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Topic: Crystallization  (Read 2769 times)

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Offline Mr.Gold

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Crystallization
« on: May 19, 2016, 07:11:01 PM »
I'm trying to essentially precipitate  a carboxylic acid salt out of the solvent....the acid is fairly non polar.

If I dissolve the carboxylic acid in isopropanol and then react it with aq naoh to produce the salt....will it precipitate out of solution?
The formula is C22H304....multiple benzene rings carboxyl group ...pretty nonpolar

Or would the sodium cation association interfere with precipitation and cause it to be polar enough to stay dissolved in isopropyl?

Offline discodermolide

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Re: Crystallization
« Reply #1 on: May 20, 2016, 12:51:24 AM »
Well chemistry is an experimental science, try it and see what happens. You can't loose any material.
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Offline Mr.Gold

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Re: Crystallization
« Reply #2 on: May 20, 2016, 10:49:53 AM »
I wish I had the luxury of time for that lol

Online Babcock_Hall

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Re: Crystallization
« Reply #3 on: May 20, 2016, 03:51:30 PM »
If you add aqueous base, there will be some water around, and I would wonder whether the sodium carboxylate salt is soluble in water.  For a non polar carboxylic acid, you could try dissolving in hot organic solvent, then adding water dropwise.  In other words, you could use a mixed solvent to recrystallize.
« Last Edit: May 20, 2016, 05:51:59 PM by Babcock_Hall »

Offline discodermolide

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Re: Crystallization
« Reply #4 on: May 21, 2016, 03:03:20 AM »
I wish I had the luxury of time for that lol


Well instead of dicking around in the forums hoping for some answer that may not work, you could have done the experiments and found an answer.
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Offline orthoformate

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Re: Crystallization
« Reply #5 on: May 22, 2016, 06:16:31 PM »
I wish I had the luxury of time for that lol

If there are no literature procedures for this crystallization, you are going to have to spend some time doing experiments. That's just the nature of the beast. :)

Offline Mr.Gold

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Re: Crystallization
« Reply #6 on: May 27, 2016, 12:03:51 PM »
Thx for all the input everyone!  Just needed to get an idea of what kinds of solvents might work...literature is really limited and so is money...I didn't want to order a bunch of solvents to experiment with and waste my bosses money....I ended up ordering ethyl acetate...but it's on back order lol....but once again  thx for all the input regardless

Online Babcock_Hall

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Re: Crystallization
« Reply #7 on: May 27, 2016, 12:29:21 PM »
One nice thing about a mixed solvent is that the overall polarity is continuously variable.

Offline critzz

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Re: Crystallization
« Reply #8 on: May 27, 2016, 02:51:32 PM »
I've had success recrystallizing a lactam by dissolving it in as little as possible in (9/1 pentane/EtOAc) while refluxing and cooling it down slowly in an oil bath (10 °C/h).

Another compound I dissolved into a small volume of EtOAc; added gradually cyclohexane until the solution became cloudy; added just enough EtOAc so the solution was transparent again; and then put it in the fridge, yielding nice crystals.
Although, in most cases when the solution cools down it turns into a cloudy solution (milk). Hate it when that happens. :(

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