Textbook Question
Explain how R and S are related to (+) and (-).
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Ch. 4 - Isomers: The Arrangement of Atoms in Space
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds:Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
Chapter 5, Problem 84e,f
Indicate whether each of the following structures is (R)-2-chlorobutane or (S)-2-chlorobutane:
e. 
f. 
Verified step by step guidance1
Step 1: Identify the chiral center in the molecule. In both structures, the chiral center is the carbon atom bonded to four different groups: a bromine atom (Br), a hydrogen atom (H), a methyl group (CH3), and an ethyl group (CH2CH3).
Step 2: Assign priorities to the substituents based on the Cahn-Ingold-Prelog priority rules. The substituent with the highest atomic number gets the highest priority. Here, Br > CH2CH3 > CH3 > H.
Step 3: Orient the molecule so that the lowest priority group (H) is pointing away from you. This is crucial for determining the configuration.
Step 4: Trace the path from the highest priority group (1) to the second (2) and then to the third (3). If the path is clockwise, the configuration is (R). If the path is counterclockwise, the configuration is (S).
Step 5: Apply the above steps to each structure (a and b) individually to determine whether it is (R)-2-chlorobutane or (S)-2-chlorobutane.
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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. In the case of 2-chlorobutane, the chirality arises from the presence of the chlorine atom and the different alkyl groups attached to the chiral carbon.
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Cahn-Ingold-Prelog Priority Rules
The Cahn-Ingold-Prelog (CIP) priority rules are a set of guidelines used to assign priorities to the substituents attached to a chiral center. According to these rules, the substituents are ranked based on atomic number; higher atomic numbers receive higher priority. If two substituents have the same atomic number, the next atoms in the chain are considered until a difference is found, which is crucial for determining the (R) or (S) configuration.
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R and S Configurations
The (R) and (S) designations are used to describe the absolute configuration of chiral centers in molecules. To determine whether a chiral center is (R) or (S), one must first assign priorities to the substituents using the CIP rules, then orient the molecule so that the lowest priority substituent is at the back. If the sequence from highest to lowest priority is clockwise, the configuration is (R); if counterclockwise, it is (S).
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Related Practice
Textbook Question
The specific rotation of (R)-(+)-glyceraldehyde is +8.7. If the observed specific rotation of a mixture of (R)-glyceraldehyde and (S)-glyceraldehyde is +1.4, what percent of glyceraldehyde is present as the R enantiomer?
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Textbook Question
Indicate whether each of the following structures is (R)-2-chlorobutane or (S)-2-chlorobutane:
c.
d.
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Textbook Question
Butaclamol is a potent antipsychotic that has been used clinically in the treatment of schizophrenia. How many asymmetric centers does it have?
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Textbook Question
Indicate whether each of the following structures is (R)-2-chlorobutane or (S)-2-chlorobutane:
a.
b.
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Textbook Question
Are the following pairs identical, enantiomers, diastereomers, or constitutional isomers?
a.
b.
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