Sauron
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Preparation of Sodium Aluminum Hydride and Lithium Aluminum Hydride
In another thread zed complained that the prep of LAH many of us have seen on Rhodium is not very satisfactory because it is wasteful of lithium
hydride.
4 LiH + AlCl3 -> LiAlH4 + 3 LiCl
and the more I thought about it the more I decided she is right.
She suggested
Li + Al + 2 H2 -> LiAlH4
which is a heat/pressure reaction. She could not immediately recall the reference.
I was curious about just how much heat and pressure was involved and this led me to an Ethyl Corp patent by Ashby. It seems his process worked better
for sodium aluminum hydride than for lithium, and anyway usually run at 5000 psig H2 pressure.
Furger paper chasing revealed an improvemnt assigned to same company by Nelson, which allowed pressures to be reduced to 1000 psig. Much more to my
liking. Especially so since NaAlH4 reacts with LiCl to produce LiAlH4.
So now we have a two step process to prepare LAH from Na, Al, H2, and LiCl. No lithium hydride required.
The Ashby/Nelson process is done in toluene not Et2O or THF. A small amount of triethylaluminum is used as catalyst.
So at this point the problem becomes: how to obtain or prepare triethylaluminum?
This is simpler than it sounds.
Caution: trialkylaluminum compounds are usually spontaneously pyrophoric. Study up on Schlenk type manipulations under dry N2.
You can start with Al (turnings, granules, powder). It needs to be clean and dry and as oxide free as possible. This is reacted with ethyl chloride or
better, ethyl bromide, adding the halide to the Al a little at a time because the reaction is exothermic and the halide volatile. A small amount of I2
is used to start things. Once the reaction subsides, add a little more halide. Repeat until complete. This is described in Brauser for diethylaluminum
bromide.
The reaction between Al and 3 EtX produced what is referred to for convenience as ethylaluminum sesquihalide Et3AlX3. In fact there is no such beast.
The sesquihalide is an rquilibrium mixture of EtAlC2 and Et2AlX. Unfortunately these cannot be fractionated. There are however workarounds.
Option 1: Reduce the dihalide to halide with an active metal alloyed with the Al in the original reaction. Mg is used in this case and the
stoichiometry dictates a 70% Al 30 % Mg alloy called magnalium. This is what is used in Brauer.
Option 2: reduce the sesquihalide with Na metal after the fact.
Option 3: complex the EtAlCl2 with NaCl, now the distillation will work because the desired Et2AlCl2 does not complex with NaCl.
EtAlCl2 + NaCl -> Na(EtAl)Cl3 solid
I am awaiting the paper on this. I do not know if this works for sesquibromide and NaBr.
I am also unsure of whether the solid complex can be reduces with Na. But, Al and EtCl are cheap so why would it matter?
All of these are viable.
Once Et2AlX is in hand, it can be reduced with Na to Et3Al. The triethylaluminum is distilled off the NaX byproduct. It is best stored either neat or
in a 25% w/w soln in toluebe and in a Sure/Pak type cylinder.
Zed calculated that the NaAlH4 prep in a 1 L autoclave like my Parr, will produce 225 g or so NaAlH4. About half a pound per run. A run like that
requires only a few ml triethylaluminum and the solvent and catalyst can be reused several times without replenishment. So a little triethylaluminum
goes a long way.
The papers I collected on these reactions are mostly in the Parr Shaker Hydrogenator thread and the Need Help From the Pyrotecnics Side thread. A few
more I will post here.
[Edited on 2-4-2009 by Sauron]
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Sauron
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From Ullmann's
2.3.2. Reaction of Aluminum With Alkyl Halides to Make Alkylaluminum Sesquichlorides
"Methyl, ethyl, and other alkyl or aralkyl halides that are not dehydrohalogenated readily, can react with aluminum metal in an exothermic process to
form organoaluminum sesquihalides in high yields [38], [39]. An important example is the reaction of methyl chloride [74-87-3] with aluminum
[7429-90-5].
