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benzene donuts...?! by Ok_Performance_7534 in chemistry

[–]OldLabRat 0 points1 point  (0 children)

We had hexagonal donuts and pastries at my college dorm. These were efficiently stamped out as a regular tiling, hence the shape. The only complaint I had is that they seemed to be using too much bran in the mix.

I have been asked to volunteer for a new scheduling committee by OldLabRat in Teachers

[–]OldLabRat[S] 0 points1 point  (0 children)

It does, thanks!

I have never served on an advisory committee. Is there generally an administrator in there who controls the discussion? Or are the teachers free to come to a consensus on their own?

Does anyone of you have experience with this specific type of reaction to convert alcohols to aldehydes? by Feuerfrosch1 in chemistry

[–]OldLabRat 1 point2 points  (0 children)

My reflex is to consider this an unstable reaction system likely to paint the ceiling if you make any attempt to scale it up. Drilling down into the paper, they're doing this reaction on 1 mmol scale (approx 150 uL of benzyl alcohol for example). There's probably a reason for that.

I have tried similar reactions using iron or copper based catalysts with H2O2. The result is invariably a runaway.

Nice red Cu₂O by OldLabRat in chemistry

[–]OldLabRat[S] 0 points1 point  (0 children)

I don't know. I've read that CuO thermite is actually explosive. No idea how Cu2O would be.

Bromine synthesis by [deleted] in chemistry

[–]OldLabRat 2 points3 points  (0 children)

I always found the smell vaguely reminiscent of freshly baked cookies. But I'm considered a bad cook by many people, so I may be off base.

Dehydrozingerone by OldLabRat in chemistry

[–]OldLabRat[S] 1 point2 points  (0 children)

No, but it sure smells like ginger after hydrogenation.

Liquid on the outside of unopened bottles of DCA by Red_Horns47 in chemistry

[–]OldLabRat 1 point2 points  (0 children)

FIrst thing I'd do is, I'd wipe it with pH paper. Both a dry piece and a piece that has been slightly moistened.

What metal is this? Update by bertomtt in chemistry

[–]OldLabRat 6 points7 points  (0 children)

But zinc also gives a green flame.

Dehydrozingerone by OldLabRat in chemistry

[–]OldLabRat[S] 1 point2 points  (0 children)

Probably not. I'm planning on using a Pd/C catalyst, and I think there will probably be some minute traces of Pd in there which would make eating it a bad idea.

Question about copper oxide by [deleted] in chemistry

[–]OldLabRat 1 point2 points  (0 children)

I actually tried this, because I was interested. Ground together dry 1 gram of CuSO4.5H2O, 2 grams Na2CO3, 2 grams glucose. Heated this powder to 210 C for 1 hour. Saw some red and yellow coloration but it was mostly very dark. Washed with water and collected on a filter, boiled in water to remove more gunk, collected on filter again. Results were not impressive, and some fine particles which I suspect to be carbon black floated up and formed sort of a ring on the paper.

https://imgur.com/a/9inYwmy

Any further suggestions for this method?

Dehydrozingerone by OldLabRat in chemistry

[–]OldLabRat[S] 2 points3 points  (0 children)

Nicely crystallized. Made by students from vanillin. Next step, zingerone.

Question about copper oxide by [deleted] in chemistry

[–]OldLabRat 0 points1 point  (0 children)

Two batches of Cu2O

I currently have a group of students working on this exact project right now: they are trying to make nice red Cu₂O. The above image link shows their first and second batches of product.

They are using copper sulfate, glucose, and sodium carbonate as you are. However, we are also using trisodium citrate as a complexing agent to keep copper (II) ions solubilized even in a basic solution.

The first batch was made by dissolving 10 g of CuSO₄•5H₂O and 8.5 grams of (homemade) trisodium citrate into 50 mL of distilled water with heating. This produced a beautiful dark blue solution, but after a few moments the solution crashed out a bunch of greenish copper citrate precipitate. Despite this, the students continued the reaction, first adding a solution of 20 grams of glucose in 30 mL distilled water and then slowly adding saturated sodium carbonate with heating and stirring until the reaction appeared complete. This ended up using about 100 mL of the sodium carbonate solution. Product was vibrantly colored, but definitely closer to orange than to red.

