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Topic: Choosing a Solvent  (Read 3488 times)

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Offline AlphaScent

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Choosing a Solvent
« on: April 15, 2014, 10:31:01 AM »
Hey All,

I did a trial reaction last night using TEMPO to go from (Z)-11-hexadecen-1-ol to the aldehyde.  It is done in air and O2 is the terminal oxidant.  When I tried to dissolve my alcohol in acetonitrile, as the experimental from my paper called for, it was more of a heterogeneous mixture.  What is the next polar aprotic solvent you would try?  I am thinking acetone or THF?  I suggest these two solvents because water is a o solvent. 2:1; acetonitrile:water.

Attached is the paper I am going off of. 

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Offline Adamcp898

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Re: Choosing a Solvent
« Reply #1 on: April 15, 2014, 10:57:01 AM »
Hadn't time to go through the paper but I'd imagine you'll have trouble getting a long chained alcohol like that to dissolve in polar solvents, particularly one miscible with water, and even if you do, adding water could cause it to come back out of solution again.

Offline AlphaScent

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Re: Choosing a Solvent
« Reply #2 on: April 15, 2014, 11:01:40 AM »
My thoughts exactly, the paper says that the aliphatic oxidations dont go to completion after 24 hours.  Mine went to 35% completion.  I am just wondering if the next move is to dial back the water or try a different solvent. 
If you're not part of the solution, then you're part of the precipitate

Offline Adamcp898

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Re: Choosing a Solvent
« Reply #3 on: April 15, 2014, 11:14:27 AM »
My thoughts exactly, the paper says that the aliphatic oxidations dont go to completion after 24 hours.  Mine went to 35% completion.  I am just wondering if the next move is to dial back the water or try a different solvent.

Oh so it did actually work. I thought you were talking about it in terms of it had been a complete failure.

Well like I said I haven't had time to look at the paper (I'm procrastinating enough as it is  ;D) but yes perhaps try doing it in just ACN, they could've been adding the water to try and emphasise the ''greenness'' of their chemistry. Or just wait for a response from someone who has an opportunity to consider it more!

Offline discodermolide

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Re: Choosing a Solvent
« Reply #4 on: April 15, 2014, 11:17:04 AM »
Use bleach and TEMPO in water dichloromethane and stirr well.
O2 is bas under oxidising conditions with acetone or tHF (peroxide formation = explosion danger)
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Offline AlphaScent

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Re: Choosing a Solvent
« Reply #5 on: April 15, 2014, 11:18:27 AM »
Thanks Adam,

I am thinking it helps with the Copper (II) Bromide solvation. 

It is  5 mol % of Cu(II)Br2, TEMPO, KOH, 2,2'-bipyridine

Then the alcohol dissolved in ACN:H2O.  Stir over night.

They oxidize Octan-1-ol to 95% with a bit of heat (40) and 7.5% TEMPO.  I just added more TEMPO and am putting a bit of heat into it.  Ill post again tomorrow about the results.
If you're not part of the solution, then you're part of the precipitate

Offline AlphaScent

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Re: Choosing a Solvent
« Reply #6 on: April 15, 2014, 11:21:01 AM »
Disco,

I must agree with you on the danger.  I will not try it.

What would the ratio of reagents be?  What % TEMPO and bleach?

I will surely try it.
If you're not part of the solution, then you're part of the precipitate

Offline discodermolide

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Re: Choosing a Solvent
« Reply #7 on: April 15, 2014, 11:22:08 AM »
Remember I sent you a copy of my papers, it's in the experimental of part 1
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Offline AlphaScent

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Re: Choosing a Solvent
« Reply #8 on: April 15, 2014, 11:24:15 AM »
I dont have any of the potassium bromide, though.  Can I do without it?  I thought the sodium hypochlorite reacts to for the hypobromite? 
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Offline discodermolide

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Re: Choosing a Solvent
« Reply #9 on: April 15, 2014, 11:31:43 AM »
No you need KBr, as it forms K bromate which is the oxidiser.
Perhaps you can get away with NaBr.
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