Benzyl Phenyl Ether from Benzyl Chloride and a Dilute Solution of Phenol

A. Introduction:

This is a procedure to make benzyl phenyl ether on the lab bench scale from phenol and benzyl chloride. It is meant to show the ease with which one can learn the basic PTC process and generate kinetic data. The reaction takes slightly more than one hour. This would make a great undergraduate physical or organic chemistry experiment since it uses standard laboratory glassware and chemicals and analytical results are obtained from a GC that takes less than 15 minutes per injection.

Please follow all proper lab safety precautions and make sure that all of the MSDS (material safety data sheets) are available and have been read and understood. Follow standard laboratory protocols for dealing with these raw materials and wastes, including the use of a well ventilated fume hood.

B. Major Equipment:*

500 ml Three Neck Round Bottom Flask
Thermometer
Mechanical Stirrer
Heating Mantle or Water Bath
Temperature Controller
Jack Stand

* excludes clamps, weighing scales, support stands etc.

C. Chemicals:

All were purchased from Aldrich (usually the lowest grade) and used as purchased without any additional purification. Tap water was used to prepare the aqueous phase. This approach was chosen to show the robustness of the process.

D. PROCEDURE

1. Prepare the aqueous phase by adding 1.88 g of phenol (20 mmoles), 1.80 g of 50 wt% sodium hydroxide (22.5 mmoles), sodium iodide (0.075 g), and 196.0 g of water to a 3- neck 500 mL reaction flask. After a brief stirring there will be about 200 g of a solution containing little less than 1.0 w/w % of phenol (in the form of phenolate). pH should be above 11.

2. Introduce a mechanical stirrer into the reactor and immerse the reactor into a temperature controlled water bath kept at 40oC (or use a heating mantle with temperature control). Keep the reactor content stirred mechanically at 600 rpm minimum.

3. Prepare the organic phase by mixing 7.59 g of benzyl chloride (60 mmols), 0.82 g of Adogen 464 or Aliquat 336 (both products consist mostly of methyltrioctylammonium chloride), and 0.45 g of 3-methylanisole. Other internal standards may work fine or one may choose an external standard. It is wise to analyze a sample of the organic phase before the reaction to confirm the GC profile in the resulting chromatogram.

4. Once the temperature of the reaction mixture reached the temperature of the bath (use a thermometer to confirm), transfer quickly the organic phase into the stirred aqueous phase. This is time zero of the reaction. The average temperature will be slightly below 40oC but the mixture will equilibrate within three minutes due to the capacitance effect of the water bath.

5. Every 10 minutes stop the stirrer and allow 1 minute for the phases to separate. Virtually no reaction will occur when the stirrer is stopped. Take aliquots of the lower organic phase and briefly centrifuge the sample before injecting the organic pahse into the GC (the density of benzyl chloride is 1.10 g/cc, the organic phase is the lower phase, even after the formation of significant quantities of the product).

6. The reaction will be complete after 70 minutes. The yield of benzyl phenyl ether based on the limiting reactant (phenol) after 30 minutes of reaction was 70 %. For all of the samples the chromatogram contained the product, the unreacted benzyl chloride (used in excess), the internal standard and minute quantities of benzyl alcohol and benzyl iodide.

ANALYTICAL

Gas Chromatograph: Hewlett-Packard/Agilent 6890 Gas Chromatograph
Integrator HP/Agilent 6890 Series Integrator
Column J&W Scientific DB-Wax column
Detector TCD detector with EPC
Initial Time 1 minute
Initial Temp 95 oC
Rate 15 oC/min,
Final Temp 225 oC
Final Time 3 minutes (total run time 12.66 minutes)
Carrier Gas Ultra pure helium from AirGas.

To determine the GC response factors against the internal standard, solutions containing four different concentrations of reactants and the standard were prepared and injected into the GC. Since no solvent was added to the reaction mixture, benzyl chloride served a dual purpose and was also the solvent. The run was not optimized. The reaction was stopped when it was considered to have produced sufficient data to determine the second order rate constant (0.12 lit/min-gmol). Please contact us if you would like help working up the data or creating the plot to determine the reaction rate constant.

Disclaimer: Value Recovery, Inc. accepts no liability for experiments done within the guidelines of this recipe. Therefore, the user explicitly accepts all the responsibility to operate the equipment is a safe and environmentally sound manner.