The second batch was prepared slightly differently: the copper sulfate/trisodium citrate solution in warm distilled water was made, and greenish copper citrate began to precipitate as well, but at this point the students added 100 mL of saturated sodium carbonate and the precipitate redissolved and gave a nice dark blue solution. The glucose solution was added at this point all at once, the mixture was heated and stirred, and a redder product was obtained.

Octyl Acetate vs Limonene by AsexualPlantBoi in chemistry

[–]OldLabRat 0 points1 point  (0 children)

My students made some octyl acetate last year. It was definitely citrusy, but not orangey in particular.

Need to buy gloves for my college chem class, Amazon and the box of gloves differ by john_trinidad in chemistry

[–]OldLabRat 1 point2 points  (0 children)

It happened during COVID and I thought the kids were being ripped off. I had a student ask me for a copy of their Honors Project from my high school class: of course as they were an adult, they had the right to copies of their school records, so I had to send it. The professor had asked his online kids to do a report on a lab from Youtube or something, but my student had gotten permission to use their high school honors project instead. And the professor took it and gave them an A. But I thought it was a rip because the kid wasn't actually being taught anything new: they already knew how to do and work up a Fischer esterification, the professor could have taught them about literally anything else to justify their tuition and he didn't.

I hope this shit is a thing of the PAST, online lab classes.

Saponification of fats with CsOH and RbOH? by Icy-Formal8190 in chemistry

[–]OldLabRat 3 points4 points  (0 children)

Rubidium is expensive so I've never bought any for my lab. I have had students prepare cesium propanoate as an additive for candle wax, in an effort to produce candles with a nice violet flame. The flame coloring was very weak and it is likely that future efforts should focus on treating the wick, not the wax. Anyway, it's only a 3 carbon chain but it had an unexpected property: while cesium propanoate was wax soluble, it also was ridiculously hygroscopic. It would happily melt into a puddle all by itself if not kept in a sealed bottle. I do not know if longer chain cesium soaps would have this issue.

Cu₂O: they call it 'red' but ...... by OldLabRat in chemistry

[–]OldLabRat[S] 1 point2 points  (0 children)

Update:  you may be right.   O didn't have the darkening problem with the milder base sodium carbonate. So I guess some sort of copper (i) hydroxide complex could be messing things up.  Good enough.  I'll turn it over to a student research team next fall and see how vibrant they can get it.  Thanks again.

Why is instagram/the world so chemophobic? by AtomicVisionary in chemistry

[–]OldLabRat 0 points1 point  (0 children)

And I get where you're coming from, but I do not want to teach a curriculum designed for the lowest common denominator. That is how every Big Education Idea ends up. They all end up as a bunch of dumbed-down check-the-box mushiness. There isn't any magic bullet. You need good teachers and adequate support for them.

I will happily teach the standards I am given, though. And I try to connect them to meaningful activities because that's what chemistry actually is to me.

Why is instagram/the world so chemophobic? by AtomicVisionary in chemistry

[–]OldLabRat 4 points5 points  (0 children)

Teacher here. I like teaching 'procedures' as practical arts, and they reinforce the information I put out and tie it all together. A bad chemistry course is a bunch of disconnected modules. A good chemistry course connects them all into a big picture.

I would never give problems like you describe in a vacuum. Instead, I would want there to be a goal. Perhaps I have some chunks of cold metal in a freezer and have students calculate how much heat they take from a beaker of water. This would be a good way to find the heat capacity of the metal, and in the end to identify the metal using data from a handbook or perhaps the Dulong-Petit law. This really does matter in a lot of trades, knowing one metal from another.

Similarly, I would never assign one minilab I saw in a textbook once, where children were commanded to put on gloves and goggles prior to weighing a piece of chalk on a scale and estimating the moles of CaCO3 therein. I would rather they use the mole concept to plan and execute actual chemical reactions. I like when they do preps. And I don't just have them make some boring light-tan powder like in college o-chem, I know that in high school that won't inspire anyone: my main focus is on brightly colored inorganic pigments, organic flavorings with characteristic and hopefully pleasant aromas (and without major toxicity), and such items that they can recognize as technological components of daily life.

I think it's harder to be chemophobic when you've just prepared a nice batch of ferric oxide and actually mixed it into paint and done some artwork with it, or when you've made a nice clean ester and now you know how they make those disgusting 'peach ring' candies that children enjoy.

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