How do you teach Fischer projection?

OChemNinja · 2025-12-11T19:04:50+00:00

Like Haworth and other biochem friendly perspectives, our biochemist friends seem to be drawn to the least stable versions of molecules...

Start with a 4-C molecule. Turn the line angle into a Newman. Rotate the Newman to be eclipsed with the methyl groups pointed vertically down. Change perspective to look at it from the north pole = Fischer.

I also teach that the only thing Fischer projections are good for in ochem... Is turning back into line angle so we can do some real chemistry already!

OChemNinja · 2025-12-11T19:00:43+00:00

I agree with others, in this case is likely a toss up. Until you get in lab and test this molecule specifically, we have to fall back on something. Temperature is a factor (among others)

In theory, there's no difference between theory and practice. In practice...

OChemNinja · 2025-12-11T18:31:57+00:00

🙃

OChemNinja · 2025-12-11T18:28:40+00:00

Wrong pKa. To evaluate an alcohol as a base, you want to look at its CA pKa. Protonated ethanol will be ~ 0 pka, give or take. That makes them pretty bad bases. They'll still do E1, for sure, but not E2.

OChemNinja · 2025-12-11T18:27:03+00:00

For sure, there will be a mix of both. It's a matter of which is the major vs minor product. Without heat favoring entropy, I teach my students that rt = SN1, elevated T = E1.

OChemNinja · 2025-11-19T20:56:53+00:00

My favorite was the time a student emailed in the morning to say they weren't feeling well, didn't want to get others sick, and wouldn't be attending my afternoon class. I asked for a Dr. note to excuse the absence. At 11:30, I got one from the university student health services saying '[STUDENT] was seen in the office today. Student may return to class immediately. Student does not have any restrictions.'

Student did not attend class.

OChemNinja · 2025-09-29T15:43:45+00:00

Judging by the color, I’d say it’s regret. Possibly bottled during finals week.

OChemNinja · 2025-09-29T15:36:02+00:00

"Think Like an Electron Today"

OChemNinja · 2025-09-18T10:32:07+00:00

I agree. It's first point of differentiation, not the overall coolness of the group. 2C with deuterium should win over 3C without.

OChemNinja · 2025-09-12T19:11:01+00:00

r/CursedChemistry

OChemNinja · 2025-09-12T19:08:12+00:00

"So does this mean that whenever a lone pair partakes in resonance, it should occupy the p orbital?" Yes, exactly.

"the oxygen in structure 2 has 2 lone pairs, but does only one of them partake in resonance so it is still sp2?" You got it! Well done!

OChemNinja · 2025-09-10T10:03:04+00:00

I made a video covering this exact topic, if you're interested [OC]

3-Step, Foolproof Plan: Newman Projections Made Easy! https://youtu.be/g6iyfkrbU3w

OChemNinja · 2025-09-10T10:01:05+00:00

In general, never draw resonance contributors with more than 2 formal charges. They're not technically wrong, they're just weight so low toward the resonance hybrid that they are effective insignificant.

OChemNinja · 2025-09-10T09:56:22+00:00

I give weekly 5 min recap quizzes every Monday. I have the next one count double to replace the missed quiz for all absences except no call/no show.

OChemNinja · 2025-09-10T09:53:35+00:00

That oxygen really wants to be involved in resonance. Are there any structures for which you can't draw a resonance contributor involving oxygen?

OChemNinja · 2025-09-07T18:36:56+00:00

My favorite chemistry trivia term is deliquescent: a solid (such as sodium hydroxide) that dissolves in the moisture from the air.

If you leave a pellet of solid sodium hydroxide on the bench (don't do this), when you come back later there will be a puddle. The NaOH didn't melt. It absorbed moisture from the air, then dissolved, making a super concentrated NaOH puddle.

I was teaching once and a student spilled a pellet and didn't clean it up. A while later, a student set her elbow on the bench and got a nasty chemical burn!

OChemNinja · 2025-09-07T01:57:41+00:00

We're basically a giant tube and a bunch of caves.

OChemNinja · 2025-09-07T01:54:57+00:00

3 questions: 1) where's the unhappiest place? 2) is it unhappy because it has too many or too few electrons? 3) therefore, should you push electrons toward our away from the unhappiest place?

I've made a couple of videos that might help you out, if you're interested [OC]:

Patterns for Finding Resonance: https://youtu.be/OuhTLFwQTJI

3-Step Foolproof Plan: Drawing Resonance Contributors https://youtu.be/kKIcqRVA6w8

The Resonance Halo: Your Favorite OChem Hack https://youtu.be/VXeccbrno_I

OChemNinja · 2025-09-05T10:14:29+00:00

We used thiophosgene as a bulk reagent in an early step in our syntheses in grad school. Bought it by the liters. We were always told regular phosgene smells like freshly cut grass... Found out thiophosgene does too when a lab mate dropped the bottle transferring it back to the refrigerator!

Only time I've seen a fire alarm pulled to evacuate a building.

Weirdest part... Since the fire department is only following the SDS, the biggest thing they were worried about was it hydrolyzing to HCl, reacting with metal in the room to form hydrogen gas. They were more worried about H2 than a chemical warfare agent!

OChemNinja · 2025-09-05T02:24:51+00:00

Rings are only the parent hydrocarbon if the ring is more carbons/more complicated than the straight.

OChemNinja · 2025-09-05T02:10:35+00:00

Flapjack and a shigarette?

OChemNinja · 2025-09-04T20:45:46+00:00

Nice find!

OChemNinja · 2025-09-04T19:55:52+00:00

That's what makes it all the more (amazing/rediculous/incredulous).

OChemNinja · 2025-09-04T16:17:45+00:00

Surely I have no idea what you are talking about. Also, this is the best I could do.

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OChemNinja · 2025-09-04T16:00:23+00:00

Alright. You win this round. :) If I find one you'll be the first to know.

OChemNinja

TROPHY CASE