The order of reactivities of the following alkyl halides for an SN2 reaction is:
Correct answer: D. RI > RBr > RCl > RF
- A. RF > RCl > RBr > RI
- B. RF > RBR > RCl > RI
- C. RCl > RBr > RF > RI
- D. RI > RBr > RCl > RF
Explanation
The reactivity of the alkyl halide in the SN2 reaction is decided by the ease with which the halide leaves the substrate. The larger the size of the halide ion, the more is the leaving ability. As per the leaving ability, the order is I−>Br−>Cl−>F-. Hence reactivity order is RI > RBr > RCl > RF due to the higher stability of I- ion (due to its higher size). Hence, I ion is easily displaced by a nucleophile.
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About Alkyl Halides
Alkyl halides are named and related to their carbon-halogen structure, polarity and reactivity. The key reactions are nucleophilic substitution by SN1 and SN2 mechanisms and elimination by E1 and E2 mechanisms, including how substrate structure, nucleophile, base, solvent and temperature influence substitution versus elimination.
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