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Author: Subject: Make Potassium (from versuchschemie.de)
blogfast25
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 Quote: Originally posted by Lambda-Eyde I'm worried about damaging my ground glass erlenmeyers when I decide to have a go at this reaction. At the moment I only have grignard magnesium (but no ether ), but I'm also getting some powder soon. I'll be trying out both, together with paraffin and some really old KOH.

Don't: almost no one has really complained about damage to glass ware (hint: we're not in aqueous media here).

Grignard magnesium should do nicely.

hames
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blogfast is it possible to use methylated spirits when making bromothane its very expensive to get pure ethanol here,only the stuff you drink but it over $60 for probly 700mls would there be other bromides formed when using metho. [Edited on 18-3-2012 by hames] blogfast25 Thought-provoking Teacher Posts: 10314 Registered: 3-2-2008 Location: Old Blighty Member Is Offline  Quote: Originally posted by hames blogfast is it possible to use methylated spirits when making bromothane its very expensive to get pure ethanol here,only the stuff you drink but it over$60 for probly 700mls would there be other bromides formed when using metho. [Edited on 18-3-2012 by hames]

If the denaturing agent used is methanol then that would blow off as bromomethane, I'd imagine. TBH, I'm no expert on synthing bromoethane, my most recent experience being a class room experiment 30 yrs ago! But methylated spirits (the colourless variety) would be my precursor of 'choice' if I had to synth it today. Nothing a little distillation couldn't do for good purity.

Careful with these haloalkanes, few of them are particularly kosher when it comes to health.

nora_summers
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I'm having some trouble making K.

I started with 20mL of baby oil, 2 grams of magnesium and 5 grams of KOH with 0.7mL of 2-methyl-2-propanol. I heated it up to 220 celsius with a condensor and a bubbler.

nothing happened after i left it for 7-8 hours. sometimes it turned yellow but 4 out of 6 times it remained clear. No potassium though.

What am i doing wrong?
blogfast25
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Did you at least get hydrogen generation early on? If not, chances are your magnesium isn't active enough.

nora_summers
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i got bubbling early on, so i think the magnesium is ok.
garage chemist
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I always had the same result with Mg filings, both selfmade and bought: vigorous hydrogen evolution at the beginning, but no potassium later. It's a sure sign that the magnesium is too coarse. Try it with Mg powder.

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nora_summers
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how fine does it have to be? i don't want to order it and find out that is too coarse as well.
Redroy
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I've had the same problems trying this myself. Bubbles away steadily as the temp increases and after 4-5 hours nothing. I've tried several different types of Mg, from granules, to shavings and powder but they've all been very old samples. Getting Mg powder here in NZ seems next to impossible so I've got a hold of a block of 99.9% Mg I'm gonna try make some powder "freshly". Hopefully that's my only problem.

On the note of glassware I've noticed on the bottom of mine (from this experiment) is some sort of clear hard crud, which I can't seem to move. Nothing I try will get rid of it. Anyone else have this issue?
blogfast25
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 Quote: Originally posted by nora_summers how fine does it have to be? i don't want to order it and find out that is too coarse as well.

Hard to say but mine, although unspecified in terms of granulometry, isn't really that fine, with the largest particles probably up to about 0.25 mm. I don't think a super fine grade is needed.

 Quote: Originally posted by Redroy On the note of glassware I've noticed on the bottom of mine (from this experiment) is some sort of clear hard crud, which I can't seem to move. Nothing I try will get rid of it. Anyone else have this issue?

It's probably stating the blindingly obvious but have you tried conc. HCl?

[Edited on 19-3-2012 by blogfast25]

garage chemist
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The Mg powder that worked for me had a particle size of 75 micrometers. I need to try this powder with my tert-heptanol, to see whether the alcohol is actually active and how fast the reaction goes.

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Vinylogous
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That's an interesting and slightly disappointing result with the tert-heptanol.

Is it possible that the magnesium alkoxide formed, (t-HepO)2Mg, is very insoluble, and essentially passivates the magnesium? Which stirring and agitating with a spatula would alleviate. It seems counterintuitive; that long alkane tail should theoretically make it easier to dissolve in paraffin. But it's worth some thought, as solubility is a rather complex matter, and often makes for paradoxical patterns.

