Draw the cis and trans isomers for the following: a. 1-bromo-4-chlorocyclohexane b. 1-ethyl-3-methylcyclobutane
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1
Remembering General Chemistry: Electronic Structure and Bonding
1.1
The Structure of an Atom
1.11
The Bonds in Ammonia and in the Ammonium Ion
1.12
The Bonds in Water
1.13
The Bond in a Hydrogen Halide
1.14
Hybridization and Molecular Geometry
1.15
Summary: Hybridization, Bond Lengths, Bond Strengths, and Bond Angles
1.16
The Dipole Moments of Molecules
1.2
How the Electrons in an Atom Are Distributed
1.3
Ionic and Covalent Bonds
1.4
How the Structure of a Compound Is Represented
1.5
Atomic Orbitals
1.6
An Introduction to Molecular Orbital Theory
1.7
How Single Bonds Are Formed in Organic Compounds
1.8
How a Double Bond Is Formed: The Bonds in Ethene
1.9
How a Triple Bond Is Formed: The Bonds in Ethyne
2
Acids and Bases: Central to Understanding Organic Chemistry
2.1
An Introduction to Acids and Bases
2.11
Buffer Solutions
2.12
Lewis Acids and Bases
2.2
pKa and pH
2.3
Organic Acids and Bases
2.4
How to Predict the Outcome of an Acid–Base Reaction
2.5
How to Determine the Position of Equilibrium
2.6
How the Structure of an Acid Affects its pKa Value
2.7
How Substituents Affect the Strength of an Acid
2.8
An Introduction to Delocalized Electrons
2.9
A Summary of the Factors that Determine Acid Strength
3
An Introduction to Organic Compounds: Nomenclature, Physical Properties, and Representation of Structure
3.1
How Alkyl Substituents Are Named
3.11
Some Cycloalkanes Have Angle Strain
3.12
Conformers of Cyclohexane
3.13
Conformers of Monosubstituted Cyclohexanes
3.14
Conformers of Disubstituted Cyclohexanes
3.2
The Nomenclature of Alkanes
3.3
The Nomenclature of Cycloalkanes, Skeletal Structures
3.4
The Nomenclature of Alkyl Halides
3.5
The Nomenclature of Ethers
3.6
The Nomenclature of Alcohols
3.7
The Nomenclature of Amines
3.8
The Structures of Alkyl Halides, Alcohols, Ethers, and Amines
3.9
The Physical Properties of Alkanes, Alkyl Halides, Alcohols, Ethers, and Amines
4
Isomers: The Arrangement of Atoms in Space
4.1
Cis–Trans Isomers Result From Restricted Rotation
4.11
Compounds with More than One Asymmetric Center
4.12
Stereoisomers of Cyclic Compounds
4.13
Meso Compounds Have Asymmetric Centers but Are Optically Inactive
4.14
How to Name Isomers with More than One Asymmetric Center
4.15
How Enantiomers Can Be Separated
4.16
Nitrogen and Phosphorus Atoms Can Be Asymmetric Centers
4.2
A Chiral Object Has a Nonsuperimposable Mirror Image
4.3
An Asymmetric Center Is a Cause of Chirality in a Molecule
4.4
Isomers with One Asymmetric Center
4.5
Asymmetric Centers and Stereocenters
4.6
How to Draw Enantiomers
4.7
Naming Enantiomers by the R,S System
4.8
Chiral Compounds Are Optically Active
4.9
How Specific Rotation Is Measured
5
Alkenes: Structure, Nomenclature, and an Introduction to Reactivity, Thermodynamics and Kinetics
5.1
Molecular Formulas and the Degree of Unsaturation
5.11
Catalysis
5.2
The Nomenclature of Alkenes
5.3
The Structure of Alkenes
5.4
Naming Alkenes Using the E,Z System
5.6
How Alkenes React, Curved Arrows Show the Flow of Electrons
5.7
Thermodynamics and Kinetics
5.9
The Difference Between the Rate of a Reaction and the Rate Constant for a Reaction
6
The Reactions of Alkenes, The Stereochemistry of Addition Reactions
6.1
The Addition of a Hydrogen Halide to an Alkene
6.11
The Addition of Ozone to an Alkene: Ozonolysis
6.12
The Addition of Hydrogen to an Alkene
6.13
The Relative Stabilities of Alkenes
6.14
Regioselective, Stereoselective, and Stereospecific Reactions
6.15
The Stereochemistry of Electrophilic Addition Reactions of Alkenes
6.16
The Stereochemistry of Enzyme-Catalyzed Reactions
6.17
Enantiomers Can Be Distinguished by Biological Molecules
6.18
Reactions and Synthesis
6.2
Carbocation Stability Depends on the Number of Alkyl Groups Attached to the Positively Charged Carbon
6.3
What Does the Structure of the Transition State Look Like?
