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Topic: NEWMAN PROJECTIONS  (Read 7051 times)

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Chickagurl

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NEWMAN PROJECTIONS
« on: October 11, 2004, 05:00:21 PM »
I am so confused right now, I have no clue what the heck i'm doing. My chem prof does not explain this stuff at all. I really have no clue how to draw out newman projections. I also have no clue how to draw out chair conformations, how do i know where to start numbering my carbons, in my tectbook it always changes and it seems like your just supposed to know... but i don't. please help me

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Re:NEWMAN PROJECTIONS
« Reply #1 on: October 11, 2004, 06:57:05 PM »
Well, the Forums are here to help.  So, one thing at a time:

Newman Projections:

These are a way to visualize the conformation of 3D molecule in 2D.  To figure out what is going on, you think about looking directly onto the end of a bond (so that you couldn't actually see the bond you are looking down).  Then you fill in the appropriate substituents around the circle representing the atom closest to you, and then "behind" the circle you fill in the substituents on the atom at the other end of the bond you are looking down.  Here is an example:



I have to go to a meeting right now.  I'll try to help with the others when I get back.

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Re:NEWMAN PROJECTIONS
« Reply #2 on: October 11, 2004, 08:51:56 PM »
Okay, I'm back.

Chair conformations:

This is just a really stylized way to represent cyclohexane rings.  I always start by just drawing a generic chair and then fill in the substituents.  The basic rule is to put as many sterically demanding groups in an equatorial position as possible.  If you draw your chair and fill in the substituents and it looks like you have most of your sterically demanding groups axial, just start over and shift all of the groups over by one carbon.  Here's an example:



Numbering:

Numbering is based on the highest "priority" group in your molecule.  This is something that you have to memorize.  In general, however, you want to give the heaviest atom the lowest number.  There are many exceptions, but that's a reasonable starting point.

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Re:NEWMAN PROJECTIONS
« Reply #3 on: October 12, 2004, 02:11:06 AM »
WOW, that is worth 5 scooby snacks right there. You are now at 20.
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Re:NEWMAN PROJECTIONS
« Reply #4 on: October 12, 2004, 12:56:12 PM »
Score!

dexangeles

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Re:NEWMAN PROJECTIONS
« Reply #5 on: November 11, 2004, 01:46:20 AM »
haha that is awesome
when i was reading the question i was wondering how someone can explain it cause they are more pictures than explanations

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