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Author: Subject: Effects of magnetic fields on radical reactions
killswitch
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[*] posted on 7-3-2012 at 10:46
Effects of magnetic fields on radical reactions


If magnetic fields are chiral, and radical reactions proceed via intermediates that possess unpaired electrons, could a strong magnetic field (1 T or more) produce a bias toward one chirality in a reaction that would otherwise produce a racemic mixture? The unpaired electrons would possess a magnetic moment, and in a solenoid, the intermediates would all be spinning counterclockwise (with the field pointing into the paper). This would disturb the otherwise random thermodynamic arrangement of the molecules.

Has this been done? If not, could it be done in principle?
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neptunium
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[*] posted on 7-3-2012 at 11:13


i guess a strong enough field would have an effect on any ionic reaction . but by following the fields line the ion would inevitably encounter other ions and combine to neutrality wich would then fall off the field and move about at random.
maybe a super strong field could have a sizable effect at macroscopic scale but what would be the benefit of such a quest?




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watson.fawkes
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[*] posted on 7-3-2012 at 13:06


Quote: Originally posted by killswitch  
If magnetic fields are chiral, [...]
Are magnetic fields chiral?
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neptunium
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[*] posted on 7-3-2012 at 13:32


not that i know of....its a chemistry term i am not aware of its use in the physics of magnetic fields

[Edited on 7-3-2012 by neptunium]




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killswitch
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[*] posted on 7-3-2012 at 16:02


Quote: Originally posted by watson.fawkes  
Quote: Originally posted by killswitch  
If magnetic fields are chiral, [...]
Are magnetic fields chiral?


They have a handedness, which is why they teach the right-hand rule in physics classes.
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neptunium
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[*] posted on 7-3-2012 at 17:52


yes sure it has to do with the orientation of the field....nothing about the molecules in this particular case



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Endimion17
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[*] posted on 7-3-2012 at 19:31


Magnetic fields aren't chiral, but they do have a slight effect on some molecules. Check this out. They used specific complex compounds and extremely strong fields.

Extreme fields on the order of neutron star fields (hundreds of thousands, millions or even tens of billions of teslas for magnetars), atoms look something like this, getting narrower as the field intensifies. I wonder what could such atoms do, chemically, if they could do anything at all.




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watson.fawkes
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[*] posted on 7-3-2012 at 20:15


Quote: Originally posted by killswitch  
They have a handedness, which is why they teach the right-hand rule in physics classes.
Handedness is a sign convention, not chirality. It's how you define your coordinate system; nothing more.

The electromagnetic field is not chiral. It's just not in the mathematics defining the classical electromagnetic field. There are chiral states of the field, most easily right- vs. left-circularly polarized light. But there's no intrinsic chirality in electromagnetism as such.

What is chiral is the weak force. The article Endimion17 posted is rather interesting exactly because they experimenters tricked the weak force to show up in a molecular context. This isn't utterly surprising, as the unification called "electroweak" was locked down in the 1980's with the isolation of W and Z bosons. It's interesting, though, that they managed to do it.
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neptunium
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[*] posted on 7-3-2012 at 21:14


the science of magnetic fields in and arround a pulsar or a magnetar is absolutley fascinating but way out of reach for any lab on earth!

interesting ideas to think about though!




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killswitch
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[*] posted on 7-3-2012 at 21:34


Quote: Originally posted by watson.fawkes  
Quote: Originally posted by killswitch  
They have a handedness, which is why they teach the right-hand rule in physics classes.
Handedness is a sign convention, not chirality. It's how you define your coordinate system; nothing more.

The electromagnetic field is not chiral. It's just not in the mathematics defining the classical electromagnetic field. There are chiral states of the field, most easily right- vs. left-circularly polarized light. But there's no intrinsic chirality in electromagnetism as such.

What is chiral is the weak force. The article Endimion17 posted is rather interesting exactly because they experimenters tricked the weak force to show up in a molecular context. This isn't utterly surprising, as the unification called "electroweak" was locked down in the 1980's with the isolation of W and Z bosons. It's interesting, though, that they managed to do it.


Well, from what I have been led to understand, a free radical with an unpaired electron would pick up a revolution about the axis of the field lines. In a DC solenoid or permanent magnet, all these radicals acquire a revolution in the same direction. I was twiddling images in my head, and it seemed that certain arrangements of molecules, particularly where the unpaired electron is on a chirality center, would produce the R or S form preferentially. If I had good modeling software, I could show you what I (think) I mean.

This may not work for simple processes, though for more complex ones wherein multiple intermediates are produced concurrently it may present a greater impact.

Then again it's late and I'm not thinking clearly. Goodnight.
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[*] posted on 8-3-2012 at 04:39


Quote: Originally posted by neptunium  
the science of magnetic fields in and arround a pulsar or a magnetar is absolutley fascinating but way out of reach for any lab on earth!

interesting ideas to think about though!


That's probably forever out of our reach, as such fields are so strong that would rip apart any matter at hundreds, thousands or more meters because of the diamagnetism (at least that).

It would be interesting to model such reactions on a computer, though. Needle-like atoms would have great troubles achieving regular covalent bonds, if that was possible at all. Ionic bonding might be easier to achieve, though the force wouldn't be the same in all directions, but relatively close to magnetars, I doubt that any conventional matter could survive. Only degenerate matter.

What stikes me is the fact that vacuum itself becomes birefringent at such high intensities of magnetic fields. For all this reasons it's quite possible there isn't a single correct representation of a neutron star. Scary magnetic field, scary gravitational field, that alone is enough to make such "star" look a lot different than simple models show.




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mrjeffy321
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[*] posted on 8-3-2012 at 09:39


Absolutely magnetic fields can effect chemical reactions, especially radical pair reactions where you have unpaired spins that must do something a certain way (be in a certain state) for the reaction to work. The spins will evolve in time in different ways in different magnetic fields. Here is an interesting example where these researchers could effectively measure the highly inhomogeneous magnetic field around an iron nano-circle using the fluorescence (or lack thereof) of a reaction:
http://pubs.acs.org/doi/abs/10.1021/nl202950h
The fluorescence is enhanced / suppressed at different locations, with differed field strengths.
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