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tofu
2010-Mar-25, 02:54 PM
Here's a shirt I found on cafepress.com that has a caffeine molecule on it:

http://www.cafepress.com/+black_tshirt,54283302

But the arrangement is a little different than what wikipedia has for caffeine. Both molecules have three methyl groups, with one written as H3C and two as CH3. But they're in different spots in the wiki version:

http://en.wikipedia.org/wiki/Caffeine

Is there any functional difference between these two molecules?

Nowhere Man
2010-Mar-25, 03:19 PM
The point being made in the diagram is that the nitrogen is bonded to the carbon atom, to which is also attached three hydrogen atoms. This is made obvious in the ball-and-stick model on the Wikipedia page.

The only difference between the Cafe Press and Wikipedia diagrams is a 180-degree rotation. Otherwise, they are identical.

Fred

tofu
2010-Mar-25, 03:35 PM
The only difference between the Cafe Press and Wikipedia diagrams is a 180-degree rotation. Otherwise, they are identical.

I don't think so.

http://www.majhost.com/gallery/tofu/babb/molecule.gif

Nowhere Man
2010-Mar-25, 03:46 PM
You're missing the point. The carbon is attached to the nitrogen, and three hydrogens are attached to the carbon. Take a look at the ball-and-stick model (http://en.wikipedia.org/wiki/File:Caffeine_3d_structure.png).

Actually, on the inverted shirt, I see H3C at the lower left and top center, and CH3 at the lower right. Because it's now upside down.

All of them are methyl groups. Some are written H3C to make clear that the carbon is attached to the nitrogen. Otherwise, it would look like the nitrogen is attached to one or more of the hydrogens.

Fred

tofu
2010-Mar-25, 04:13 PM
The question in my original post was, "is H3C the same as CH3"

If the answer is "yes," then that takes care of my question.

But the two diagrams are not "the same," any more than 1/3 is "the same" as 0.33... and one was not a rotated version of the other. If they represent the same molecule that's cool. I get that it's possible to write something in two different ways and have it represent the same thing.

So, there's no rule about how a methyl group should be written, is that it? Any of these different diagrams are the same molecule?

http://www.majhost.com/gallery/tofu/babb/molecule2.gif

Strange
2010-Mar-25, 04:16 PM
The question in my original post was, "is H3C the same as CH3"

If the answer is "yes," then that takes care of my question.[/img]

Yes. ;)

(But if the CH3 group was connected to a different N then you would have a different (isomeric) compound.)

rommel543
2010-Mar-25, 04:23 PM
Caffeine is C8H10N4O2. The 2 nitrogen pairs are at the core with the other molecules binding to it. The location of the CH3 and H3C in the diagram doesn't matter, as long as it's connected to one of the nitrogen and the number of them is correct.

ABR.
2010-Mar-25, 04:30 PM
Perhaps it would help if you drew out the entire molecule instead of using the shorthand notation for the methyl groups? Here (http://journals.iucr.org/b/issues/2005/03/00/lc5020/lc5020fig3.html) is the first such diagram I found via Google. I'm sure someone here probably knows of a better one.

NEOWatcher
2010-Mar-25, 04:44 PM
All of them are methyl groups. Some are written H3C to make clear that the carbon is attached to the nitrogen. Otherwise, it would look like the nitrogen is attached to one or more of the hydrogens.
Isn't the line ending at the C denote that it's attached there, not the arrangement of H to C?

I'm interpreting this thread that they used one or the other so that the notation does not clutter the diagram by putting the notation as far from the rest of the other lines as possible.

rigel
2010-Mar-25, 04:47 PM
yes the two are the same molecular structure, with the methyl groups are written a little differntly. To see this take off all the hydrogens and you have the same structure. You can do this since are no isomeric carbons.

Swift
2010-Mar-25, 05:32 PM
So, there's no rule about how a methyl group should be written, is that it? Any of these different diagrams are the same molecule?

http://www.majhost.com/gallery/tofu/babb/molecule2.gif

No and yes

Fazor
2010-Mar-25, 05:36 PM
That brings up the question; why use two different notations for the same thing in the same diagram?

Nowhere Man
2010-Mar-25, 05:53 PM
The question in my original post was, "is H3C the same as CH3"

If the answer is "yes," then that takes care of my question.
I was trying to lead you to that conclusion without saying "yes" out loud.


