LF l33t chemist

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moritheil
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LF l33t chemist

Postby moritheil » Tue Dec 09, 2003 7:12 am

Has anyone here taken upper-level inorganic chem before? :) I'm sure some of you have. I'm trying to understand this assignment:

Y2Br2C2 is metallic in two dimensions. The C-C distance of the C2 n- unit corresponds to a C=C double bond. (that's C sub 2 superscript n-)

What formal e- distribution does this suggest? Describe the electronic structiure of the formal e- distribution for C2 n-. Explain its conductivity in two directions. Contrast your answer to the bonding predicted in the first part.


I'm not really sure what it means by formal e- distribution. From what I understand it wants the formal charges followed by corresponding e- distributions? Once I lay out the e-s I should then be able to describe the e- structure.

As for that last part, I assume they mean that the C=C would imply nonconductivity.

Any constructive help is appreciated ;) Thanks guys!
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Postby Kifle » Tue Dec 09, 2003 10:58 am

I'm not a chemistry buff by any means. I haven't taken it since my freshman year in college, but I think the C=C just means a double covalent bond between two carbon atoms. Then again I was only in an intro to organic chem class, so I probably have no idea. Sorry mori. If it were math or physics I could probably help more :)
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Postby Abbayarra » Tue Dec 09, 2003 1:36 pm

I am a chemist, but I have not used this in years.
There is a formal way of describing electron distribution. You should be able to find this and then describe how the electrons are distributed in a carbon carbon double bond. You should then be able to describe the conductivity of this bond of the electrons and then contrast this to the metallic bond described which will be different and then talk about how this alters the electron distribution of this molecule.
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Postby rylan » Tue Dec 09, 2003 2:41 pm

Oh yeah, its something like 1s1,2s2,2p2,3n5 etc, but unfortanately I don't remember how to do it correctly as its been a while. And yup, C=C is a coubld covalent bond, so they are sharing two electron rings.
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Postby moritheil » Tue Dec 09, 2003 5:10 pm

Thanks. I'm still looking up formal e- distribution. Abba, your reply seems to indicate that it isn't necessarily related to formal charge at all. Is this true? I can't find formal e- dist. in the book and I'm pretty sure the prof didn't mention it by name.

As near as I can tell, the C=C e- distribution should look something like :C::C: ... unless by "describe" you mean I ought to go through and attempt to assign e-s to MOs.

What's really bothering me is that I can't shake the feeling that the 3d crystal structure of Y2Br2C2 is involved in the explanation of why it conducts in 2 dimensions.

Oh and PS: For those wondering, he said we were encouraged to ask anyone for help, be they other students, grad students, or chemists we know.

PPS: On an unrelated note, has anyone ever heard of a synthesis of elemental F2 that does NOT involve electrochemistry? That is, a straight chemical synthesis? The only way I can think of doing this is to find something that evolves F2 when heated and then synthesize that... but I have no idea what that would be.

THANKS! :)
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Postby Auril » Tue Dec 09, 2003 6:34 pm

Not sure if this helps, but I think the C=C bond is flat. It can't rotate, and is fixed in place, making the other links somewhat fixed as well.
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Postby Clangeddin » Tue Dec 09, 2003 7:31 pm

moritheil wrote:PPS: On an unrelated note, has anyone ever heard of a synthesis of elemental F2 that does NOT involve electrochemistry? That is, a straight chemical synthesis? The only way I can think of doing this is to find something that evolves F2 when heated and then synthesize that... but I have no idea what that would be.

THANKS! :)


You can generate hydrofluoric acid through direct chemical synthesis, but everything I've ever read about elemental fluorine requires an electrolysis of potassium hydrogen fluoride in anhydrous HF solution. I gotta think that electrolysis is the only way you CAN do it, since fluorine's so damn electronegative.
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Postby Ihazim » Tue Dec 09, 2003 8:25 pm

"As for that last part, I assume they mean that the C=C would imply nonconductivity. "

c c double bond implies sp2(trigonal planar) geometry, there's some overlapping p orbitals in that allowing the electrons to "flow". That's where you get conjugation from.

maybe electron distrubution meant 1 set of sigma electrons, 1 set of pi and then 2 sets of non bonded inside sp2 configuration?

f-f, flourine is so reactive i bet if you put it in a container that could actually hold it it would react with itself. it has an electronegative pull of 4!
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Postby moritheil » Tue Dec 09, 2003 9:03 pm

Woot thanks guys!

I found Fluorine synthesis. As I suspected, you have to make some unstable molecule containing fluorines in it, and heat it to decompose it. This was only figured out in the 1980s, so it's what I think our prof wants (something fairly recent). Inorg. Chem, 1986.


I've found that the structure of CaC2 is the "rock salt" crystal arrangement, so all I have to do now is figure out where Y2 and Br2 would go in there. =)

Now, if the C=C isn't what they meant by "contrast your answer to your description of the bonding predicted by formal e- distribution," what is? I was thinking that the C=C bonds are covalent, and hence not metallic conductors.



Edited cause Spelling > me.
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sp configuration

Postby Abbayarra » Wed Dec 10, 2003 3:31 am

When you have a carbon double bond the s and p electron orbitals are involved. The geometry is going to be trigonal planar.

>c=c< is the way it looks

Br
>C=C<
............ Br

It is all in one plane, no more time, more later if I feel like it.
Back to work
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Postby Stamm » Wed Dec 10, 2003 4:31 am

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Re: sp configuration

Postby moritheil » Wed Dec 10, 2003 7:59 am

Abbayarra wrote:When you have a carbon double bond the s and p electron orbitals are involved. The geometry is going to be trigonal planar.

>c=c< is the way it looks

Br
>C=C<
............ Br

It is all in one plane, no more time, more later if I feel like it.
Back to work


If I understand you, the Brs are out of the plane, bonded to the C=C ? Hm.
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Postby Gerad » Wed Dec 10, 2003 9:18 am

Stamm wrote:My cats breath smells of cat food.


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Postby Gormal » Wed Dec 10, 2003 5:04 pm

Kaluha + Vodka + Cream = White Russian

Chemistry at its finest!
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Postby Yasden » Wed Dec 10, 2003 7:08 pm

Gormal wrote:Kaluha + Vodka + Cream = White Russian

Chemistry at its finest!


*slap* That's a woman's drink sailorboy. Add pepsi to it and you've got a bulldog!

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moritheil
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Postby moritheil » Wed Dec 10, 2003 7:59 pm

I = pwn3d.

=(
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Postby Kifle » Thu Dec 11, 2003 2:20 pm

Stay out of chemistry...it sucks. Next time get into a nice physics class and come back here for help ;)
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