For me, it's also a timely discussion in that a short while ago (from my records on August 19 2019) I was looking at the Wikipedia article on aspartame when I realized that there was a significant error on the page. The skeletal formula was correct but the ball-and-stick model was incorrect in that it had an extra hydrogen tacked onto the aspartic acid group—the NH2 was misrepresented as NH3.
Being somewhat surprised at the error—as one would have thought that both representations would have been generated in the same software, Avogadro etc., thus the error should have occurred in both or not at all—so I dug a little deeper. I recalled that I had previously visited Wiki's Aspartame page some years back so I went looking to see if I had kept a copy of the page and sure enough I had saved it (it's not unusual for me to save Wiki pages).
Anyway, upon reexamination of the earlier page, I found that the ball-and-stick formula was also incorrect therein. Clearly, I'd not noticed the error back then.
The date of that earlier viewing was April 5, 2012, so the Wikipedia page has had that blatant error present for over 9 years—it could be much longer as I never checked when the page was originally posted! Given both its notoriety and controversy, how could such a large mistake exist in this Aspartame page for so long without anyone noticing it?
I then tried to correct the error. I attempted to edit the page only to be informed that my domain was unacceptable and so I could not do so. I then resorted to contacting Wiki by other means and informing them of the error and they corrected fault within hours.
If anyone has a reasonable explanation for why this error could exist so long on Wiki without being corrected then I'd love to know. Moreover, why would only the balls-and-stick be in error when it is normal for both representations to be generated on a common piece of software?
Second Matter:
"Searle patented this product, naming it Nutrisweet and Equal. Officially, aspartame has a half-life of about 300 days in solution at about pH 4, about the pH of soft drinks, but half life means that half if it as gone by that time. And if the cans are exposed to a hot storeroom or stored in a warm summer garage, they may deteriorate faster."
I'd rarely have the opportunity to drink 'old' artificially sweetened drinks of this sort. First I don't drink many of them, and second, I only buy them in the supermarket where there's a very fast turnover of stock.
That said, I find Diet Coca Cola unbearably sweet and almost undrinkable when its chilled and completely undrinkable when warm, the others, Zero etc., I find so sweet that they're undrinkable under any conditions.
Could it be that drink manufactures are actually increasing sweetness past the so-called 'bliss point' to allow for the deterioration/aging of aspartame? Perhaps they're aiming for some 'ideal' or average date past manufacture where the maximum number of punters would likely be consuming the stuff.
Does anyone know or have factual information about such matters?
>I was looking at the Wikipedia article on aspartame when I realized that there was a significant error on the page. The skeletal formula was correct but the ball-and-stick model was incorrect in that it had an extra hydrogen tacked onto the aspartic acid group—the NH2 was misrepresented as NH3.
I am sure you meant well, but as far as I can see, the original ball-and-stick model was indeed correct--and the current edited version is wrong.
Amino acids, as well as most things made from amino acids, exist as zwitter ions in solid form as well as in aqueous solution. The carboxyl groups are comparatively strong acids, the amino groups are comparatively strong bases, so there is a proton transferred to NH2, making it NH3+. That proton is missing from the carboxyl group resulting in a carboxylate group (COO-). The positive and negative charges cancel each other and the result is a zwitter ion with two charged atoms/groups, but no charge overall.
The newer version still has a carboxylate group (COO-), but no NH3+ group, making it negatively charged. That probably exists, at high pH values.
I've yet to check Wiki as of today, so I don't know if the site has changed since last August or not. I will check momentarily.
I acknowledge what you say and I'm not necessarily disputing your points. If this is the result of another of the many nomenclature problems that plague and beset chemistry then I'm damn-well sick of it (and I'm certainly not alone).
It's about time that someone—some authoritative body, most specifically IUPAC et al, sorted this mess out.
PS: you haven't really answered why both the skeletal and ball-and-stick would be different. Moreover, the skeletal outline in the story is also the usual default (i.e.: the same as in both versions of Wiki and in ChemSpider).
IUPAC has nothing to do with it--aspartame is a trivial name. It's no mess, either--chemists know that 1M sulfuric acid does not contain any H2SO4, even though H2SO4 is sulfuric acid.
The skeletal and ball-and-stick structures differ precisely because they weren't created from the same source--the author of the ball-and-stick structure cites a crystallography paper as their source, and solid crystals consist of zwitter ions.
That type of problem is found throughout chemistry but usually an accepted nomenclature applies (when it doesn't is when we get into troubles).
So why did Wiki make the change when I pointed the matter out if it is incorrect?
I'd now suggest you get it corrected.
Edit: also tell Wiki that it shouldn't post inconsistent information as it only confuses (similarly ChemSpider).
Edit 2: 'aspartame is a trivial name'. Very true, but aspartame is not known to the world by its IUPAC name, even at best it still means that a nomenclature problem exists.
