Talk:Raney nickel

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Article milestones Date Process Result October 26, 2005 Peer review Reviewed December 12, 2005 Good article nominee Listed January 29, 2006 Featured article candidate Promoted Current Status: Featured article

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Contents 1 Aluminium content 2 Teratogenicity of nickel 3 Aminolysis of alcohols ? 4 Factual inaccuracy in lead 5 Removed statements in the Applications section 6 aluminium dissolved?

[edit] Aluminium content

What is the usual aluminium content of Raney nickel? Might it be better to discribe it as finely divided nickel, rather than nickel-aluminium alloy? Physchim62 08:59, 22 October 2005 (UTC)

Off the top of my head I can tell you that the final Al content using a 50/50 starting alloy is usually between 10 to 20%. Of this percentage Al is present mostly in the nickel aluminide phase (NiAl), but depending on activation conditions more or less Al is leached from the other phases. I don't think describing it as a nickel-only catalyst is accurate, but describing it as mostly-Ni would be ;-) -- Rune Welsh | ταλκ | Esperanza 09:22, 22 October 2005 (UTC)

I was able to check my references just now, the average Ni content in commercial samples derived from a 50/50 starting alloy is 85%. So there you go. -- Rune Welsh | ταλκ | Esperanza 15:27, 22 October 2005 (UTC)

Are these percentages by mass or by molar fraction? The atomic mass of nickel is twice that of aluminium... Physchim62 19:31, 27 October 2005 (UTC)

Somehow I didn't see this comment before. Percentages are given by mass (% wt). -- Rune Welsh | ταλκ | Esperanza 16:09, 30 November 2005 (UTC)

[edit] Teratogenicity of nickel

The article states that nickel metal is a known teratogen: do we have any references for that? It might also be better to describe it as a suspected carcinogen, given its IARC classification... although if you ingest it, it will transform into Class 1 nickel chloride in the stomach... Physchim62 08:59, 22 October 2005 (UTC)

The source is in the linked MSDS in the reference section: [1] -- Rune Welsh | ταλκ | Esperanza 09:22, 22 October 2005 (UTC)

[edit] Aminolysis of alcohols ?

The third sentence under the "Applications" section states:

It [Raney nickel] "has also found use in the alkylation of amines and the aminolysis of alcohols."

Can someone explain what aminolysis of alcohols is? Maybe provide a general chemical reaction using R groups or, otherwise, an example of a specific chemical reaction? It seems to me that aminolysis would be the cleavage or splitting of an amine, but an alcohol is typically not an amine. H Padleckas 07:02, 26 October 2005 (UTC)

Sorry, you're right. It's amination of alcohols, the exact opposite. -- Rune Welsh | ταλκ | Esperanza 10:30, 27 October 2005 (UTC)

OK, thank you. Now it makes sense. H Padleckas 03:32, 28 October 2005 (UTC)

[edit] Factual inaccuracy in lead

In a materials science context, an amorphous solid is noncrystalline; however, according to the article, Raney nickel is composed of fine crystals ("fine grains" and "crystallite sizes" both imply this). This should be corrected. - Bantman 19:32, 13 December 2005 (UTC)

Very true. Fixed. -- Rune Welsh | ταλκ | Esperanza 13:27, 25 December 2005 (UTC)

[edit] Removed statements in the Applications section

I removed two statements in the Applications section.

Raney nickel is frequently used for organic syntheses in the laboratory, where it is often used as a practical alternative to aqueous reducing agents, such as sodium borohydride, in most of the reactions outlined above.

-and-

Thus the use of Raney nickel in this reaction may be used as a convenient alternative...

The reason is that Raney nickel is NOT the practical alternative to anything. Because of it's extreme pyrophoricity, Raney nickel is dangerous to handle in most laboratories. In my experience, Raney nickel has been the last alternative, and is only used when other options are impractical or don't work.

Don't get me wrong. I've used Raney nickel many times, but to say that it's a practical and convenient alternative is just wrong. ~K 19:33, 29 January 2006 (UTC)

I disagree. Reductive amination is a good example where Raney nickel and Pd/black are used instead of NaBH4 and related compounds. Also, Raney nickel is almost always stored in water so direct exposure to water is a non-issue. Replacing water with another solvent is pretty much trivial with the use of a manifold. -- Rune Welsh | ταλκ 19:59, 29 January 2006 (UTC)

You are correct. Reductive amination works very well with Pd-on-carbon and with sodium cyanoborohydride. Both of these reagents give high yields comparable with RaNi. Therefore, since both of these reagents are easy to handle and not pyrophoric, why not use them before trying RaNi. Remember, I'm not dissuading usage of RaNi, but rather, not suggesting it is better than other alternatives.

Regarding the water, I don't understand the problem. (I think I either miswrote something or you misread something.)

Finally, I apologize for offending you about editting first and explaining later. It was not my intention to offend. My only excuse is I was "Being Bold". I find this method the best way of getting things done quickly. If you feel, this method is wrong and there's a better way to go about it, please tell me. ~K 20:43, 29 January 2006 (UTC)

You mentioned that pyrophoricity is an issue when handling RaNi in the lab. I tried to say that it isn't because it's sold in a slurry and handling under inert atmosphere in a manifold is simple, so there's little risk of exposure. Also, while its true Pd/black is used as an alternative to RaNi when yields are comparable, the removed text mentioned clearly that RaNi is an alternative to aqueous reducing agents. The problem with those is usually the separation of the aqueous phase and the formation of potentially toxic byproducts. Case in point, the frequent use (until recently) of NaBH3CN in reductive amination.

I have nothing against people being bold, but please consider that when the article is under a greater attention than usual (as is the case during an FAC nomination) it would be preferable to discuss things first. -- Rune Welsh | ταλκ 20:57, 29 January 2006 (UTC)

[edit] aluminium dissolved?

dissolves most of the aluminium out of the alloy.

I was under the impression that 2NaOH + Al -> H2 + Na2AlO2 (sodium aluminate) as covered in the reaction section. You can try this at home with some draino and alfoil: put the alfoil in a glass jar with a hole in the top, add a few flakes of draino and a little water, put the lid resting on the top, wait short while then light the hole with a taper. The lid will go up in the air with a nice bang.

This isn't really dissolving, but instead a chemical reaction. (I guess people tend to be a bit causal with dissolve - 'acid dissolves metal') njh 10:16, 21 February 2006 (UTC)

Most of the sources I consulted tend to refer to the leaching process as "dissolving" at some point during the discussion. This is probably because the excess NaOH prevents the precipitation of sodium aluminate so it remains effectively "dissolved" in solution. -- Rune Welsh | ταλκ 11:09, 15 August 2006 (UTC)