6.4
Electrophilic Addition Reactions Are Regioselective
6.5
The Addition of Water to an Alkene
6.6
The Addition of an Alcohol to an Alkene
6.7
A Carbocation Will Rearrange if it Can Form a More Stable Carbocation
6.8
The Addition of Borane to an Alkene: Hydroboration–Oxidation
6.9
The Addition of a Halogen to an Alkene
7
The Reactions of Alkynes An Introduction to Multistep Synthesis
7.1
The Nomenclature of Alkynes
7.11
Synthesis Using Acetylide Ions
7.12
An Introduction to Multistep Synthesis
7.2
How to Name a Compound That Has More than One Functional Group
7.3
The Physical Properties of Unsaturated Hydrocarbons
7.4
The Structure of Alkynes
7.5
Alkynes Are Less Reactive than Alkenes
7.6
The Addition of Hydrogen Halides and the Addition of Halogens to an Alkyne
7.7
The Addition of Water to an Alkyne
7.8
The Addition of Borane to an Alkyne: Hydroboration–Oxidation
7.9
The Addition of Hydrogen to an Alkyne
8
Delocalized Electrons and Their Effect on Stability, pKa, and the Products of a Reaction
8.1
Delocalized Electrons Explain Benzene’s Structure
8.11
Antiaromaticity
8.12
A Molecular Orbital Description of Aromaticity and Antiaromaticity
8.13
More Examples that Show How Delocalized Electrons Increase Stability
8.14
A Molecular Orbital Description of Stability
8.15
How Delocalized Electrons Affect pKa Values
8.16
Delocalized Electrons Can Affect the Product of a Reaction
8.17
Reactions of Dienes
8.18
Thermodynamic versus Kinetic Control
8.19
The Diels–Alder Reaction Is a 1,4-Addition Reaction
8.20
Retrosynthetic Analysis of the Diels–Alder Reaction
8.4
How to Draw Resonance Contributors
8.5
The Predicted Stabilities of Resonance Contributors
8.6
Delocalization Energy Is the Additional Stability Delocalized Electrons Give to a Compound
8.8
The Two Criteria for Aromaticity
8.9
Applying the Criteria for Aromaticity
9
Substitution Reactions of Alkyl Halides
9.1
The Mechanism for an Sn2 Reaction
9.2
Factors that Affect SN2 Reactions
9.3
The Mechanism for an SN1 Reaction
9.4
Factors That Affect SN1 Reactions
9.5
Benzylic Halides, Allylic Halides, Vinylic Halides, and Aryl Halides
9.6
Competition between SN2 and SN1 Reactions
9.7
The Role of the Solvent in SN1 and SN2 Reactions
9.8
Intermolecular versus Intramolecular Reactions
9.9
Methylating Agents Used by Chemists versus Those Used by Cells
10
Elimination Reactions of Alkyl Halides, Competition Between Substitution and Elimination
10.10
Substitution and Elimination Reactions in Synthesis
10.11
Approaching the Problem
10.2
An E2 Reaction is Regioselective
10.3
The E1 Reaction
10.4
Benzylic and Allylic Halides
10.5
Competition Between E2 and E1 Reactions
10.6
E2 and E1 Reactions are Stereoselective
10.7
Elimination from Substituted Cyclohexanes
10.8
A Kinetic Isotope Effect Can Help Determine a Mechanism
10.9
Competition Between Substitution and Elimination
11
Reactions of Alcohols, Ethers, Epoxides, Amines, and Thiols
11.10
