Fluxionality And Dynamic NMR

Question 1

Dynamic spin character

Answer 1

Molecule has some E=C character giving limited rotation, NMR loses ability to distinguish between rotamers as speed of rotation increases, separate proton signals coalesce into a singlet

Question 2

What’s dynamic NMR useful for

Answer 2

Studying molecular rearrangements

Question 3

Types of molecular rearrangements

Answer 3

Ligand rotation, pseudo rotation, π-σ-π inter conversion of alkyl ligands

Question 4

Ligand rotation

Answer 4

Rotation about bond in the ligand

Question 5

Pseudo rotation

Answer 5

Concerted swapping of axial/equatorial ligands

Question 6

π-σ-π interconversion of alkyl ligands

Answer 6

Averaging of signals caused by conversion of binding modes