orthocresol

That is OK, as I have no intention of continuing this discussion. I understand now where the disagreement lies. It is not about systematic or preferred naming (I never brought that up, so you saying that I conflated it with something else is slightly ironic), nor is it about the provenance of your Gold Book citation (note that there's no need to perform a generic search for the text, as the Gold Book tells you where the definition is taken from). The issue is just that you think this thing can be called, or considered, a polymer.

Why do you think the Gold Book definition of chain is at all relevant to a molecule that is neither a polymer nor a macromolecule?

Looking at your edit: you claim that there isn't a clear line, but there is at least some kind of line: which part of cyclohexane-1,3-dicarboxylic acid satisfies this definition "If a part or the whole of the molecule has a high relative molecular mass and essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass"? Answer: it doesn't. It's not a macromolecule or a polymer.

So your claim is that, while the Blue Book assigns a preferred name, you can use polymer terminology from the Gold Book to assign a systematic name to a molecule that is decidedly neither a polymer nor macromolecule?

There is a misunderstanding here. The Gold Book entry explicitly says "chain (in polymers)". The given compound is not a polymer, and even if it were, the cited definition does not help in choosing a preferred IUPAC name. In this context the "chain" that user55119 mentioned refers to something entirely different, namely the "parent structure" as described in P-12 of the IUPAC Blue Book. I don't mean to be unkind, but I do mean to be blunt, since this "discussion" has gone on so long already: you have based your answer on a definition that is irrelevant, which unfortunately makes it incorrect.

Basically, I get that the summary of this is that we're trying to explain why the ratio [A-]/[HA] changes in the presence of other residues. Your theory is that the pH changes. This is ok from a mathematical point of view, because it'll let you use the HH equation to calculate it. But from a chemical point of view, it would be more correct to say the pKa changes, and thus at a given pH we have a different ratio of [A-]/[HA]. This is equally valid mathematically.

@bonCodigo Hmm, I'm not really sure what to answer. I don't think your original argument (about pH being changed by other residues) makes sense. I do think the answers in the linked post makes sense, it's basically saying the same thing I said above.

I think your argument is kind of a reversal of this. Like, you're saying that [A-]/[HA] changes because of nearby residues, and thus the pH is different. I'm not sure whether that's a valid perspective to take: I think it might be, but I don't think that's the way most chemists would view it. Perhaps there's a different paradigm in biochemistry, but I wouldn't be qualified to comment on that. :)

There's a certain role that everything plays here — pH is the thing you can vary (by adding more acid), pKa is the thing that is a constant (by definition! — it is an acid dissociation constant), and [A-]/[HA] is the thing that responds to the change in pH.

@bonCodigo Of course, there is a relationship between them. But you can't conclude from this that pH affects pKa. Let's look at another example: F = ma. Just because you push something harder, it doesn't mean that the mass changes, right? The mass is a constant; the acceleration is the thing that changes. Likewise, in the HH equation, when you change the pH, it's not the pKa that changes, it's the ratio of A- to HA.

Does that make sense? Please ping me otherwise I might not see your response! I might be a bit slow in replying, because work is really busy and I don't hang out here very much, but I'll try not to vanish.

In that case, the pKa of acetic acid that is quoted refers to unsubstituted acetic acid. When you add a chlorine to it, it's no longer acetic acid so its pKa is different. In our case, the pKa's of amino acid residues that are quoted (let's say aspartic acid) usually refers to aspartic acid on its own. When you put it in a different environment, the pKa changes, because it's no longer really aspartic acid, it's now an aspartic acid residue with a bunch of stuff around it.

I think the step that I don't agree with is, you're implying that the presence of other residues => different local pH (and that this effect can somehow be calculated using the H–H equation). As a chemist, or well, an ex-chemist(!) I don't really see it that way. I just view it as the pKa being different, so you just plug in a different value to the H–H equation. My intuition is that this is entirely analogous to the case of adding a substituent to a carboxylic acid.

That's the way I see it, at least.

But pH is not something that affects pKa — it is just a measure of how many free protons are available. The things that are affecting pKa are not protons — they are other residues (which may or may not carry some protons with them, but the point is, they are not free protons, or H3O+).

Hmm, I don't think I would describe it this way. The pKa is a measure of how easy it is to protonate something. This does change based on other things around it. As a simpler example, in organic chemistry, pKa changes when you add a substituent to a carboxylic acid, for example.

