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Extraction of benzoic acid

  • #1

Homework Statement


Why is it possible to use dimethyl ether as a solvent for extraction of benzoic acid and not dioxane?


Homework Equations





The Attempt at a Solution



I'm thinking that it's because dioxane has more of a hydrophobic character since it has many carbons, but then wouldn't this make it a good solvent since benzoic acid has many carbons also? This question doesn't seem hard, I'm just a little stumpped and looking for a little tip. Thanks :)
 

Answers and Replies

  • #2
chemisttree
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You are extracting an aqueous solution of benzoic acid... sodium benzoate, right? An aqueous solution, right?
It's in water, yes?
 
  • #3
Correct.
 
  • #4
Borek
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WATER.

(This was a hint).
 
  • #5
Sorry, I doubled check and this is not the case. I didn't give enough information in the problem statement, I'm sorry. A solution containing biphenyl and benzoic acid is mixed with water and ether. We originally need to extract both of these compounds into the ether phase which is what the question is asking. (We extract the benzoic acid into the aqueous phase later on). I'm really sorry again guys, I screwed up this question lol. Thanks for your help and patience.
 
  • #6
symbolipoint
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Guess is that both are soluble in ether. How many extractions to take all of the two organic compounds from the water into the ether, not sure. Since the two listed are both organic, one might guess that extraction into ether goes well.
 
  • #7
Borek
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We originally need to extract both of these compounds into the ether phase which is what the question is asking.
What ether phase?
 
  • #8
symbolipoint
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Sorry, I doubled check and this is not the case. I didn't give enough information in the problem statement, I'm sorry. A solution containing biphenyl and benzoic acid is mixed with water and ether. We originally need to extract both of these compounds into the ether phase which is what the question is asking. (We extract the benzoic acid into the aqueous phase later on). I'm really sorry again guys, I screwed up this question lol. Thanks for your help and patience.
What ether phase?
What is the solvent of the original sample? Would the assumption that it is in water, be incorrect?

You gave "dimethyl ether" as the solvent to use for extraction. Is the benzoic acid in its acid form or is it in the neutralized form?

May be schoolboy10 or another member can give some facts to explain what is possible.
 
  • #9
Yeah I'm sorry again guys, I screwed up the question in the beginning by not giving enough info lol. Benzoic acid is originally mixed in ethanol. We then place this in a separatory funnel with water and ether. This is where the question applies. Why can't we use dioxane as the ether to extract benzoic acid, but we can use dimethyl ether.

This is confusing to me because I would think that dioxane is more similar to benzoic acid than dimethyl ether is.
 
  • #10
chemisttree
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OK then. You start with an aqueous solution that has a little ethanol in it. It's in water essentially. You are extracting an aqueous solution since the benzoic acid is in water. What is it about dimethyl ether that would allow you to extract something from water? How about dioxane?

Hint: Borek was right... WATER is a hint.
 
  • #11
I'm guessing benzoic acid is more soluble in dimethyl ether than water, but in water more than dioxane?
 
  • #12
chemisttree
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Write down the properties of dimethyl ether and the properties of dioxane. Compare and contrast. Remember that WATER is a hint.
 

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