Textbook Question
Convert the line-angle drawings into Fischer projections.
(a)
5. Chirality
Fischer Projection
2:58 minutesProblem 7c
Textbook Question
Draw Fischer projections of the following molecules.
(c) 
Verified step by step guidance1
Step 1: Understand the structure provided. The molecule has an amine group (NH₂) attached to a chiral carbon, along with a phenyl group (Ph) and a methyl group (CH₃). The dashed wedge indicates that the NH₂ group is oriented away from the viewer.
Step 2: Recall the rules for drawing Fischer projections. In a Fischer projection, the horizontal lines represent bonds coming out of the plane (towards the viewer), and the vertical lines represent bonds going into the plane (away from the viewer). The chiral carbon is at the intersection of the lines.
Step 3: Assign priorities to the substituents based on the Cahn-Ingold-Prelog rules. The NH₂ group has the highest priority, followed by the phenyl group (Ph), the methyl group (CH₃), and finally the hydrogen atom.
Step 4: Orient the molecule so that the lowest priority group (hydrogen) is on the vertical line pointing away from the viewer. This ensures the correct stereochemistry is represented in the Fischer projection.
Step 5: Draw the Fischer projection. Place the NH₂ group and the phenyl group on the horizontal lines (coming out of the plane), and the methyl group and hydrogen on the vertical lines (going into the plane). Ensure the stereochemistry matches the original molecule.
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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 behind the plane of the page, while horizontal lines represent bonds that project out towards the viewer. This format is especially common for carbohydrates and amino acids, allowing for easy visualization of chiral centers and their configurations.
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Chirality and Stereocenters
Chirality refers to the property of a molecule that makes it non-superimposable on its mirror image, often due to the presence of one or more stereocenters. A stereocenter is typically a carbon atom bonded to four different substituents, leading to two possible configurations (R and S). Understanding chirality is crucial for accurately drawing Fischer projections, as it determines the spatial arrangement of the substituents around the stereocenter.
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Configuration Notation (R/S)
The R/S notation is a system used to specify the absolute configuration of chiral centers in molecules. To assign R (rectus) or S (sinister) configuration, one must prioritize the substituents attached to the stereocenter based on atomic number, with higher atomic numbers receiving higher priority. This systematic approach is essential for accurately representing the stereochemistry in Fischer projections and understanding the molecule's reactivity and interactions.
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