Question

Weekend Challenge Question (Organic Chemistry)

Answer 1

The reaction below is one of the many examples of a "Mannich Reaction". It is a reaction that often occurs in nature and is used to synthesize alkaloids (natural products with a basic nitrogen on the molecule). Suggest a plausible mechanism for this reaction using curved arrow notation.

Answer 2

so i got stuck, i don't even know if this is close to right, but i'm trying to get as much practice as i can as i got and orgo test coming up this week. Don't tell me there answer! maybe just a hint? haha

Answer 3

Where exactly is it that you're stuck? Your 1-phenylethanone and 1-phenylmethanal initial steps are correct. I' will suggest that you leave the 1-methylmethanal product as an imine ion. Due to the instability of the ion itself, it's what is going to drive the reaction between your two products leading to your final product. Otherwise, you're on the right track!

Just a suggestion, I'm not sure if your professors were as strict as mine were with curved arrow notation, but you might want to make sure you're using the right curved arrow notation in your mechanisms. From experience, I can tell you that it's very painful seeing a professor/ T.A. either 1. not grade the problem at all or 2. take off 4+ points for incorrect use of curved arrow. That way, the grader knows exactly what you're thinking and they know that you know what's actually happening.

Answer 4

okay cool, i'ma give it a try. I noticed i pushed arrows from the positive to the negative charge and i know it's supposed to be the other way around (negative attacks positive). Other than that (and messiness), is there anything in specific i should watch out when drawing the arrows?

Answer 5

okay, thanks dude !

Answer 6

This was a tough problem. Since you're almost done, I think you're prepared. Wish you the best of luck on your exam!

Answer 7

dope. thanks man!

Answer 8

Alright, here's my shot at it, I kind of hoped that 21.55 as a pKa was low enough for the hydrogen on acetophenone to be plucked off by the catalyst and pray to saint Le Chatlier for his principle to pull me through on this one.

Answer 9

What a unique approach. But catalysts are usually there to make a reaction favorable under unfavorable conditions, so I don't \(think\) that Le'Chatliers principle is needed for this for that reason. But, I'm not a PhD student nor a grad student, yet. So what I said is only a educated guess and I could be wrong :)

How I approached it was that you have two things that can abstract the acetophenone hydrogen: water or your methylamine. pKa of water is 15.7 and pKa of methylamine: 10.6

Answer 10

I guess what I was thinking was "acid catalyzed" rather than just some metal, honestly it's been about a year since I last had an organic chemistry class so I'm surprised I made it as far as I did.

Organic chemistry would be nice if they made a wolfram alpha-esque program for it where you could choose parts of a reaction and get it to fill in the rest for you and have a handy "show steps" button.

Answer 11

That would make the class a lot easier for a lot of students probably. There's a website that has it for the common mechanisms you learn in your year of organic chemistry and a few more advance mechanisms that aren't covered but are also important in medicine and other areas of chemistry: http://www.monomerchem.com/display4.html

There's also the chemical synthesis database which has hundreds of synthesis and mechanisms which are also used often in real life applications along with their boiling point and melting points (more of a reference site): http://www.chemsynthesis.com/

And the final one I have used before was: http://aceorganic.pearsoncmg.com/epoch-plugin/public/welcome.html
it's the closest thing there is to a wolframalpha-type calculator for organic chemistry. I hope you find them useful.

Answer 12

Thanks, I just book marked them and am browsing through them. I lead study groups in organic chemistry I and II during the semester at the university I go to, so this is probably a great resource for me to review and to refer them to. If you know anything more that you feel would be good to students, feel free to send them my way!

Answer 13

Ah, yes. I used the last one to draw structures when I did final exam practice problems when I was T.A. for organic, as well as took a few practice problems from here: http://ochem.jsd.claremont.edu/practice.htm

If you're a chemistry or biochemistry (chemistry emphasis, NOT biology biochemistry), then let me know. I have tons of bookmarked sites that I used for inorganic as well, such as: http://symmetry.otterbein.edu/gallery/index.html

Answer 14

Wow that might be perfect, I'm signed up to take Inorganic this fall. I've taken Physical Chemistry I and II along with several years of calculus, linear algebra, and self taught some diff eq, so if possible I'd like any kind of in-depth theory/math based resource you have to help me bring together a better understanding of quantum mechanics before the end of the year.

My goals right now include understanding Bell's theorem and really understanding how Heisenberg came up with matrices and how eigenvalues connect to solving the Schrodinger equation since that's kind of fuzzy to me. I'll be taking Diff Eq this semester, so that should help a little I guess. Then there's Pauli spin matrices, the actual matrix derivation of the uncertainty principle, and several other random things I'd like to understand on a deeper level. You seem to be a few steps ahead of me, but I'm a Chemistry/Math double major right now. If you know any good places to find explanations of anything, I'm just interested in understanding how all these weird and yet real things work haha.

Answer 15

I have a quantum chemistry book that talks about everything you're talking about, but it's pretty advance. Too advance for me. I could barely understand anything. The math and physics was heavy!
I could share it with you if you're still interested. I was molecular synthesis, I suggest taking partial differential equations (if you can). It really helps in chemical statistics (which is by far the most intense chem course i took as an undergrad).

As for inorganic, it really depends on your professor. Whether they decide to focus on more theory and quantum aspect, or they can focus more on the kinetics and more concepts.
Hopefully you have kinetics and concepts because I was exposed to theory & quantum and it was TEDIOUS. No math, but the problems took too long to fully complete.
Anyways, if you have questions, feel free to message me if you're still interested in the book(s). I can definitely share them with you no problem. Maybe via dropbox if you have an account.