penalise use of sticks in this structure-wat does it mean? :S

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SilentGirl
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#1
Report Thread starter 14 years ago
#1
I keep seeing this on the AQA chemistry as level mark scheme.
How am I supposed to show a mechanism with out drawing the sticks?? Dont sticks represent bonds between the atoms? Is it sum other stick??
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PoisonDonna
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#2
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#2
Hmmm.

Say you've got butadiene, you can represent that in two ways.

C=C-C=C and you would show all the hydrogens as well.

Then to me, the stick form would be:

=-= but the bonds are at angles and hydrogens aren't shown.

If they say stick form, I assume the second version (left one in pic below) is what they talk about, and I know at A Level we had to do the first version, and show all the hydrogens.

Image
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Lulu*et*Moi
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#3
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#3
Isn't it when you just draw the sticks without the actually hydrogen atoms on them. Like
-C- instead of H-C-H. I always do that
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SilentGirl
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#4
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#4
(Original post by PoisonDonna)
Hmmm.

Say you've got butadiene, you can represent that in two ways.

C=C-C=C and you would show all the hydrogens as well.

Then to me, the stick form would be:

=-= but the bonds are at angles and hydrogens aren't shown.

If they say stick form, I assume the second version (left one in pic below) is what they talk about, and I know at A Level we had to do the first version, and show all the hydrogens.

Image
You knw the one you drew on the right, that wont be penalised right?? Otherwise in what other way am i gona show mechanisms and also in the books I see that kind of drawing (right habd side one type)!

Thanks.
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SilentGirl
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#5
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#5
(Original post by Lulu*et*Moi)
Isn't it when you just draw the sticks without the actually hydrogen atoms on them. Like
-C- instead of H-C-H. I always do that
LOL that hard tho, drawing without including hydrogen atoms..clever geneous u r lol but do not do it hehe.
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zippy_gerbil
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#6
Report 14 years ago
#6
(Original post by Lulu*et*Moi)
Isn't it when you just draw the sticks without the actually hydrogen atoms on them. Like
-C- instead of H-C-H. I always do that
Yep, it just means you have to show the H atoms at the end of the stick instead of assuming they're there
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MC REN
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#7
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#7
Isn't it that you have to draw the bonds at (roughly) the correct angles rather than all at 90' to not get penalised?
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PoisonDonna
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#8
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#8
Yep, draw the one on the right and you're fine. Both images are correct, but I know at A Level we had to draw in aaaaall hydrogens. Was a pain in the arse :p:
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PoisonDonna
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#9
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#9
(Original post by MC REN)
Isn't it that you have to draw the bonds at (roughly) the correct angles rather than all at 90' to not get penalised?

Hmm. Wouldn't have though so, because when you're drawing all hydrogens in, adding bond angles too would make the sructure more messy than is required.
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SilentGirl
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#10
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#10
Thank you so much all of you. LOL never knew that stick thing was soo 'odd' lol.

Back to my past papers lol..

Good luck with ur exams.
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MC REN
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#11
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#11
(Original post by PoisonDonna)
Hmm. Wouldn't have though so, because when you're drawing all hydrogens in, adding bond angles too would make the sructure more messy than is required.
Hmm, I think what I did at a-level (AQA) actually was just write it like CH3 - CH3, etc, with zig-zag structure and only actually drawing the sticks when I needed to show it in a mechanism, like:

CH3-CH2-Br

I think they'll probably penalise you for drawing all the hydrogens because it is messy and pointless (and as you said almost necessitates drawing everything at right angles which is just wrong)
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PoisonDonna
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#12
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#12
(Original post by MC REN)
Hmm, I think what I did at a-level (AQA) actually was just write it like CH3 - CH3, etc, with zig-zag structure and only actually drawing the sticks when I needed to show it in a mechanism, like:

CH3-CH2-Br

I think they'll probably penalise you for drawing all the hydrogens because it is messy and pointless (and as you said almost necessitates drawing everything at right angles which is just wrong)
I don't think they can penalise for drawing hydrogens, but then again I can't see why they would penalise for drawing the stick structure either, but it appears they do. I know when I did it we had to draw all hydrogens, but I did the welsh board, WJEC.

I reckon if you draw it all out it can't be a bad thing, especially as the mark scheme mentions penalising for stick structures.
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Botticello
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#13
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#13
Yep, it means don't just draw the lines as shorthand, draw every hydrogen
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orbitingful
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#14
Report 4 years ago
#14
The left pic would never get penalised in an AQA A Level exam if a question asked you to draw the 'structure' of a compound - it is called the skeletal formula! Definitely not 'sticks'!
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