Order of Reactivity in SN2 Reaction

SN2 (Substitution Nucleophilic Bimolecular) is a type of reaction that involves the substitution of a leaving group by a nucleophile. The order of reactivity in SN2 reaction depends on the nature of the leaving group and the substrate. The correct increasing order of reactivity of the given SN2 reaction is 1>4>3>2.

Explanation

1. CH2=CH-Br: The substrate has a primary carbon atom and a weakly electronegative bromine atom as a leaving group. The carbon-bromine bond is relatively weak, and the substrate is easily attacked by a nucleophile. This makes it the most reactive substrate.

2. CH2=CH-I: The substrate has a primary carbon atom and a strongly electronegative iodine atom as a leaving group. The carbon-iodine bond is stronger than the carbon-bromine bond, and the substrate is less reactive than the first substrate.

3. CH3CH2CH2-I: The substrate has a tertiary carbon atom and a strongly electronegative iodine atom as a leaving group. The carbon-iodine bond is stronger than the carbon-bromine bond, and the substrate is less reactive than the first two substrates.

4. CH3OCH2CH2-I: The substrate has a secondary carbon atom and a strongly electronegative iodine atom as a leaving group. The carbon-iodine bond is stronger than the carbon-bromine bond, and the substrate is less reactive than the first three substrates.

Conclusion

The correct increasing order of reactivity in the given SN2 reaction is 1>4>3>2. This order is based on the nature of the leaving group and the substrate. A substrate with a weaker leaving group and a primary carbon atom is more reactive than a substrate with a stronger leaving group and a tertiary carbon atom.