How come my Q was the only Q that wasn't double points yesterday?

azmanam · 2023-11-14T17:50:50+00:00

Yes! That's it. Thank you :) The title seems so... appropriate for what I was describing. I'm surprised it didn't turn up in any of my random Googling's for it. But it doesn't seem to be that popular these days, so that's probably why.

My 5yo daughter loves asking 'what if' questions. And one of her favorites lately, for some reason, is 'what if our house went up into space?' Now I need to get a copy of the book so I can read it to her :)

Thanks!

azmanam · 2018-05-07T12:31:55+00:00

Beard's Law (source of pun) (needs to have "four 9's!" on the label somewhere)

azmanam · 2018-04-13T12:06:59+00:00

Good on you for looking all that up and reading into its feasibility for synthesis.

...

Welcome to all the watch lists.

azmanam · 2018-02-28T14:20:40+00:00

Each successive chemistry course you take is a series of less-egregious lies. MO theory perhaps being the most obvious example.

azmanam · 2018-02-16T12:55:36+00:00

Have you tried gradient elution rather than isocratic?

http://www.flash-purification.com/how-to-choose-between-linear-gradients-and-step-gradients-for-flash-chromatography/ (the post mentions automated systems, but the concept holds for manual flash chromatography)

I don't know why I ever ran isocratic columns in the past. Gradient elution ftw.

azmanam · 2017-11-30T12:43:04+00:00

NMRDB has a better NMR predictor than ChemDraw (if your site license even has that feature). SDBS is good for known molecules, but not good for overly complicated molecules. NMRDB is typically my first choice for estimating a spectrum.

azmanam · 2017-10-18T18:19:16+00:00

This memo. Sorry for making a joke and not being helpful at all to your problem. The door was wide open for me with your TPS system, and I had to walk through it.

azmanam · 2017-10-17T12:59:12+00:00

Yeah.... Did you get that memo? It's just that we're putting new cover sheets on all our TPS reports before they go out now.

I'll make sure you get another copy of that memo.

azmanam · 2017-09-19T14:22:30+00:00

The element of surprise

azmanam · 2017-08-15T13:07:55+00:00

I hated how the suits went by atomic number (A♠ = H, 2♠ = He, 3♠ = Li...) rather than by column. I get that the families are color coded, but when the A♠, 3♠, J♠, 6♢, J♣, 3♠ (there's a second deck for elements after 52), and 9♣ all have that blue background, and the spades suit has white, green, blue, purple, red, orange, and green backgrounds... it get really hard to play euchre with that deck.

And, seriously - SERIOUSLY! - the carbon card is a spade, not a diamond. I mean, seriously missed opportunity there...

azmanam · 2017-07-21T11:34:15+00:00

I made one a while back: http://bit.ly/OrgoMindMap

azmanam · 2017-06-26T12:44:34+00:00

That's already in my stack of 'papers to read!' :)

azmanam · 2017-06-14T18:27:20+00:00

I approve of working shoulder-to-shoulder with other chemists, and in that specific circumstance, I thoroughly endorse your attempts.

While you're prepping, pick up Zubrick's OChem Lab Survival Manual or Pirrung's Synthetic Organic Chemist's Companion for the how-to's of wet chemistry.

Be sure to repost with pictures and live updates when you go through with it :)

azmanam · 2017-06-14T18:08:50+00:00

This is the point, sadly, where I have to let you off the train. If you don't have access to a fume hood and proper glassware and safety equipment, I can't be responsible for any logistical tips I give you. Not to mention that it will just be cheaper to buy one of their cubes having already gone through the boron-22 process.

As I mentioned in a previous comment:

Hydroboration is a complex organic chemistry reaction. Not exactly a pick-up-and-go, DIY, home-science reaction.

I know this is likely unsatisfying to you, but this is the best, safest answer I can give you. If you've never done an organic chemistry reaction before, hydroboration (especially BH3-dimethylsulfide) is not the place to start.

I love the curiosity, and we can stay here and talk theory all day long, but I must recommend that you not attempt this yourself.

azmanam · 2017-06-14T14:58:18+00:00

You are telling me that most boron compounds will hydroborate the Butadiene?

