Vanillyl alcohol from Vanillin

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Experiment 8 – Vanillyl alcohol from Vanillin.
Pre-Lab: Read the experiment. Record the following in your notebook: of
Physical properties (solubility, m.p., b.p.) and the structures of Vanillin and Vanillyl
alcohol. Obtain and turn in the literature IR spectra for both compounds.
The aldehyde Vanillin, the major flavor component of vanilla extract, is easily
reduced to the corresponding alcohol via treatment with sodium borohydride in aqueous
base.
Procedure:
Add to a 125 mL Erlenmeyer flask, 3.8 g of Vanillin and 30 mL of 1 M NaOH.
Stir with magnetic stirrer and stir bar to dissolve the vanillin and cool the contents in an
ice bath for about 10 minutes.
In several portions over about 5 minutes with stirring, add a total of 0.7 g of
sodium borohydride. Remove ice bath and stir at room temperature until solution is clear
or 20 minutes (whichever comes first).
Cool the mixture in an ice bath. Add 30 mL of 2M HCl to the reaction mixture in
~2 mL portions with vigorous swirling (lots of foaming will occur ± careful not to add
too much HCl at once). A precipitate should be visible during the addition of acid. If the
product has not precipitated from the solution after all the HCl has been added, use a
glass stir rod and scratch the sides of the flask to initiate precipitation.
Collect the product by vacuum filtration. Add ~5-10 mL of water to the reaction
flask and cool the mixture. Use it to rinse the previously filtered material.
Allow the product to dry over a day or two and then determine the mass of the
product. Obtain the infrared (mull) ± a small amount of product is added to a mortar
along with a drop of mineral oil. The mixture is ground into a paste with a pestle. A small
amount of paste is placed on the salt plates and the IR obtained.
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Name ___________________________ Section 326L-_______ Date _________
Report:
1. Write a complete, correct mechanism for the reaction.
2. Calculate the moles of vanillin and sodium borohydride used. Determine the limiting
reagent. Calculate a percent yield for the reaction. (Show your work-hLQW« each NaBH4
can reduce 4 eq. of Vanillin).
3. Report the important IR stretches with assignments of OH, CO, CH stretches for
experimental and literature data. (Hint ± generate your own data table similar to the tables
in previous labs).
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4. Discussion: Did you indeed make the desired product? Discuss why you think you
did or did not. Use the data to support your conclusions. Compare your data to the
literature. Discuss any differences.