ECHET96 Article 107:

Rzepa, Henry (
Tue, 23 Jul 1996 17:45:58 +0000

I find this paper a fascinating combination of
NMR, synthesis and theory in which both E/Z amide
isomerism and 7-ring conformational flipping
are studied. Rate contants were obtained via
coalescence temps for observed sharp singlets
and also benzylic triplets. Delta G for the
latter is of course an approximation, since the
equations for a triplet are more complex
than those used for a singlet.

Did the authors try resolving the delta G
values into H and S for any example, using
variable temperature analysis of a system
(we find the program gNMR excellent for this
Although this normally leads to the same G
values, such a deconvolution often throws
up quite interesting deltaS values (assuming
that the value can be trusted, it is notoriously
error prone), and can often pick up steric
or stereoelectronic effects in such systems.
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