Sciencemadness Discussion Board

how do you make Red Al

smartgene1 - 22-5-2017 at 15:25

how do you manufacture vitride

Melgar - 24-5-2017 at 13:49

You need to start with sodium aluminum hydride, which is made in a similar way as lithium aluminum hydride. Then react with two molar equivalents of methyl cellosolve. I think. I'm pretty sure the synthesis is still proprietary. It definitely starts with sodium aluminum hydride though.

[Edited on 5/24/17 by Melgar]

zed - 28-5-2017 at 15:12

On the bright side, NaAlH4 is not impossible to make. And, as I recall, it is much less expensive than LiAlH4.

clearly_not_atara - 28-5-2017 at 15:34

We have a thread on making R2AlH by elimination of alkenes from R2AlEt, R2AlPr or R2AliBu, where Pr=n-propyl iBu=isobutyl, and in theory you ought to be able to make a dialkoxyaluminium hydride and react this with a sodium alkoxide to obtain the trialkoxyaluminium hydride... this is not Red-Al, but it is close enough for some things.

EDIT: Actually, maybe you can make it all a bit easier if you do it in reverse:

EtAlCl2 + 3 NaOMe >> NaEtAl(OMe)3 + 2 NaCl

NaEtAl(OMe)3 + heat >> NaHAl(OMe)3

[Edited on 28-5-2017 by clearly_not_atara]

S.C. Wack - 28-5-2017 at 17:33

It was published and patented. There are options. One pot preparation from the metals and alcohol is not impossible and construction of the proper apparatus could be rewarding for someone with a bunch of sodium and a tank of hydrogen.

[Edited on 29-5-2017 by S.C. Wack]

Alice - 29-5-2017 at 02:16

The direct synthesis involves seriously elevated pressure.

See: The chemistry of sodium alkoxyaluminium hydrides

Red-Al (Vitride) synth

dan.vlad - 8-11-2017 at 20:25

Maybe someone can post the Red-Al synthesis please ?
Thank you

Opylation - 13-10-2020 at 18:29

Quote: Originally posted by clearly_not_atara  
We have a thread on making R2AlH by elimination of alkenes from R2AlEt, R2AlPr or R2AliBu, where Pr=n-propyl iBu=isobutyl, and in theory you ought to be able to make a dialkoxyaluminium hydride and react this with a sodium alkoxide to obtain the trialkoxyaluminium hydride... this is not Red-Al, but it is close enough for some things.

EDIT: Actually, maybe you can make it all a bit easier if you do it in reverse:

EtAlCl2 + 3 NaOMe >> NaEtAl(OMe)3 + 2 NaCl

NaEtAl(OMe)3 + heat >> NaHAl(OMe)3

[Edited on 28-5-2017 by clearly_not_atara]


I know this is a relatively old thread but I wanted to know if you had any articles that list this type of reaction? I could only find the route starting with MAlH4. I also couldn’t find anything about aluminum hydride preparation via alkene elimination nor the thread you were speaking about. When I search R2AlH in tfse I could only find this thread and another about an improved MAlH4 prep that reduced MH waste when reacting with AlCl3.

I’ve also been curious about the preparation of useful reducing agents by using gallium to depassivate aluminum. Trialkoxyaluminum would be easily made and then from there maybe reacting with a metal hydride? Even though metal hydrides are a pain to make, if you don’t have powdered metal then the lack of surface area takes forever to prepare the product. You can’t use borosilicate glass because the heat and temp will cause the alkali metals to react with the glass. I was curious as to whether a sodium hydride preparation using a method similar to what Nurd Rage uses with his sodium metal preparation. Heat up sodium metal in paraffin oil until it melts on high stirring and then use hydrogen to prepared NaH. Still unsure about the logistics, I’ve read NaH will etch glass easily. But it seems like it could work, at least with my very limited knowledge. Similar to a catalytic hydrogenation.

EDIT: I may have spoke too soon. I did find an attached paper regarding dialkoxyaluminum hydride preparation staring from alcohol, aluminum, and tertiary amines

[Edited on 14-10-2020 by Opylation]

Attachment: Dialkoxyaluminum hydride.pdf (365kB)
This file has been downloaded 363 times

zed - 17-10-2020 at 03:20

Maybe, but the way I remember it. NaAlH4... Hydrogen, with Metallic Sodium and Aluminum powder, plus Heat, in a stirred pressure reactor With Toluene as a solvent. Sodium Hydride forms rather quickly, over an extended period of time it complexes with the Aluminum.

Not especially arduous, if you have a pressure reactor. And a tank of hydrogen.

I suppose, Mineral oil might work as well as Toluene. But, I'm inclined to think a stirred pressure reactor would be helpful.

Sometimes, Parr or Autoclave Engineers... units are available at reasonable prices.

Of course, in gentler times, the average guy could just go out and buy Complex Metal Hydrides.
Might still be able to, but they aren't inexpensive, and suppliers are much less congenial than they used to be.

https://www.ebay.com/itm/Custom-Dual-Reactor-Vessel-System-H...

Interesting units. Didn't really fancy driving cross country in the middle of a pandemic. Doesn't say what the volume of the reactors is. But, I'm inclined to believe they are of sufficient size to produce a kilo or two of NaAlH4 per cycle. Oh yeah, the units are at the bottom of the page. Sold already.

[Edited on 17-10-2020 by zed]

[Edited on 17-10-2020 by zed]

[Edited on 17-10-2020 by zed]