Organic Chemistry 1 · Substitution pathways
Finkelstein reaction — iodide exchange in acetone
Conditions: NaI with chloroethane in acetone; follow the forward halide-exchange event. Salt precipitation favors net exchange but is not an electron-pushing step. Na⁺ and Cl⁻ remain explicit in the final bookkeeping snapshot.
Draw this problem yourself
Drag from the electrons that move to where they go, or tap one and then the other. Every arrow is checked; Hint helps when you're stuck. No account needed.
The mechanism, step by step
Next plays each step's curved arrows and explains them. The written steps are below.
Read all 2 written steps
Draw the exchange event
This is a concerted encounter, not ionization to an ethyl carbocation.
The curved arrows
- The nucleophile uses a lone pair to bond to the carbon bearing the leaving group.
- The leaving group takes the C–leaving-group bond pair as the new bond forms.
Exchanged halide
Iodide loses one lone pair and its negative charge on bonding to carbon; chloride gains the departing pair and becomes the counteranion. Precipitation changes phase, not covalent electron accounting.
What you'll practice
Distinguish a nucleophilic halide from the departing halide while conserving both ions.
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