If you are using comparative bond strengths to determine if a reaction is favorable, you need to consider the bonds in the products as well as those in the reactants You can even do the finkelstein on aromatic rings if you add catalytic copper (i) iodide and a diamine to activate it. The article by gillespie argues you should avoid the phrase ionic character because ionic and covalent aren't mutually exclusive
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It's pretty clear from dipole moment in diatomic lif and quantum calculations that ~0.9 electrons are transferred
That deals with the thermodynamic parts of reactivity, in the sense that it explains why some reactions with iodine require elevated temperatures for any significant conversion, whereas reactions with.
The reaction mechanism is actually Yes, the finkelstein can work in other solvents, especially with the correct activators