Author Topic: Short Questions Thread  (Read 10820 times)

Vesp

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Re: Short Questions Thread
« Reply #860 on: May 04, 2011, 10:31:24 PM »
I would do, or at least look into normal acetamide synthesis, than replace the appropriate things...

Perhaps Ethyl Acetate + Dimethylamine solution => DMA

Or as you suggested - the dehydration of dimethylamonium acetate...
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Sedit

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Re: Short Questions Thread
« Reply #861 on: May 08, 2011, 12:44:08 AM »
I just want to make sure I understand this, if I made the acetate salt of an amino acid and slowly heated it that should form the acetamide of the amino acid correct.
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Vesp

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Re: Short Questions Thread
« Reply #862 on: May 08, 2011, 03:45:15 AM »
Not sure about that... but I do not see why not?
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Re: Short Questions Thread
« Reply #863 on: May 08, 2011, 09:45:16 AM »
Ok, for generating the DMA, I'm thinking of dripping DMF into a hot saturated solution of NaOH. The hot temperature should help speed up the basic hydrolysis and lower the solubility of the dimethylamine. The NaOH should neutralise the formed formic acid and then the dimethylamine is passed through a drying tube if needed and the into GAA. Does anybody know the conditions need to form DMA/DMF from the acid and dimethylamine? Thanks!

Bluebottle

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Re: Short Questions Thread
« Reply #864 on: May 08, 2011, 03:13:09 PM »
Quote
I just want to make sure I understand this, if I made the acetate salt of an amino acid and slowly heated it that should form the acetamide of the amino acid correct.

Microwaves have been known to help too.
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Shake

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Re: Short Questions Thread
« Reply #865 on: May 08, 2011, 03:20:35 PM »
Palladium i see you are running a DMA wacker ayyy hmmm ;)

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Re: Short Questions Thread
« Reply #866 on: May 08, 2011, 04:09:07 PM »
I'm still just researching it, but I hope to give it a go. Do you think that setup will work? Are you buying or producing the DMA? I wonder how the reaction would go with just air pressurised to approx. 5 atm. I suppose experimentation is king!

Balkan Bonehead

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Re: Short Questions Thread
« Reply #867 on: May 08, 2011, 09:09:54 PM »
What is the solubility of phenylacetic acid in saturated brine likely to be? I am guessing it would be very low due to the salting out effect.

akcom

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Re: Short Questions Thread
« Reply #868 on: May 08, 2011, 09:26:29 PM »
the solubility will be almost 0

Shake

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Re: Short Questions Thread
« Reply #869 on: May 08, 2011, 10:11:11 PM »
Quote
I'm still just researching it, but I hope to give it a go. Do you think that setup will work? Are you buying or producing the DMA? I wonder how the reaction would go with just air pressurised to approx. 5 atm. I suppose experimentation is king!

check the ref, palladium catalysed oxidation of naturally occouring allybenzenes you got for me,
interestingly it notes that DMF was used under the same co catalyst free conditions and yeilded 84 yeild of the methyl ketone with high selectivity, as in, only 6% of the aldehyde was generated.
the rxn just ran slower, i believe the conditions were, 10atm pure 02, 60c for 6 hours. 1-2% mol PdCl2 catalyst

this is a contrast to another ref that said DMF yeilded nothing. I am inclided to believe that is a mistake or something as i see no reason why it would be so inneficient

I have seen several refs that describe DMF as also being able to keep PdCl2 catalyst from deactivating, just not as effective as DMA

IMO the most attractive thing about the 02 DMA wacker is the abitlity to extract the ketone from the DMA catalyst solution with heptane,
add more alkene and continue the rxn with almost the same yeilds the second time around. I am not sure why this cannot be done with DMF..

From what i can tell, these oxidations ran  the same from 5atm - 10atm so 5atm will suffice, but pressurised with only air.. I am not sure. Every singe DMA wacker i have seen was super high yeilds,
none of the refs seem to test the boundrys of just how low you can go with pressure and RXN time. some ran for 3 hours at 60C with 90+ conversion.

I think there is a chance air would work, becasue the reaction is so selective in DMA without copper co catalyst, the ketone is virtually the only thing being made.

If you did it with air, i would take it upto 70 - 80 psi, also, an idea i had was to take apart an electric hot blanket, take the wiring out and wrap it around the vessel, then duct tapethe whole thing..
that should keep it close to 50-60C not to mention the heat generated from auto shaking (jigsaw, or reciprocating saw) it actually gets that hot on its own if it shakes hard enough..

DMF and DMA are both pretty toxic, i wouldnt be playing around trying to make it, if i were you id try to buy it.

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Re: Short Questions Thread
« Reply #870 on: May 08, 2011, 11:02:29 PM »
Ok, I just checked the refs again. Here's what it says about DMF in "Palladium-Catalyzed Oxidation of Phenyl-Substituted Alkenes using Molecular Oxygen as the Sole Oxidant"
Quote
The reaction with styrene (and with 2-vinylnaphthalene,
as it will be shown below) also occurs smoothly
in another amidic solvent, DMF, although at a slightly
lower rate
(Table 1, run 3 vs. run 1). This result is remarkable
in light of a previously reported observation
that 1-decene gives only a trace yield of the corresponding
methyl ketone in DMF under similar conditions.[
15] Thus, DMF also acts as an efficient solvent to
promote the regeneration of the palladium species
at
the oxidation of styrene without the need of co-catalysts
or special ligands, making more flexible the
choice of solvent for practical purposes. Selectivity for
acetophenone in DMF is slightly lower then in DMA
(83 vs. 92%), but the reaction variables have not been
optimized yet.