I'm not sure how interested anyone is still in the rather-long-chain tert alcohols, but Fractionated Palm Oil is composed of a large percentage (can't find a suitable chart at the moment) of C8, C10, and C12 fatty acid triglycerides. It could be transesterified to fatty acid methyl esters, and possibly fractionally crystallized to obtain what is mostly methyl octanoate.

Reacting MeMgBr with methyl octanoate would afford 2-methylnonan-2-ol. (I know there is the thread specifically on alcohols, but it's buried a few pages back, and didn't want to necro it)

Additionally, butyl cellosolve (2-butoxyethanol) is readily available OTC online and cheap. No idea how the ether functionality would hold up to metallic K at various temperatures, but I know brake fluid was entertained as a coalescing fluid; 2-butoxyethanol by itself, or a derivative thereof, may be useful for this purpose. If one were really crackers, they could possibly even fashion a tert alcohol out of it (conversion to the 1-halo-2-butoxyethane, then Grignard with acetone), but I reckon that's way out of the scope of most of us here. Just jogging the brain juices.

[Edited on 22-3-2012 by Vinylogous]
blogfast25
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 Quote: Originally posted by Vinylogous I'm not sure how interested anyone is still in the rather-long-chain tert alcohols, but Fractionated Palm Oil is composed of a large percentage (can't find a suitable chart at the moment) of C8, C10, and C12 fatty acid triglycerides. It could be transesterified to fatty acid methyl esters, and possibly fractionally crystallized to obtain what is mostly methyl octanoate. Reacting MeMgBr with methyl octanoate would afford 2-methylnonan-2-ol. (I know there is the thread specifically on alcohols, but it's buried a few pages back, and didn't want to necro it) Additionally, butyl cellosolve (2-butoxyethanol) is readily available OTC online and cheap. No idea how the ether functionality would hold up to metallic K at various temperatures, but I know brake fluid was entertained as a coalescing fluid; 2-butoxyethanol by itself, or a derivative thereof, may be useful for this purpose. If one were really crackers, they could possibly even fashion a tert alcohol out of it (conversion to the 1-halo-2-butoxyethane, then Grignard with acetone), but I reckon that's way out of the scope of most of us here. Just jogging the brain juices. [Edited on 22-3-2012 by Vinylogous]

The possibility of using fractionated palm (coconut) oil for the purpose of obtaining C8 and higher 2-methylalkan-2-ol type t-alcohols has been discussed in the thread you mentioned.

As regards solvents with oxygen atoms, I've tried several and they all react with the potassium. I can't see something derived from butoxyethanol being much different.

Regards your point on metal alkoxides and their solubility: it's difficult to find data on that, which means we're driving blind here. The failure of t-heptanol has put a bit of a dampener on things...

[Edited on 24-3-2012 by blogfast25]

[Edited on 24-3-2012 by blogfast25]

hames
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sorry for so much spoonfedding but I am a noob,would 4a molecular sieves be suitable for t-butanol also I have access to surfactants that are 100% c-8 to c-12 ethoxylated alcohols is their any way to extract the alcohol out of it,I get heaps of it and its thrown out as waste its a product called teric made by huntsman there are a few different ones but i have heaps of most types

[Edited on 24-3-2012 by hames]
AndersHoveland
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 Quote: Originally posted by blogfast25 As regards solvents with oxygen atoms, I've tried several and they all react with the potassium. I can't see something derived from butoxyethanol being much different.

Ethers do not react with potassium, at least not at room temperature.

But in this reaction, I thought we wanted the tert-butyl ether to react. At least to form butoxide, which solubilizes the potassium ions.

The main reason tert-butyl alcohol is used seems to be that it is not so easily reduced like other alcohols.
blogfast25
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 Quote: Originally posted by AndersHoveland Ethers do not react with potassium, at least not at room temperature. But in this reaction, I thought we wanted the tert-butyl ether to react. At least to form butoxide, which solubilizes the potassium ions. The main reason tert-butyl alcohol is used seems to be that it is not so easily reduced like other alcohols.

Room temperature is of no use. To obtain coalescence you need to be above the MP of K.

