Methyl Salicylate Post-Lab Questions

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[chrisf]

3) In this experiment, excess methanol was used to shift the equilibrium toward the formation of more product. Describe other methods for achieving the same result.

I suppose you could increase the temperature.. but I'm not sure what else. Maybe use an excess of salicylic acid instead of the methanol?

4) How are excess sulfuric acid and the excess methanol removed from the crude ester after the reaction has completed?

We used H₂SO₄ as a catalyst, added in excess. As a catalyst, it's not consumed and we need to remove it from the crude ester so we have a pure final product. It has us do a serious of washes, one of which is with NaHCO₃. I believe what's happening here is:

H₂SO₄   +   NaHCO₃  ->  Na₂SO4   +   CO₂   +  H₂O

Basically, we're converting it to sodium sulfate, carbon dioxide (as a gas?) and water. In the sep funnel, we separate off the methylene chloride layer and discard the aqueuous layer.

As for the excess methanol, I'm not sure..

Here's our extraction sequence:

Initial Reaction: salicylic acid + methanol -> methyl salicylate + water

Extraction:

Mixture + methylene chloride -> drain lower layer and keep for extraction
Lower Layer + methylene chloride -> drain lower layer and keep for extraction
Lower Layer + water -> drain lower layer and keep for extraction
Lower Layer + sodium bicarbonate -> drain lower layer and keep for extraction
Lower Layer + sodium bicarbonate -> drain lower layer and keep for extraction

Then we add anhydrous sodium sulfate to help remove the water from mixture.

Instead of doing a vacuum distillation here, we just boiled off the methylene chloride and called it product.

But I'm not positive about the answer to this question....

6) Interpret the principal absorption bands in the infrared and NMR spectra of methyl salicylate.

I'm going to get an IR and NMR spectra scan up here and interpret it and see what people think...

[valdorod]

I am taking an educated guess here, but I would expect the excess methanol to become part of the aqueous layer.  When you remove the aqueous layer from the top of the funnel I would expect it to be made up of the water used for washing and the excess methanol.

As for the NMR see if the following helps




       ppm   Int.  Assign.
      170.59   188      1
      161.75   297      2
      135.69   693      3
      129.98   990      4
      119.17  1000      5
      117.59   713      6
      112.48   317      7
       52.21   713      8