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zouden said:
I don't feel that my knowledge is lacking.

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zouden said:
Making biochemistry students learn quantum mechanics would be a waste of everyone's time.

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Zanthius said:

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johnm214 said:
What exactly are you referring to?

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Well, electron configurations and the shapes of electron orbitals are derived from quantum mechanics, which again is related to orbital hybridization and molecular geometry. Why do you think aromatic compounds are much more stable than other conjugated systems, and why must there must be 4n + 2 π-electrons in aromatic compounds? Can you explain this to me without involving quantum mechanics?

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Shapes of electron orbitals:  Doesn't really matter.  We know what they are, and that's good enough


Shapes of hybrid orbitals:  Easily explained as a function of the momentum of the electron, and the fact that electron are attracted to the nucleus yet repelled by each other.  A qualitative understanding is all that's required.  Look at all the hybrids- they are all as close to the nucleus as possible while as far apart from the other orbitals as possible, both attracted to the nuclues and repelled byt he other areas of electron density.  The  sp3 is clearly in a tetrahedral shape as that's the arrangement that gets the four orbitals as far away from each other as possible.  Simple.

stability of aromatics compared to other conjugated systems-  less localization.  Having charge in one spot is higher energy than having charge spread out in many spots- we allready know electrons repel each other.  Additionally, there is less concentrated charge with which other species may interact, and so the reactivity is lower.  Conjugated systems have much higher concentrations of charge than similar aromatic systems, they are more reactive because of this.

4n+2 electrons in aromatics: Obvious from understanding bonding. Its like asking why carbon is more stable with 8 electrons in the valence shell.  While you may be able to explain it deeper with quantum, it doesn't matter so far as I can see.  I'm sure there's some phenomena where the reason for this becomes relevant but I'm not aware of it- its always been good enough to know that that period is stable with 8 electrons in the valence shell.




All of these are just logical extensions of experimentally determined principles.  None of these seem to clearly require quantum for sufficient understanding to do chemistry of the usual traditional sort.

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zouden said:
It's just not relevant. Making biochemistry students learn quantum mechanics would be a waste of everyone's time.

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Exactly


How would it help?  Like qubit said, when you get to huge molecules the principles of quantum seem very far away.  Its easy enough to just realize that charges repel like charges to explain the shape of an enzyme

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johnm214 said:
Conjugated systems have much higher concentrations of charge than similar aromatic systems, they are more reactive because of this.

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(Zouden)Yeah but you don't have to know quantum mechanics to understand the citric acid cycle. It wouldn't even help. In an ideal world we'd learn everything of course, but in the real world we have to specialise. I have a degree in biochemistry but I only briefly touched on quantum mechanics in first year. I don't feel that my knowledge is lacking.

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How would it help?  Like qubit said, when you get to huge molecules the principles of quantum seem very far away.  Its easy enough to just realize that charges repel like charges to explain the shape of an enzyme

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Natural selection builds child brains with a tendency to believe whatever
their parents and tribal elders tell them. Such trusting obedience is
valuable for survival: the analogue of steering by the moon for a
moth. But the flip side of trusting obedience is slavish gullibility.
The inevitable by-product is vulnerability to infection by mind
viruses. For excellent reasons related to Darwinian survival, child
brains need to trust parents, and elders whom parents tell them to
trust. An automatic consequence is that the truster has no way of distinguishing
good advice from bad. The child cannot know that 'Don't
paddle in the crocodile-infested Limpopo' is good advice but 'You
must sacrifice a goat at the time of the full moon, otherwise the rains
will fail' is at best a waste of time and goats. Both admonitions sound
equally trustworthy. Both come from a respected source and are
delivered with a solemn earnestness that commands respect and
demands obedience. The same goes for propositions about the world,
about the cosmos, about morality and about human nature. And,
very likely, when the child grows up and has children of her own, she
will naturally pass the whole lot on to her own children - nonsense
as well as sense - using the same infectious gravitas of manner.

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And here are trees and I know their gnarled surface, water and
I feel its taste. These scents of grass and stars at night, certain
evenings when the heart relaxes—how shall I negate this world
whose power and strength I feel? Yet all the knowledge on earth
will give me nothing to assure me that this world is mine. You
describe it to me and you teach me to classify it. You enumerate its
laws and in my thirst for knowledge I admit that they are true. You
take apart its mechanism and my hope increases. At the final stage
you teach me that this wondrous and multicolored universe can be
reduced to the atom and that the atom itself can be reduced to the
electron. All this is good and I wait for you to continue. But you
tell me of an invisible planetary system in which electrons
gravitate around a nucleus. You explain this world to me with an
image. I realize then that you have been reduced to poetry: I shall
never know. Have I the time to become indignant? You have
already changed theories. So that science that was to teach me
everything ends up in a hypothesis, that lucidity founders in
metaphor, that uncertainty is resolved in a work of art. What need
had I of so many efforts? The soft lines of these hills and the hand
of evening on this troubled heart teach me much more. I have
returned to my beginning. I realize that if through science I can
seize phenomena and enumerate them, I cannot, for all that,
apprehend the world. Were I to trace its entire relief with my
finger, I should not know any more. And you give me the choice
between a description that is sure but that teaches me nothing and
hypotheses that claim to teach me but that are not sure.

- Albert Camus

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Zanthius said:

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johnm214 said:
Conjugated systems have much higher concentrations of charge than similar aromatic systems, they are more reactive because of this.

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Well, suppose you have a conjugated ring that doesn't have 4n+2 π-electrons. Does this ring have a higher concentration of charge compared to a conjugated ring with 4n+2 π-electrons?

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johnm214 said:
yes, that's what I just said, right?  If your saying I'm wrong please provide an argument. 

benzene has less localized charge than cycloheptatriene or cyclopentadiene and is therefore less reactive.

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Okay, what about cyclooctatetraene

Does this molecule have a higher concentration of charge compared to benzene?

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C.M. Mann said:
I am sorry but I can't agree with this statement! You don't think physics would help a Chemical Engineer?  Science is myopic, everyone should broaden their understanding of their surroundings.

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zouden said:
Chemical engineers already learn a lot of physics. But there's only so much you can study in 4 years, so it makes sense to focus on certain things, don't you think?

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Zanthius said:

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zouden said:
Chemical engineers already learn a lot of physics. But there's only so much you can study in 4 years, so it makes sense to focus on certain things, don't you think?

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Well, personally I think it has a higher inherent value for individuals to learn broadly, than to specialize too much. Specialization might be good for satisfying the needs of your society, but not necessarily as good for your own understanding.

Also, maybe our society would be better if people tried to optimize themselves, instead of trying optimize our society.

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Yes, I sorta agree with what you're saying, but I don't think things need to change. Students are already presented with a wide range of things they can study; I could have taken a quantum physics class at any point in my biochemistry degree. Full credit is still awarded. But I chose not to because I think physics is boring compared to biology.

That said, I still know more about quantum physics than my colleagues, because I am still interested in it. I'd much prefer to discuss Heisenberg than last night's football game.

Anyway, my point is that I don't think quantum physics should be a necessary part of a biochemistry degree, but students should be (and are) free to choose it.