Talk:Patent Blue V

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"Patent Blue V, also called Food Blue 5" and "Though there is lot of ambiguity of the name patent blue v and it is different than food blue 5" appear contradictory, and the latter appears out of place. But I am leaving this to dye/chemistry experts. Steven Alexander 20:39, 18 March 2010 (UTC) —Preceding unsigned comment added by Stevena (talk • contribs)

Which atoms are charged?

The article defines the structure as "It is a sodium or calcium salt of [4-(α-(4-diethylaminophenyl)-5-hydroxy- 2,4-disulfophenylmethylidene)-2,5-cyclohexadien-1-ylidene] diethylammonium hydroxide inner salt." That sounds like "[4-(α-(4-diethylaminophenyl)-5-hydroxy- 2,4-disulfophenylmethylidene)-2,5-cyclohexadien-1-ylidene] diethylammonium hydroxide inner salt" is the net neutral compound on which one or more acidic hydrogens are replaced with Na/Ca ions. Parsing further, "[4-(α-(4-diethylaminophenyl)-5-hydroxy- 2,4-disulfophenylmethylidene)-2,5-cyclohexadien-1-ylidene] diethylammonium" sounds like a simple cation (with R₂C=N⁺Et₂ as the key structural aspect) and "hydroxide" is obviously an anion. That's not an inner salt because the anion is not part of the same covalent structure as the cation. However, a "sulfo" group (RSO₃H) is usually strongly acidic, so complexing this thing with hydroxide would just deprotonate one of those units. The result would indeed be an inner salt (sulfoxide anion in same structure with ammonium cation) and water as a byproduct. We have two available diagrams on commons,

choice 1
choice 2

Choice 1 illustrates the inner salt (with a second deprotonation, which makes this the counteranion for the "sodium or calcium salt of..." full chemical). That is the form at would exist at medium or high pH. Choice 2, which is used on most languages' wikipedia articles, is fully protonated, and would only likely exist at very low pH (preventing either acidic sulfo group from becoming deprotonated).

So...what is the actual chemical we should be representing? The inner salt (just the net-neutral organic compound), the fully protonated one (having all functional groups neutralized as much as possible is standard for most organic compound articles), the doubly-deprotonated form (the organic part of most common way it is formulated, but not the full salt compound), or the sodium or calcium salt (the actual chemical claimed to by the title compound)? I do note that the article discusses a color change that occurs at varying pH, so perhaps multiple forms should be included as part of that discussion. DMacks (talk) 02:53, 4 July 2014 (UTC)[reply]

The CAS number in the article resolves to the calcium salt via Scifinder (Na salt is 20262-76-4, lone inner salt is 25305-77-5). the Ca form has 20 times more articles concerning it than the others; so if you're planning on adding a chembox I would be in favour of showing the Ca form there and discussing the others in the body text if needed. Project Osprey (talk) 14:27, 4 July 2014 (UTC)[reply]
Choice 1 seems to be the right form in the sodium salt and at a neutral pH. --Leyo 22:09, 4 July 2014 (UTC)[reply]