Textbook Question
For each Fischer projection, label each asymmetric carbon atom as (R) or (S).
(g)
(h)
(i)
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Ch.5 - Stereochemistry
Wade9th EditionOrganic ChemistryISBN: 9780135213728
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Table of contents
- Ch.1 - Structure and Bonding107
- Ch. 2 - Acids and Bases; Functional Groups115
- Ch.3 - Structure and Stereochemistry of Alkanes100
- Ch.4 - The Study of Chemical Reactions99
- Ch.5 - Stereochemistry93
- Ch.6 - Alkyl Halides; Nucleophilic Substitution118
- Ch. 7 - Structure and Synthesis of Alkenes; Elimination158
- Ch.8 - Reactions of Alkenes171
- Ch.9 - Alkynes91
- Ch.10 - Structure and Synthesis of Alcohols143
- Ch.11 - Reactions of Alcohols104
- Ch. 12 - Infrared Spectroscopy and Mass Spectrometry22
- Ch. 13 - Nuclear Magnetic Resonance Spectroscopy45
- Ch. 14 - Ethers, Epoxides, and Thioethers72
- Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy89
- Ch. 16 - Aromatic Compounds74
- Ch. 17 - Reactions of Aromatic Compounds126
- Ch. 18 - Ketones and Aldehydes193
- Ch. 19 - Amines129
- Ch. 20 - Carboxylic Acids77
- Ch. 21 - Carboxylic Acid Derivatives141
- Ch. 22 - Condensations and Alpha Substitutions of Carbonyl Compounds175
- Ch. 23 - Carbohydrates and Nucleic Acids93
- Ch. 24 - Amino Acids, Peptides, and Proteins54
Chapter 5, Problem 19a,b
For each Fischer projection, label each asymmetric carbon atom as (R) or (S).
(a) 
(b) 
Verified step by step guidance1
Step 1: Identify the asymmetric carbon atoms in each Fischer projection. An asymmetric carbon is bonded to four different groups. For structure (a), the central carbon is asymmetric as it is bonded to CHO, CH2OH, H, and OH. For structure (b), the central carbon is asymmetric as it is bonded to CH2OH, CH2OH, H, and Br.
Step 2: Assign priorities to the substituents attached to the asymmetric carbon based on the Cahn-Ingold-Prelog (CIP) rules. The priority is determined by atomic number: higher atomic numbers get higher priority. For structure (a), the priorities are: CHO (1), OH (2), CH2OH (3), H (4). For structure (b), the priorities are: Br (1), CH2OH (2), CH2OH (3), H (4).
Step 3: Orient the molecule so that the lowest priority group (H) is pointing away from you. In a Fischer projection, the vertical bonds are considered to be pointing away from the viewer, and the horizontal bonds are pointing toward the viewer.
Step 4: Determine the order of the remaining substituents (1 → 2 → 3) in a clockwise or counterclockwise direction. If the order is clockwise, the configuration is (R). If the order is counterclockwise, the configuration is (S).
Step 5: Label the asymmetric carbon atoms in each structure as (R) or (S) based on the analysis from Step 4. Ensure the configuration is consistent with the orientation of the molecule in the Fischer projection.
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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 represent bonds that project towards the viewer. This format is essential for identifying chiral centers and determining the configuration of stereoisomers.
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Monosaccharides - Drawing Fischer Projections
Chirality and Asymmetric Carbon Atoms
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 atom, or chiral center, is 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 molecule's stereochemistry.
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Cahn-Ingold-Prelog Priority Rules
The Cahn-Ingold-Prelog (CIP) priority rules are a systematic method for assigning (R) or (S) configurations to chiral centers in organic molecules. According to these rules, substituents attached to the chiral carbon are ranked based on atomic number, with higher atomic numbers receiving higher priority. The configuration is determined by the orientation of the substituents when the lowest priority group is oriented away from the viewer.
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01:48Why stereoisomers need their own naming system.
Related Practice
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)
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Textbook Question
For each Fischer projection, label each asymmetric carbon atom as (R) or (S).
(c)
(d)
Textbook Question
Draw a Fischer projection for each compound. Remember that the cross represents an asymmetric carbon atom, and the carbon chain should be along the vertical, with the IUPAC numbering from top to bottom.
(c) (S)-1,2-dibromobutane
(d) (R)-butan-2-ol
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Textbook Question
Draw a Fischer projection for each compound. Remember that the cross represents an asymmetric carbon atom, and the carbon chain should be along the vertical, with the IUPAC numbering from top to bottom.
(e)
1
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Textbook Question
For each Fischer projection, label each asymmetric carbon atom as (R) or (S).
(e)
(f)
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