Preparation of coumaryl alcohol

Joseph Sampson, 10/21/21

This is a continuation of a project started in 2018 by A. Tibbs.

Coumaryl alcohol is a monomer of lignin.

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  Caption1

Coumaryl alcohol will be synthesized from coumaric acid through two separate reactions:

1. First, coumaric acid will be converted into ethyl coumarate by through esterification. This will involve converting the carboxylic acid group into an ethyl ester group.
2. Finally, ethyl coumarate will be converted into coumaryl alcohol through a reduction reaction.

The experiment performed is based off of a published paper in which the authors previously synthesized coumaryl alcohol. The "Synthesis of p-Coumaryl Alcohol" subheading is what's important.

• Initial procedure for the Synthesis of Coumaryl Alcohol (simplified):

1. Add 1g (0.0061 moles) of p-Coumaric acid and 5mL (0.07 moles) acetyl chloride into a round bottom flask containing 50mL of dry ethanol. The total concentrations of coumaric acid and acetyl chloride in solution should be 0.111M and 1.27M each.
2. Stir at room temperature for 17 hours.
3. After 17 hours, evaporate the solvent.
4. Repeat steps 1-3 again.
5. Recrystallize the product from ethyl acetate (product should be ethyl p-coumarate).
6. Add 640mg of ethyl coumarate to 30mL of toluene and place this solution on ice and under nitrogen.
7. To the mixture on ice and under nitrogen, SLOWLY add 12mL of DIBAL-H.
8. Stir for 1hr while still ice-cooling and under nitrogen.
9. Add 5mL ethanol to quench the reaction and then mix some more.
10. Partially remove the solvent under reduced pressure (???)
11. Add 50mL water and mix.
12. Transfer mixture to separatory funnel and add ethyl acetate, shake it up, and then extract the aqueous layer. The organic layer contains coumaryl alcohol [don’t lose any of it!!].
13. Repeat step 12 three more times (4 extractions total).
14. Recrystallize the organic layer (coumaryl alcohol) from dichloromethane. The product should look like pale yellow crystals.