This contrasts with the report of this reaction in the paper "Wacker-Type Oxidation of Internal Olefins Using a PdCl2/N,NDimethylacetamide Catalyst System under Copper-Free Reaction Conditions"
Quote
Initially, trans-4-octene (1) was treated with 5 mol%
PdCl2 in a mixture of an organic solvent and water with 3 atm
of O2 under copper-free reactions conditions. In a DMA
solution, oxidation of 1 proceeded to give 4-octanone (2) as
the sole product in 91% yield without isomerization or
chlorination of 1 (Table 1, entry 1). The use of N-methylpyrrolidone
(NMP) also gave 2 in good yield (Table 1,
entry 4). Other solvents, such as N,N-dimethylformamide
(DMF), dimethyl sulfoxide (DMSO), acetonitrile, and toluene
resulted in low yields of 2, which was accompanied by the
formation of isomers of 1 or 2
(Table 1, entries 5–8).

Personally I would be more inclinded to believe the former paper as it deals specifically with Phenyl-Substituted Alkenes including safrole.
« Last Edit: May 08, 2011, 11:22:33 PM by Palladium »

Shake

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Re: Short Questions Thread
« Reply #871 on: May 08, 2011, 11:11:50 PM »
yeah, thats pretty much what i said ;)

i have more examples though of DMF yeilding nothing without the co catylist than the you posted, if you check the structure of the two they are really similar, difference is a methyl group. I dont see why it wouldnt be just as good as DMA just slower..

as you said experimenting is king!

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Re: Short Questions Thread
« Reply #872 on: May 08, 2011, 11:20:42 PM »


I think I'll just have to splash out and pick myself up a mini oxygen cylinder so! I'll probably give it a small scale try in DMF first. If thats not a winner I'll see if I can make or otherwise procure some DMA. Will you be able to give it a try soon Shake?
Also I have meant to ask you why do you say to use shaking rather than simple magnetic stirring? Is it said in the refs, is it better for gas uptake in reaction involving oxygen like this, or do you just like living up to your name :P

Shake

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Re: Short Questions Thread
« Reply #873 on: May 09, 2011, 06:03:17 AM »
agitation gets gasses into solution a thousand times better.. what will be pressurized that can actually use mag stirring?

the reaction conditions are, on average 50 - 80c ranging upto 40 hours, and upto 10atm pressure which is like 140 psi.. SO if one is to skimp on the psi down to 60 and use say 50C heating then use a jigsaw shaker as agitation i believe that just might compensate for any other vairiables, ie catalyst deactivation, slower reaction rate due to DMF ect ect..

agitation mixes this thing so hard it is completely foam inside the vessel, also, the agitation a jigsaw provides at full speed caused the reaction to heat up from room tempreture to a point where it was almost too hot to touch which may even do away with the need to apply external heating on say a 4 hour run in DMA

there are alot of variables here, and the DMA has all round good results with stirring, well, i think if it is on the mechanical shaker maybe just air would do the trick?

maybe we should make a new thread for this soon.

First a run in DMF, a plan will have to be made based on the ref. all previous DMF 02 wacks have used cucl2 and i believe that has been a reason for low yeilds, long rxn times, and aldehyde.

big tell tale that your rxn in happening is the smell, you just know when it is working..

EDIT, again, DMA boasts the abitilty to extract with n-heptane, recharge vessel and run again. this is even stated in the ref using eugenol. so this might a reason to wait to get DMA
« Last Edit: May 09, 2011, 06:15:54 AM by Shake »

psychexplorer

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Re: Short Questions Thread
« Reply #874 on: May 09, 2011, 01:36:47 PM »
Glass carboys and champagne bottles seem to be popular pressure vessels, but not at 10atm.

Rather moot, though, because agitation is the best method for mixing a gaseous reactant into solution.

I do wonder how well aquarium airstones would work at atmospheric pressure, both at 21% O2 and 100% O2.

Being able to eliminate pressure, repetitive motion mechanical concerns, and nonatmospheric oxygen sources, all at once, would represent a major advance in ketone production.

Shake

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Re: Short Questions Thread
« Reply #875 on: May 09, 2011, 08:40:03 PM »
fitting a tyre valve in a thermous lid, and simply put it on a mag stirrer in a pot of warm water that is 1 way of doing it like the ref

thermous should be able to take alot of pressure i would imagine.. although SRV is light weight there is better options for mechenical shaking.

even a bit PVC tube about a foot long with lid on either end, with rubber seals, and a tyre valve in that. that would take the pressure too, not sure about the chemicals though


Shake

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Re: Short Questions Thread
« Reply #876 on: May 13, 2011, 10:42:39 PM »
Would it be safe to fill an old empty propane tank with oxygen??


Evilblaze

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Re: Short Questions Thread
« Reply #877 on: May 14, 2011, 11:13:51 AM »
Would it be safe to fill an old empty propane tank with oxygen??

No!

This would be a really bad idea. This is why they don't fill any esle gas in a cylinder used for a specific gas.
E.g.: If you want to fill an argon or nitrogen tank with hydrogen then at the Messer/Linde or any else gas company they will probably laugh you out, because it is not safe.

And propane tanks are usually made from aluminum alloys, or if You are lucky, then steel, but non of these are suitable for high pressure (150-200bar) oxygen.

Shake

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Re: Short Questions Thread
« Reply #878 on: May 14, 2011, 11:53:49 AM »
ill take that as a yes

Quote
Mix A chemical with B chemical, add 10% from a C chemical and hope the best.

haha evilblaze that cracked me up

 

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Re: Short Questions Thread - Aluminium ethoxide + sodium hydroxide =?
« Reply #879 on: May 15, 2011, 05:39:32 AM »
I'm working on an equation for a process - if the by-product of a reaction is Aluminium triethoxide in ethanol, then the addition of dry sodium carbonate should give sodium ethoxide and insoluble aluminium carbonate, shouldn't it?
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