symboom
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Lithium Hydride synthesis
Hydride reducing agents are on of the most useful reducing agents able to turn acetic acid to ethanol and many other reactions
Make lithium
https://m.youtube.com/watch?v=eytU_eY-dfk
Extract lithium
https://m.youtube.com/watch?v=IPo57gpi870
know this can be pyrophoric is the main problem and storage under ether or THF which is used in the synthesis of sodium borohydride
According to prep chem
Knife cleaned lithium is washed with dried ether and then is transported into a steel tray. The metal tray is usually made of stainless steel. In
order to remove impurities, which could contaminate lithium, stainless steel tray is heated for 6-8 hours at 900-1000° C by passing hydrogen during
that process. The stainless steel tray with lithium is covered with ether and placed in a steel tube, and this – in a porcelain or quartz tube
(reactor).
Preparation of lithium hydride
The ether and are are removed by passing dry hydrogen stream through the steel tray and the reactor tube. The tube is slowly heated to 100° C, and
then, without interrupting the flow of hydrogen, the temperature of the furnace is gradually increased to 600-630° C. At the end of the process still
allowing hydrogen to flow, the temperature of furnace is increased to 700 to 720° C. Under these conditions, fusion of lithium hydride occurs. For
the preparation of lithium hydride hydrogen must be well purified. By reacting lithium with not quite pure hydrogen often ignition if the metal itself
occurs. The hydrogen gas could be dried over phosphorus pentoxide and finally purified by passing through melted sodium or potassium. Lithium hydride
is colorless solid exposed to moisture breaks down, however it reacts with oxygen only in high temperature.
More info
At 500° C. lithium combines with hydrogen, becoming coated with a superficial layer of the hydride. At bright redness the combination is complete,
and is attended by incandescence. The preparation of the hydride is effected by passing a current of dry hydrogen over the heated metal below 710°
C., the product being a transparent, vitreous, opalescent mass, with the formula LiH. On exposure to light it acquires a blue colour, without change
in composition. Its melting-point is 680° C., its dissociation-pressure at this temperature being about 27 mm. The density of the hydride is 0.816,
and its molecular volume 9.77.
The alkali-metal and alkaline-earth-metal hydrides exhibit a slight decrease of stability with increase in the atomic weight of the metal, lithium
hydride being the most stable member of the series. At the ordinary temperature, in absence of moisture, atmospheric oxygen, chlorine, and
hydrochloric acid have no action upon it. Both types of hydride absorb hydrogen, those of the alkaline-earth-metals to a greater extent than those of
the alkali-metals. All these metals combine vigorously with hydrogen, those of the alkaline earths becoming heated to incandescence, a phenomenon
probably due to the greater solubility of their hydrides in the metals.
This reaction is especially rapid at temperatures above 600 °C. Addition of 0.001–0.003% carbon, or/and increasing temperature or/and pressure,
increases the yield up to 98% at 2-hour residence time.[3]:147 However, the reaction proceeds at temperatures as low as 29 °C. The yield is 60% at 99
°C and 85% at 125 °C, and the rate depends significantly on the surface condition of LiH.[3]:5
Less common ways of LiH synthesis include thermal breakdown of n-butyllithium (150 °C), or ethyllithium (120 °C), as well as several reactions
involving lithium compounds of low stability and available hydrogen content
n-butyllithium
pyrophoric (inflames in air),
decomposes to corrosive LiOH
The standard preparation for n-BuLi is reaction of 1-bromobutane or 1-chlorobutane with Li metal
If the lithium used for this reaction contains 1–3% sodium, the reaction proceeds more quickly than if pure lithium is used
Problems that can occur
Lithium reacts with glass so it must be melted on a steel tray
My modification in which hydrogen is supplied by a ballon not sure if ether vapors or THF is used will it dissolve the ballon
The reaction vessel must be full of hydrogen no oxygen
Another issue is adding ether back to the reaction vessel once it has cooled down and lithium hydride has formed is pyrophoric this might be achived
wiith the ether container be attached to the reaction vessel next to the ballon with a three way valve
Explosive limits
Hydrogen
Hydrogen gas forms explosive mixtures with air in concentrations from 4–74% and with chlorine at 5–95%. The explosive reactions may be triggered
by spark, heat, or sunlight. The hydrogen autoignition temperature, the temperature of spontaneous ignition in air, is 500 °C (932 °F).