3 CH3Cl + 2 Al -> (CH3)3Al2Cl3 (15)
The reaction is carried out with aluminum in the form of turnings, shavings, granules, or powder. Oxygen and moisture must be rigorously excluded. The
reaction can be initiated with a small amount of mercury or iodine. It also can be started by treating the aluminum with an alkylaluminum halide. A
portion of the residue from a previous reaction is effective.
The products are equilibrium mixtures of the codimer (R2AlX · RAlX2) and homodimers [(R2AlX)2 and (RAlX2)2], in which the two aluminum atoms of each
component are halogen-bridged as shown by compound 3, Section 2.1. Physical Properties.
In the reaction of methyl chloride [74-87-3] with aluminum, small amounts of ethane are formed by an apparent Wurtz-like reaction. With ethyl
chloride, some butane is produced; also, dehydrochlorination of ethyl chloride can occur to form byproduct ethylene and excess Al – Cl bonds in the
product. The ethylene may form oligomers in the mixture by a cationic mechanism. The byproduct reactions are favored by higher temperatures and
therefore can be minimized by careful temperature control. When byproduct reactions take place to a significant extent, the excess Al – Cl content
in the R3Al2Cl3 product can be decreased by addition of the calculated amount of R3Al. Overall, however, it is critical to control reaction conditions
as slight excursions can result in catastrophic events.
Products can be recovered by settling and decantation, filtration, or distillation. Large quantities of methyl- and ethylaluminum sesquichlorides are
produced industrially by this method. They are used as alkylating agents, catalyst components, and for making other methyl- or ethylaluminum
chlorides.
Process Example. Production of ethylaluminum sesquichloride by reaction of ethyl chloride with aluminum is illustrated by this patent example [39]. A
9.5 × 10–2 m3 closed steel reactor, fitted with a reflux condenser and equipped for vacuum distillation of product, was first purged with nitrogen.
After addition of 13.6 kg of aluminum powder and a catalyst mixture composed of 3.6 kg diethylaluminum chloride and 410 g iodine [7553-56-2], the
reactor contents were stirred and heated slowly to 130 °C. The temperature was maintained at 120 – 150 °C during addition of 50 kg ethyl chloride
over a period of 3 h.
The product can be flash distilled under vacuum, or it can be drained from the reactor and clarified by settling or by filtration of black residual
metal solids. Iodine can be omitted from the procedure, in which case the induction period may be increased.
2.3.3. Reduction of Alkylaluminum Sesquichlorides to Make Trialkylaluminums
The alkylaluminum sesquihalide products from aluminum reactions with alkyl halides can be converted to dialkylaluminum halide or trialkylaluminum
materials by treatment with active metals, such as sodium [7440-23-5] or magnesium [7439-95-4] [38], [39]. For example, diethylaluminum chloride or
triethylaluminum can be produced from ethylaluminum sesquichloride by sodium reduction.
2 (C2H5)3Al2Cl3 + 3 Na -> 3 (C2H5)2AlCl + Al + 3 NaCl (16)
3 (C2H5)2AlCl + 3 Na -> 2 (C2H5)3Al + Al + 3 NaCl (17)
A magnesium-aluminum alloy can provide the reduction function concurrently with reaction between aluminum and the alkyl halide.
The sesquichloride reduction process is currently the most economical route available for production of trimethylaluminum.
Trialkylaluminum products made by this process generally contain trace levels of residual chloride but do not contain Al – H or other low-level
components found in the aluminum-hydrogen-olefin processes (Section 2.3.1. Hydroalumination to Produce Trialkylaluminums).
The components of ethylaluminum sesquichloride cannot be separated economically by fractional distillation because of unfavorable vapor pressure
relationships. However, diethylaluminum chloride can be distilled from the crystalline sodium chloride complex that forms with ethylaluminum
dichloride [22].
(C2H5)3Al2Cl3 + NaCl ® (C2H5)2AlCl + Na[Al(C2H5)Cl3 (19)
Process Example. Diethylaluminum chloride has been made industrially according to Equation 16. In a patent example [39], ethylaluminum sesquichloride
(26.5 kg) added to a nitrogen-purged 9.5 × 10–2 m3 reactor, was heated to 175°C. Then, while the mixture was stirred vigorously, 1.1 kg sodium was
added over a 30 min period; the mixture was further heated at 155 – 190°C for 60 min. The diethylaluminum chloride product distilled from the
reactor at 100 – 161°C (1.3 – 6.1 kPa).
