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Video Solution: (a) Write Newman projections for the gauche and anti conform...

Problem

(a) Write Newman projections for the gauche and anti conformations of 1,2- dichloroethane (ClCH2CH2Cl). 

Video Transcript

So, now we're going to go ahead and draw a Newman projections for the gauche and anti orientations of 1,2-dichloroethane, so let's say we've got something like this, we know we've got two carbons because we got an ethane and we know that we've got a chlorine on each one. So, our anti that we're looking from this direction, for looking down this bond, right? What we know is that we're going to have the Y shape since our chlorine is in plane facing down, we have hydrogen on the left and the right and then we've got over here, in the back we've got our Cl, these are hydrogens, right? And guys that is our anti orientation or gauche would look something like this, right? We can just keep our back carbon to the exact same, Cl, H and H and then just rotate this chlorine so that it's near here, right? So, Cl and then we get our hydrogens here. Now, guys when we actually look at the dipole moment of this molecule we do get a reading, which means that we cannot have this as the main structure, okay? Well, the exclusive structure, right? We know we can have a mixture of confirmations where we have this and we also have some gauche, right? Because we know that our chlorine can also be on this side, so it's 2/3 of the time it could be in gauche excluding favorability because of the electron repulsion, right? So we know that absolutely we cannot say that this is the only structure, the only conformation that exists we need to have at least some percentage with this, okay? Because if not we would just have our dipoles cancel here. Alright guys, let me know give any questions, if not, let's move on.

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