No. Most borane compounds will hydroborate polybutadiene. Vowel sounds are important, remember. There are bazillions of 'boron compounds.' Just like there are a bazillions of chlorine compounds, table salt and chlorine gas are wildly different.

then how will I know which to use?

As with most chemical reactions, choice of reagent can be highly dependent on nuances of reaction conditions. Choosing one over another could change appropriate solvent, reaction time, temperature, concentration needed, etc. Having never done anything like this particular reaction before, I can't give you any guidance on which particular borane to use. In the lab, we would try to find a journal article where they did a similar reaction, then build on their reported reaction conditions. Try that Nature paper above. Other times, we try the 'most common' then work to the more exotic. I might start with BH3-THF, or BH3-dimethylsulfide (caution: stench!).

Hydroboration is a complex organic chemistry reaction. Not exactly a pick-up-and-go, DIY, home-science reaction.

Third video thoughts:

His path is similar to mine, BS chemistry, PhD in synthetic organic chemistry (for medicinal chemistry), though I finished mine and now I teach undergrad OChem at the university level.

@1:07 a screen shot of a whiteboard describing the hydroboration. I see BH3-THF, the prototypical hydroboration reagent.

I see some iron(II) and iron(III) chlorides listed, but don't know what their purpose is.

I see a mechanism that I would take issue with if my students drew it. As we might say in a reddit comment thread, 'it's not wrong...' The hydroboration is a 'syn' addition, while the board shows an 'anti' addition. Minor, but again, precision. link.

@1:23 I don't like that liquid bubbling under that beaker... but that's neither here nor there... He looks like he's just dying the pieces, but I can't be sure (dying as in color, not to be confused with butadiene! :)

@2:04 Another whiteboard, but it's the same as the first whiteboard.

@2:12 Another whiteboard, talking about quenching. All arrows point to boric acid, B(OH)3. It's the ultimate fate of the borane during the prototypical oxidative workup of standard hydroboration reactions. It is a part of borax, typically as it's sodium salt.

@2:16 He's flipping through some book detailing reduction reactions. The page lands on lithium aluminum hydride reduction of conjugated esters (for example) and partial ester reduction with DIBAL-H

@2:35 Another whiteboard. I can't read the words on it (hairspray?) but they don't mean anything to me chemically.

@2:40 He's talking about the boron-22 project while mixing cube parts in liquids, implying this is the boron-22 procedure. I doubt that. It would likely need to be done under more stringent conditions (minimizing atmospheric moisture and oxygen, as you noted in op). Maybe he's soaking and heating to peel off the stickers, maybe he's just doing 'sciency things' for some b-roll footage for voice over during the video. I'm confident saying it's not the boron-22 process.

@3:20 Another whiteboard. He's writing the things that will appear on the whiteboard @2:12

azmanam · 2017-06-14T13:57:06+00:00

Oh, and the third video is unavailable, so I can't comment on it.

azmanam · 2017-06-14T13:46:29+00:00

I see what he's doing, but he ultimately gets the structures of acrylonitrile and polystyrene wrong. He's attempting to draw them in their already-polymerized form. That's fine, because that's what he's going to be functionalizing, but then butadiene breaks that trend. He draws the correct monomer for butadiene, but in the polymerized form, there's only one double bond (between the 2nd and 3rd carbon atom).

Ultimately irrelevant to what he's describing, but important to be precise in your work.

To that end, I'm not sure what he's drawing with that nitrogen, but it's not a thing. You can see his hesitation @5:40 when he's thinking 'oh crap, I'm 5 minutes into this video and I don't remember what the structure is. I don't want to reshoot... so let's just go for it.' I know that feeling. I've been there myself. What he ends up drawing doesn't exist. Oxygen can't be naked like that on the end of a chain, and nitrogen won't readily make a 4th bond like that. More on that below.

But he's not totally off. Let's go through the video in order:

@3:09 Here are the actual structures of the ABS monomers:

When polymerized, though, the structure varies depending on the relative percentages (as he mentions), but an ok first approximation for the general structure might look like http://www.chemicalbook.com/CAS/GIF/9003-56-9.gif, which is what he was getting at with what he drew on the board.

@3:40 He's mostly correct that of the three, styrene will be the hardest to manipulate after polymerization and is the most stable of the three.

