Author Topic: Short Questions Thread  (Read 10820 times)

akcom

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Re: Short Questions Thread
« Reply #1080 on: October 26, 2011, 02:00:00 PM »
It's certainly possible.  Only way to find out is run the reaction.  N2 is definitely preferable.

Tungsten.

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Re: Short Questions Thread
« Reply #1081 on: October 26, 2011, 02:47:14 PM »
It's certainly possible.  Only way to find out is run the reaction.  N2 is definitely preferable.
Yeah. I just don't really have access to N2.

Since the reagents in the reaction are quite inexpensive I will give the propane atmosphere a try asap. Most likely that will be sometime in April though... Ugh. I will definitely report my findings though.
-W

akcom

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Re: Short Questions Thread
« Reply #1082 on: October 26, 2011, 03:17:20 PM »
Obviously the situation could be different in your neck of the woods, but a FOAF was able to get a small aluminum 10lb gas tank (used for beer or something) off the web for under 100 USD.  Local welding shops fill it up for under 20 bucks.  I don't have an exact count, but I'm told it it'll last for quite a few reactions assuming you're not using 100L flasks lol

Tungsten.

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Re: Short Questions Thread
« Reply #1083 on: October 26, 2011, 05:01:45 PM »
That makes sense. I could probably just buy one of those small propane tanks and get it refilled. I guess I could always just tell the guy who works at the welding shop it's for paintball...

Just out of curiosity, why do welding shops carry N2? It doesn't seem useful for welding.
« Last Edit: October 26, 2011, 05:04:56 PM by Tungsten. »
-W

akcom

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Re: Short Questions Thread
« Reply #1084 on: October 26, 2011, 07:16:58 PM »
Hell if I know :)  I see AirGas trucks there all the time.  Maybe its just profitable for them to sell it since its they already get other gases and the tanks don't cost much?

lugh

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Re: Short Questions Thread
« Reply #1085 on: October 26, 2011, 07:24:57 PM »
Quote
Just out of curiosity, why do welding shops carry N2? It doesn't seem useful for welding

Listed uses found from online data resources include metallurgy, fire fighting, gas shielding, food processing, food storage, plastics processing, brewing and soft drink industries, tire and shock absorber inflation, semiconductor manufacturing, oil and gas recovery, deep freezing medical supplies, cryogenic surgery, concrete hardening and cryocondensation  8)
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Vesp

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Re: Short Questions Thread
« Reply #1086 on: October 26, 2011, 07:37:19 PM »
It is to provide a protective atmosphere, same reason they sell Argon.
If the pKa value of propane is an issue, would butane or methane be better? Not sure if you would be able to use methane but it is pretty common as natural gas.. Again, tainted with sulfides for detection.

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RoidRage

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Re: Short Questions Thread
« Reply #1087 on: October 26, 2011, 09:09:09 PM »
Has anyone completed the wacker in less than 8 hrs? I read a paper on a 3 hour reaction (small scale) gave it a go but i think my safrole is freezing out of the dcm... the paper confirmed safrole was non existant via gc....

Yes I normally let it runs for 6 hours and that's it. I've read that paper about the reaction being run to completion in 3 hours too at 1/10 MM scale. I'd like to confirm this at bigger scales, but I unfortunably do not have TLC plates around to follow the reaction.

akcom

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Re: Short Questions Thread
« Reply #1088 on: October 26, 2011, 11:37:03 PM »
The time the reaction takes to complete is not so much a function of scale as it is of catalyst loading and reagent concentration

RoidRage

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Re: Short Questions Thread
« Reply #1089 on: October 26, 2011, 11:46:12 PM »
The time the reaction takes to complete is not so much a function of scale as it is of catalyst loading and reagent concentration

Make sense, thanks

JustDreaming

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Re: Short Questions Thread
« Reply #1090 on: November 13, 2011, 04:26:12 PM »
Regrettably I am struggling with gassing anhydrous ammonia into a solution.

Essentially I am generating the gas in a filtration flask, passing it through a gas-drying bottle over NaOH where it dries, and then up and through a pipet submerged in an ice-bath cooled ethanol solution in a round bottom flask.

