Newman projection for 2-butene

[browncomputer]

What would be the newman projection for 2-butene between C-1 and C-4? Would it just be all Hydrogens on the spokes of the wheel of the newman?
or would you have to account for the double bond?

I ask this because in 1001 ochem, #129 says that 2 conformers exist for 2-butene so i was trying to draw out the newman.

thanks!

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[Czarcasm]

That's strange. I don't think I've ever seen a newman projection depicted that way, but I suppose it would look something like this (where free rotation exists about the 1-2 and 3-4 c-c single bond):

Carbon 2 would only have 1 Hydrogen, because it's double bonded to one carbon and single bonded to another (4 bonds total).
Might want confirmation on this as this is just based on my understanding of what Newman projection's are suppose to represent. There could be some rule that I'm not aware of 😛

Edit: I suppose the two confirmations they are referring to are just 1 staggered and 1 eclipsed confirmations considering any rotation about the single bonds would be symmetric.

 

[browncomputer]

can newman projections only be drawn for carbons that are right next to each other? for instance, can i draw this as a newman? because conformers only exist when "isomers can be interconverted exclusively by rotations about formally single bonds"

So would this be a possible newman?



Edit: update image

 

[Czarcasm]

View attachment 180539 can newman projections only be drawn for carbons that are right next to each other? for instance, can i draw this as a newman? because conformers only exist when "isomers can be interconverted exclusively by rotations about formally single bonds"

So would this be a possible newman?



Edit: update image

It will always be between two neighboring carbons that can freely rotate. That is essentially what the Newman projection represents. (It's not possible to have a newman projection between C1-C4). In my newman projection above, I depicted it between C-1 and C-2 (looking directly through the C-1, which was closer, C-2, being further (the circle in the NP). This picture might help you see this better:

Bare in mind the hybridization of some of these carbons are sp3 hybridized (generally the ones depicted in Newman projections). This is essentially why you have 3 sticks pointing out of the center of the circle. Also, the circle represents the neighboring carbon that you're looking through. I'm not best at explaining this type of stuff, so you're probably better off looking this up, lol.

 

[browncomputer]

okay, i see. so the newman projections are for:

• neighboring carbons
• can be between an sp3 and sp2 as seen in the above example

thanks!

 

[Czarcasm]

okay, i see. so the newman projections are for:

• neighboring carbons
• can be between an sp3 and sp2 as seen in the above example

thanks!

You got it bud!