(Hive Bee)
10-27-02 16:44
No 373403
(Rated as: excellent)
The Raney nickel catalyst was introduced in 1927.
Mister Raney treated a special alloy, prepared essentially by the fusion of approximately equal parts of aluminium and nickel at 1200 - 1500 °C, with alkali which dissolves the aluminium and leaves the nickel as a finely-divided black suspension. The catalyst is thoroughly washed to free it from alkali. It is stored under absolute ethanol in and air-free container and it is measured in the form of a suspension. The catalyst must be handled under a solvent at all times as it is highly pyrophoric. The advantages of this catalyst are that it is cheaper and less delicate than platinum, fairly large quantities of organic substrate may be hydrogenated and the process is reasonably rapid.
W2 Raney nickel preparation
Place a solution of 190 g of NaOH in 750 ml of water in a 2-litre beaker equipped with an efficient stirrer (1), cool in an ice bath to 10 °C and add 150 g of nickel-aluminium alloy in small portions, with stirring, at such a rate that the temperature does not rise above 25 °C. If excessive foaming is encountered, add 1 ml of octan-1-ol. When all the alloy has been introduced (about 2 hours), stop stirring, remove the beaker from the ice bath and allow the contents to attain room temperature. When the evolution of hydrogen becomes slow, heat the reaction mixture gradually (2) on a water bath, until the evolution again becomes slow (about 8 - 12 hours); add distilled water to restore the original volume, stir the mixture, allow to settle and decant the supernatant liquid. Transfer the nickel to a stoppered graduated cylinder with the aid of distilled water, and decant the water again. Add a solution of 25 g of NaOH in 250 ml of water, shake to disperse the catalyst thoroughly, allow to settle and decant the alkali solution. Wash the nickel by suspension in distilled water and decantation until the washings are neutral to litmus, then ten times more to remove the alkali completely (25 - 40 washings are required) (3). Repeat the washing process three times with 100 ml of rectified spirit (95 % ethanol) and three times with absolute ethanol. Store the catalyst in bottles which are completely filled with absolute ethanol and tightly stoppered; the product is highly pyrophoric and must be kept under liquid at all times. The Raney nickel cantained in this suspension weights about 75 g.
In the practical applications of Raney nickel it is more convenient to measure the catalyst than to weigh it. The product, prepared as above, contains about 0.6 g of catalyst per ml of settled material: a level teaspoonfull is about 3 g of nickel.
Notes
(1) The stirrer should be provided with a motor which will not ignite the hydrogen - an induced motor or an air stirrer is suitable. The stirrer itself may be of glass, Monel metal or stainless steel.
(2) The heating should not be too rapid initially or the solution may froth over.
(3) The number of washings may be reduced to about twenty, if time is allowed for diffusion of the alkali from the surface of the catalyst into the surrounding wash-water. Use 750 ml of water in each washing, allow diffusion to proceed for 3 - 10 minutes, stir again and decant the supernatant liquid as soon as the catalyst settles to the bottom.
(Hive Bee)
10-28-02 16:05
No 373815
Wow, nice post Cyrax.
But, you 'd better went to your bed yesterday night to have a good night sleep - instead of posting this shit at half past one in the night. Especially since noone seems to appreciate it (with the exception of a moderator mabey ... to which I say thanks
). Indeed Cyrax, why bother ... Raney nickel is widely available in the chem. stores. You can buy it just as easily as a kilo of kitchen salt. And besides, other catalysts are far less expensive and more easily made (especially Adam's catalyst). So, why waste your energy ... you 'd better do something more usefull with your precious time.
(Hive Prodigy)
10-28-02 16:23
No 373825
I loved the post. I am very interested in non-palladium/platinum hydrogenation catalysts.
Urushibara nickel is very interesting because of its ease of preparation, but so far it appears to lack the strength of reduction that raney nickel posesses.
I see much value in this post, as I do in just about all of yuor posts. Please dont feel unappreciated.
PrimoPyro
(Title Addict/Eraser)
10-29-02 10:56
No 374135
dang cyrax.... take it easy man. jetson also enjoyed your write-up bud.
the devil is so lonely
(Newbee)
10-29-02 11:03
No 374142
Wow, nice post Cyrax.
But, you 'd better went to your bed yesterday night to have a good night sleep - etc.
sometime its a tuff house -
getting your due share of attaboys -
it don't come easy
AKA
THANK YOU SIR!!!
(Hive Bee)
11-01-02 07:55
No 375390
Cyrax its a good post, I allways saw Ni(H) as a winner since it of corse will reduce both the pi-bond and nitro group in one step instead of going with NaBH4 to fix pi-bond than amalgam to fix nitro to amine... or have I missed something ;)
Never underestimate the power of retrosynthesis.
(Hive Bee)
11-02-02 10:31
No 375769
You could do that reduction if you have an autoclave in your bedroom
. Check out what our friend Barium said.: Post 365551 (Barium: "If you UTFSE and check Rhodium´s site you´ll find ...", Methods Discourse)
(Hive Bee)
11-02-02 14:56
No 375825
Perhaps it could be possible to use Raney-Ni in a one-pot reaction if CTH conditions are used. I imagine a reaction envolving hydrazine hydrate + Raney-Ni could do the trick. Or reduction of the nitro group first with Raney-Ni/hydrazine hydrate and after filtering off the catalyst reduction of the double bond with diimine generated in situ from hydrazine hydrate/hydrogen peroxide?
Quidquid agis, prudenter agas et respice finem!