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Purpose of ether in Grignard reagent preparation

  1. Mar 16, 2009 #1
    1. The problem statement, all variables and given/known data

    Regarding the preparation of benzoic acid via a Grignard reagent:

    *Initial bromobenzene solution includes bromobenzene, magnesium metal and anhydrous ether.

    Once the initial bromobenzene/Mg solution undergoes boiling, you forget to add additional anhydrous ether to the reaction mixture - what happens?


    2. The attempt at a solution

    I believe that the Grignard reagent would precipitate without the presence of ether - all of the Grignard reagent would be formed, but it would ultimately be all solid. That is, the ether keeps the Grignard reagent in an aqueous phase. Is this correct?

    Thanks in advance!!
     
  2. jcsd
  3. Mar 17, 2009 #2

    Borek

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    Staff: Mentor

    In LIQUID phase.

    Not that I know anything else, but Grignard doesn't survive aqueous.
     
  4. Mar 17, 2009 #3

    chemisttree

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    Your initial conditions show that your reaction pot contains ether as well as Mg and bromobenzene. Assuming that the ether doesn't boil away, adding additional ether will do what?

    Hint: Assume that your product doesn't precipitate.
     
  5. Mar 19, 2009 #4
    The ether facilitates the reaction? So, essentially, the presence of ether allows for the formation of the Grignard reagent? Without ether, it wouldn't form....?
     
  6. Mar 20, 2009 #5

    chemisttree

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    No, the ether is the solvent. It is a coordinating solvent so it accociates with magnesium salts (like the Grignard). When you add more solvent you dilute the reaction mixture.

    So, what would happen if you left it out? What is the next step? Is it a particularly vigorous reaction? (remember that ether is a very low-boiling solvent)
     
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