Okay, I see.

@BuckThorn I have to admit, I miss getting a notification when there's a new meta post. :)

I might be wrong, of course, as (1) I don't see the behind-the-scenes stuff anymore, and (2) I don't really spend all that much time here.

For what it's worth, I don't think Chemistry has a huge issue with ChatGPT / other generative AI at the moment? There's already a lot of pseudo-correct stuff out there on main site, written and posted by real humans. I feel like most of my comments here nowadays are pointing out errors in posts, and I don't think the voting system is succeeding in quality control. Obviously, this could get worse if people started posting ChatGPT answers here. I haven't seen any of them yet, though.

I'm no longer privy to whatever was posted privately in Mod Teams. But if it's as bad as it sounds, then I understand why drastic action has to take place.

@Loong Some xkcd comics are relatable. This one is a bit eh. That said, I think most professional chemists tend to find chemistry jokes boring...

firstly, VΔp + pΔV is not defined (what is V in the first term - is it initial volume V_1 or final volume V_2?), and secondly, even if you fix V = V_2 and p = p_2 (or V_1 and p_1) it does not expand to the same expression

@Curio Δ(pV) = p_2V_2 - p_1V_1

@TheDragonOfFlame Your question contains a technical contradiction. A hydrocarbon contains only C and H. But anyway, you're probably looking for aldehyde, ketone, or more generally a carbonyl compound.

(It's already way better than writing papers, though. I really don't enjoy writing papers because everything has to be so... perfect. :/)

You can imagine how much of a pain it is writing my thesis now, haha.

@Martin-マーチン I wish I could :') Well, the problem is that I always post something, and then I think "I could have phrased this better".

Gotta cram all those edits in the first 5 minutes...

I'm still inevitably confused when I try to see deleted comments, though.

And I can even edit the list of duplicates.

Mmmm. Quite pleased that I can still dupehammer (some) questions.

...

I could flatter myself into thinking I should've stayed on, but that's mostly arrogance, and there were enough reasons prompting my decision to step down anyway.

Plus, of the remaining (older) mods, andselisk and Martin are as good as we're gonna get, imo. I'd be a lot more worried if they weren't staying on.

@Mithoron Oh, sure. There's always a learning curve. I also think some of those meta posts could have been delayed until post-election. But I think it's infinitely better than having the election cancelled, which seemed like a very realistic possibility.

It doesn't need to be a poison: people study this kind of thing regularly for normal drugs, google 'pharmacokinetics' for example

@ChocolateOverflow "How much control" - some, in the sense that switching up the chemical composition will have an effect. Not a lot, in the sense that there is no easy, scientific way to predict or calculate how fast something acts. You effectively need to do trial and error.

I wonder if resuscitating chat is going to be a priority going forward?? The old mods certainly didn't care much about chat. (Sheesh)

Yay! I'm very glad we have some new mods. :D

@HenriMenke Thanks again - much appreciated. Yes, I'm 'just' a chemist so the equations I have are quite simple. ;) re. tax: I confess I don't know how it works, but I will make sure to check if I buy.

@HenriMenke Thanks very much. Here's a MWE (you just need to put in the font commands). Could you use Minion Pro for the text font as well? gist.github.com/yongrenjie/1461dec1ebf16c4f7e9285f21673cc7a - Thanks also for the note about the single font. I was thinking about the basic set myself (I am outside the EU, so it is a tiny bit cheaper, perhaps the only good thing that has resulted from Brexit so far...). But the screenshots in your answer lead me to agree that it's unnecessary.

Hi all, I'm wondering if anybody here has the Minion Math fonts and would be willing to compile & screenshot a handful of equations for me. Context: I've so far used Minion Pro/Libertinus Math for my thesis, am contemplating whether to get a license for Minion Math, and would like to test a bit before I buy. (Given the money, I'd like for it to be a significant improvement.)

LOL the bot actually made me sound really stupid. I love it

@ElectionBot who is the worst mod and why is it andselisk

@YusufHasan If nobody has voted, how can we have a winner?

@KarstenTheis My sense of humour has always been awfully dry, to be fair.

smh terrible chemistry mods

Site's definitely dead if nobody even bothers voting in the election

@KarstenTheis Oh yes. Occasionally we do.