In this example, an excess of ethylaluminum sesquichloride was employed to facilitate draining the voluminous byproduct salt and aluminum solids from
the reactor. In an alternate approach, a heavy hydrocarbon oil, added prior to reaction, may be employed to remove the solids in slurry form,
permitting the use of a stoichiometric ratio of ethylaluminum sesquichloride and sodium reactants.
2.3.5. Reproportionation Reactions
When alkylaluminum halide or trialkylaluminum compounds and aluminum trihalides are combined, reproportionation reactions occur rapidly under ambient
blending conditions, releasing small amounts of energy [38], [39]. These reactions are of industrial importance in making, e.g., diethylaluminum
chloride or ethylaluminum dichloride. Either can be formed, depending upon reactants and stoichiometry chosen.
2 (C2H5)3Al + AlCl3 -> 3 (C2H5)2AlCl (21)
(C2H5)3Al + 2 AlCl3 -> 3 C2H5AlCl2 (22)
(C2H5)3Al2Cl3 + (C2H5)3Al -> 3 (C2H5)2AlCl (23)
(C2H5)2AlCl + AlCl3 -> 2 (C2H5)AlCl2 (24)
This method is particularly useful for making alkylaluminum halides that cannot be produced via the reactions of aluminum with alkyl halide, e.g.,
diisobutylaluminum chloride and isobutylaluminum dichloride. These are preferred over the corresponding ethyl homologues as co-catalysts in certain
olefin polymerization systems."
I have emphasized the key sections on bold. Note that one mol of Et3Al will react with one mol of the "sesquichloride" Et3AlCl3 to give three mols
Et2AlCl, which can then to reduced with Na to 2 mols Et3Al - a more efficient exploitation of the sesquichloride than other methods, (Eq 23)
[38] A. von Grosse, J. M. Mavity, J. Org. Chem. 5 (1940) 106 – 121.
[Edited on 3-4-2009 by Sauron]
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Sauron
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The angels of References appear to be pulling a work slowdown, so that paper from Liebig's Annalen has not materialized. However no matter as I found
this short and sweet note from the Ethyl Corp. in 1938 describing their prep of ethylaluminum sesquichloride and related compounds, and inclusing the
separation of RAlX2 from R2AlX by complexing the former with NaCl.
This invovles adding an excess of NaCl, heating, and distilling the liquod diethylaluminum chloride from the solid complex. As the original mixture is
almost exactly 1:1 this amounts to 50% based on the somewhat imaginary sesquihalide Et3AlCl3.
This is similar to the yield obtained by reduction of the sesquihalide with Na metal. But obviously NaCl is cheaper and easier to obtain than Na.
Interestingly they used by preference Alcoa #12 alloy which is 8% Cu but the Cu does not appear to react with the halide nor is it observed upon
analis of the alkylaluminum products. I see no reason why c.p. Al will not work just as well.
Attachment: ja01276a504.pdf (83kB)
This file has been downloaded 807 times
[Edited on 4-4-2009 by Sauron]
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watson.fawkes
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Quote: Originally posted by Sauron  |
Interestingly they used by preference Alcoa #12 alloy which is 8% Cu but the Cu does not appear to react with the halide nor is it observed upon
analis of the alkylaluminum products. I see no reason why c.p. Al will not work just as well. |
I can think of
two possibilities:
* The alloy is more easily machinable into pieces of high surface area.
* The copper is catalytic. I noted that they add AlCl<sub>3</sub> or the product of a previous preparation. The copper chloride species
are perhaps intermediates.
A point on semi-industrial manufacturing occurred to me. The byproduct EtAlCl<sub>2</sub>.NaCl might work as a raw ingredient to a
subsequent batch. Since the raw ingredients are solid and gas with liquid products, the double salt byproduct will be in intimate contact with the
co-solution of the two product species. Since the equilibrium of this solution is an equal partition, half of the byproduct should be converted as
well. The upshot would be a sequential-batch process in which there would be a constant volume of byproduct at any given time.
