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Chemistry LibreTexts

Substitution Solutions

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The above substitution mechanism is bimolecular (SN2) because there is a strong nucleophile given as well as an aprotic solvent.  Remember: a strong nucleophile favors SN2 and an aprotic solvent will also favor SN2

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The above substitution mechanism is unimolecular (SN1) because there is not a strong nucleophile present.  Remember: a weak nucleophile favors SN1 and because the electrophile leaves first, a carbocation is formed.  Therefore, the nucleophile, CH3CH2CH2OH can attack both the front and the back, resulting in a racemic mixture.