: Daniel S. Dyer
Publisher:
ISBN:
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Languages : en
Pages : 70

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Book Description
The temperature and solvent dependence of the nuclear magnetic resonance (nmr) spectra of a number of amides has been studied. Hindered internal rotation about the C(O)-N and aryl-nitrogen bonds was detected in a series of N-acylhydrazobenzenes. In this series of compounds, hindered rotation about the C(O)-N bond afforded, in most cases, a mixture of cis-trans isomers in solution. These isomers were easily detected by nmr spectroscopy. Thus the free energies of activation, at the coalescence temperatures, for the hindered rotations were calculated. Similar temperature dependence studies on the nmr spectra of N-phenylacetamide and N-(o-tolyl) acetamide also afforded evidence for hindered internal rotation about the C(O)-N bond. However for these compounds, one isomer predominated to such a degree in solution that the presence of the second isomer was barely detected by nmr spectroscopy. A temperature dependence study of the fluorine-19 resonance spectra of both 1 and 2 deg rotation about the C(O)-N bond. However for the first time, coupling between the trifluoromethyl group and a nitrogen proton was observed. Also the proton nmr spectrum of 1,1,1-trifluoroacetamide, itself, in a dry acetone solution at low temperatures afforded the direct observation of two separate signals for the two nitrogen protons. (Author).