Talk:Nascent hydrogen

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"In chemistry, nascent hydrogen is non-ionised, monatomic hydrogen (H0) that exists transiently after the reduction of hydrogen ions."

I dont think that nascent hydrogen is real, sort of a folk-tale from the era when heterogeneous catalysis was less well understood. Indeed one can reduce diverse substrates with H+ plus metal, but is there really any evidence that free H forms even transiently? Instead, the so-called nascent hydrogen is just metal hydrides or H chemi-sorbed on the metal, and such ensembles are the reducing agents.

Vast amounts of atomic H exist in interstellar regions, but its high dilution precludes any chemistry.

So I recommend that this definition be changed into a disclaimer.Smokefoot 06:13, 29 January 2006 (UTC)

By that same token then there is no H+, ionic proton, because it's always absorbed to either and H₂O molecule giving an H₃O+, or sorbed into the dangling electrons on a metal surface, or sorbed to whatever it can find. We still talk about protons or hydrogen ions in acids. By the way a free proton is very rare, but it apparently does form in superacids such as HF/SbF₅ mixes, detectable by NMR, and even there you can argue that it's not free, but it's surrounded by an ionic cage of counterions that compensates for its positive charge. So no, there is no free atomic hydrogen just like there is no free proton, except in extreme cases, - I can think of hot plasma hydrogen gas quenched by liquid hydrogen that has a few neutral hydrogen atoms for a few nanoseconds during the quench - but even without these extreme cases of superacids or plasma, we still talk about pH or hydrogen ion concentration, or of atomic hydrogen at electrodes. That they are stuck to other things while waiting to react with something, because it's a lower energy state to wait like that, whether it's an H+ stuck to a water molecule, or an H0 stuck to a graphite/metal surface, that's besides the point, because it should be understood anyway that they are temporarily stuck to something. Sillybilly 09:06, 29 January 2006 (UTC)

Your comment about H+ being virtually unknown is very welcome indeed. The same can almost be said for F- and OH-. Nonetheless H+ in some form does exist, H9O4 + or where-ever one chooses to stop including the solvation shell. I am not disputing Hdot, I am disputing "nascent hydrogen" because of the implication of free (or even solvated) H. Yes, there are probably plasma situations where Hdot is involved, but the nascent hydrogen lore are not part of such discussion.Smokefoot 20:45, 29 January 2006 (UTC)

Also the idea of free Hdot in "nascent hydrogen" implies an outer sphere mechanism for reduction of protons, vs direct bonding of H+ to the reducing center.Smokefoot 23:54, 29 January 2006 (UTC)

Now that you say Hdot, a free radical hydrogen, I recall the free radical chain reactions: for instance hydrogen and chlorine gas mixture ignited by light, similar to how methane gets chlorinated. There are both chlorine atom radicals, and hydrogen atom radicals in that process: Cl₂+hʋ → 2 Cl*, Cl*+H₂ → HCL + H*, H*+Cl₂ → HCl + Cl*. In such cases the existence of atomic H* is fairly certain, unless, for some reason, the H* is nowhere near as stable as, say a CH₃* radical during methane chlorination, and instead it spends its time as a hydrogen bonded H₂Cl* resonance complex waiting for the available chlorine molecule to attack. There are definitely free radical chlorine atoms, and I'm guessing there are also non-resonance-complex free radical hydrogen atoms too. But when we speak of nascent hydrogen, we customarily mean a "just reduced" hydrogen at some conductor surface, such as graphite. I'm trying to picture a just reduced hydrogen generated someplace else than conductor surface, for instance an alkali metal dissolved in liquid ammonia that has a few drops of water added, or even just liquid ammonia itself reacting to form the amide. Such reactions are slow, as the need for an iron catalyst shows in the liquid ammonia case, hydrogen or any gas generation is extremely hard without some high energy sites available (such as high energy silica crystal defect sites with dangling unbonded electrons) to form a bubble, or a large surface area exchange surface that proceeds without bubble formation, such as hemoglobin bound carbon dioxide gets released in your lungs. But in such non-conductor-surface generated hydrogen atom cases how do you tell a nascent hydrogen? From its reducing potential? The alkali metal solution itself would have at least as much reducing potential, and it would be meaningless to talk about nascent hydrogen as a reducing agent, when you already have much more potent "nascent" alkali metals or high reducing potential organic molecules doing the same job even better. Unless you can come up with a sterically hindered molecule that's capable of being reduced, but can only sterically fit a hydrogen atom and not something larger, such as a sodium atom, but now this discussion is starting to be an overkill. Nascent hydrogen is a general term used for high reducing power, freshly generated hydrogen either by electrolysis or a metal/acid reaction, or a metal/base reaction (such as zinc/potassium hydroxide) that has to be used instantaneously before it turns into a low energy molecule that's not reactive without a catalyst such as nickel or palladium. There are limits to language itself, and if we probe too deeply into the meanings we may end up in a world without coherence. if nothing else, nascent hydrogen is still a concept, just like epicycles, phlogiston, caloric and luminiferous ether have been concepts, even if we later found out that they are incoherent with experimental reality and thus concepts that must be abandoned. Is the concept of nascent hydrogen so far off from reality and logically inconsistent with experiement to the point that it must be abandoned? Sillybilly 03:12, 30 January 2006 (UTC)

