Conformational and configurational dynamics of a highly fluorinated hydrazone.

The relative populations of two rotamers in the hydrazone of 2H-perfluoro-2-methyl-3-pentanone can be altered from one extreme to the other by increasing the Lewis basicity of the solvent, and the equilibrium E/Z ratio grows correspondingly. Both trends reflect an increase in the effective size of the amino group as a result of hydrogen bonding. The rate of E/Z interconversion is insensitive to the choice of solvent, consistent with the conclusion that the isomerization occurs via N-inversion and not C=N bond rotation.