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Vanillin Synthesis from 4-Hydroxybenzaldehyde

Page history last edited by PBworks 12 years, 6 months ago


“Vanillin Synthesis from 4-Hydroxybenzaldehyde” 



Changes to published procedure:

We scaled up the procedure – Part I 0.5g 4-hydroxybenzaldehyde.


The product from Part I (3-bromo-4-hydroxybenzaldehyde) was isolated by liquid-liquid separation and solvent evaporation.



All of the product from Part I was used for Part II.


We used boiling water baths to heat the reaction for Part II.


We did not do the column chromatography step.

We performed a GC-FID of the products from both Part I and Part II.



+ A little more challenging procedure – a nice fit for late 2nd semester.

+ The product smells nice – olfactory confirmation of a successful synthesis.



± It is very difficult to distinguish between 4-hydroxybenzaldehyde, 3-bromo-4-hydroxybenzaldehyde, and vanillin by TLC (hexane/DCM/ethyl acetate 3:3:4).

± Our GC did not distinguish between 3-bromo-4-hydroxybenzaldehyde, and vanillin.

± In this case the melting point should be an indication of purity: 4-hydroxybenzaldehyde (117-119), 3-bromo-4-hydroxybenzaldehyde (130-135), vanillin (81-83)




- We had a hard developing this lab successfully. In hindsight, I think we failed to appreciate the need to heat the reaction in Part II to a much higher temperature than would be achieved by simple reflux conditions.

– In my opinion, working with bromine and ethyl ether should be avoided whenever possible.


Inquiry & Extension ideas.

● Could be part of an exploration of an Electrophilic/Nucleophilic Aromatic Substitution study.


Student Comments 2008: Vanillin Synthesis from 4-Hydroxybenzaldehyde


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