Talk:Ammonium bifluoride

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IUPAC Name = Ammonium hydrogen [[di]fluoride —Preceding unsigned comment added by (talk) 05:11, 12 February 2009 (UTC)

Systematic name of ammonium bifluoride[edit]

Please, follow the discussion here at at: Wikipedia_talk:WikiProject_Chemicals#Systematic_name_of_ammonium_bifluoride.

... Excerpt from this discussion:

Because of the increasing notoriety of WP, the intricate and inappropriate systematic names for simple inorganic compounds are potentially very misleading for ungraduate students and inexperienced users. An example of inappropriate names are:

SystematicName = Ammonium difluorohydrogenuide (substitutive)
Ammonium difluoridohydrogenate(1-) (additive)

It makes no sense for a simple inorganic compound:
NH4HF2 is nothing else than NH4F · HF and it certainly does not deserve these systematic names, particularly ammonium difluorohydrogenuide: it is wrong and should it be correct, it is never used. ..., Shinkolobwe (talk) 12:46, 31 December 2010 (UTC)

If the entry is irrelevant, inappropriate, and unsourceable, then I propose that such a useless entry be deleted. --Plasmic Physics (talk) 21:15, 31 December 2010 (UTC)
Dear Plasmic Physics, thank you for your answer. Best wishes for 2011. I just made again a verification of the systematic names you proposed for ammonium bifluoride. Hereafter the results of a quick Google search:
* Ammonium difluorohydrogenuide: 1 result; it only links to the substitutive systematic nomenclature name you added yourself to the chembox of ammonium bifluoride on Wikipedia.
* Ammonium difluoridohydrogenate: 11 exact results rendered from about 29 total results (very few results and most often pointing to unreadable pages with long scrolling lists).
In both case, Wikipedia was listed at the top of the search results. This illustrates the considerable power of a single edit made on Wikipedia: it has a very high impact on the results from a Google search and is proposed to the reader in the first place. That is why edits dealing with chemical nomenclature or systematic IUPAC names are not anodine and have to be done with great care and more circumspection. Incorrect and misleading so-called systematic IUPAC names could rapidly acquire a high popularity amongst undergraduate students if they lack of critical mind and believe all what they read on Wikipedia. It could result in a poor evaluation at their exams and a loss of credibility for Wikipedia in general and the Chemistry Portal in particular. Hereafter, the result of a search for Ammonium bifluoride on PubChem Compound:

Ammonium difluoride;
Ammonium hydrofluoride;
Acid ammonium fluoride
IUPAC: azanium fluoride hydrofluoride

CID: 14935 links to several synonyms (37 in all) at:
Amongts all the synonyms in the list, I could not find the two systematic names (additive and substitutive) you derived from your own understanding of the IUPAC rules.

Interestingly, as illustrated by a figure presented here on the site of Pubchem, ammonium bifluoride is a compound with a very strange crystallographic structure: its crystal lattice contains a mix of ammonium and fluoride ions with neutral undissociated molecules of hydrofluoric acid. I understand it like if HF was playing the role of water molecules in the crystal lattice of a salt. It is a little bit like if NH4F was hydrated with neutral HF molecules. Or could it be seen as a clathrate with non-dissociated HF molecules trapped in the cage of ammonium fluoride. I am happy to have discovered that today (yesterday, I thought that HF was dissociated in H+ and F ions in the crystal lattice of this compound) :-).
As you agreed just hereabove, I will also suppress the two inappropriate systematic names from the chembox of ammonium bifluoride. Thank you for your answer and the discovery of this unusual crystal lattice. Appreciated. Best regards, Shinkolobwe (talk) 16:04, 1 January 2011 (UTC)
"I thought that HF was dissociated in H+ and F ions in the crystal lattice of this compound" Now why exactly is F- supposed to move away from H+? Where are there any isolated H+ centers? Naked fluoride is extraordinarily basic. It took me a while to figure this out too.--Smokefoot (talk) 16:27, 1 January 2011 (UTC)
Smokefoot, Thank you very much for your very judicious comment. It is true that HF is a very weak acid, simply because the fluoride mono-atomic anions is very small and strongly attracts the proton. I totally overlooked the text on top of the ammonium bifluoride page, simply because all my attention was drawn by the problematic systematic names in the diff view. It is the picture on Pubchem with the non-dissociated HF molecule that let me think more into detail to the structure of this compound. And quite logically, the considerable strength of the hydrogen bond between a small fluoride anion and a HF molecule explains the formation of the difluoride anion: F- + HF —> HF2-. It is also well explained on the discussion page of potassium bifluoride. Best wishes and a happy new year, Shinkolobwe (talk) 16:55, 1 January 2011 (UTC)

