Fischer Projections - Online Tutor, Practice Problems & Exam Prep

Fischer Projections Concept 1

Hey, everyone. So in this video, we're going to talk about Fischer projections. Now they themselves are 2D representations of chiral molecules where chiral centers are symbolized by the intersection of two lines. And here we're going to have solid wedges, so these solid wedges here are for our horizontal lines, the lines on the sides. And then here we're going to have our dashed wedges or lines, so these are dashed. These are for our vertical lines. Here we can transform this representation into a Fischer projection. So what we do here is we would not show the carbon, and we would show that carbon which is chiral being connected to those same groups. Now, remember, a chiral carbon or chiral center is when carbon is connected to four different groups. So we have x, y, z, and w here. These are representative of four different structures. Alright. So then we're going to write them in. So this would be y up here, z here, oh, man. x here. z here and w over here. So we've just created our Fischer projection. And the carbon is still here, it's just invisible. It's still chiral, so I'm putting an asterisk next to it to represent that it's still a chiral center. Alright. So just remember, here we have the showing of our chiral carbon with wedged and dashed bonds, and we've just converted it into a Fischer projection, where we have eliminated the stereochemistry and made it 2D. So the lines themselves no longer have wedged or dashed representations.

Fischer Projections Concept 2

When drawing Fischer projections, aldehyde and ketone groups are always represented on top. If we take a look here at this illustration, we start out with our bond line form. Don't worry, you're not going to have to convert from the bond line form to the wedge dash form. So, I'm just showing you that this here can be restructured to give us this form here. And it's in this form here that's important for you to know how to go from it to your Fischer projection. Now remember, your Fischer projection is a 2D representation, so we will not have stereochemistry. That means we would eliminate these dashed bonds and these wedged bonds when drawing it. Now, here we have this, this, and this as our chiral centers in terms of this, carbohydrate. And so, this carbon here, we illustrate it as this carbon here. This carbon here would be this carbon here. And this carbon here would be this carbon here. We already have our aldehyde here, and we already have our CH₂OH group here on the bottom. All we have to do now is just add what's connected to these 3 chiral carbons. We have an H and an OH, HOH, and then HOH again. So we've gone from the wedge dash form to our Fischer projection form, which again is just a 2D representation. Remove the stereochemical bonds, no wedge bonds, no dash bonds to give us our Fischer projection at the end.

Fischer Projections Example 1

Here it says, convert the wedge dash structure to a Fischer projection. Remember, a Fischer projection is a 2D representation of our monosaccharide unit here. So, that means we need to eliminate all our wedged and dashed bonds. So here we'd have still our CH₂OH which we show. Here we do not show the carbon but it's double bonded to the oxygen. And we have our 2 chiral carbons. Each one would still be connected to an OH and an H respectively. And then finally, we wrap it up with a CH₂OH here on the bottom. So this would represent our Fischer projection where we've converted our wedge dash structure to it. Again, it's a 2D representation. You need to eliminate your wedged and dashed bonds.