Thanks for your input sillybilly, requesting that you format and insert this into the current article. I don't think that it currently reflects a scientific viewpoint, more like borderline psuedoscience. 59.167.106.233 14:32, 1 January 2007 (UTC)

I think it would be good if someone knowledgeable were to just start over and rewrite this or perhaps just move it to a subsection on hydrogen (I think this may be preferred). The sections with citation needed seem very weak and possibly wrong. The formation of hydrogen atoms should not be that difficult to conclude. I should not be the least surprised that heat hydrogen above 2000 degrees will homolyze hydrogen. I might expect uv light can also homolyze it. I am unaware of any special properties or reactions of atomic hydrogen, but I have never searched for any either. If that is how atomic hydrogen is produced, then I think some explanation should be provided to support the other or low energy methods suggested. If there is to be any credence, this needs to be consistent with common thermodynamics (this is a speculative comment without any justification).

The atomic hydrogen torch, I guess I could change this to hydrogen torch, but I will leave that to anyone willing to just rewrite this. The rocket example, just delete it. It made no sense and after skimming the NASA article, it is just wrong. True, light fuels may be able to lift greater payloads, but they are taking liquid hydrogen and freezing it into a solid form. I think the idea is that a gel mixture could be used as the rocket fuel (with atmospheric combustion?). Let me give this a second thought. If this entire section were moved to a subsection of hydrogen, then the rocket fuel example as a use of solid hydrogen could remain. It is kind of interesting, just not an example of atomic hydrogen. Petedskier (talk) 18:50, 23 July 2011 (UTC)

Nascent hydrogen is thought to be important as a mechanism by which Hydrogen Induced Cracking (HIC) (blistering) of steels occurs in an wet-H2S-bearing fluid. The Ho diffuses into the metal, meets an inclusion and forms H2 with another Ho. The H2 formed cannot diffuse back out of the metal crystal structure and the pressure creates internal de-lamination of the (generally rolled) plate, and this can further propagate to other layers as SWC - step-wise cracking. This is a definite failure mode of Carbon Steels in H2S evironments in the oil industry. NACE MR-0175 mentions HIC, and NACE TM0284 covers the requirements for steel to resist HIC. Whether nascent hydrogen is real or not, this form of cracking is very much real and I woudl say this article needs to consider this — Preceding unsigned comment added by 194.105.190.93 (talk) 14:50, 20 February 2012 (UTC)

I am interested in the anecdotal evidence concerning the formation of certain highly toxic gases, and also on the implications of nascent hydrogen on the corrosion of steels under operating conditions. In the case of nuclear waste management and treatment, particularly defense nuclear wastes generated during the cold war this is a very important consideration. My experience suggests there are certain conditions where the formation of gases, namely the toxic hydrides such as H2S, H2Se, H2Te, and arsine could explain certain unusual and unexplained acute exposures of workers. Other incidents have apparently led NIOSH to warn of the exposure of arsenic compounds to "nascent hydrogen" due to the formation of arsine gas.

With regard to corrosion, it seems to me that the greater tendency of monatomic hydrogen to diffuse into steel, if such a thing is possible given the reactivity of hydrogen atom, needs to be settled. I have seen "inexplicable" examples of corrosion of 304 stainless steels in nuclear waste service, apparently similar to what is described by the writer above (HIC). I would like to throw my hat in with the writers above that pragmatism associated with issue needs to be supported: what can newly-formed hydrogen do, and when does it do it? In some cases a theoretical explanation can't wait.

Revision of article

I revised the lede and then noticed that the article delves into atomic hydrogen. We have a separate article on atomic H, and we probably dont wan to mislead readers into thinking that nascent and atomic H are the same thing. Also some of the content has been challenged for a long time. So I propose to remove or move most of the material about hydrogen atoms. But I welcome alternative views. I confess to thinking that nascent anything is usually bunk. --Smokefoot (talk) 02:22, 18 May 2013 (UTC)

Agree I don't understand why atomic hydrogen is mentioned here. Perhaps the author thought that the Bouveault–Blanc reduction involved radical hydrogen? I've copied the mechanism across to aid the article's description; assuming the image in correct then I think its safe to remove any mention of atomic hydrogen. Project Osprey (talk) 11:39, 18 May 2013 (UTC)

What is nascent hydrogen then, nothing more than an extinct notion? Plasmic Physics (talk) 14:22, 18 May 2013 (UTC)