Diethyl ether
autoignition temperature of diethyl ether is 160 °C (320 °F)
Lithium melting point
180.50 °C
[Edited on 13-7-2017 by symboom]
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JJay
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I have been planning on trying this at some point. Small Scale Synthesis of Laboratory Chemicals suggests using a steel test tube containing lithium
in a quartz tube with a hydrogen atmosphere at 700 degrees. Lithium hydride forms on the surface of the molten lithium, and being denser than lithium,
it sinks to the bottom, allowing the molten lithium to further react with hydrogen.
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tsathoggua1
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That is an attractively simple synthesis of lithium hydride. You mention the hydride itself absorbs hydrogen. Is this hydrogen absorption one
resulting in a higher-order hydride of lithium, or is it rather a solution of H2 in LiH, akin to how sodium when molten above a narrow temperature
range dissolves in fused NaOH? or some sort of interstitial compound (like for example potassium graphite) ? and to what extent does the hydride take
up additional H2?
And with regards to it being used as a reagent, if it is a solid solution is it ideal to leave it in there for reductions, or melt it and degas it in
a vacuum chamber previously purged with hydrogen or an inert like argon or helium (nitrogen being reactive with lithium, unlike the other alkali
metals)
The dramatic effect of traces of carbon are interesting. What is the mechanism for this? And does it mean that such entities as potassium graphite
could be made to take up hydrogen to form an intercalated potassium hydride in graphite, with a view to using the product as a reducing agent for
reactions potassium itself is not capable of on its own?
Not sure if Li intercalates well with graphite, whilst I have never attempted it, I definitely recall reading that sodium does not, unlike potassium
and the other, higher group I metals, intercalate very well with graphite, due to the decreased size of the sodium atom, although whether this is is
specific to sodium, with its just so happening to have the wrong steric properties to do so, or whether it is simply too small and accordingly one
could therefore expect Li to do so even less well, or not at all, I can recall reading no mention ever.
This sounds like just the sort of thing that would make for the ideal use of my remaining Li, I've something like 25 grams left in the form of
squares, cut from strips, which after use of some, after opening the dry-bag filled with inert gas it came in, it was opened with the smallest
practical cut made to decrease the opening for O2 to enter, before re-purging with dry Ar, folding closed, before stuffing the bag itself into a
preserve jar with about an inch or so deep layer (not in direct contact with the Li) of a mixture of anhydrous CaCl2 and fine (something like 500-600
mesh) magnesium dust to serve as a scrubber for any O2 not displaced when filling both the packet with the Li inside and the jar itself with argon,
the jar threads wrapped in teflon tape heavily and the lid set on firmly. Its been there for about 5-7 months without any visible signs of corrosion
or change from when it was first bought. And I'd have a lot more use for LiH than I will for the metal (and in any case if I need more Li metal I can
buy it, or else gut the now rather excessively large collection of buggered up e-cig batteries, which have both a high capacity and correspondingly
decent quantity of lithium within and a pretty obscenely high attrition rate.
For drying the H2, is it really necessary to employ P2O5, which is substantially more expensive, and whilst I can, it is not so easy to obtain as
concentrated sulfuric acid. Would pre-drying using a conventional dessicant and then leading the H2 stream through a long, tall, narrow glass
container filled with 98% (or boiled until the azeotropic acid is reached, followed by continued distillation until the water content has been carried
away as the azeotrope) suffice?
On the idea of carbon in trace quantities by some manner promoting the reaction, would it even be necessary to add carbon, when using a steel
container if high-carbon tool steel were used as the vessel? I have some wide-ended diamond-cutter drills for drilling glass, ceramics and metals of
extreme hardness (IIRC 16mm is the widest I have, 17mm perhaps) that would certainly be capable of boring a hole in carbon steel.
If using a steel vessel that can withstand the heat, what is the purpose of enclosing the Li within a boat fabricated from carbon steel and then this
within its own quartz tube?
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symboom
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Potassium hydride is produced by direct combination of the metal and hydrogen:
2 K + H2 → 2 KH
This reaction was discovered by Humphry Davy soon after his 1807 discovery of potassium, when he noted that the metal would vaporize in a current of
hydrogen when heated just below its boiling point.
could it be made from lithium hydroxide electrolysis hydrogen and oxygen should also be formed
Potassium hydride is soluble in fused hydroxides (such as molten sodium hydroxide) and salt mixtures, but not in organic solvents
im wondering which one is the easiest to form
supposedly adding calcium helps in the adsorption of hydrogen gas
hydrogen is generated sodium hydroxide and aluminum being lead through a desiccator into a large balloon
an apparatus of copper or steel is made one end connected to a valve that allows for controlled input of hydrogen lithium that has been coated in
ether is put in the pipe the other end of the pipe leads into ether
Side note I read that If you chill a block of magnesium, it adsorbs hydrogen; when you heat it, it releases the hydrogen again in gaseous form.
