OChem 2 - LiAlH4 vs NaBH4 - Lab Question

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In summary, the conversation discusses the use of lithium aluminum hydride (LiAlH4) as a reducing agent in place of sodium borohydride (NaBH4) in a lab experiment. The speaker asks for advice on how the procedure and conditions would need to be altered to accommodate LiAlH4, which is a stronger and more flammable reducing agent. They also mention that they have not covered this material in class yet and are struggling to find the answer. Ultimately, they come to the conclusion that LiAlH4 could be used with THF or an ether in the first step, followed by hydrolyzing with an aqueous acid in the second step.
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Ony
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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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  • #2
So which solvent did you use with NaBH4?
 
  • #3
DrDu said:
So which solvent did you use with NaBH4?
First step was NaBH4/methanol and quenching step was NaOH/H2O
 
  • #4
What happens if you try to dissolve LiAlH4 in methanol?
 
  • #5
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 :(.
 
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  • #6
Come on, I gave you a hint. I am sure you find out yourself.
 
  • #7
I think I figured it out, I could use LiAlH4 with THF or an ether and then quench with H2O.
 
  • #8
Sounds good, although my OC is very rusty and I never worked with LiAlH4.
 
  • #9
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)
 

FAQ: OChem 2 - LiAlH4 vs NaBH4 - Lab Question

1. What is the difference between LiAlH4 and NaBH4 in OChem 2 lab?

LiAlH4 and NaBH4 are both reducing agents commonly used in organic chemistry labs. The main difference between them is their strength, with LiAlH4 being a stronger reducing agent than NaBH4. This means that LiAlH4 is more reactive and can reduce a wider range of functional groups compared to NaBH4.

2. Which reducing agent should I use in my OChem 2 lab experiment?

The choice of reducing agent depends on the specific functional group you are trying to reduce. If the functional group is more difficult to reduce, such as a carboxylic acid or ester, then LiAlH4 would be a more suitable choice. However, if the functional group is less reactive, such as a ketone or aldehyde, then NaBH4 may be sufficient.

3. Can I substitute LiAlH4 with NaBH4 in my OChem 2 lab experiment?

In most cases, LiAlH4 and NaBH4 are not interchangeable. As mentioned earlier, LiAlH4 is a stronger reducing agent and can reduce a wider range of functional groups. Substituting one for the other may result in a different product or no reaction at all.

4. What safety precautions should I take when handling LiAlH4 or NaBH4 in the OChem 2 lab?

Both LiAlH4 and NaBH4 are highly reactive and should be handled with caution. It is important to wear appropriate personal protective equipment, such as gloves and goggles, and work in a well-ventilated area. These reducing agents should also be stored in a dry and air-tight container to prevent any reactions with moisture.

5. Are there any alternative reducing agents to LiAlH4 and NaBH4 in OChem 2 lab?

Yes, there are other reducing agents that can be used in OChem 2 lab experiments, such as DIBAL-H and LAH-THF. However, these may also have specific limitations and should be used according to the requirements of the experiment. It is always important to consult with your lab instructor before using any alternative reducing agents.

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