SN2 Reaction Mechanism

Question

I need help drawing out the full SN2 reaction mechanism of 2-naphthol and butyl tosylate in NaOH and EtOH to form 2-butoxynaphthalene. I have the structures drawn out but am not sure how the mechanism goes for this. Thanks!

Answer 1

To draw out the full SN2 mechanism for the reaction of 2-naphthol and butyl tosylate in NaOH and EtOH, we’ll need to break it down step by step. Here’s how it proceeds:

Reactants:

1. 2-Naphthol - Naphthalene ring with a hydroxyl group (-OH) at position 2.
2. Butyl Tosylate (butyl p-toluenesulfonate) - Butyl group attached to a tosylate (–OTs) group, which is a good leaving group.
3. NaOH (Sodium Hydroxide) - Acts as a base to deprotonate the 2-naphthol and generate a strong nucleophile.
4. EtOH (Ethanol) - Solvent that facilitates the reaction.

Step-by-Step Mechanism:

Step 1: Deprotonation of 2-Naphthol

1. NaOH (sodium hydroxide) deprotonates the hydroxyl group of 2-naphthol, converting it into a naphthoxide ion (O-), which is a stronger nucleophile than the neutral hydroxyl group.
2. Equation:
3. 2-naphthol + NaOH → Naphthoxide ion (O-) + Na+ + H2O

Step 2: Nucleophilic Attack

1. The naphthoxide ion (O-) attacks the carbon attached to the tosylate group on butyl tosylate. This happens via a backside attack, characteristic of an SN2 mechanism.
2. The tosylate group (–OTs) is displaced as the leaving group in this one-step process, leading to the formation of the new C-O bond between the butyl group and the naphthoxide ion.

Step 3: Formation of 2-Butoxynaphthalene

1. The product is 2-butoxynaphthalene, where the naphthoxide group has bonded to the butyl group. The leaving group, tosylate (OTs-), is expelled during the nucleophilic substitution.
2. Equation:
3. Naphthoxide ion + Butyl Tosylate → 2-Butoxynaphthalene + Tosylate ion (OTs-)

Step 4: Role of Solvent (EtOH)

1. Ethanol (EtOH) acts as a solvent to stabilize the reaction intermediates and transition state, as well as solvate the leaving group (tosylate), which aids in its departure.

Overall Reaction:

2-Naphthol + Butyl Tosylate + NaOH → 2-Butoxynaphthalene + Tosylate ion (OTs-)