01-19-03 01:01
No 399625
small scale hydrogenation
swim is interested if anybee has attempted or has any thoughts of an improvised setup to do small scale hydrogenation of a substance say in the order of < 3g. i am considering using an erlenmyer or testtube as reaction vessel.
The molar qty of hydrogen required for the reaction is low. However i am concerned that the reaction will require a much larger quantity of hydrogen since much will be disolved into the solvent (kept at rt) and also to get a sufficient hydrogen loading on the supported palladium or platinum catalyst. Around 30psi would be the target pressure.
since one idea involves using a syringe (microwaved generated H2) to inject the H2 into the testtube or flask does anyone have any estimate of the the physical quantity of hydrogen required given absorbtion by solvent and catalyst and whether this idea may be feasible.
Do any other bees have ideas of another type of arrangement that could work given that the rental on a hydogen tank and regulator is very expensive and could attract unnecessary attention. the main obstacle as swim sees it is that the hydrogen generator will only create a low pressure flow of gas whereas swim needs a high pressure source in order to be able to vent and pressurise the reaction flask.
(Chief Bee)
01-19-03 01:08
No 399629
What kind of reaction are you intending to perform? For such small reaction sizes I would reccommend trying to adapt your reduction to CTH conditions with ammonium formate and Pd/C.
(Hive Addict)
01-19-03 01:42
No 399637
here's a thought this is the way I like to make hydrogen:
Get a bug sprayer, fill it aqueous NaOH and add balled up aluminium foil or aluminum powder to the solution open the valve and purge, then after you purge it connect it to tubing in line to a vacum and suck out the remaining air repeat this step.
It is advantageous to put a pressure gauge in line with the valve, be careful not to excedd pressure limits.
(Chief Bee)
01-19-03 02:28
No 399649
Hydrogen Gas generation with Magnesium (../rhodium /hydrog
(Hive Addict)
01-19-03 06:36
No 399688
At this scale CTH is the way to go. The hydrogen produced with H2SO4 will for sure poison your catalyst, the one made with NaOH will do this probably. (I assume here that you would use non lab-grade chems as if you had those you also had some formiate).
Should you decide to use external hydrogen production anyways for what causes eve, then srubb your hydrogen at least through a saturated KmNO4 solution followed by a drying tube. Hydrogen from the bottle is only sufficient if it is rated for fuel cell use. Welding hydrogen is not recommended. (there are local differences and differences by manufacturer - but thats gambling).
Hydrogen clean enough for use in catalytic hydrogenations can be made by alcohol dehydrogenation (EtOH over copper in gasphase for example) but for nano thats not worth the effort.
ORG
(Hive Addict)
01-19-03 07:16
No 399695
I only use technical grade hydrogen and it works just fine. Iīve never had any problems using it.
Catalytic hydrogenation freak and the sluttiest slut of all sluts
(Hive Addict)
01-19-03 11:25
No 399739
and now mail algebra the name of your supplier please.
I donīt know where algebra lives but I know that standards are different all over the world.
You are playing in your own class Barium with sophisticated materials and techniques. Out of reach for most this makes your writeups practical worthless - for most bees. But highly interesting they are of course! And always excellent!
Hydrogen for fuel cells is btw also industrial hydrogen. I spoke of welding hydrogen.
ORG
(Hive Addict)
01-19-03 15:16
No 399775
How about just plain old H2O + Mg --delta T--> H2 + Mg(OH)2 for H2 generation? I bet the temp of the water would be a great way to control the amount of H2 being produced.
It is seductive, way too seductive. -Eleusis
(Stranger)
01-20-03 19:11
No 400057
Thanks for the good suggestions. Yes, swim has been leaning more toward CTH, but for completeness is interested in the simplest setup that might be put together a for H2 gas hydrogenation. A big advantage of CTH is the ease with which TLC tests can be made to monitor the reduction. The disadvantage is that CTH has less supporting refs for the type of reactions that swim is interested in - mostly ring reduction of hetrocycles and non aromatics and the difficulty of procuring a hydrogen donor. In any case this may all be for nothing since swims catalyst source has fallen through.
Ammonium formate is out of reach (Leuckart) unless preped from materials available otc. hypophosphite is not available although phosphinic acid and salts are.
Regarding ammonium formate, - this is apparantly a better hydrogen donor than either formic acid or NaCOOH. I am aware of Rhodium's synth of formic acid from oxalic acid and glycerol however I am thinking that H202 oxidation of formaldehyde might be a better option. This is supposedly much easier than trying to oxidise methanol all the way to formic acid.
I am wondering if the reaction in italics proposed below might be adapted to go straight to Nh4COOH by substituting NaOH with NH4OH to create the alkaline conditions.
2HCHO + 2 NH4OH + H2O2 ----> 2HCOONH4 + 2 H2O + H2
The formed volatiles would just be evaporated off leaving behind ammonium formate - followed by a recrystalisation?. Remembering that for swim's purposes yield is not important although purity is what byproducts might be formed that could not be just boiled off. The imine base of formaldehye and ammonia? Otherwise using NaOH as the base would require distilling the formic acid out of H2SO4 followed by titration with aqueous ammonia.
Alkaline Reaction
2HCHO + 2 NaOH + H2O2 ----> 2HCOONa + 2 H2O + H2
HCHO will be oxidized to formate / formic acid. The reaction will take 10 - 180 minutes depending on reaction temperature, pH, and H2O2 charge. With moderate temperatures (< 40 deg C) and a pH of 10 - 11, the H2O2 demand should be about 0.8 parts H2O2 per part HCHO, which translates into an H2O2 cost of about $0.75 USD per lb-HCHO. It is possible to reduce the H2O2 demand by increasing the NaOH charge (to 2 - 3 g/L) and elevating the temperature (to 60 - 80 deg C) to affect aldol condensation. In this case, the H2O2 demand should be about 0.3 parts H2O2 per part HCHO, which translates into an H2O2 cost of about $0.30 USD per lb-HCHO. However, these savings are partially offset by the higher NaOH charge (about $0.25 USD per lb - HCHO).
source: http://www.h2o2.com/applications/industr
(Hive Bee)
11-01-03 03:06
No 468101
Can SWIM do a Reductive Amination instead of a Reductive Alkylation with a CTH reaction in good yiels??
For example: P2P with 5% or 10% Pd/C in GAA and Ammonium Formate.
(Chief Bee)
11-01-03 07:19
No 468124
../rhodium/pdf /redamin.cth-p
../rhodium/pdf /redamin.hcook
Post 335851 (Sunlight: "MDA and MDMA from CTH reductive amination", Novel Discourse)
(Hive Bee)
11-02-03 03:36
No 468282
From Post 335851 (Sunlight: "MDA and MDMA from CTH reductive amination", Novel Discourse)
We made recently a homemade catalyst to see if it could work. We thouhgt about an OTC an easy way, first we got activated charcoal from a pet shop, it was powdered with a cofee grinder.........
I've made different homemade catalysts for CTH rdxns and my homemade catalyst always gave poor yields.
I don't know how fine a coffeegrinder grinds but I think Freifelder says that the thinner the catalyst the more active. A 5% Pd/C that is very fine can be more active than a 30% Pd/C catalyst which is not that finely grinded.
Maybe that's the reason why his Pd/C catalysts sucks