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A Organic Chem problem

  1. Jul 29, 2004 #1
    Well i am having problem prepearing this alcohol from bromobenzene and 1-butene




    please help.This question is from Solomons organic chem.
     

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    Last edited: Jul 29, 2004
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  3. Jul 29, 2004 #2
    Maybe you should redraw the target, you've got three bonds to oxygen. And I could be mistaken but I think you're missing a carbon.
     
  4. Jul 29, 2004 #3
    Well i made a little mistake in the bond to oxygen atom but have updated the figure and corrected it.
    please help.
     
  5. Jul 29, 2004 #4

    GCT

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    Right off the top I can suggest a nucleophilic attack through a elimination-addition (not addition elimination) mechanism. Look it up in the book, it is the chapter regarding phenols. Adding a hydroxyl group to the double bond of butene results in an nucleophilic compound with the negative charge on the terminal carbon, this terminal carbon compound under the right conditions perhaps can participate in a substitution reaction replacing bromine (NOT sn2 sn1 pathway). Some problems in the solomons book require a bit of the imagination, you need to suggest a possibility without any knowledge of the existence of such pathways and reactions. Although there may be a existing, commonly used reaction to achieve this product.


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  6. Jul 29, 2004 #5
    Here is another way I thought of to synthesize your desired compound:

    1) Turn bromobeneze into a grignard reagent by the usual methods. Put it aside.

    2.) Do a hydroboration oxidation on the terminal alkene to create the primary alcohol.

    3) Do a swern oxidation on the primary alcohol to create the aldehyde.

    4). React the created grignard reagent with the aldehyde and then add some acid. Your result will be your desired product.
     
  7. Jul 29, 2004 #6
    Are you sure that's the right number of carbons? If so, ozonolysis with reductive work-up of the butene, followed by Grignard addition of the bromobenzene to the aldehyde.
     
  8. Jul 30, 2004 #7

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    The regiochemistry of the alcohol would be wrong with the hydroboration/oxidation thing.


    Ozonolysis would carve out a carbon. The product drawn has 10.
     
  9. Jul 30, 2004 #8

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    How about epoxidation of the alkene with MCPBA, then make the Gilman reagent of the bromobenzene (nBuLi, then CuI). Mixing that with the epoxide should open the epoxide at the less hindered position and give the right regiochemistry.
     
  10. Jul 30, 2004 #9

    I'm not sure what you are talking about. Hydroboration oxidation of a terminal alkene leads to a primary alcohol. Hydroboration oxidation adds an OH to an alkene in what appears to be an "anti Markovnikov" fashion. You would get 1-butanol with Hydroboration oxidation.
     
  11. Jul 30, 2004 #10
    well i tried some but i am not getting desired roduct.
    well i got by one of the suggestion of hydroboration oxidation alcohol but it give wrong osition of hydroxyl group.
    it should on next carbon but got on first carbon of sidechain.
    problem is age 563 12.20 of organic chemistry by craig fryhle and solomons 7th edition.
     
  12. Jul 30, 2004 #11
    I'm don't understand what you are saying. With hydroboration oxidation you want the primary alcohol CH3CH2CH2CH2OH. Then when you oxidize it you get the aldehyde CH3CH2CH2COOH. Reacting that with the grignard reagent will give you your product.
     
  13. Jul 30, 2004 #12

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    Grave, write it out on paper. That method would give the alcohol at the benzylic position (off of the carbon directly attached to the phenyl ring) but the drawing shows (C6H5)CH2CH(OH)CH2CH3.

    Amb, have you learned about epoxides and Gilman reagents yet, because I am pretty sure that is the way to do it.
     
    Last edited: Jul 30, 2004
  14. Jul 30, 2004 #13
    well i have learned about epoxides
    but gilman i dont know that. it's not in solomons which i am primarily following in undergraduate chemistry text.
     
  15. Jul 30, 2004 #14
    Lithium dialkyl cuprate...thats called Gillman Reagent I think (R2CuLi). A very important reaction indeed. Look it up in Morrison & Boyd and you will find a nice explanation too.

    Cheers
    Vivek
     
  16. Jul 30, 2004 #15

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    Yeah, R2CuLi, they aren't always referred to as Gilman reagents, but that's what I learned them as. They are similar to Grignard reagents, but the copper makes them "softer" anions so they behave a bit differently. They are very good at opening epoxides. They are also useful for adding into alpha-beta unsaturated carbonyl systems, since they add 1,4 (Michael addition) instead of 1,2 like Grignards.
     
  17. Jul 30, 2004 #16
    Yes, ozonolysis cleaves a carbon. Yes, the product has ten carbons. BnBr plus butene makes eleven carbons.

    I'm guessing you're confusing BnBr with PhBr.
     
  18. Jul 30, 2004 #17
    Ah yes thank you movies I see now. I really need to put on my glasses before doing O Chem. Theoretically you could just do all the steps I listed and dehydrate OH of the benzylic position to give the double bond. Then you could just rehydrate it to move the OH over to the right carbon, of course the yield might not be to good, but who cares, its answers the question.
     
  19. Jul 30, 2004 #18

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    CSF, the question says bromobenzene, not benzyl bromide.
     
  20. Jul 30, 2004 #19
    Whoops, you're right. My mistake.
     
  21. Jul 31, 2004 #20

    GCT

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    I apologize, I meant the benzyne mechanism, not elimination addition.



    There are several problems with your proposal, right of the bat I don't believe that a grinard reagent can be formed with bromobenzene.


    Again, not very plausible, similar reasoning as above.

    Which chapter is your problem on ambuj?

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