Reference https://www.physicsforums.com/threads/lithium-hydride-as-ene...
Interesting note
CaH reacts with Lithium as a cold gas releasing 0.9eV of energy and forming LiH molecules and calcium atoms.
[Edited on 23-8-2017 by symboom]
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clearly_not_atara
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EtLi seems like the most practical route to me, particularly if it can be made from EtCl which is itself easy to make.
The difficulty is in finding a solvent in which you can carry out the decomposition. I think the best idea I have is refluxing s-trioxane
(1,3,5-trioxane), which is somewhat less flammable but still not acidic or reducible, compared with heavy alkanes or dibutyl ether. S-trioxane boils
at 115 C, so hopefully that would work.
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symboom
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The solvent choice sounds good although mineral oil has a high boiling point for some reason it makes me think of potassium preparation http://www.sciencemadness.org/smwiki/index.php/Potassium
good choice of solvent is tetralin or Shellsol D70, however these are difficult to find and mineral oil or kerosene may be used,though success with
these alternatives has yet to be substantially demonstrated.
This was said about making potassium. these may work for the decomposition reaction. Many ethers do not react very fast with lithium hydride
Thank you for making a wiki for lithium hydride
Sciencemadness User mabus :-)
I always check updates are on the wiki project.
Besides Sodium cyanoborane
Lthium Hydride is a Precursor to powerful reducing agents
The easiest
Lithium borohydride
Lithium aluminium hydride,
Aluminium hydride
Aluminum hydride is prepared by treating lithium aluminium hydride with aluminium trichloride
Aluminium hydride even reduces carbon dioxide to methane under heating:
4 AlH3 + 3 CO2 → 3 CH4 + 2 Al2O3
Wow thats powerful magnesium reacts to form carbon and magnesium oxide and the reduces further
Lithium borohydride
Alternatively it may be synthesized by treating boron trifluoride with lithium hydride in diethyl ether
BF3 + 4 LiH → LiBH4 + 3 LiF
Treating diborane with sodium amalgam gives NaBH4 and Na[B3H8][14] When diborane is treated with lithium hydride in diethyl ether, Lithium borohydride
is formed:[14]
B2H6 + 2 LiH → 2 LiBH4
Unfortunately its not borane formed by HCl and magnesium boride
[Edited on 23-8-2017 by symboom]
[Edited on 23-8-2017 by symboom]
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clearly_not_atara
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Oh, there is one other reaction that produces hydrides. Sodium oxide, lithium oxide, etc all absorb hydrogen to form mixtures of hydride and
hydroxide. I'm not sure how to separate these, but I think the hydrides are generally insoluble in anhydrous ammonia whereas the hydroxides might
dissolve.
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zed
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Ummm. The formation of NaH is not especially difficult, though it does require a Paar-type pressure reactor.
The high pressure hydrogenation of Na, and Al, in toluene.....produces first Sodium Hydride, and then Sodium Aluminum Hydride.
Lithium Aluminum Hydride, can then be produced from NaAlH4 by Metathesis. NaAlH4+LiCl -> LiAlH4+NaCl
At least, that is the way I remember it.
[Edited on 23-8-2017 by zed]
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symboom
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Paar-type pressure reactor Im not sure if its needed for lithium metal
potassium hydride is formed in a steam of hydrogen at boiling point of potassium humfry davy in 1800
Here is my idea
https://m.youtube.com/watch?v=b9UF6wycia8
https://m.youtube.com/watch?v=mDmy4crrF5g
The second one shows preparation
The type of simple vessel I was thinking of for making lithium hydride this video is about the reduction of copper oxide with hydrogen so same set up
copper oxide replaced with hydrogen
Small scale is a good start
The best solution is use an alkali metal that reacts with hydrogen the best ceasium compared to lithium which absorbs hydrogen better I dont know
Lithium reaction with titanium hydride
[Edited on 24-8-2017 by symboom]
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symboom
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So I have an update I thought that lithium metal attacks glass when molten so I put a piece of metal but still it cracked and seemed to react with
glass just before I added hydrogen gas dont worry I had miligrams of amount and the lithium was being stored under ether.
Powerful Reducing agents are the one non otc that is really needed in amature organic chemistry
Chem player on youtube has made copper hydride
With sodium hypophosphite and copper sulfate
http://www.prepchem.com/synthesis-sodium-hypophosphite/
Sodium hypophosphite
Sodium hydroxide and white phosphorous which some have isolated or converted from red phosphourous.
Left the link to show copper hydride could be otc
Not sure how it compared to other reducing agents
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