Outcomes of supplementary controls for the systematic IUPAC names[edit]

After better understanding the exact – and more complicated than initially expected – nature of the quite unusual HF2 species present in the ammonium hydrogen difluoride, and after an interesting discussion with Smokefoot on the subject, I started to doubt about the incorrect character of the systematic names proposed by User:Plasmic Physics. To avoid to possibly throw the baby with the water of the bath, I continued to search for these systematic names for ammonium bifluoride in the IUPAC 2005 Redbook. Hereafter, the results of my last searches which are also consistent with my previous searches with Google: an additive systematic name is well possible and confirmed by the IUPAC 2005 Redbook (however, 11 or 29 occurrences only can be found with Google!), but no substitutive name can be derived or confirmed (zero occurrence with Google and in the 2005 Redbook) (cfr, our previous discussion on the question in the next section of this talk page).

According to International Union of Pure and Applied Chemistry (2005). Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005). Cambridge (UK): RSCIUPAC. ISBN 0-85404-438-8. Electronic version. (Table III continued, p. 268 in the PDF, p. 256 on paper), the suffix "uide" is defined as follows:

"uide": suffix specifying the addition of hydride to a parent structure, accompanied by locants and multiplicative prefixes if appropriate, e.g. tellanuide, TeH3.

There is clearly no hydride (H) present in the bifluoride anion which only contains one central proton sandwiched between two fluoride anions: F … HF or F–H–F or HF2. So, clearly, this unusual anion in which a strong hydrogen bond is gluing together a small fluoride anion and a non-dissociated HF molecule cannot be named difluorohydrogenuide and it also explains why no substitutive systematic name is given by IUPAC for the hydrogen bifluoride anion.

However, the additive systematic name difluoridohydrogenate(1–) is well given as an example in the IUPAC 2005 Redbook: see item 20 (HF2) in the section IR-7.3 on "Additive Nomenclature", p. 126 in the PDF file, and p. 114 on the paper hardcopy.

However, I would also suggest to omit this additive systematic name from the chembox of ammonium bifluoride because the notion of hydrogenate is very rarely encountered in chemistry, not widely adopted amongst the chemistry community, and most importantly, to avoid to confuse the audience and to be misleading for novice and experienced users.

Sorry to have been so long in these explanations for this very particular case involving the quite uncommon strong hydrogen bond F … HF. Best regards, Shinkolobwe (talk) 00:13, 2 January 2011 (UTC)

Analogy in chemical formula: KHF2 or KFHF[edit]

Verbatim transcription of another interesting discussion from potassium bifluoride.

Which is the correct way to note the chemical formula? Is it KHF2 or KFHF or is either acceptable? The bifluoride ion is [F-H-F]- so I thought it should be written KFHF to represent the true structure. Deano8216 (talk) 15:04, 2 November 2010 (UTC)

formulas are funny things and their presentation does not necessary follow obvious logic. Chemist write this compound as KHF2. We never write it as KFHF, but a good chemist would know what you mean and would be impressed that your formula indicates that you know something about the structure. I have always thought that sulfuric should be written (HO)2SO2 instead of H2SO4, but (HO)2SO2 ain't going to happen, as they say.--Smokefoot (talk) 18:03, 2 November 2010 (UTC)

As the value of the ionic radius of ammonium and potassium cations are very close together, the same consideration also likely applies to ammonium bifluoride, Cheers, Shinkolobwe (talk) 00:30, 2 January 2011 (UTC)