Illustration from Scientific Research

The Boltzmann distribution of isomers shifts towards a single stereoisomer at low temperatures; for example, a free energy difference of ~5 kJ mol -1 would give an ~90:10 equilibrium mixture at room temperature, but >98:2 at 159 K, so NMR data would be expected to show a single, major species, as is apparent when comparing the three spectra in c .

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