“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.
Positive
+ A little more challenging procedure – a nice fit for late 2nd semester.
+ The product smells nice – olfactory confirmation of a successful synthesis.
Neutral
± 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)
Negative
- 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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