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Author Topic: Transesterification  (Read 824 times)

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AlphaScent

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Transesterification
« on: September 12, 2018, 09:31:11 AM »

I have a silly question.

Is there a simple way to transesterify a methyl ester to the isopropyl or t-butyl ester?

Is Le Chatlier all we really need to consider?  Large excess IPA and a drop of acid? 
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wildfyr

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Re: Transesterification
« Reply #1 on: September 12, 2018, 11:39:34 AM »

I would probably heat it, but yep, that should do the trick. Use sulfuric acid, it is by far the best for that reaction.
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AlphaScent

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Re: Transesterification
« Reply #2 on: September 13, 2018, 04:33:18 AM »

Thats what I thought but my PI said I should look into it.  It may not be that simple.  I am going to try it and see.  I figured reflux as well would be needed.

Cheers!
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rolnor

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Re: Transesterification
« Reply #3 on: September 13, 2018, 08:47:58 AM »

You can use base-catalyst also, NaH in excess IPA.
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wildfyr

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Re: Transesterification
« Reply #4 on: September 13, 2018, 11:29:00 AM »

That sodium hydride approach is more sensitive to water. Your alcohol better be bone dry. I've done the esterification of a carboxylic acid with squeeze bottle methanol with a drop of sulfuric acid in a scint vial.

Granted I don't know if isopropanol will be that easy. Drying to over sieves is probably a good idea.

If you want to do the base route I'd would say buy anhydrous sodium isopropoxide instead of screwing around with sodium hydride and that oil that comes on it.
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rolnor

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Re: Transesterification
« Reply #5 on: September 14, 2018, 07:01:55 AM »

If you use sodium isopropoxide it must be fresch, old bottles will containe manly carbonate and/or hydroxide. You can make it from sodium metal also with IPA.
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wildfyr

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Re: Transesterification
« Reply #6 on: September 15, 2018, 03:28:28 AM »

I hope the acid one works, all these others require actual effort.
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AlphaScent

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Re: Transesterification
« Reply #7 on: September 17, 2018, 02:57:20 AM »

3.2 mmol carboxylic acid (instead of methyl ester); I had some from the previous Krapcho decarboxylation
7 mL IPA
4 drops sulfuric

Gave beautiful isopropyl ester....Thanks Fischer!!
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AlphaScent

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Re: Transesterification
« Reply #8 on: September 17, 2018, 02:57:45 AM »

oh...and reflux overnight
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wildfyr

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Re: Transesterification
« Reply #9 on: September 17, 2018, 05:51:23 AM »

It's nice to hear someone come back and report a successful reaction. Too often we give advice and "poof" they are gone.

Although you are a bit more of a regular alpha :)
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AlphaScent

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Re: Transesterification
« Reply #10 on: September 17, 2018, 07:30:06 AM »

I used to be on way more ofter but I have been in grad school.  Just started 4th year.  Need to make my way back.

This way of making the isopropyl ester is hopefully going to help me.  I am doing ozonolysis right now trying to make the ester/aldehyde.  The methyl ester was too reactive to the Grignard reaction that followed.  Even at reduced temp.

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