But the two diagrams are not "the same," any more than 1/3 is "the same" as 0.33...Oh, let's not get into that (http://www.bautforum.com/off-topic-babbling/14593-do-you-think-0-9999999-1-infinite-9s.html) again! :doh::)


If they represent the same molecule that's cool. I get that it's possible to write something in two different ways and have it represent the same thing.Bingo. Writing -CH3 or H3C- is shorthand for drawing

|
C
/|\
H H H
So, there's no rule about how a methyl group should be written, is that it? Any of these different diagrams are the same molecule?

http://www.majhost.com/gallery/tofu/babb/molecule2.gifRight, they are all the same molecule. The upper-right and lower-left diagrams are easier to read (IMHO) because they're spread out a bit more. You can take mirror images of these diagrams and say that they're all the same, as well (caffeine has no stereoisomers).

It comes down to aesthetics, convention, and training. Chem students have this worked out by the end of their first year.

Fred

TheOncomingStorm
2010-Mar-25, 07:48 PM
No and yes
no it is, yes and no.

SeanF
2010-Mar-25, 09:51 PM
That brings up the question; why use two different notations for the same thing in the same diagram?
Huh - I know nothing about chemistry, but I've gotten it from reading this thread.

The line from the "N" needs to connect to the "C" (not to the "H"), and it just looks better to put the "H3" so the entire notation extends away from the center.

Thus, you use "H3C" on the left side of the diagram but "CH3" on the right side - so, in both cases, the "C" is towards the middle.

Strange
2010-Mar-25, 10:23 PM
That brings up the question; why use two different notations for the same thing in the same diagram?

They are not different notations, they are they same notation written differently :)

pzkpfw
2010-Mar-25, 11:21 PM
no it is, yes and no.

Please explain...

TheOncomingStorm
2010-Mar-25, 11:35 PM
Please explain...
Just having fun with Swift.

Nick Theodorakis
2010-Mar-26, 03:35 AM
In three dimensions, the bonds coming from the carbon atom in the methyl group (CH3, or H3C, if you prefer) are symmetrically situated by pointing to the vertexes of an imaginary tetrahedron the carbon atom is in the middle of. The methyl group is free to rotate around the carbon-nitrogen bond. Both CH3 and H3C are just short-hand two-dimensional representations; the latter is just used as an aesthetic choice the artist might use if thinks the hydrogens will look too scrunched up against the rest of the molecule.

DonM435
2010-Mar-26, 01:41 PM
Isn't there a rule for writing compounds wherein you put the element with the positive electrovalency on the left and the one with the negative electrovalency on the right? That's why sodium chloride is NaCl and not ClNa, and why water is H2O and not OH2.

But I seem to recall that carbon and hydrogen are rather close in this particular respect, so it's a tossup. Or am I thinking of hydrogen and nitrogen?

Swift
2010-Mar-26, 01:46 PM
Isn't there a rule for writing compounds wherein you put the element with the positive electrovalency on the left and the one with the negative electrovalency on the right? That's why sodium chloride is NaCl and not ClNa, and why water is H2O and not OH2.

But I seem to recall that carbon and hydrogen are rather close in this particular respect, so it's a tossup. Or am I thinking of hydrogen and nitrogen?
That rule only applies to compounds with ionic bonding, not compounds with covalent bonding. And it applies more to writing out in a single line the formula (C8H10N4O2), not a structural representation.

Fazor
2010-Mar-26, 02:14 PM
Huh - I know nothing about chemistry, but I've gotten it from reading this thread.

The line from the "N" needs to connect to the "C" (not to the "H"), and it just looks better to put the "H3" so the entire notation extends away from the center.

Thus, you use "H3C" on the left side of the diagram but "CH3" on the right side - so, in both cases, the "C" is towards the middle.

Yeah. I missed that in all the discussion, but that makes sense now. And as for knowing nothing about chemistry; that's probably the branch of science I have the least knowledge in. And that's saying a lot, as I have very little knowledge in most branches of science. Unless, is beerology a science yet? :)

Swift
2010-Mar-26, 02:54 PM
Unless, is beerology a science yet? :)
There is a lot of chemistry, biochemistry, and biology in beer making, so sure, why not.
http://www.websmileys.com/sm/drink/trink39.gif

DonM435
2010-Mar-26, 04:38 PM
As yeasts are involved, it's microbiology and mycology as well!

