Question

Recrystallization of Acetanilide was conducted using water as our solvent.

First we had to choose a solvent based (water was chosen as our solvent due to it not dissolving acetanilide at room temp but dissolved it when heated)

Then we performed recrystallizaation, vacuum filtration and then melting point measurements.

For the post lab discussion for recrystallization of acetanilide report we have to address several different arguments. The ones below I'm not sure what to focus on to completely defend what it asks.

1. Would it be possible that the material used for the recrystallization underwent a chemical rxn during this process? Does the product have a different physical appearance than what you started with? How do you know that your isolated product didn’t change into a different substance?

2. Is it possible for two different substances to accidentally have identical melting points? Did your product’s melting point match the known melting point range of acetanilide? How strong is the claim that the product you obtained is acetanilide based on just this single match?

3. Since impurities (in organic compounds) lowers melting point temps and leads to an increase in the range, it should be easy to show that the product is not benzoic acid by mixing the two compounds and observing a melting point temp that is lower than either of the two components. Why can’t you use this approach to prove that your sample is acetanilide?

The first response I received said "do not studied this yet" which initiated chegg to send me an email saying "your question needs to be edited"

I explained the experiment that was conducted

The assignment is a discuss and those are the arguments I need to discuss and include within the discussion...

Answer 1

All answeres/responses are given in blue color.

Would it be possible that the material used for the recrystallization underwent a chemical rxn during this process?

No. The water does not react with the acetanilide, hence it cannot have any chemical reaction with the product.

Does the product have a different physical appearance than what you started with? How do you know that your isolated product didn’t change into a different substance?

Yes. It is possible, because after recrystallization the purity of the product increases as this process removes the impurities present in the product. Generally the color and appearance of the product changes to much brighter and more crystalline in nature. By identification of the product by mixed m.p. (using std Acetanilide), IR, NMR techniques, one can confirm that the product has not changed to different substance.

Is it possible for two different substances to accidentally have identical melting points?

Yes, possible.

Did your product’s melting point match the known melting point range of acetanilide?

If the product is more than 99 % pure, its melting point range should match the reported/known melting point range.

How strong is the claim that the product you obtained is acetanilide based on just this single match?

Since, there is no possibility of formation of any other solid reaction product in the synthesis of acetanilide, and if after purification by aqueous recrystallization, the melting point matches with the known melting point range, then the claim of obtained product as Acetanilide is quite strong.

Since impurities (in organic compounds) lowers melting point temps and leads to an increase in the range, it should be easy to show that the product is not benzoic acid by mixing the two compounds and observing a melting point temp that is lower than either of the two components. Why can’t you use this approach to prove that your sample is acetanilide?

It is true that the presence of impurities in the compound under test, lowers the melting range, but this approach will not establish that the obtained product is Acetanilide. For example, I can take any X, Y, Z solid compound and mix with the obtained product and get the lower melting range. But again it will tell that the obtained product is not X, Y or Z but cannot tell that it is Acetanilide.

The best way is to use standard Acetanilide substance and mix it with the obtained recrystallized product, and if there is no or negligible change in the melting point range, then we can conclude that the obtained product is Acetanilide only.

The first response I received said "do not studied this yet" which initiated HomeworkLib to send me an email saying "your question needs to be edited"

Hope your questions are answered adequately.