Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: iScience on October 12, 2013, 02:41:53 AM
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what ring conformation is graphite in? chair i'm guessing? is it any different at the ends of the layers?
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Can you draw graphite for us, does it resemble a polycyclohexane structure?
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yes
http://www.nano-enhanced-wholesale-technologies.com/faq/carbon-forms.htm
so i'm guessing that's a yes that they are chairs?
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Do they look like chairs in your link? What is the empiricle formula for graphite?
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additional hint:
take a look at the pictures in your link: graphite is "many layers of graphene, staggered"
regards
Ingo
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I think the poster was asking about the difference between "arm-chair" and "zig-zag" graphene. After visiting the Wikipedia link, I wonder this also.
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I think the poster was asking about the difference between "arm-chair" and "zig-zag" graphene. After visiting the Wikipedia link, I wonder this also.
Looks like it's the same material with a different orientation. It makes a difference at a ribbon, not at a sheet.
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I think the poster was asking about the difference between "arm-chair" and "zig-zag" graphene.
that's not my understanding of the original question: he was asking about graphite, not graphene
to explain the structure, I offered to take a look at graphene from his own very link , where garphene is described as follows:
. one atom thick flat layer of hexagonal carbon rings.
. looks like a honeycomb or chicken wire in structure
(from: original link by author; additional accentuation in bold by me)
regards
Ingo
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I think the poster was asking about the difference between "arm-chair" and "zig-zag" graphene. After visiting the Wikipedia link, I wonder this also.
actually this was more along the lines of what i was talking about (sorry i guess i wasn't clear); though i don't know what 'arm chair' is; i just learned it as the 'chair conformation'. to clarify my question, i wanted to know what the cyclohexane ring conformations were in each graphene sheet OF graphite.
also, unless you're dealing with an hopg, i heard that natural graphite is a mess; that it's not really clean layers and there are kinks and bumps all over the graphite structure. is this true?
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i wanted to know what the cyclohexane ring conformations were in each graphene sheet OF graphite.
its the same as in naphthalene, anthracene, benzyo[a]pyrene , (...), i.e. condensed aromats in general: it's planar (but very huge at that)
(...)i heard that natural graphite is a mess; that it's not really clean layers and there are kinks and bumps all over the graphite structure. is this true?
as with almost all crystalline substances dealing with like 1020 atoms and more: yes, there every once in a while will occur some errors
it is very very very difficult to have really good single crystalline structures at large scale, unless you intentionally make them, and this is true for graphite, also
regards
Ingo
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stupid question; but just to be certain.. ....poly[trans-decalin] conformation right?
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stupid question; but just to be certain.. ....poly[trans-decalin] conformation right?
no , not right
... and the stupid question I'm just asking myself is, whether you at least bother with reading the what we're answering here, let alone trying to understand it
its FLAT! like glassplates stapeled above each other!
... and only if you look at a single plane from top, you'll see that the carbon atoms (that ALL lie in the plane: no ups and downs here whatsoever) will form perfect hexagons
Ingo
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if that's so, then what determines in what direction the hydrogens are oriented? or is it random (ie 50% oriented up 50% oriented down)? Also, how is it planar? my chem professor told me that chairs were the most stable conformation; does pi stacking have anything to do with pulling each adjacent layer into the planar shape?
graphene on google images shows up as planar. if this is true, what gives the sheet a planar conformation instead of giving it a series of the 'more stable' chair conformation?
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if that's so, then what determines in what direction the hydrogens are oriented? (...)
hydrogens? what hydrogens? in GRAPHITE ?
I'm outa here, before I start violating forum rules..
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i thought graphite was just layers of graphene and i thought graphene was just a series of cyclohexanes (ie no double bonds). if that's the case each carbon is only bonded to 3 other carbons, where's the fourth bond?
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Why not look at this page?
http://en.wikipedia.org/wiki/Graphite (http://en.wikipedia.org/wiki/Graphite)
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i've already been to that website. it just says "C" for chemical formula. This doesn't tell me why there is no fourth group.
and for crystal structure it said hexagonal, which i already knew. i'm sorry, is this really such a stupid question? my understanding was that graphite nothing more than sheets of graphene, sheets of poly cyclohexanes. cyclohexanes have hydrogens on them. i'm asking why there is no hydrogens for each cyclohexane unit. unless adjacent layers are contributing to the fourth bond for each carbon? looking at the crystal structure of graphite i don't see how this can be the case, but if there are no hydrogens in graphite, the fourth bond must be bonded to a carbon, which has to be from one of the adjacent layers, but how can this be the case? graphite has a hexagonal close packed configuration. and some of the carbons in a cyclohexane unit will be too far away from the other carbons on an adjacent layer to form any bonds.
http://i.imgur.com/eFsrbYG.gif
i drew a red circle around the carbon that i'm referring to; the one i'm saying that would have a hard time forming any bonds with the adjacent layer. Am i looking at this the wrong way?.. should i be looking at the space filling model?..