The open question is whether the double salt dissolves or not. Even a relatively low solubility would be sufficient. Stirring might be required for an
adequate reaction rate.
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Sauron
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The closest common alloy is 2024 and even closer is 2019.
Anyway no other report on reaction of Al and alkyl halides makes such a claim. The most common catalyst is I2,
If "magnalium" 70% Al 30% Mg is available then no EtAlCl2 is isolated, as the Mg reduces it to Et2AlCl. In this case the use of the complex is not
required nor possible.
Certainly it would be convenient to make use of the complex if possible. Perhaps it might be broken thermall.
And the other option if the Al/Mg is not available is to merely make the sesquihalide and convert it to a mol or two of Et2Al.
Thereafter, further sesquihalide is reacted with Et3Al to produce Et2AlCl thus exploiting the sesquihalide's two components in full.
Et3Al2Cl3 + Et3Al -> 3 Et2AlCl
So the complex is only involved in the first mol or two, and the "waste" in not ongoing thereafter.
Of course the Na reduction of diethylaluminum chloride is not quite mol for mol
3 Et2AlCl + 3 Na -> 2 Et3Al + Al + 3 NaCl
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zed
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My beloved little grand daughter Munchkinkiss, has suggested to me that one might intimately wrap together a 70/30 mixture of fine Aluminum Wire with
fine Magnesium wire, place a length of that wire in a vacuum, and then conduct the current from two wired in parallel 12 volt car batteries thorough
it, thereby blowing it to molten smithereens. The beads of metal recovered might then approximate the composition of the required alloy.
I'm not sure she's right, but she might be. Such an arrangement is surely capable of quickly melting the metal without oxidation. As I recall, it
will instantly explode 12 gauge copper wire into a brilliant flash of light and a dispersed collection of bright micro-BBs.
When you try this trick on copper, in the atmosphere, you get a hot copper wire.
When you do it in the perfect insulation of a vacuum; Shazzam! You get instant molten copper.
Personally, I hope there is a better way to get through that NaAlH4 synthesis.
Either via a catalyst other than Triethylaluminum, or by an easier synthesis of Triethylaluminum.
There is a suggestion that there may be an industrial synthesis of triethylaluminum, that utilizes only Al+H2+Ethylene.
http://books.google.com/books?id=j3AwCqvqIzEC&pg=PA1122&...
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Sauron
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Did you read my last few posts?
Starting from Al + EtX only, no alloy, you get quant. yield of an equal mixture of EtAlX2 and Et2AlX. In the case of X = Cl or Br, these are
impractical to fractionate, but X= I can be fractionated. So one possibility is to use EtI.
EtCl and EtBr are cheaper, and in this case, adding NaCl to the mixture (say 1,1 mol per mol of EtAlX2) and heating produces a solid comples NaEtAlCl3
from which the Et2AlCl can be distilled.
Or reduce the mixture with Na and distill of the Et2AlCl
Whichever choice, you can now reduce the Et2AlX with Na and obtain Et3Al.
If you do not yet have sufficient Et3Al, you can just make more of the mixture from Al and EtX and now you can forget about NaCl, Na metal, and
fractionation because Et3Al reacts with both components of the mixture to produce, for every mol reacted, 3 mols of Et2AlX.
Well, actually it is only reacting with EtAlX2 in a disproportionation but the net result is 2 new mols of Et2AlX and the mol that was already there,
so 3 mols.
NOW reduce with Na and you get 2 mols Et3Al (and some NaCl).
My point is that the alloy is a luxury not a necessity.
The technical challenge is to be competent at airless procedures.
The exonomic hurdle is having the requisite autoclave - I do.
The easier prep of LiAlH4 is the one from LiH and AlCl3 in ether.
But we decided is was wasteful of LiH.
I do not think the hydroaluminolysis of ethylene is a bench scale procedure. In any case the process uses selfsame triethylaluminum as catakyst. Back
to square one.
What we maybe can ask ourselves is whether Li wire, melted in paraffin oil and dispersed as sand, will take up H2 under pressure? If so then making
LiH is easy and the wastefulness issue goes away.
