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Ch.5 - Stereochemistry
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
All textbooksWade 9th EditionCh.5 - StereochemistryProblem 19e,f
Chapter 5, Problem 19e,f

For each Fischer projection, label each asymmetric carbon atom as (R) or (S).
(e) Fischer projection diagram showing asymmetric carbon atoms labeled for R and S configurations.
(f) Fischer projection diagram showing asymmetric carbon atoms labeled as (R) or (S) for structures A to F.

Verified step by step guidance
1
Step 1: Identify the asymmetric carbon atoms in each Fischer projection. An asymmetric carbon is a carbon atom bonded to four different groups. In both structures, the two middle carbon atoms are asymmetric.
Step 2: Assign priorities to the substituents around each asymmetric carbon based on the Cahn-Ingold-Prelog (CIP) priority rules. Higher atomic numbers get higher priority. For example, -OH has a higher priority than -H.
Step 3: Determine the configuration (R or S) for each asymmetric carbon. To do this, orient the molecule so that the lowest priority group (usually H) is pointing away from you. Then, trace the path from the highest priority group (1) to the second (2) and third (3). If the path is clockwise, the configuration is (R); if counterclockwise, it is (S).
Step 4: For the first structure, analyze the top asymmetric carbon and assign its configuration (R or S) using the steps above. Repeat the process for the bottom asymmetric carbon.
Step 5: For the second structure, repeat the same process as in Step 4. Assign the configuration (R or S) for the top and bottom asymmetric carbons. Ensure to double-check the orientation of the lowest priority group to avoid errors.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Fischer Projections

Fischer projections are a two-dimensional representation of three-dimensional organic molecules, particularly useful for depicting stereochemistry. In these diagrams, vertical lines represent bonds that project away from the viewer, while horizontal lines indicate bonds that project towards the viewer. This format is especially helpful for visualizing the configuration of chiral centers in molecules.
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Chirality and Asymmetric Carbons

Chirality refers to the property of a molecule that makes it non-superimposable on its mirror image, often due to the presence of asymmetric carbon atoms. An asymmetric carbon, or chiral center, is a carbon atom bonded to four different substituents, leading to two possible configurations: (R) for rectus (right) and (S) for sinister (left). Identifying these centers is crucial for understanding the stereochemistry of organic compounds.
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Cahn-Ingold-Prelog Priority Rules

The Cahn-Ingold-Prelog (CIP) priority rules are a systematic method for determining the (R) or (S) configuration of chiral centers. According to these rules, substituents attached to the chiral carbon are ranked based on atomic number, with higher atomic numbers receiving higher priority. If two substituents have the same atomic number, the next atoms in the substituent chain are compared until a difference is found, guiding the assignment of (R) or (S) based on the spatial arrangement.
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Related Practice
Textbook Question

For each Fischer projection, label each asymmetric carbon atom as (R) or (S).

(g)

(h)

(i)

1
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Textbook Question

For each Fischer projection,

1. make a model.

2. draw the mirror

3.. determine whether the mirror is the same as, or different from, the original ­structure.

4. draw any mirror planes of symmetry that are apparent from the Fischer projections.

(c)

(d)

1
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Textbook Question

For each Fischer projection, label each asymmetric carbon atom as (R) or (S).

(c)

(d)

Textbook Question

For each pair, give the relationship between the two compounds. Making models will be helpful.

(a) (2R,3S)-2,3-dibromohexane and (2S,3R)-2,3-dibromohexane

(b) (2R,3S)-2,3-dibromohexane and (2R,3R)-2,3-dibromohexane

1
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Textbook Question

For each Fischer projection, label each asymmetric carbon atom as (R) or (S).

(a)

(b)

Textbook Question

For each pair, give the relationship between the two compounds. Making models will be helpful.

(c)

(d)