The main reason, at least going by the proposed reaction mechanism, that t-butanol (and 2M2B) work is that they form alkane soluble alkoxides with K and Mg.

nora_summers
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I think my magnesium is pretty fine, so before I buy even finer magnesium, is there anything else I can try instead to make this reaction work? I tried shaking and stirring but that didn't do anything i could see.
CrEaTiVePyroScience
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@UnintentionalChaos I have tried to make sodium with it and my friend also tried it but it didn't worked. Believe me don't try it , it will waste alot of your time. It just doesnt work for sodium =/

[b/]NOTE: But before you even do this experiment let me warn you: This ruins your glass equipment I was surprised after making seven times potassium metal that my glass was extremely thin , unusable. I figured out this is because potassium hydroxide is corrosive to glass. So don't use your new glassware like I did , use old glassware.[b/]

For me secondary alcohols as isproponal so I used tertiary alcohols as tertiary butanol as catalyst.
I haven't readed all 39pages of the forum so I might have mentioned things that other people already did , sorry if so.
But if you have any other questions about the proces I would love to tell you, just ask!
CrEaTiVePyroScience
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@redroy Yes potassium hydroxide is corrosive to your glassware!!Text
White Yeti
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I'm not sure if anyone already asked this, so forgive me if it has already been mentioned.
@blogfast25, you've had success with 2-methyl-2-butanol as catalyst. But this alcohol boils below 200C (which is from what I understand the temperature for this reaction to work).

Is it possible that the catalyst is simply being lost due to heating and that it's not being re-condensed completely? I understand that the condenser is meant to catch all the vapours, but nothing is perfect, and the amount of catalyst used is so small that this might be a legitimate source of error and a reason why many have tried this method, and failed.

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blogfast25
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 Quote: Originally posted by White Yeti Is it possible that the catalyst is simply being lost due to heating and that it's not being re-condensed completely? I understand that the condenser is meant to catch all the vapours, but nothing is perfect, and the amount of catalyst used is so small that this might be a legitimate source of error and a reason why many have tried this method, and failed.

Total reflux is total reflux: decent cooling catches anything that is basically non-gaseous at RT. BTW, so far I've only used a modified graduated pipette (about 300 mm long, ID about 7 mm), wrapped in moist kitchen towel (keeping the kitchen towel moist by drizzling iced water on it from time to time!) as a "refluxer" [cough!]. Worked perfectly...

Woelen used a Liebig condenser with some air (instead of water) as cooling agent blown through it and got good quality metal w/o any surprises.

No, loss of catalyst through the cooler is one of the least likely reasons for failure IMHO.

Anyone with a minimum of determination, decent chemicals and some patience can do this succesfully...

[Edited on 15-4-2012 by blogfast25]

Pok
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 Quote: Originally posted by White Yeti Is it possible that the catalyst is simply being lost due to heating and that it's not being re-condensed completely?

I think that this problem can only occur at the beginning (t-butanol addition). Very soon the reflux becomes weaker and after some time you even don't smell the alcohol anymore. Maybe at this point the alcohol is already bound as a compound (catalyst mechanism) in the liquid mixture - and doesn't exist in a free state. Some time after the t-butanol addition the reflux doesn't seem to be crucial. I always let the toilet paper dry on the outside of my glass pipe after a while....and no t-butanol loss seems to result.
Redroy
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 Quote: @redroy Yes potassium hydroxide is corrosive to your glassware!!

Yes I know it's corrosive, however it looks like a deposit, not corrosion / pitting.
blogfast25
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 Quote: Originally posted by Redroy Yes I know it's corrosive, however it looks like a deposit, not corrosion / pitting.

Post reaction the bottom of your reactor is covered with mainly MgO. It dissolves readily in dilute HCl. I've never experienced damage to the (borosilicate) glass. Remember that we're in strict anhydrous conditions here and well below the MP of pure KOH.

ALWAYS make sure during clean-up that you've reacted away any residual potassium, best by using alcohol or IPA. Then clean your reactor with dilute HCl.

alkalimetals
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If I use as solvent C11-C13 alkanes with 0.001% of aromatics does it work?
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 Sciencemadness Discussion Board » Fundamentals » Chemistry in General » Make Potassium (from versuchschemie.de) Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication   » References Non-chemistry   » Forum Matters   » Legal and Societal Issues   » Whimsy   » Detritus   » The Moderators' Lounge