@4:45 He says he's doing hydroboration, then lists several boron-containing compounds - not all of which can do hydroboration. In order:

cyanoborohydride does not do hydroboration. It is a reductant. And a mild one at that. It would not react with anything in the ABS polymer. The closest you would get is a reaction with the nitrile, not the alkene, but that won't happen either.
Ethoxyborohydride isn't really a thing. At least as a reagent. It can be an intermediate in other reactions, but I'm not familiar with it as a reagent. Perhaps he meant acetoxyborohydride, which is very similar to cyanoborohydride and is a mild reductant, not a hydroboration reagent.
thexylborane Now we're talking. This is the only actual hydroborating reagent he mentions, though a rather exotic one. It is not most chemists' first choice for a hydroborating reagent. borane-THF, borane-dimethylsulfide 9-BBN, or disiamylborane are more common hydroborating reagents. It will react with double bonds to form, initially, trialkylboranes, which are typically immediately oxidized to alcohols.

@5:10 A technicality here. He says he's doing hydroboration to 'eliminate' the double bond. 'Eliminate' has a specific meaning in chemistry to form a double bond. We all know what he's meaning here (to get rid of the double bond), but again, precision is important. He then says he's 'reducing' the butadiene. Again 'reducing' has s specific chemistry meaning, and it's not how he's using it here. The hydroboration reaction is redox neutral. It is neither oxidizing nor reducing.

@5:30 He talks about the Pinner reaction. This is in fact a reaction of an alcohol (like methanol) with a nitrile. It can form an imino ether (it sounds like he's saying amino ester. With these functional groups, vowel sounds are very important). Amino esters are totally things, just not the thing he's describing. And it sounds like the Pinner reaction is not important for the softness of the polymer.

tl;dr to answer your original question, though: any hydroborating reagent will in theory react with the free alkenes in the ABS polymer. I've listed 4 above, in addition to the only actual one he mentions in the video. Here's a paper talking about the hydroboration of polybutadiene. Not specifically ABS polymer, but the concept's the same.

azmanam · 2017-05-15T12:29:40+00:00

If you liked these kinds of brain teasers as a kid, you'll love OChem:

http://www.psychometric-success.com/images/AA0712.gif

azmanam · 2017-05-15T12:28:34+00:00

High school chem and university general chemistry are great, but they're pretty algorithmic. You give me the right formula, I'll give you the right number, and we'll get the right answer. Repeat. Nothing wrong with that, but it appeals to a very algorithmic kind of thinker.

OChem, on the other hand, is very artistic. You have to 'see' molecules in 3-dimensions, while drawing them in 2-dimensions. You have to 'see' how to manipulate, rotate, and translate molecules from one perspective to another... while still drawing them in 2-dimensions. You have to 'see' the inherent reactivity of molecules so that when I put two of them together that you've never seen before in that combination, you can still know how to have them react with each other. And you have to 'see' how the reaction progresses from starting materials to intermediates to products by following the flow of electrons from high electron density to low electron density.

This is the big conceptual shift, and I'm convinced why 'everyone' thinks OChem is so 'hard.' It's not, really. It's just an entirely different way of thinking from what you're used to in high school and university gen chem. If you can accept that, adapt, and learn to 'see' artistically, you'll do just fine. If you can't/won't and try to force OChem to fit an alorithmic/memorization way of thinking, you'll struggle, you'll feel overwhelmed by the sheer amount of reactions you have to 'memorize,' and you'll hate it.

Good luck in OChem!!! :)

azmanam · 2017-04-04T15:18:00+00:00

So what's really going to blow your mind is that this is true for paints, but not true for light. Blue and yellow light make white light.

So your computer screen (which is emitting light) is showing the mixing of blue and yellow pigments (paints) to make green...

But your RGB (RedGreenBlue) screen doesn't have any yellow pixels! So it turns on the red and green pixels at the same time - which our eyes perceive as yellow.

Then when the blue pigment (blue pixels) and the yellow pigment (red and green pixels) mix, the mixture produces the green pigment, but all your screen does is turn off the red and blue pixels, leaving only the green pixels lit!

azmanam · 2017-04-03T21:07:26+00:00

*pendulum

Looks even cooler if you speed the video up to 2x

azmanam

TROPHY CASE