Use a Newman projection to draw the most stable conformation of 3-methylpentane, looking down the C2—C3 bond.
Alright guys. So, for this question what we need to do is it gives us 3 methyl pentane, let's go ahead and draw that out, this is our three methyl pentane and what we need to do is convert this into a Newman projection, right? Looking down the c2, c3 bond and in the most stable form. So first, let's just think of our eyeball here, right? this is where we're looking, right here, down our c2 c3 bond, so we're going to say that this is going to be our front carbon and this is going to be our back carbon for our Newman, so there's our front carbon and there's our back carbon, right? Now, all we need to do is take a look at what's going, what would be to the left of us, what would be to the right, if you're looking right down that c2 c3 bond, so if we're looking at that bond notice we have a methyl group going in this direction right, there's a one methyl and then everything else would just be a hydrogen. So, here's hydrogen and hydrogen, okay? But our methyl is in that exact position right there. Now, let's look at the other position, the one in the back. Now, at the back we have a methyl that looks like it's going up, right? Okay, and then what else do you see? well, we have an ethyl group going to the right of us, right? So we would draw it over here and then what else are we missing, just another hydrogen, okay? So we just converted our 3 methyl pentane into a Newman projection. Now, is it in the most stable conformation? Well, notice that here we have a CH3 and a CH3 and this would be a CH2 and a CH3, so it's going to be the bulkiest group here, it looks like it's going to be that ethyl group over here, right? With the CH2 CH3, okay? Now, notice that we have one gauche interaction going on, right? At 60 degrees, right here, and that is between a methyl group and a methyl group. Now, this is pretty good, right? Because, let's say we had a methyl and an ethyl. Now, that would it be the most stable conformation but the one we drew it in where there's only one gauche interaction between our two smaller substituents, right? These methyls, is pretty good, so we're going to say that we actually do this in the most stable conformation right, this one is going to be the most stable and we're done guys, so hopefully this makes sense, just remember when we're looking it tells you to look through that c2 c3 bond, all we need to do is convert this to a Newman and then see which groups are coming off where, imagining that you're looking in a straight line right down that bond. Alright guys. So, let me know if you have any questions.