mississippichem

I was thinking about "“Healthy citizens are the greatest asset any country can have”"

 

Or was it the one about being able to count on Americans to do the right thing?

Those are both applicable but I was hinting at

The best argument against democracy is a five-minute conversation with the average voter.

People cast their ballot at the voting booth out passion or fervor for issues that don't matter or don't exist.

For anyone who watches South Park: (American comedy cartoon, probably not funny to people not living in the US)

I get the "Theytookerjubs!" vibe from the beligerent anti-Obama crowd sometimes.

Point out anything you wish, but I see the liberal left as wanting to change everything for which our constitution stands. Hope and Change, what a joke.

No, the joke is baseless assertions stated as fact. From the evidence presented, I must conclude that only believe these things because you want to .

There is a relevant Winston Churchill quote here...I think most of you already know it.

I have read said lament before. Some powerful ideas those are. I think every math teacher should be required to read and summarize it before being allowed to teach.

+1

chilled_fluorine,

 

Firstly, if you want to debate mod note, do so via the report feature or PM.

 

Secondly, you've had two experienced chemists tell you that this thread presents no obvious danger to a passer by. We are mindful of people's safety here and you can rest assured that if anything in this thread did present a serious risk to inexperienced readers, we'd deal with it.

I think it is noteworthy that discussing, in theory, what might result from a dangerous procedure is very different from advocating that someone conduct said procedure. Also it's very different than giving explicit technical/logistical details on how to carry out that dangerous procedure.

Have you considered dynamic light scattering instead?

EDIT: spelling

it can be real in the near future i am currently working on it

I assume you have an x-ray crystal structure for it if you've isolated it...

I guess it exists because someone has measured the IR absorption spectrum of the stuff.

What I don't believe is that it's stable.

Any idea what the proposed structure is? Everything I'm trying to come with on my end looks crazy.

I would like a link to the work as well.

Then I shall admit that I'm wrong, and benzene was a bad choice for an example.

Thank you for your polite concession.

I've enjoyed the discussion thoroughly and will be glad to continue if you have further questions or comments.

You do realize, do you not, that if you could supply enough energy to make one of these states, and it lasted even for

a microsecond, that the state could be said to 'exist', in a physical sense, and all of this elaborate explanation would be

moot.

 

I know that I'm being very stubborn, and that this bothers you no end, but it's not for the purpose of bothering you,

it's the principle of the thing, in this case a physical principal, that may apply throughout Nature.

Nope. As I said before, the electronic structure of benzene is such that no excited state will yield a Kekule structure!

Do the Huckel calculation for the groundstate and it will be obvious. It's not a question of what might happen, we already know. The book is closed on aromaticity.

I try to imitate my dog's philosophy on life:

Eat, be happy, don't question it. Simply exist. Chew computer cables if you get bored.

That if there exists two states of the same energy that in principle can change among themselves in time,

and are quantum mechanically distinguishable, there will be two states that in reality are superpositions of those

states and differ in energy. And that forms the basis or Resonance Bonding. And so far nothing said falsifies

the original premise.

 

It doesn't matter if the time-changing states last a millionth of a millionth of a second, if they exist in principal

the effect occurs.

Saying it again doesn't make it so. Assuming your original premise is true (it's not). How are the two resonance forms of benzene distinguishable?

Sure it provides insight. It shows you when to apply the concept, when it will occur and when it will not. And it

helps other people have ( not yourself ) a way of seeing and understanding it.

I don't see how. It explains a known phenomenon with a process that is known not to occur. There is already a different explanation available that is in line with the experimental evidence. The two resonance forms of benzene do not convert between each other. Any explanation that claims they do is of no use IMO.

And it may not be unphysical at all! It may well be possible to excite a benzene molecule into one or the other states.

So you are saying there are cyclohexatriene like excited states of benzene? Surely not. The first excited state of benzene promotes a pi electron into a pi-star orbital. That's not a sigma orbital . You'll never be able to get the symmetry of a cyclohexatriene. I can't see how any conceivable excited state of benzene would give you a C_3v structure.

If the switching between resonance forms is unphysical, why consider it at all? It provides no computational insight and no useful intuition.

The Benzene Molecule

This is a description of the 'other kind of bonding' that occurs in Nature, resonance bonding. We all know about Coulomb bonding, the type that is determined by electric charge, and which holds the electrons to the nucleus.

 

Resonance bonding ( RB ) is purely quantum mechanical in its working, it has no classical equivalent. It's very important in Chemistry, but it's important in another way too, for it holds the nucleons together in an atomic nucleus.

 

The requirements for RB to occur are simple and easily met in Nature, so it is a frequent occurence. It needs:

 

Two states with nearly the same energy, which can change back and forth with time.

The two states have to be distinguishable,

in the quantum mechanical sense of distinguishabilty.

Benzene has two states with the same energy, which are distinguishable in the QM sense by being mirror images of each other. Benzene has six Hydrogen and six Carbon atoms, and it has six electronic bonds between the carbon atoms, three double and three single bonds. The single and double bonds can switch between themselves. If we make a 'naive' calculation of the binding energy of benzene we will get a certain value, let's call it the 'zero' energy because it has zero free energy by out calculation.

 

Now one thing about RB is that it doesn't care about the mechanism of how the states swap back and forth, it only cares about the rate, so it is a general mechanism, and only needs the two requirments.

Now the rules of QM say that if there are two states that change back and forth with time, there have to be two superpositions of those states which don't change with time, and which are superpositions of the time states, but differ in energy. So our zero of energy gets split into two new levels, by our non-naive new calculation, one above and one below our original zero. The difference in energy is equivalent to a photon well into the ultraviolet range, so that benzene absorbs strongly in UV.

