Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: IceSpiceFan#1 on April 21, 2023, 05:08:50 PM
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In our chemistry project we tried to synthesize benzoic acid through oxidation of benzylic alcohol and potassium permanganate. These reactants are warmed with the presence of sulfuric acid until the violet color of permanganate has been removed. The solution should be clear, but there is a yellow substance on the top.
Even after vacuum filtration and recrystallization there is still hint of yellow within the crystals.
Furthermore, there is a noticeable smell of cherries, which indicates a presence of benzaldehyde. We therefore speculate that it might be benzaldehyde, as it is a middle product of the first oxidation of benzylic alcohol.
We have tried to fix this by adding more oxidants, which was in vain, as the yellow was still there. We also tried to add more acid, which made it even more yellow and gave it a more intense smell of benzaldehyde. This made us even more confused :-\
Picture of the synthesis I posted on r/chemistryhelp
https://preview.redd.it/i3py0etp18va1.png?width=1536&format=png&auto=webp&v=enabled&s=49a17400f0ed4975bfa63ddb034a964f84cd45d3
Hope you guys can help :)
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There does seem to be useful feedback at reddit (
https://www.reddit.com/r/chemistryhelp/comments/12tydzc/why_do_i_have_yellow_stuff_in_my_oxidation_of/ ).
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You can check this site also to understand the impurity-
https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Organic_Chemistry_Lab_Techniques_(Nichols)/03%3A_Crystallization/3.02%3A_Uses_of_Crystallization/3.2B%3A_Purification_of_Product_Mixtures