[smghz]

I have a few questions on Newman Projections.

• What is the best way to finding all Newman projections of a particular structure? My way is to keep the front unmoved but rotate the back one atom at a time clockwise or counterclockwise. But I saw some answers that keep everything the same but just change the places of two non-adjacent atoms. Is that right to do?
• Is there a particular method to speedily know how many staggered and/or eclipsed projections a structure has?
• What is the rationale behind this answer
  
  I got confused because I thought that the bottommost methyl should exchange places with the corner left H.
• When a question asks for the most stable conformation, and there are wedges and dashes in the original structure, is it okay to move the atoms so that they don't accurately match the wedges and dashes for the sake of achieving a more stable conformation?
• Finally, how important is directionality in drawing Newman projections? Sometimes I flip the directions, is that okay?

thanks

[Babcock_Hall]

1.  It is OK to rotate either the front atom or the rear atom, but offhand flipping does not sound correct.  I would have to see what you mean, however, before I would conclude that flipping was what was being done.
2.  It is typical at the level of sophomore organic chemistry to show Newman projections at 60° increments.
3.  Add up the steric energies for each interaction that you find.  Let's see your work.
4.  In my opinion a wedges-and-dashes representation is meant to indicate configuration, not necessarily the lowest energy conformation.  You will have to find the lowest energy conformation yourself.
5.  I am not 100% certain what you mean by flipping.  However as long as one's representation is accurate, I don't see a problem with, for example, choosing carbon-2 as the front carbon versus choosing carbon-3.

[marcelbombka]

100000 hours of watching lectures online = walk away with nothing.
<15 minutes with khanacademy = everything clicks + makes sense.

[Vidya]

Babcock_Hall has cleared everything.
I will try to make it more clear ...

I have a few questions on Newman Projections.

• Finally, how important is directionality in drawing Newman projections? Sometimes I flip the directions, is that okay?

when we make Newman projection ..we rotate it only in one direction(either clockwise or anticlockwise)  by 60 °  to get a new conformation.If you flip direction you will get repeated or old conformation and if you move only in one direction after every rotation you geta new Conformation. You can get infinite conformations but we make only most stable(fully staggered) and least stable conformations (fully eclipsed).

I have a few questions on Newman Projections.

I got confused because I thought that the bottommost methyl should exchange places with the corner left H. [/li]
[li]When a question asks for the most stable conformation, and there are wedges and dashes in the original structure, is it okay to move the atoms so that they don't accurately match the wedges and dashes for the sake of achieving a more stable conformation?[/li][/list]

Look at the wedge and dash 3D structure ...methyl  and H are on the same side ..in one case behind the plane and other case in front ...so in newman projection they will appear on the same side of the projection.If you interchange
methyl and Hydrogen position then it means one is on the wedge and other is on the dash which is not the case.

I have a few questions on Newman Projections.

• Is there a particular method to speedily know how many staggered and/or eclipsed projections a structure has?
• What is the rationale behind this answer
  
  
  thanks
  

If you to rotate it by 60 ° each time and total angle of rotation is 360°.Total number of conformations in every molecule is 360/60 =6.So you can not have more than or less than 6 conformations.During rotations eclipsed is converted to staggered and staggered to eclipsed form.So you will get 3 eclipsed and 3 Staggered Conformations .

 [/list]

[smghz]

Thank you for your answers, I greatly appreciate them.  I have now understood the concept of having a Newman projection make for the most stable conformation of a molecule while maintaining its original structure. But can this same logic be used for the problem below?

I have put two answers, one based on my outdated thinking and the new one based on what I learned here thankfully. I kinda favor the latter.



thanks