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it just says "C" for chemical formula.
Maybe that is becouse it's just formed out of Carbon.
Please, link the source where you saw that carbon was formed of cyclohexanes...
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That is because it is ONLY carbon. It is an allotrope of carbon.
No hydrogen, nothing but carbon, the element carbon.
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You could try googling 'bonding in graphite'. This was the first result for me. Copied below from; 'http://www.chemguide.co.uk/atoms/structures/giantcov.html'
The bonding in graphite
Each carbon atom uses three of its electrons to form simple bonds to its three close neighbours. That leaves a fourth electron in the bonding level. These "spare" electrons in each carbon atom become delocalised over the whole of the sheet of atoms in one layer. They are no longer associated directly with any particular atom or pair of atoms, but are free to wander throughout the whole sheet.
If you are interested (beyond A'level): The bonding in graphite is like a vastly extended version of the bonding in benzene. Each carbon atom undergoes sp2 hybridisation, and then the unhybridised p orbitals on each carbon atom overlap sideways to give a massive pi system above and below the plane of the sheet of atoms.
The important thing is that the delocalised electrons are free to move anywhere within the sheet - each electron is no longer fixed to a particular carbon atom. There is, however, no direct contact between the delocalised electrons in one sheet and those in the neighbouring sheets.
The atoms within a sheet are held together by strong covalent bonds - stronger, in fact, than in diamond because of the additional bonding caused by the delocalised electrons. So what holds the sheets together?
In graphite you have the ultimate example of van der Waals dispersion forces. As the delocalised electrons move around in the sheet, very large temporary dipoles can be set up which will induce opposite dipoles in the sheets above and below - and so on throughout the whole graphite crystal.
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[...] I heard that natural graphite is a mess; that it's not really clean layers and there are kinks and bumps all over the graphite structure.
Graphite is absent from Nature. It's strictly man-made by pyrolysis of varied compounds like tar, sisal, polyacrylonitrile, gaseous hydrocarbons.
Especially coal is a hydrocarbon, with some more elements. It's carbon-rich, but a hydrocarbon - this allows to light it, while graphite doesn't burn.
Docs about graphite differ an awful lot from an other (except when copied as usual), even for properties as basic as density. The start compound defines much the produced graphite, the process also: impregnation steps, atmosphere, pyrolysis duration. Carbon is known precisely only as diamond.
I have never read a report about a graphite single-crystal, from which some properties like density could have been measured. Since graphite sublimates first, it takes 108 bar to melt it at 4,600K ±300K (admire the precision), so I guess nobody has crystallized it.
Most materials are usually polycrystalline, but graphite is much worse: its pure and ordered form is unknown.
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Graphite is absent from Nature. It's strictly man-made by pyrolysis of varied compounds like tar, sisal, polyacrylonitrile, gaseous hydrocarbons.
Not true, http://lmgtfy.com/?q=graphite+mine
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in addition:
Anthracite coal (http://en.wikipedia.org/wiki/Anthracite) is up to 98% pure , naturally occurring carbon, mostly graphite
regards
Ingo
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Benzene also is 92% pure carbon like anthracite is - but I wouldn't call it graphite.
As it look, mining companies also call "graphite" a coal that contains more carbon than anthracite, but it's far from what users expect from technological graphite. A matter of wording then.
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(...)but it's far from what users expect from technological graphite
no Sir: this is "technological" graphite, with all the bells and whistles (> 94% C , if memory serves)
somewhat more than half of the world's demand in technical grade graphite of approx 1,12 million t/a is being mined this way
regards
Ingo
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Each carbon shares three of it's free electrons with another carbon, leaving one free electron to be delocalized about the structure. So yes graphene is an example where carbon doesn't form four bonds. because of the free electron it can conduct electricity, one of the few nonmetallic substances to be able to do so
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Technological graphite is manufactured in a long process. It's not a natural product. At 94% carbon, you have naphthalene for instance, which doesn't qualify as graphite.
You may have a look for instance at:
Survey and future trends of graphite technology, by E.J.Dunn, in 1962, ASD-TR4I1-35
www.dtic.mil/dtic/tr/fulltext/u2/274027.pdf
"There are presently three practical approaches to the manufacture of graphites: the
conventional method, the hot working method, and the pyrolytic method. The hot working
and pyrolytic methods have been developed to the point of practicality since 1958.
Conventional Method
The conventional production method wherein a filler such as petroleum coke is
mixed with a binder, coal tar pitch, baked and then graphitized upward of 4500°F..."
I feel reasonable that refractory material used to make ovens differ from a fuel.