Skip to main content
Ch. 4 - Isomers: The Arrangement of Atoms in Space
Bruice - Organic Chemistry 8th Edition
Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook
Chapter 5, Problem 23c,d

What is the configuration of each of the following?
c. Fischer projection of a chiral molecule showing bromine, hydrogen, and two carbon chains.
d. Structural representation of a molecule with multiple carbon chains, illustrating chirality in Fischer projections.

Verified step by step guidance
1
Step 1: Identify the chiral center in each molecule. A chiral center is a carbon atom bonded to four different groups. For molecule (c), the central carbon is bonded to CH3, Cl, H, and CH2CH3. For molecule (d), the central carbon is bonded to CH3, H, CH2CH2CH3, and CH2CH3.
Step 2: Assign priorities to the substituents attached to the chiral center based on the Cahn-Ingold-Prelog priority rules. The priority is determined by the atomic number of the atoms directly attached to the chiral center. For both molecules, Cl has the highest priority (atomic number 17), followed by CH2CH3, CH3, and H (lowest priority, atomic number 1).
Step 3: Orient the molecule so that the lowest priority group (H) is pointing away from you. This is crucial for determining the configuration correctly.
Step 4: Determine the order of the remaining three groups (1st, 2nd, and 3rd priority) as you move clockwise or counterclockwise around the chiral center. If the order is clockwise, the configuration is R. If the order is counterclockwise, the configuration is S.
Step 5: Apply the above steps to both molecules (c) and (d) to determine their configurations. Ensure that the lowest priority group (H) is oriented correctly before assigning R or S.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
6m
Was this helpful?

Key Concepts

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

Chirality

Chirality refers to the geometric property of a molecule that makes it non-superimposable on its mirror image. A chiral molecule typically has a carbon atom bonded to four different substituents, leading to two distinct configurations known as enantiomers. Understanding chirality is crucial for determining the configuration of chiral centers in organic compounds.
Recommended video:
Guided course
05:10
What is chirality?

Fischer Projections

Fischer projections are a two-dimensional representation of three-dimensional organic molecules, particularly useful for depicting the stereochemistry of chiral centers. In these projections, vertical lines represent bonds that extend away from the viewer, while horizontal lines represent bonds that come towards the viewer. This format helps in visualizing and analyzing the configuration of chiral molecules.
Recommended video:
Guided course
09:56
Monosaccharides - Drawing Fischer Projections

R/S Nomenclature

R/S nomenclature is a system used to assign configurations to chiral centers in molecules. The 'R' (rectus) and 'S' (sinister) designations are determined based on the priority of substituents attached to the chiral carbon, following the Cahn-Ingold-Prelog priority rules. This systematic approach is essential for accurately describing the stereochemistry of chiral compounds.
Recommended video:
Guided course
03:07
R and S Naming- Step 4