[Edited on 5-4-2009 by Sauron]
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Sauron
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The following is the abstract of the Ziegler article from Annalen 629 (1960) pp 33-49. Thanks fo Formatik for prompt amd excellent translation
Aluminium trialkyls form complex compounds of the coordinative 4-count aluminium of the sort M[AlR3X] (M= alkali metal, X = halogen, cyanogen) with
many alkali halogenides as well as with alkali cyanides (and evidently generally -pseudohalogenides). Their stability increase with the ionic volume
of the alkali metal, and decrease with increasing size of the halogen as well as the alkyl of the aluminium. The complex formation is restricted by
lithium to (analgous to the halogenides) lithium hydride. For trimethyl and -triethylaluminium, it is without exceptions under the fluorides and
cyanides of sodium to cesium. Under the chlorides, it is restricted to K, Rb, Cs and under the bromides, to Rb and Cs. Complexes of alkali iodides do
not exist, though those of tetralkylammonium iodides do. - The stability relationships of the halogenide complexes can be taken out of plausible basic
suppositions of relations of the lattice energy of the alkali halogenides and are pointed to without contradiction. - In addition to the 1:1
complexes, 1:2 complexes of the kind MX.2 AlR3 (X = H, F, Cl, CN) exist. Both aluminium trialkyls are bound variously strong in those. All of these
compounds are electrolytes, however the 1:1 complexes of the alkali fluorides show only around 1/100 of the conductivity of the 1:2 complexes and the
other alkali halogenide complexes. - The complex compounds, NaF.Al(CnH2n-1)3 and NaF.2Al(CnH2n+1)3, are proven up to n = 4, after n = 6 they are
certainly unstable. Further on up in the homologous rows can be achieved with potassium fluoride. - Principally, similar laws apply to the alkali
halogenide complexes of R2Al.halogen. M[AlR2Cl2] exists when M = K, but not when M = Na. - Complex formation occurs further with carbonates and
carbonic acid salts. However, these complexes are unstable and quickly change through intramolecular reactions.
Aluminiumtrialkyle geben mit vielen Alkalihalogeniden sowie mit Alkalicyaniden (und offenbar allgemein -pseudohalogeniden) Komplexverbindungen des
koordinativ 4-zähligen Aluminiums vom Typ M[AlR3X] (M = Alkalimetall, X = Halogen, Cyan). Ihre Stabilität nimmt mit dem Ionenvolumen des
Alkalimetalls zu, mit dem des halogens sowie mit der Größe der Alkyle am Aluminium ab. Die Komplexbildung beschränkt sich beim Lithium auf das (den
Halogeniden analoge) Lithiumhydrid. Gegenüber Aluminiumtrimethyl und -triäthyl tritt sie bei den Fluoriden und Cyaniden von Natrium bis Cäsium ohne
Ausnahme ein. Bei den Chloriden ist sie auf die des K, Rb und Cs, bei den Bromiden auf die des Rb und Cs beschränkt. Komplexe der Alkalijodide gibt
es nicht, wohl aber solche von Tetraalkylammoniumjodiden. - Die Stabilitätsverhältnisse der Halogenidkomplexe lassen sich aus bestimmten
plausiblen Grundannahmen heraus zu den Gitterenergien der Alkalihalogenide in Beziehung setzen und in sich widerspruchsfrei deuten. - Außer den 1 :
1-Komplexen existieren 1 : 2-Komplexe der Art MX·2 AlR3 (X = H, F, Cl, CN). Die beiden Aluminiumtrialkyle sind in ihnen verschieden fest gebunden.
Alle diese Verbindungen sind Elektrolyte, jedoch zeigen die 1 : 1-Komplexe der Alkalifluoride nur rund 1/100 der Leitfähigkeit der 1 : 2-Komplexe und
der anderen Alkalihalogenid-Komplexe. - Die Komplexverbindungen NaF. Al(CnH2n - 1)3 und NaF·2Al(CnH2n+1)3 sind bis n = 4 nachgewiesen, ab n = 6
sind sie sicher instabil. Weiter herauf in der homologen Reihe kommt man mit Kaliumfluorid. - Grundsätzlich ähnliche Gesetzmäßigkeiten gelten für
die Alkalihalogenid-Komplexe von R2Al·Halogen. M[AlR2Cl2] existiert, wenn M = K, nicht aber, wenn M = Na. - Komplexbildung tritt weiter ein mit
Carbonaten und carbonsauren Salzen. Die Komplexe sind jedoch instabil und verändern sich rasch durch intramolekulare Reaktionen.
