Draw Fischer projections of the following molecules: (a) The S enantiomer of 2-bromobutane (b) T

step 1 We're at problem 36. Okay, we're given four molecules here. Part A is your bromobutane. Part B i

Draw Fischer projections of the following molecules: (a) The...

Key Concepts

Enantiomerism

Enantiomerism is the phenomenon whereby two molecules are non-superimposable mirror images of each other. These mirror images, or enantiomers, have identical physical properties except for their interaction with polarized light and chiral environments. In biological systems and many synthetic applications, enantiomers can exhibit very different behaviors, making their identification and representation in forms like Fischer projections critically important.

Cahn-Ingold-Prelog Priority Rules

The Cahn-Ingold-Prelog (CIP) priority rules are a systematic method for ranking substituents attached to a chiral center in order to determine its absolute configuration. Priorities are assigned based on the atomic number of the atoms directly attached to the stereocenter, with higher numbers signifying higher priority. In cases where atoms are identical, the analysis moves outward along the chain until a point of difference is found. This system underpins the assignment of R and S configurations in stereochemistry.

Chirality

Chirality refers to the geometric property of a molecule that is not superimposable on its mirror image. Molecules with one or more chiral centers have hands-on identities similar to left and right hands, which are mirror images but cannot be aligned perfectly. This property is critical in many areas of chemistry and biochemistry as it can greatly affect how molecules interact with other chiral substances, including biological receptors.

Fischer Projection

A Fischer projection is a two-dimensional representation used primarily in organic chemistry to depict the stereochemistry of molecules with chiral centers. It simplifies the three-dimensional structure to a flat arrangement where vertical lines represent bonds going away from the viewer, and horizontal lines represent bonds coming out towards the viewer. This method is especially useful for carbohydrates and amino acids, allowing for easy assignment of stereochemistry.

R and S Configuration

The R and S notation is part of the Cahn-Ingold-Prelog priority rules, which provide a standardized method for assigning the absolute configuration of chiral centers based on the priority of the attached substituents. 'R' (from the Latin 'rectus', right) indicates that the sequence of priorities proceeds in a clockwise fashion, while 'S' (from 'sinister', left) indicates a counterclockwise sequence. Correct assignment is essential in understanding the stereochemistry and reactivity of molecules.

Transcript

00:01 We're at problem 36.

00:02 Okay, we're given four molecules here.

00:04 Part a is your bromobutane.

00:07 Part b is your aline.

00:11 Part c, we have two hydroxypropinoic acid.

00:15 Okay, so hopefully you see why that is.

00:18 We have three carbons, right? one, two, three.

00:22 And this makes it the propanoic acid, and we have the two hydroxy group.

00:29 And finally, we have our three methyl hexane.

00:33 So 3 methyl hexane, you have 6 carbons, and you have that methyl group on carbon 3.

00:40 All right.

00:41 So this problem is asking for us to draw these molecules.

00:45 So part a, we want an s in nantrumor, okay, part b we want r.

00:51 Part c, we want r, and part d we want s.

00:55 So the way we're going to do that is we're going to take these groups.

01:03 So these groups hanging off of the molecules.

01:07 We're going to take those and draw them either going into the board or out of the board in order to create that inanchomer that we're looking for.

01:17 So part a here we want an s inantrumor.

01:21 So usually this, not usually always.

01:27 So bromine in this case would be your priority number one.

01:31 This is your priority number two and this is your priority number three okay so if you do that you're going to have this clockwise direction i'll just put it off to the side you're going to have this clockwise direction which will give you an r in angiomer which is not what you want so in order to to flip that we want the hydrogen remember there's a hydrogen that is with the bromine here you want this hydrogen to be going out of the board okay, so once it is going out of the board and it is priority four, this rnannchomer is going to turn into s...

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