Draw a Fischer projection of ( S )-proline.

Name: Problem 26, Chapter 26: Organic Chemistry
Uploaded: 2020-06-02T19:07:23-08:00
Duration: 2 min 45 s
Channel: Dalton Hilovsky
Description: Draw a Fischer projection of ( S )-proline.

Key Concepts

Fischer Projection

A Fischer projection is a two-dimensional representation of a molecule's three-dimensional structure. It is especially used in carbohydrate and amino acid chemistry to depict chirality and stereochemistry. In this projection, vertical lines represent bonds going away from the viewer, while horizontal lines represent bonds coming toward the viewer, allowing for an unambiguous depiction of the stereocenters.

Chirality and Absolute Configuration

Chirality refers to the property of a molecule having a non-superimposable mirror image, which is central to understanding its biological function and chemical reactivity. Absolute configuration, described by the (R)/(S) system, is determined by the spatial arrangement of substituents around a stereocenter using the Cahn-Ingold-Prelog priority rules. In this system, (S) indicates that the substituents are arranged in a counterclockwise order when viewed from a specific angle.

Cahn–Ingold–Prelog Priority Rules

These rules are used to assign priorities to the groups attached to a chiral center based on atomic numbers and connectivity. The groups are ranked, and the molecule is oriented so that the lowest priority group is positioned away from the observer. This ordering is essential for accurately assigning an (R) or (S) configuration to the molecule.

Cyclic Amino Acid Structure

Certain amino acids, like proline, feature a cyclic structure where the side chain forms a ring with the amino group. This unique structure affects both the conformational flexibility and the stereochemical depiction in projections. When drawing a Fischer projection of a cyclic amino acid, special attention is needed to correctly represent the connectivity and spatial arrangement of its rings and chiral centers.

Transcript

00:01 All right, so we're going to draw a fissure projection for s -proline.

00:04 You'll remember that proline is special because it forms that five -membered ring with its r -group and the amino.

00:11 So you'll see on the left i have kind of just the general thing for a fisher projection.

00:16 Notice that the ones going to the left and the right are coming out of the plane of the page on wedges.

00:23 All right, so if i draw a pretty general structure of a fish projection for an amino acid, i typically start with c.

00:30 And that's going to be at top.

00:34 And then my r group is typically at the bottom.

00:37 All right, so what i'm going to notice here is that this is important because then i'm also going to have these right there.

00:45 And that means the hydrogen is going to be either left or right.

00:48 So the hydrogen or the lowest priority is going to be either here or here.

00:53 That's important because that means the configuration would be flipped from what we'd normally kind of view it as.

00:58 So what i'm going to do to find s -proline is first i'm going to draw what the structure of an an r proline would look like, or at least the priorities of that, and then basically flip it.

01:09 Right.

01:10 So what i mean by that is because this carbonylic acid is always at the top, i know that that's going to be my second priority.

01:18 I know the r group is going to be the third priority, right? so i need to arrange the nitrogen and the hydrogen such that i will get what i consider it to be the r configuration.

01:30 Right.

01:31 So in order to do that, i'm going to put my one in my first.

01:33 4 here...

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