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11:49 AM
Congratulations to us all - i actually found a wifi connection here in Higashi-Hiroshima, so I did not miss it @LordStryker... I am looking forward to what happens next ;)
 
 
4 hours later…
3:59 PM
Is there any "easy" way to learn MO theory and the basics of molecular symmetry so that I can present general and organic chemistry at a more rigorous level?
The way it is presented now is a bit appalling ...
 
@Dissenter, I like Fleming's book, Molecular Orbitals and Organic Chemical Reactions for a (mostly qualitative) text accessible without a rigorous background in quantum chem., group theory, etc.
 
Thanks Greg E.
On the other hand do you think it's useful to try to introduce these concepts at an introductory level?
Right now the way everything is presented is fluffy and even my prof admits he's forgot everything there is to know about more advanced chem
As he says he's just trying to get us to do orgo in an "emotional" way
 
Well, the utility of a qualitative understanding is obviously much lower than understanding quantum chem at a fundamental level, but it's still helpful
 
This is literally the extent of his TA's theoretical knowledge:
"Well, I don't know if that reaction will occur, because it'll be fucking with benzene, and benzene is very stable"
 
Well, I think there's value to learning about MO on a qualitative level, and the time investment and difficulty of doing so isn't huge.
Learning rigorous quantum chem is a huge undertaking. I'm working through three different textbooks on it right now, and I've got a few more on my list, and I still don't think I have more than a rudimentary functional comprehension of it.
 
4:10 PM
Great to hear that the time investment and difficulty isn't huge
 
Yeah, by comparison to really learning fundamental quantum chem, it's tiny.
 
My favorite is when the prof starts saying that the parallel pi orbitals in say pyridine are like the buns of a hamburger
And that the lone pair on the N in pyridine is orthrogonal to the pi orbitals, and so it is like a "frog's tongue"
and readily snatches protons
All the reasoning in his damn class is circular because that's the best we can do myself included
 
I'm inclined to say learning more about physical chem is probably a better use of time, however, than qualitative MO.
Particularly if what you're looking for is justifications based on first principals.
And working through a decent textbook on pchem is really a necessary prerequisite for much advanced chemistry, and much easier than tackling quantum chem on a deep level.
I like McQuarrie's textbook, personally. Fleming also has a good pchem book.
Actually, scratch that last bit, it's not Fleming I'm thinking of, it's Atkins.
 
Ohh okay
I just don't like math
^The problem with 99% of people who take chem nowadays
 
Yeah, unfortunately.
 
4:18 PM
"Never do electrophilic aromatic substitution with fluorine or iodine, because you'll die."
 
Well, I think the standard way to install those on an aromatic is through a diazonium salt. So, yeah, you might.
 
"With one you die, and with the other you die waiting."
 
Ha, sounds about right.
 
Wait why diazonium salt?
We just learned about metal catalysts
I.e. Br2 substitution with FeBr3
 
Well, N2 is such a strong leaving group that it can be displaced by copper(I) salts like CuI.
And fluorines can be installed by preparing a diazonium tetrafluoroborate (BF4-) salt and allowing it to decompose thermally.
 
4:24 PM
Oh okay
Makes sense
You know my bio professor took bond breaking as exothermic
 
Ugh.
 
ATP + H2O -> ADP + Inorganic phosphate group + energy
Therefore, breaking a phosphate/phosphate bond in ATP is exothermic
What he really meant to say is that the net result of hydrolysis is exothermic
 
Yes, I would hope that was his intent.
 
It wasn't
He put that exact equation on the board and said hey, exothermic bond breaking!
So I got that in class clicker question wrong
 
That's unfortunate. You have my sympathies.
 
4:29 PM
I'm at the horrible stage at which I know, to a good extent, what things that my profs say are bullshit, but I have barely any recourse since I don't have the time (or intelligence) to learn more
Right now I should really be studying orgo and trying to get an "emotional" handle on it
 
hiya
 
Well, time is definitely a scarce resource. I'm not aware of anyone, short of a very few authentic geniuses, who did not struggle for literally years to understand quantum chem deeply. That's the experience of every grad student and professor I've spoken to, anyway.
@Omen, hello.
 
ima just exploring the sites
 
@GregE. In all fairness the qualitative models developed thus far are still pretty powerful
Perhaps it'll be useful too to stress that models are models and no model is perfect
 
@Dissenter, yeah, no question.
 
4:40 PM
I hate it when one of my profs say to draw a lewis structure; that's the "best thing" you can do
Ehh not really
It's one thing to use a model; it's another to ignore all of its shortcomings
 
Yeah. Most of the time, in practice, I'm totally pragmatic about it. Most of the time, I'll use VB theory because it's usually simpler and it usually allows for reasonably accurate predictions. If it fails, I'll try to consider things via qualitative MO theory.
 
My favorite is when he criticizes other professors for using hypothetical compounds such as "compound A" or "B" when he himself uses imaginary compounds such as IBrF2
Ternary interhalogen ftw!
 
Yeah, that does seem to evince a lack of self-awareness.
 
Can we explain why IBrF2 might not exist or be exceedinlgy unstable through qualitative MO theory?
 
I might be wrong, but I think it's energetically unstable by comparison to the diatomics it can decompose into.
I suppose you could explain that via poor bonding orbital overlap due to large differences in size and energy.
But, that's a totally off-the-cuff response, I'd have to look at some thermodynamic data and maybe orbital energies to be more certain.
 
4:55 PM
Also are the lone pairs in water equivalent?
 
okay, see you all later
 
I don't think they are. If I remember correctly, they're not in degenerate MOs.
 
That's what I remember too
So much to learn!
We're all in varying states of ignorance
Some worse than others
I feel like truth is like the story of the blind men and the elephant
Each felt a different part and came to a different conclusion
 
Yeah, but hopefully they're not deaf and/or mute. Then they can discuss their observations and possibly arrive at a consensus.
 
Or they might choose to be deaf
^Big problem with some people
 

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