Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: Miriiii on April 29, 2019, 08:41:22 AM
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So I stupidly enrolled in biochemistry this semester despite having not been in a chemistry class since I was 15. I have a lot of basic questions.
I am trying to memorise the structure of proline. Noticed that its side chain is 3 CH2 groups. 2 Are CH2, one is H2C, what's the difference. Why would you write them differently?
Similarly, I've noticed that NH2 groups are written as H2N a lot of the time, why? When do you flip this around?
Cheers! And respect to you chem people, trying to wrap my head around this is doing me in.
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You have a molecule H2N-R-X another one is Y-R-NH2. At least it doesnt matter how you write it.
Or you have H2C=CH2 which show the doublebond between the carbon atoms. It is not wrong to write CH2CH2.
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These are the same things, just seen from different sides.
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If you wrote CH2=O for, e.g., formaldehyde, it could be mistaken which nucleus is attached to the oxygen. With H2C=O, it is unambiguous that the carbon is attached to the oxygen. Likewise for O=CH2. This is really most important when you are drawing bonds.