1. You still haven't answered why other more authorative sites such as ChemSpider also display ball-and-stick as per the later Wiki version. (If more than one authorative site does so then there must be some reason for it - for this common consistency.)
2. You have failed to realize the significance of being consistent in presentation especially when stuff is presented in encyclopedic form. To do so in any other way is misleading.
That means that the skeletal and ball-and-stick depictions should be consistent with each other (otherwise it's confusingly - except for geniuses such as yourself of course).
Can't you understand that many people compare both models and that they expect them to match? (It's common practice to count the hydrogens on both to cross reference the chemical formula, etc., etc. - that's a common teaching practice where I come from.)
3. I never said that I disagreed with your assessment of the chemistry and I still don't. In fact, I do understand what you are talking about but (a) it's irrelevant if I do or don't in this instance and (b) expressing the more 'complex' state of molecules isn't normal practice in encyclopedic references. Yes, I'd agree that in textbooks such detail is normal but not here.
If you want to be precise to the nth degree and grind things superfine AND also be consistent across chemistry (i.e.: have common and consistant [standard] nomenclature to describe things) then you could not describe water as just 'H2O'.
OK: now where do we start for a proper formulaic description of water?
We would have to add in hydronium - or should that be hydroxonium (I learned the latter but I'm happy with both). Or should we refer to that as 'oxonium' only? Or should we start the description with something as confusing as:
Water = H20+H3O+ +... . ('water'
+ oxonium-type ion and then some extras)
How do we describe the protonation in its fullest form (as a formula)?
As you ought to know, this gets even more complicated, should we add in all known cations (Zundel, etc.) for a basic description of water just to ensure the formula is complete in all circumstances (cover all states/conditions)? (And then add a footnote that we may still not have them all as others may still be there - yet to be discovered).
Of course not. It's ridiculous.
Any chemist who works at that level already knows this stuff so it's unnecessary to describe the 'basic' molecule - dare I say it - in anything other than in its simplest (basic) form.
>1. You still haven't answered why other more authorative sites such as ChemSpider also display ball-and-stick as per the later Wiki version. (If more than one authorative site does so then there must be some reason for it - for this common consistency.)
I do not owe you any answer, let alone why someone who is not me decides to represent anything in any form. Both versions (the original ball-and-stick model and the current skeletal structure) are valid, though one of them accounts for protolysis, and one doesn't.
>2. You have failed to realize the significance of being consistent in presentation especially when stuff is presented in encyclopedic form.
My point was not that the current version is or isn't consistent, my point was that it is WRONG.
For me, it's also a timely discussion in that a short while ago (from my records on August 19 2019) I was looking at the Wikipedia article on aspartame when I realized that there was a significant error on the page. The skeletal formula was correct but the ball-and-stick model was incorrect in that it had an extra hydrogen tacked onto the aspartic acid group—the NH2 was misrepresented as NH3.
Being somewhat surprised at the error—as one would have thought that both representations would have been generated in the same software, Avogadro etc., thus the error should have occurred in both or not at all—so I dug a little deeper. I recalled that I had previously visited Wiki's Aspartame page some years back so I went looking to see if I had kept a copy of the page and sure enough I had saved it (it's not unusual for me to save Wiki pages).
Anyway, upon reexamination of the earlier page, I found that the ball-and-stick formula was also incorrect therein. Clearly, I'd not noticed the error back then.
The date of that earlier viewing was April 5, 2012, so the Wikipedia page has had that blatant error present for over 9 years—it could be much longer as I never checked when the page was originally posted! Given both its notoriety and controversy, how could such a large mistake exist in this Aspartame page for so long without anyone noticing it?
I then tried to correct the error. I attempted to edit the page only to be informed that my domain was unacceptable and so I could not do so. I then resorted to contacting Wiki by other means and informing them of the error and they corrected fault within hours.
If anyone has a reasonable explanation for why this error could exist so long on Wiki without being corrected then I'd love to know. Moreover, why would only the balls-and-stick be in error when it is normal for both representations to be generated on a common piece of software?
Second Matter:
"Searle patented this product, naming it Nutrisweet and Equal. Officially, aspartame has a half-life of about 300 days in solution at about pH 4, about the pH of soft drinks, but half life means that half if it as gone by that time. And if the cans are exposed to a hot storeroom or stored in a warm summer garage, they may deteriorate faster."
I'd rarely have the opportunity to drink 'old' artificially sweetened drinks of this sort. First I don't drink many of them, and second, I only buy them in the supermarket where there's a very fast turnover of stock.
That said, I find Diet Coca Cola unbearably sweet and almost undrinkable when its chilled and completely undrinkable when warm, the others, Zero etc., I find so sweet that they're undrinkable under any conditions.
Could it be that drink manufactures are actually increasing sweetness past the so-called 'bliss point' to allow for the deterioration/aging of aspartame? Perhaps they're aiming for some 'ideal' or average date past manufacture where the maximum number of punters would likely be consuming the stuff.
Does anyone know or have factual information about such matters?