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OChem 2 - LiAlH4 vs NaBH4 - Lab Question

  1. Jan 26, 2016 #1

    Ony

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    • Poster has been reminded to use the HH Template in future schoolwork threads
    Hey guys! New to the forum here, I've come here several times before for insight on various topics and you guys have always been so helpful!

    I noticed I couldn't find anything similar to this question while I was doing my lab report and I'm quite lost, to be honest..

    1) Lithium aluminum hydride would also reduce cyclohexanone to cyclohexanol. List three changes that would have to be made to the procedure/conditions to accommodate lithium aluminum hydride, instead of sodium borohydride.

    I know that LiAlH4 is more flammable and pyrophoric, I know it is a much stronger reducing agent, but what would you have to change in the procedure/conditions if we were to use it instead of NaBH4? Safety conditions would have to be slightly amended, but I'm not really sure where else to go.

    The lab in question was reducing a ketone ( cyclohexanone ) to an alcohol ( cyclohexanol ) using NaBH4 as your reducing agent. It was a pretty simple lab.

    Thanks in advance for the help!
     
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  3. Jan 27, 2016 #2

    DrDu

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    So which solvent did you use with NaBH4?
     
  4. Jan 27, 2016 #3

    Ony

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    First step was NaBH4/methanol and quenching step was NaOH/H2O
     
  5. Jan 27, 2016 #4

    DrDu

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    What happens if you try to dissolve LiAlH4 in methanol?
     
  6. Jan 27, 2016 #5

    Ony

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    Will it reduce the methanol?

    edit: it should help to know that we haven't covered this material in class yet, unfortunately I got the bad lab schedule. This is due in 1hour and I still can't find the answer. I've been watching videos and reading but I'm still so lost :(.
     
    Last edited: Jan 27, 2016
  7. Jan 27, 2016 #6

    DrDu

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    Come on, I gave you a hint. I am sure you find out yourself.
     
  8. Jan 27, 2016 #7

    Ony

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    I think I figured it out, I could use LiAlH4 with THF or an ether and then quench with H2O.
     
  9. Jan 27, 2016 #8

    DrDu

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    Sounds good, although my OC is very rusty and I never worked with LiAlH4.
     
  10. Jan 27, 2016 #9

    Ony

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    Thanks for your help! You steered me in the right direction and got me to find the answer.

    The first step you would use LiAlH4 in THF or an ether, and then you would hydrolyze that in a second step using an aq. acid, (H3O+/H2O)
     
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