So far I have gassed 3 moles of ammonia, and captured ~1/4 of a mole in the (95%)ethanol solution, this can NOT be as a good as it gets :P. I was considering maybe stuffing some cleaned/degreased steel wool into the flask to sort of create some back pressure as well as aid in dispersing it through out the solution? Does anyone have any tips or hints?

This is for the preparation of alkylamines, not sketchy reduction procedures.
« Last Edit: November 13, 2011, 04:27:49 PM by JustDreaming »
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Tungsten.

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Re: Short Questions Thread
« Reply #1091 on: November 13, 2011, 06:38:09 PM »
Gasses are more soluble in cold liquids? :-\

A fritted filter or gas washing bottle would probably help a lot if you had them...
-W

lugh

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Re: Short Questions Thread
« Reply #1092 on: November 13, 2011, 07:10:24 PM »
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JustDreaming

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Re: Short Questions Thread
« Reply #1093 on: November 13, 2011, 11:14:11 PM »
Gasses are more soluble in cold liquids? :-\

A fritted filter or gas washing bottle would probably help a lot if you had them...

Yes in general gasses are more soluble in cold liquids. In this case this applies.

@Lugh, thanks for the link :). I'll have to set something up like that when I can get more glass-ware. I'd imagine there's a relatively easy way to increase the yield here without such a set-up. Someone on SM used a similar set up(to the one I describe) and got some outstanding results, I'm just not sure what the difference is that made there's so much better? hmm... pressure maybe?
« Last Edit: November 14, 2011, 12:19:10 AM by JustDreaming »
This never really happens, but an eye still see's these things. It keeps happening. You just don't see it.

lugh

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Re: Short Questions Thread
« Reply #1094 on: November 14, 2011, 12:53:51 AM »
Quote
I'll have to set something up like that when I can get more glass-ware.

It would be far cheaper to use suitably chemically resistant polymer ware as opposed to glass ware  8)

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Goldmember

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Re: Short Questions Thread
« Reply #1095 on: November 17, 2011, 06:14:38 AM »
Any suggestion on what one could do with a shitload of 5,5-dimethylhydantoin?
 I had an idea for a use for it ages ago but that brainwave escapes me(coke analogue synth` perhaps?). :-\
Im thinking n condensation ,along the lines  of Benzylhydantoin / Phe-hydantoin etc, but unless I can come up with some wizz-bang ring opening ,"hey presto and now its drugs", this wasnt my original thought and is quite boring really.

This shit is building up and she would really like to put it to good use.


Please all and any suggestions welcome. No spoon feeding required just a hint will do.

fresh1

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Re: Short Questions Thread
« Reply #1096 on: November 18, 2011, 12:27:29 AM »
Quote
but unless I can come up with some wizz-bang ring opening ,"hey presto and now its drugs", this wasnt my original thought and is quite boring really.

lol yeah I know the feeling :P sorry no good ideas here at the moment ::)

 I wish!

 f1's no help here :o
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jkl

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Re: Short Questions Thread
« Reply #1097 on: November 30, 2011, 02:13:21 AM »
CAn someone help me with mandelic acid....

one had D-(-)-mandelic acid, and want more

but there are so many kinds is there one better then the other?

oldguy

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Re: Short Questions Thread
« Reply #1098 on: December 03, 2011, 11:47:57 PM »
I was looking at some aluminum weigh boats, seems like they might be a good compromise between heavy duty foil and flashing or pie pans.  Haven't had a chance to digest one in alkali to see what remains.  Anyone have any experience with weigh boats as a relatively pure aluminum source?  Any thoughts?

oldguy

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Re: Short Questions Thread
« Reply #1099 on: December 06, 2011, 12:42:08 AM »
Would any problems be expected if using several stacked vacuum-jacketed Vigreux columns for distillation of ketones or amines?  Seems to me there might be less problems with pressure drop and flooding than if using a jacketed Hempel column packed with Rashig rings or saddles to give an approximately equal number of theoretical plates, but it's quite possible (likely?) I'm missing something.