We should create an article on the chemical nature of atomic hydrogen to allow for a move of all atomic hydrogen content. Such a page would cover atomic hydrogen's role in hydrogen alloys. Plasmic Physics (talk) 14:24, 18 May 2013 (UTC)

Yes I think nascent hydrogen is probably best thought of as an obsolete concept from a time when people were a little more wobbly on mechanisms. With regard to content moving, we have an article on Hydrogen atom, so that is a natural place to move some content, to the extent anything really needs to be moved vs just removed as duplicating that article. Hydrogen atom seems to be a decent article, although it quickly becomes an exposition on quantum mechanics. --Smokefoot (talk) 00:30, 19 May 2013 (UTC)

I think that simply merging the information with Hydrogen atom will create a conflict of interest. The article deals exclusively with atomic protium, whereas the information in question deals with atomic hydrogen subject to natural abundance. Plasmic Physics (talk) 00:51, 19 May 2013 (UTC)

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This article is entitled Nascent_hydrogen. Unfortunately it seems to be mostly about atomic hydrogen. I can guess why. Presumably an early version asserted the old idea that the reducing power of nascent hydrogen is due to atomic hydrogen and someone else tried to debunk it. Unfortunately anyone now wanting to find out what nascent hydrogen is will have to grapple with quite complex arguments about dissociation energy and so on and make the connection themselves: that whatever it is, it isn't what the old theory thought! Likewise, anyone who already knows the term from basic chemistry and wants to learn more will be similarly disappointed. I am in the latter category and not up to the required task of re-writing the article but I would repectfully suggest that the article be re-written. I would suggest the article should open by explaining that: A chemical reduction which cannot be performed by hydrogen gas can often be accomplished by conducting, in situ, a reaction which normally liberates it. This system is traditionally refered to as "nascent hydrogen" meaning it relies on hydrogen that has just been born. An old theory explained the phenomenon in terms of (mono)atomic hydrogen deemed to be created before the formation of ordinary diatomic hydrogen gas. This explanation is largely obsolete, but the term is still sometimes/loosely/commonly used for reductive systems which create hydrogen in situ. You can then launch into why the theory isn't viable and so on! The main article needs to describe the relevant chemistry - types of nascent hydrogen producers: iron plus acid, zinc/aluminium plus alkali, others... types of reduction that it is especially useful or otherwise for - polar bonds?, C-C multiple bonds?, saturating aromatics?; particular reductions, will it reduce nitros?, aldehydes?, alcohols?, all the usual stuff. Thanks for listening. Derek Potter (talk) 04:56, 25 December 2008 (UTC)

Last edited at 04:56, 25 December 2008 (UTC). Substituted at 00:51, 30 April 2016 (UTC)

Absolute garbage?

This article is absolute garbage. Of course the dissociation of hydrogen molecules in a plasma is not a 'myth'.162.211.117.81 (talk) 06:04, 24 June 2018 (UTC)

"absolute"? Really? Nascent hydrogen is a myth. Atomic hydrogen is not.--Smokefoot (talk) 13:16, 24 June 2018 (UTC)

Could it be possible that these two states are identical?--5.2.200.163 (talk) 16:13, 25 June 2018 (UTC)

I think that was one of the original ideas, that nascent = atomic H. You could look around for supporting sources. My recollection is that most instances of "nascent hydrogen" were very old (when chemical concepts were primitive) and experimentally involved heterogeneous mixtures (e.g. of bits of sodium metal) that probably effect electron transfer followed by protonation (PCET in modern parlance). See if you can find some decent literature.--Smokefoot (talk) 16:38, 25 June 2018 (UTC)

I see that atomic hydrogen is not mentioned in the article.--5.2.200.163 (talk) 16:17, 25 June 2018 (UTC)

You might add it. --Smokefoot (talk) 16:38, 25 June 2018 (UTC)

Obsolete scientific theories category

Should this article be categorized in "Obsolete scientific theories"? --SoledadKabocha (talk) 23:45, 20 October 2019 (UTC)

Article dwells on the debunking of "H dot" but does not provide a modern explanation

The article seems a bit too obsessed with disparaging the "classical" theory that "nascent hydrogen is atomic hydrogen", but does not offer an alternative explanation for the phenomena (enhanced reduction capability of metal-acid and other reactions that produce hydrogen in situ). --Jorge Stolfi (talk) 02:36, 24 December 2019 (UTC)

Well it doesnt really matter (to me) if this page is for some venting or is obsessive. Its a flawed concept with zero redeeming value. So it doesnt matter if readers come away with little new knowledge other than nascent state is complete nonsense. There is no "enhanced reduction capability of metal-acid and other reactions that produce hydrogen in situ". That is the point. IMHO. --Smokefoot (talk) 12:39, 25 December 2019 (UTC)