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.

2) Rank the nucleophiles given below based on high, mediocre, and low nucleophilicity and reason why based on their structures. HO-CH3, H2N-CH3, KO-CH3, KO-C(CH3)3

Answer 1

HCl HC OH нас H3 CH₂ t-Butyl alcohol Mechanism: eel HS 'CHE t-Butyl chloride CH₃ Нас - - ён H₃C -C- oH - CH₃ 1-H₂O CH3 CH₃ - cel CH₃ се stable 3o carbocation only sNI reaction is occurs here. Reaction processed by formation of stable carbocation. t-Butyl alcohol have no good leaving CN2 reaction is not occurs in one step. Coup so sw2 AYO

CH₂Ook is a strong base and strong nucleophile CHO has lower size and cHo ho acts high electron density so as good nucleophile. Ko-c(CH₂) is the strongest base but size of this nucleophile is so large it can't as a good nucleophile due to steric hindrance with electophilic substituent and CH₂ - 0 H H₂N-CH3 act as modarate nucleophile as the lone pair present in and each molecule a act as nucleophile. They both have comparable size and comparable nucleophilicity. But Hyöt acts as more g nucleophilic substituent than CH₃-NH₂ . nucleophilicity strong: CH₂ OK modarate: СН3 он CH₃-NH₂ poor: KO-C(CH3)₂