 

We can 'tune' the benzene molecule into the visible range by substituting heavier molecules like Chlorine for some of the Hydrogen. If we attach ionizing radicals like amines and acidics to opposite ends of the benzene, it will have a large electric dipole moment, and be a strong absorber and reflector of visible light, and that is how most dyes are made.

 

If we place two benzene molecules close together they can also have some resonance bonding between them, so that benzene melts and vaporizes tht higher temperatures then other similar sized molecules.

 

We can make molecules with four or eight carbon atoms that are otherwise similar to benzene, but they are not mirror images of each other. They do not exhibit strong bonding.

The statements I bolded are problematic. It is known that the resonance forms of benzene do not convert back and forth in time, by definition of a resonance hybrid. Also, there is no spectroscopic evidence of two degenerate electronic states switching back and forth. All six hydrogen atom protons are equivalent on the NMR timescale meaning that they all are de-shielded equally. You can also use reactivity arguments to show that this is not true.

If you want to approximate the energy gap between the first excited state and the ground state of benzene (what would explain its UV absorbance) you need to solve a Schroedinger equation for a particle on a ring which has energy eigenstates [math] \frac{n^{2}\hbar ^{2}}{2mr^{2}} [/math]. That will give you an idea of where the first excited state lies. Subtract out the ground state energy and you'll get a decent number for the maximum absorbance wavelength for the [math] \pi \rightarrow \pi ^{*} [/math] transition in benzene. Also, remember that you can't neglect the sigma bonding electrons here either because they occupy the lowest states of the ring so the transition is not from the first to the second state on the hypothetical ring.

If you want a good calculation you'll need to setup a Slater determinant of the basis functions and feed that through the Hartree-Fock equation. For a decent calculation that is easier than the Hatree-Fock, you can evoke the variational theorem and use Huckel theory to diagonalize an easy Hamiltonian where all the non-adjacent overlap integrals are taken to be zero (a pretty good approximation...sometimes).

I think you may be mixing up the concept of degeneracy with aromaticity. The ground state for pi electrons in benzene is doubly degenerate, which only by coincidence corresponds to the two degenerate resonance forms that constitute the resonance hybrid. The excited states have 2n-fold degeneracy so this analogy is useless in the excited states. You can't mix valence bond theory with molecular orbital theory!

my theory can explain these http://www.ibtimes.co.uk/articles/360217/20120706/unusual-binary-stars-close-orbit-discovered.htm

Let's see it! An experiment, a mathematical derivation...anything would be an improvement on the evidence you've presented thus far.

No familiar...but I know and understand them...why?

As is mentioned above, observable quantities in QM come by allowing operators (you can write them as matricies, just like good ole' linear transformations) to act on states represented by vectors. There is an inherent uncertainty between conjugate pairs of observables because you have to pick the order in which the matricies operate on the vector, and it matters.

Google "commutators in quantum mechanics" for a better and more rigorous explanation.

It is obviously seven minutes of terror for the humans watching remotely from mission control in Pasadena, California. Entry, descent, and landing is a hand wringing time. Not quite so obviously, it is also seven minutes of terror for the humans who designed and built the Mars Science Laboratory entry, descent, and landing systems. Those systems have to be fully autonomous.

It's not seven minutes of terror for the hypothetical Martians who will observe a terrifying Earth craft whizzing down from orbit to drop off a robot?

dapifo,

Are you familiar with matrix multiplication?

the faradian is a couple....the faradian is a couple....the faradian is a couple

You're not really making any sense friend. Can you try to explain your ideas using standard science terminology? Science words have very precise and very specific meanings, failure to follow this convention results in mass forum hysteria and people not understanding your points.

Here's the thing about the [math]10^{40,000}[/math] number: apply the calculation to a Miller-Urey style experiment. The calculated odds of the experiment working should be appallingly low, and yet it worked — complex molecules formed. This, one must conclude that the calculation is pure crap. The outcomes are not due to random chance. The model is falsified.

As you noted before, the rules of chemistry are no where near random.

It should be insightful to point out that organic chemistry would be impossible if every reaction yielded a complete random mixture of every possible bond beaking broken and or made.

The calculation is even more crappy if you consider that different molecules have different half-lives and different energetic barriers to decomposition/subsequent reaction.

You can throw a hundred reagents in a flask and, in theory (perhaps not in practice) predict all the products and their relative abundances. NOT random at all!

I would simply give humans all the deepest secrets of physics, sit back and watch what fascinating contraptions they build.

My holy book would read more like a textbook.

The Book of Mississippichem 13:7: thou shalt conserve thy energy, and it shall not be created nor destroyed lest I smite thee...and the inner product shall be unto the integral as the integral is unto the inner product; and the people rejoiced as their polynomials had been normed in his holy metric.

I'm confused - I have a hobby that prompts people to endlessly remind me that perpetual motion is impossible. And yet everything I see and know states that motion is the only constant. Umm??? So confused. Edification please.

 

Thanks in advance to the forum.

 

I am positively delighted to have found this forum. This is better than s'mores (though nothing beats a campfire for pure enjoyment).

Is there anything specific about perpetual motion, or the impossibility of, that you would like to know?

You can look at this from many angles. There are thermodynamic and mechanical arguments to name two.

Tom's free physics advice:

Over 20,000 served

Thanks for your unrelenting efforts. Maybe after you retire from SFN we can get Brian Cox to give a speech in your honor.

If you zoom the image can read in the back "Made in China"

These days even the Martians are outsourcing labor to China!