N-chloromorpholine to transfer their active chlorine to a suitable acceptor have been determined from both thermodynamic and kinetic standpoints. The secondary chloramines, although extremely weak bases, appear to react only in their protonated form. Of the tertiary N-chloro-ions. only N-chloroquinuclidinium ion and related bridgehead-nitrogen compounds are sufficiently stable to permit evaluation of their thermodynamic properties. The tendency to donate positive chlorine changes at pH 7 by a factor of lo6 on going from diethylchloramine to Nchloroquinuclidinium ion. The work partly overlaps the classical studies of Soper and his co-workers although the experimental approaches and some of the results differ substantially.
Conformational analyses by 1H NMR and potential-energy calculations are reported for the ergot alkaloids ergotamine and ergotaminine, both as free bases and as the protonated species. In the neutral forms in CDCl3. two strong intramolecular hydrogen bonds fix the molecules in folded conformations, but the protonated species adopt a more extended conformation, with a single intramolecular hydrogen bond. Of the 24 alternative conformations available to ergotamine, the most likely biologically active species in environments with low dielectric constants, e.g., the presumed ergotamine binding site, is the folded, hydrogen-bonded conformation observed for the neutral molecule in CDCl3 solution.
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