Swift
2010-Mar-26, 05:05 PM
And of course, when you start testing your beers, you get physiology and more biochemistry. And if you do too much testing, maybe even some criminology. :D

Fazor
2010-Mar-26, 05:21 PM
. . . maybe even some criminology. :D
Which is, of course, the only type of "ology" that I have any actual (but still meager) formal training! Woohoo!

pzkpfw
2010-Mar-26, 10:16 PM
Given the way the diagram shows the separate groups of CH3 / H3C, which seems to emphasise that they are identifiable "sub molecules" or something, ...

Would the full thing ever be written as:

(CH3)3N4O2 ?


[ As opposed to the C8H10N4O2 in posts #7 and #21]


Just curious.


P.S. Now that I write this I note the numbers of Carbon and Hydrogen shown in post #7 and #21 don't match what I'd expect.

What did I miss?

(I did chemistry only to 7th form (High School), didn't do any at University...)

Strange
2010-Mar-26, 10:22 PM
Would the full thing ever be written as:

(CH3)3N4O2 ?

There are various ways like that it could be written.


P.S. Now that I write this I note the numbers of Carbon and Hydrogen shown in post #7 and #21 don't match what I'd expect.

What did I miss?

The other 5 carbons in the two rings (not explicitly shown in the diagrammatic version).

DonM435
2010-Mar-26, 10:23 PM
Right. The representation with the parentheses is a "structural formula," and is usually preferred. I forget what the call the other one, but its only advantage is that it makes it easier to compute the atomic mass.

Nowhere Man
2010-Mar-26, 11:36 PM
The other 5 carbons in the two rings (not explicitly shown in the diagrammatic version).And the extra H that hangs off the C in the pentagon ring.

C8H10N4O2 is accurate but could be any number of compounds.

Fred

mike alexander
2010-Mar-27, 03:46 AM
I was at a lecture up at University of Washington last month where Alan Marshall from the National High-Field Magnet Laboratory talked about ultra-high resolution mass spectrometry. They can get such a high resolution with their new ICRMS that they can separate every theoretically possible compound of a nominal molecular weight.

That's kick-butt mass work.

PraedSt
2010-Mar-27, 07:00 PM
The higher the zapping energy, and the stronger the magnetic field, the higher the resolution? Could one theoretically use the LHC as a kick-butt mass spectrometer?

01101001
2010-Mar-27, 07:21 PM
The higher the zapping energy, and the stronger the magnetic field, the higher the resolution? Could one theoretically use the LHC as a kick-butt mass spectrometer?

Lawrence Lab Berkely: Another Magnet, and Another World Record (http://www.lbl.gov/Science-Articles/Archive/sb-AFRD-magnet-record.html)


The LHC, for example, is slated to use 8.3-tesla magnets to accelerate protons to 7 trillion electron volts before smashing them into each other.

National High Magnetic Field Laboratory: Meet the Magnets :: The 45 Tesla Hybrid (http://www.magnet.fsu.edu/mediacenter/features/meetthemagnets/hybrid.html)


This magnet combines a superconducting magnet of 11.5 tesla with a resistive magnet of 33.5 tesla. It is in wide demand among scientists across the globe. Although we operate several world-record magnets, this is the only one featured in the Guinness Book of World Records.

National High Magnetic Field Laboratory: Ion Cyclotron Resonance (ICR) Overview (http://www.magnet.fsu.edu/usershub/scientificdivisions/icr/index.html)


Four complete FT-ICR mass spectrometers are available and feature high magnetic field (currently 7, 9.4 and 14.5 T) and multiple ionization techniques (micro- and nanoelectrospray, atmospheric pressure photoionization, electron and field desorption ionization).

HenrikOlsen
2010-Mar-28, 08:27 PM
Would it be a different compound if the methyl group on the 5 atom ring was attached to the other nitrogen atom and how does structural formulae distinguish?

ETA some searching indicates the answer is "yes" and "it's complicated" (I couldn't figure out the rules for where you start counting) and that the molecule is called isocaffeine.

PraedSt
2010-Mar-29, 03:50 AM
...It's the other way round I see. Thanks.