Question

Introduction Alkyl halides can be prepared from alcohols by reactions with hydrogen halides (HCI, HBr, or HI) via nucleophilic substitution. In this type of reaction, the nucleophile displaces a leaving group from a carbon atom of an organic substrate (here the alcohol once protonated). Both electrons of the new bond to the carbon are provided by the nucleophile while the leaving group departs with both electrons of its bond to the substrate. There are two limiting mechanisms that are most common in describing nucleophilic substitution reactions at sp carbon centres : (1) a direct displacement (SN2) process and (2) a process that generates an intermediate carbocation (SN1). Which mechanism is a better description depends on the structure of the molecule containing the leaving group, the nature of the leaving group, the size of the nucleophile, and the polarity of the solvent. This experiment is a near-perfect example of an Sn1 substitution. H3COH + HCI H3CCI + H2O (Equation 1) H3C CH3 H3C CH3 In this reaction, you will prepare 2-chloro-2-methylpropane (t-butyl chloride) from 2- methyl-2-propanol (t-butyl alcohol) using HCl as the strong acid and chloride source. Note that HCI first activates the alcohol in an acid/base reaction before the Sn1 reaction proceeds. The final product is characterized by its yield, boiling point, and density. The presence of a halide atom is confirmed with a silver nitrate test.

3) Name two solvents that are commonly used for SN2 reactions. because they considerably slow down SN1 reactions.

Answer 1

1. For SN^{​​​​​}​​​​​2 reaction polar aprotic solvents are the best solvents.

2. So DMSO, Acetone, DMF or acetonitrile are the solvents which we can use for SN2 reaction.

3. We use polar protic solvents then they will stabilise the nucleophile and slow down the SN2 reaction.

4. So polar aprotic solvents will not stabilise the nucleophile and slow down SN2 reaction and it moves toward SN1 reaction.