Furfuryl chloride can undergo substitution by both SN2 and SN1 mechanisms. Since it is a 1° alkyl halide, we expect SN2 but not SN1 reactions. Draw a mechanism for the SN1 reaction shown below, with careful attention to the structure of the intermediate. How can this primary halide undergo SN1 reactions? Why is there no competition with E2 or E1 mechanisms?
Solution 68SP :
Here, we have to draw a mechanism for the SN1 reaction shown below, and state how can this primary halide undergo SN1 reactions. And also mention why is there no competition with E2 or E1 mechanisms.
Primary halides usually undergo SN2 reactions as they have less steric hindrance(it is prevention of chemical reaction by large groups present in a molecule) to the nucleophilic attack and also they are less stable.
Furfuryl chloride which is a primary alkyl halide has lone pair of electrons on the oxygen atom, which participates in the formation of bond when nucleophile attacks it and hence it undergoes SN1 reaction. This mechanism is explained below.
The mechanism for the given SN1 reaction is shown below :
The C-Cl bond in the furfuryl chloride compound undergoes dissociation and the furanium ion is formed as product. This ion is cation and is stabilized by resonance as shown above. The formate ion of the sodium formate compound acts as nucleophile and attacks the substrate(substrate is the compound that is being attacked by the nucleophile. Hence, here furfuryl chloride is the substrate ). This nucleophilic attack is shown in the next step