[Edited on 6-4-2009 by Sauron]
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Sauron
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A careful reading of the all important 1940 paper by Aristid V.Grosse (J Org Chem 5, 106) provides the important reminder that the sodium reduction of
ethylaluminum "sesquihalide" can proceed to the triethylaluminum in one step without isolation and puridication of the intermediate reduced
diethylaluminum halide.
The reduction of the sesquigalide mixture to Et3Al proceeds with a yield of 40-50% while the Ba reduction of pure Et2AlX2 has a yield of 60%.
The "shortcut" reduction is according to the following equation
Et3Al2X3 + 3 Na -> Et3Al + Al + 3 NaX
Any excess of Na must be carefully avoided in order to preclude formation of the nonvolatile tetraethylaluminum compound.
So this simplification allows a shorter route from Al metal and alkyl halide.
If the Mg/Al alloy is on hand then its use affords Et2AlX2 directly and the overall yield from starting materials is slightly higher, but not enough
to make acquisition or preparation of the alloy absolutely vital
Furthermore according to Grosse the disproportionation of sesquiha;ide with R3Al proceeds to a 77% yield. Since this affords Et2AlX which still must
be reduced with Na to get Et3Al, it is clear that the product of these yields (77% x 60%) is little better than the 40-50% yield of the Na reduction
of sesquihalide to trialkylaluminum.
The Grosse paper is posted by me on page 2 of the Parr Shaker Hydrogenator thread if anyone wants recourse to it.
[Edited on 6-4-2009 by Sauron]
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panziandi
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This link provides data regarding sodium aluminium hydride. It also shows relative reaction rates for reduction of groups with SAH vs LAH
http://www.albemarle.com/TDS/Fine_chemistry_services/SC2035F...
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Sauron
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Thanks, that ought to be useful.
EtAlCl2 is a strong Lewis acid and a useful catalyst for ene reactions between aldehydes and alkenes. This is in contrast to the MeAlCl2 which is a
weak Lewis acid. Go figure.
[Edited on 6-4-2009 by Sauron]
Attachment: jo00152a011.pdf (207kB)
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Sauron
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Update
The acquisition of custom alloy turnings 69% Al 31% Mg ("magnalium") is moving ahead, I am in touch with a UK source and his prices are reasonable. We
are ironing out some details.
This w/w% amounts to 2 g-atoms Al and 1 g-atom Mg as required by the stoichiometry for the prep and reduction of Rt3Al2X3 to Et2AlX (X = Cl, Br, I).
[Edited on 9-4-2009 by Sauron]
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benzylchloride1
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This is a fascinating way of making sodium and lithium aluminum hydrides. I would advise handling aluminum alkyls in a glove box or with a vacuum line
because of their spontaneously flammable nature. I have some experience with working with air sensitive compounds. How do you plan to handle the
triethylaluminum? Do you have a glove box and high vacuum line? I am currently aquiring the glassware and equipment to construct my own high vacuum
line. I have a single bank manifold, but it is not the ideal setup. I am planning on buying a used glove box off of Ebay. There is a seller that has
listed several times a glove box that is in good condition for around $400. I would buy it if I had the money. The glove box listed for $7000 new in a
recent Cole Parmer catalog.
Amateur NMR spectroscopist
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Sauron
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Yes I have a full size airlock equipped lighted and electrically serviced Labconco glove box equipped for Ar or N2.
I also have the requisite autoclave (Parr 1 liter SS316 stirred and heated with temp controller and T/C. This unit is rated 1900 psig @ 350 V,
Overkill for this reaction.
The triethylaluminum will be stored in steel or SS sample cylinders with Swagelok diaphragm valves, filled in the glove box, and aliquots drawn by
gastight syringe in the glove box.
