Experiment 10: Phase Transfer Catalysis

At the end of the phase transfer catalysis experiment, what molecule gave the spot with the highest Rf value when you ran the TLC?

allyl 2‐naphthyl ether

Phase transfer catalysts promote certain reactions by:

changing the solubilities of one of the reactants and thus increasing its concentration in the other phase

The Williamson ether synthesis between 2-naphthol and allyl bromide in the presence of strong base and benzyltriphenylammonium chloride as a phase transfer catalyst in dichloromethane solution is known to proceed in reasonable yield. The need for a phase transfer catalyst would be removed if a polar aprotic solvent such as DMSO were used as a reaction solvent. Why is DMSO not used as a solvent for this reaction?

Because of risks associated with toxicity.

The Williamson ether synthesis between 2-naphthol and allyl bromide in the presence of strong base and benzyltriphenylammonium chloride as a phase transfer catalyst in dichloromethane solution is known to proceed in reasonable yield. Why will the reaction fail to work if the solvent is switched to ethanol while retaining the same reactants, phase transfer catalyst, and base?

Because the base would deprotonate ethanol and create a second nucleophile.

In the phase transfer catalysis experiment:

NaOH was used to produce the naphtholate anion

Sodium hydroxide can cause severe damage to skin and eyes.

True

In the phase transfer catalysis lab, what was the purpose of putting calcium chloride in your organic layer after workup?

to remove water from the organic solution

Which of the following compounds is a phase transfer catalyst?

Benzyl tri‐n‐butylammonium chloride

Gloves and goggles are not required when handling sodium hydroxide.

False

Lachrymators like allyl bromide are specifically dangerous because of their explosion hazard.

False

The primary risk associated with dichloromethane is its flammability.

False

Unused allyl bromide can be disposed of in the aqueous waste.

False

In the phase transfer catalysis experiment, you synthesized a naphthyl ether from allyl bromide and the naphtholate ion. Which type of reaction did this proceed through?

SN2

List the procedural steps, from start to finish, that are required to convert 2-naphthol and allyl bromide into allyl 2-naphthyl ether.

The reaction is performed on a small scale by mixing the alcohol, the haloalkane, and the phase transfer catalyst in a conical vial. Sodium hydoxide (base) is added to initiate the reaction. The reaction flask is covered and stirred to conduct reaction to prevent evaporation of the solvent. The progress of the reaction is monitored by TLC so that no time is wasted. The reaction solution is then dried over calcium chloride to remove any remaining water. The product is purified by column chromatography and collected by evaporation.