SN2 REACTION (Part 1)

The SN2 (substitution nucleophilic bimolecular) reaction is a type of chemical reaction that involves the replacement of a leaving group (such as a halogen) in a molecule with a nucleophile (an atom or group of atoms with a pair of electrons to donate). The reaction occurs in one step, where the nucleophile attacks the carbon atom attached to the leaving group, and the leaving group departs at the same time. The reaction is called SN2 because it involves two molecules interacting with each other, namely the nucleophile and the molecule with the leaving group.

SN2 reactions are typically observed in alkyl halides, where the carbon atom attached to the halogen is also bonded to one or two other carbon atoms. The reaction proceeds through a transition state in which the nucleophile forms a new bond with the carbon atom, while the leaving group departs with a pair of electrons. SN2 reactions are known to invert the stereochemistry of the molecule, meaning that the arrangement of atoms around the carbon center is reversed from its starting configuration. SN2 reactions are important in many fields, including organic chemistry, biochemistry, and pharmaceuticals.

ANSWER (C)

EXPLAINATION

The rate of an SN2 reaction depends on several factors, including the steric hindrance around the carbon center, the strength of the bond between the leaving group and the carbon atom, and the basicity and nucleophilicity of the attacking nucleophile. Based on these factors, the reactivity of the given compounds towards SN2 reaction can be ranked as follows:

1-chloro-1-cyclohexyl methane (I) - This compound has the most steric hindrance around the carbon center due to the presence of two bulky cyclohexyl groups. This steric hindrance makes it difficult for the attacking nucleophile to access the carbon center, and as a result, the reaction rate is expected to be the slowest among the given compounds.

1-chlorocyclohexane (II) - This compound has a bulky cyclohexyl group, which makes the carbon center more hindered, thereby slowing down the rate of SN2 reaction. However, the reaction can still occur due to the moderately good leaving group (chloride ion).

1-iodobutane (III) - This compound is expected to undergo SN2 reaction the fastest because iodine is a good leaving group, and the carbon center is relatively unhindered. Additionally, the high polarizability of the iodine atom makes it easier for the nucleophile to attack the carbon center.

1-chlorobutane (IV) - This compound is also expected to undergo SN2 reaction relatively quickly due to the relatively low steric hindrance around the carbon center, and the chloride ion is a moderately good leaving group.

Overall, 1-iodobutane is expected to undergo SN2 reaction the fastest, while 1-chloro-1-cyclohexyl methane is expected to be the slowest