In order to make honey mustard, I mix honey and mustard. But the resulting mixture is less viscous then both honey and mustard. How does mixing two viscous substances give a less viscous one?
In its open-chain form, glucose possesses an aldehyde group; however, glucose does not test positive with 2,4-dinitrophenylhydrazine (which typically forms a yellow/orange/red precipitate with carbonyl compounds).
Why is this so? Is this a reflection of the cyclic hemiacetal form (where the alde...
@M.A.R. I wish I taught. I had students in the previous lab for as long as two weeks apiece but then they either were reassigned or their short stay was over.
Life is … well, I’m looking for a job while my former boss apparantly had an open favour with another professor at the group, so I’m synthesising OLED materials. Pretty boring syntheses but at least they work.
I read somewhere that the hybridization arguments for Gen. Chem are post hoc. Chemists rationalize geometry with hybridization and we apply it the opposite way
The molecular structure is determined by many factors: Attraction and repulsion, covalent and ionic and non-covalent interactions. Orbitals can be used as a model to predict an optimal structure (global minimum) or a intermediate (or conformer, etc.). But how these orbitals look like, is nothing we really know.
@Martin-マーチン OK, good reminder. So out of the different models, whichever predicts the reaction the best is more favorable, right? So is hybridization better or worse than the other, competing models or are there inconsistencies for all of them?
TBH, I'm not entirely sure what the competing models comprise of, really.
Essentially there are two models: Valence Bond Theory (uses hybridisation) and Molecular Orbital theory (doesn't use hybridisation). These are the popular ones, and they do a rather good job at explaining and predicting things.
When they are done in a way that the solutions are complete, then both models produce the same solution.
@Martin-マーチン What I'm trying to understand is, on what basis do criticisms become valid? Say, they say d-orbital involvement is SF6 to computed to be less than what the hybridized models suggest. Does this have consequences in, for instance, bond length, or were later calculations simply inconsistent with d expansion?
Unfortunately, hybridisation often gets taught as a complete theory with the ability to predict things. That is wrong. Also often this is called Valence Bond theory, but it is not. In organic chemistry some people use a weird hybrid of the two theories, kind of like cherry picking. In a simplified way this might work, often enough it shouldn't because it works due to error cancellation and stuff...
@M.A.R. the results were inconsistent with the expectation
The other one about transition complexes makes more sense since it's a shaky argument of assuming excitation to a higher energy d-orbital works (or are they the same argument?) but the rebuttal for sp3d2 has simply been "No, doesn't work"
Is this the part where I throw my hands in the air with a "Oh my God, quantum chem is even WORSE than organochem"? :P
Oh well, the outside world can be tricky. But so can the inside world. And not only with learning you have to convince yourself to do it. Usually though, learning is a more fun activity...
Well, I've got to go now. I still have to do some things... I'm sure I'll see you next time around...
By accident I found out that on this site the privilge reduced adds at 200 reputation does not exist according to the help page. Is there a reason for this?
@Jan Heh, part of the neighborhood has stray-ish but pretty tame dogs and cats. It's fun when you suddenly see a kitty run so silently and fast in front of you and turn around and see it pissed off a dog
The dogs always bow and go away when they see a hoomin