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Author: Subject: The short questions thread (2)
Formula409
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[*] posted on 31-7-2009 at 05:33


Does anybody know a synthesis for 3-methoxy-4-halobenzaldehyde from reasonably common materials? I thought it would be a simple case of bromination of Vanillin. I was mistaken.

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sonogashira
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[*] posted on 2-8-2009 at 10:28


Hi, I have a possibly very silly question but i will ask anyway - with slight shame: :)

Is it possible to convert a primary amine hydrochloride to an amine acetate by adding glacial acetic acid and distilling?

I hope that the HCl will fly away and be left with the acetate salt:). Has anyone done this?

The problem with the compound is that is very unstable in base. The acetate salt can be recrystallized and therefore purified; but this is not possible with the HCl which is the product of the last step- hence the need to convert in acidic conditions.

Thanks for any wisdom!!


[Edited on 2-8-2009 by sonogashira]
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12AX7
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[*] posted on 2-8-2009 at 10:54


The pH is never even low enough to form HCl, let alone enough to evaporate.

Ion exchange sounds like a better idea. Load resin with acetate, flush, voila, no more chloride.

Tim




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sonogashira
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[*] posted on 2-8-2009 at 11:47


But maybe with a large excess it will push the equilibrium in the correct direction- do you think?

I know pH is against me but I wonder if the large excess could save the day :D
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Nicodem
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[*] posted on 2-8-2009 at 11:58


Just do a salt metathesis with a few % excess of anhydrous sodium or potassium acetate in ethanol. Stir and slightly heat for some time, cool, filter of the NaCl/KCl precipitate and concentrate. The product might not be cleanly acetate and there will be some Na/K chlorides left (their solubility in ethanol is not negligible!), but at least it is simple enough (provided the acetate is soluble in ethanol like it is usually the case with most amine acetates that are large enough).
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sonogashira
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[*] posted on 2-8-2009 at 12:17


Thanks, i'll try that. I just thought that perhaps silver acetate in dilute acetic acid could be used also - but i'll have look into that. Thanks for the guidance!:)

[Edited on 2-8-2009 by sonogashira]
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Klute
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[*] posted on 2-8-2009 at 12:25


Why not just freebase the hydrochloride and titrate with GAA?



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12AX7
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[*] posted on 2-8-2009 at 18:08


Oh, as precipitation goes, lead acetate would be nearly as complete as silver acetate, and quite a bit cheaper (and photostable!).

Klute:
Quote:
The problem with the compound is that is very unstable in base.


Tim




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Picric-A
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[*] posted on 3-8-2009 at 07:55


As i dont have access to references anymore i will post this here.
Does anybody have access to this article?;
http://pubs.acs.org/doi/abs/10.1021/ie50532a036
thanks
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sonogashira
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[*] posted on 3-8-2009 at 08:22


Thank you for that information also Tim, i did not know that lead salts could be used too.

I have tried several small tests from the procedures recommended, and the products are now crystallizing overnightI think all will go well and i will chose the one which gives best yield for the bulk of the product.

Thank you for all the help- and best wishes;)

Here you go Mr Picric Acid:

Attachment: picric.pdf (574kB)
This file has been downloaded 2934 times

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Picric-A
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[*] posted on 3-8-2009 at 14:22


@sonogashira - Sweet! thanks for your help m8!
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itchyfruit
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[*] posted on 5-8-2009 at 06:32
Frozen Acetic acid


I've just realised that putting my acetic acid in the fridge was not a good idea, it's frozen solid, will it be ok if i just defrost it or have i ruined it?
I know i'm stupid, but i now know that acetic acid freezes at 16oc so i have learnt something!!!
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DJF90
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[*] posted on 5-8-2009 at 07:12


just leave it to defrost and it'll be back to normal.
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[*] posted on 5-8-2009 at 07:14


Cool, Thanks
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Jor
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[*] posted on 5-8-2009 at 07:40


My acetic acid is always frozen during the entire winter! ;)
It's really beautiful to see the huge mass of crystals.

Once, it was far below 16C and the acetic ascid was still not frozen. This was because for something to crystallise, you need a nucleation point (thats what its called right?), and when the bottle is standing completely still that is not present. But then I picked up the bottle and shook it. The effect was beautiful, a liter of acetic acid crystallising in a few seconds.

If you want to store your acetic, even in the cold, add a little water. 100% AcOH freezes at 16C, 96% at 10C, etc. I store a small bottle of 80% AcOh during winter, and that doesn't freeze.
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itchyfruit
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[*] posted on 5-8-2009 at 08:58


Weirdly, i just assumed that it wouldn't freeze until below 0oc but then what do i know,and we all know what they say about assumption :D
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[*] posted on 6-8-2009 at 07:43


Does anyone know what, besides fuel, you could use powdered hexamine for on a camping trip?
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[*] posted on 6-8-2009 at 07:50


Quote: Originally posted by gnitseretni  
Does anyone know what, besides fuel, you could use powdered hexamine for on a camping trip?

Well, if you bruise yourself while setting the tend, you can always use its aqueous solution as antiseptic.
You can also use it as repellent for bears if you thermolyse it on a hot pan. I doubt it would be very effective though.
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[*] posted on 6-8-2009 at 09:37


antiseptic huh. What if, while performing hydrolysis, i held a wet cloth above it to absorb the formaldehyde vapor.. would that make for an even better antiseptic?
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[*] posted on 6-8-2009 at 10:45


Isn't formaldehyde carcinogenic?


I think that would work, as I believe it is used as a source of formaldehyde.
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[*] posted on 8-8-2009 at 18:30


Can Benzyl Iodide be made by iodinating toluene with molecular iodine under UV like how benzyl chloride and bromide can be made?

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[*] posted on 8-8-2009 at 19:07


I can't find what this compound is it called ......is it 2 chloro- benzyl propane.....?

C6H5CH2CH(Cl)CH3....as i'm interested in doing a Finklestein swap with bromine

..................solo

[Edited on 9-8-2009 by solo]




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[*] posted on 8-8-2009 at 19:20


I'd call that 2-chloro-1-phenylpropane, solo. :)

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[*] posted on 8-8-2009 at 19:51


You can also name it 2-chloropropyl benzene if you like. The Finklestein should proceed smoothly with this compound.




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[*] posted on 9-8-2009 at 00:36


Quote: Originally posted by Formula409  
Can Benzyl Iodide be made by iodinating toluene with molecular iodine under UV like how benzyl chloride and bromide can be made?

Most probably no and almost certainly not with I2 for what I know, but I have not checked the literature so don't take my word for granted. Benzyl iodide is a photolabile compound anyway.
Besides in the radical halogenation of toluene with either chlorine or bromine you do not use UV light as this is too inefficient, visible light is used - direct sunlight for example, or a strong halogen or mercury lamp, even a normal incandescent lamp works to some degree. Blue light (energy maximum at about 425 nm) gives a higher rate of chlorination than ultraviolet (about 370 nm) because it more effectively penetrates a solution containing free chlorine. (cited from Kirk-Othmer's chapter on benzyl chloride production) See Len's prepublication on the topic.
Quote:
I can't find what this compound is it called ......is it 2 chloro- benzyl propane.....?

C6H5CH2CH(Cl)CH3....as i'm interested in doing a Finklestein swap with bromine

The Finklestein reaction using the normal protocol (NaI in refluxing acetone) is terribly slow on secondary alkyl chlorides like this one. It would probably work, but it might take a couple of days reflux. In any case you would need to monitor the reaction progress anyway.




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