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benzylchloride1
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I am planning on buy one of the portable plexiglas type glove box as I cannot afford one of the more expensive types. How well do these type of glove
boxes work for handling highly air sensitive materials. The one I was looking at on Ebay has an air lock and electrical services. Plexiglas does not
hold up well with organic solvents so I will have to be extremly cautious when I obtain one of these glove boxes to avoid damage to it by spilled
solvents.
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Sauron
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In addition to the airlock this has a large door to allow karger equipment in and out, I would set one or more teflon or SS trays in the bottom to
protest the fiberglass floor.
Plexiglass is acylic. DCM is solvent for acrylic and is how you glue acrylic together. So rule #1 with an acrylic box is: no DCM spills. Check the
chemical compatibility tables for other solvents and reagents.
I paid $400 for my box, the shipping from Missouri to SF CA was truck and then it went ocean to Bangkok. I probably have $15900 in it nit counting new
gaintlets $400 so these things are not cheap.
You know the drill, pump the box out then flush it with dry B2 or Ar depending on what you will work with, the gas needs to be dry and O2 free (use
catalytic traps.) Repeat the purge and flush till an indicator inside shows no moisture and no O2.
The airlock has its own gas controls so it can be purged and flushed independently. That is the point.
Depending again on the task at hand, you either run the box at skughtky positive pressure to mantain the integrity of the inert dry atmosphere.
Or at a slight negative pressure when using the box as a containment for say carcinogen, or otherwise obnoxious materials. This way any leaks are
inbound.
The most usual gauntlets are neoprene, and you wear cotton lab gloves under to absorb sweat.
[Edited on 11-4-2009 by Sauron]
Sic gorgeamus a los subjectatus nunc.
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benzylchloride1
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Mood: Pushing the envelope of synthetic chemistry in one's basement
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I located a Labconco carcinogen handling glove box on Ebay for $220. I am wondering if this box would work for inert atmosphere work. It has a blower
attached to the top of it. The box seems to be in excellent condition with gloves and has an air lock with a larger door which would be helpful. The
plexiglas one does not have the large door. I will continue to watch and will buy when the I find the best deal. Until then I will be putting together
a vacuum line. The Parr reactors seem to be out of my price range currently.
Amateur NMR spectroscopist
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Sauron
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It depends on what fittings the box comes with, I would not count on the gloves being in serviceable condition.
Sic gorgeamus a los subjectatus nunc.
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aliced25
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Aluminium hydride can be hydrogenated directly to Aluminium Hydride (AlH3).
LiH can be turned into LiAlH4 with a Ti.doped AlH3 solution in THF (Et2O doesn't work).
The pressures are 32 bar for the AlH3 production at 300K and RT, 13 bar for the catalyzed reaction.
Given I've shown elsewhere that it is possible to produce 99.9% H2 at up to 100 bar, surely someone can work out the rest? I can grab the
diagrams of the Parr Reactors they are using - the magnetic stirrer mechanism isn't exactly rocket science.
Attachment: Graetz.etal.Regeneration.of.LiAlH4.pdf (919kB)
This file has been downloaded 666 times
Attachment: IV.H.12.Atomistic.Transport.Mechanisms.in.Aluminium.Based.Hydrides.pdf (465kB)
This file has been downloaded 648 times
Attachment: Graetz.Reilly.Wegrzyn.Direct.Hydrogenation.of.Aluminium.at.Low.Pressure.pdf (202kB)
This file has been downloaded 622 times
[Edited on 19-5-2013 by aliced25]
From a Knight of the Realm: "Animated movies are not just for kids, they're also for adults who do a lot of drugs." Sir Paul McCartney
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Bot0nist
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Mood: Streching my cotyledons.
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This is all extremely intresting chemistry, and it would be quite a feat for an amatuer to pull off these industrial routes at home. Unfourtunatly, it
is way beyond my scope, so I will just continue to buy it from Elemental. I know its expensive, and paying for that exemption packaging sucks, but
when I need some LAH, thats the route I take...
U.T.F.S.E. and learn the joys of autodidacticism!
Don't judge each day only by the harvest you reap, but also by the seeds you sow.
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