Quaternary Ammonium Hydroxides Undergo Elimination Reactions
11.11
Thiols, Sulfides, and Sulfonium Salts
11.2
Other Methods Used To Convert Alcohols into Alkyl Halides
11.4
Elimination Reactions of Alcohols: Dehydration
11.5
Oxidation of Alcohols
11.6
Nucleophilic Substitution Reactions of Ethers
11.7
Nucleophilic Substitution Reactions of Epoxides
11.8
Arene Oxides
11.9
Amines Do Not Undergo Substitution or Elimination Reactions
12
Organometallic Compounds
12.1
Organolithium and Organomagnesium Compounds
12.3
Organocuprates
12.4
Palladium-Catalyzed Coupling Reactions
12.5
Alkene Metathesis
13
Radicals, Reactions of Alkanes
13.10
More Practice with Multistep Synthesis
13.11
Radical Reactions Occur in Biological Systems
13.12
Radicals and Stratospheric Ozone
13.2
The Chlorination and Bromination of Alkanes
13.3
Radical Stability Depends on the Number of Alkyl Groups Attached to the Carbon with the Unpaired Electron
13.4
The Distribution of Products Depends on Probability and Reactivity
13.5
The Reactivity–Selectivity Principle
13.6
Formation of Explosive Peroxides
13.7
The Addition of Radicals to an Alkene
13.8
The Stereochemistry of Radical Substitution and Radical Addition Reactions
13.9
Radical Substitution of Benzylic and Allylic Hydrogens
14
Mass Spectrometry, Infrared Spectroscopy, and Ultraviolet/ Visible Spectroscopy
14.1
Mass Spectrometry
14.13
The Position of Absorption Bands
14.14
The Position and Shape of an Absorption Band is Affected by Electron Delocalization, Electron Donation and Withdrawal, and Hydrogen Bonding
14.15
The Absence of Absorption Bands
14.16
Some Vibrations are Infrared Inactive
14.17
How to Interpret an Infrared Spectrum
14.19
The Beer–Lambert Law
14.2
The Mass Spectrum, Fragmentation
14.21
The Visible Spectrum and Color
14.22
Some Uses of UV/ VIS Spectroscopy
14.3
Using The m/z Value of The Molecular Ion to Calculate The Molecular Formula
14.4
Isotopes in Mass Spectrometry
14.5
High-Resolution Mass Spectrometry Can Reveal Molecular Formulas
14.6
The Fragmentation Patterns of Functional Groups
14.9
Spectroscopy and The Electromagnetic Spectrum
15
NMR Spectroscopy
15.1
An Introduction to NMR Spectroscopy
15.11
What Causes Splitting?
15.13
Coupling Constants Identify Coupled Protons
15.14
Splitting Diagrams Explain the Multiplicity of a Signal
15.15
Diastereotopic Hydrogens Are Not Chemically Equivalent
15.17
Protons Bonded to Oxygen and Nitrogen
15.20
13C NMR Spectroscopy
15.22
Two-Dimensional NMR Spectroscopy
15.4
The Number of Signals in an 1H NMR Spectrum
15.5
The Chemical Shift Tells How Far the Signal Is from the Reference Signal
15.6
The Relative Positions of 1H NMR Signals
15.7
The Characteristic Values of Chemical Shifts
15.9
The Integration of NMR Signals Reveals The Relative Number of Protons Causing Each Signal
16
Reactions of Carboxylic Acids and Carboxylic Derivatives
16.1
The Nomenclature of Carboxylic Acids and Carboxylic Acid Derivatives
16.12
How the Mechanism for Nucleophilic Addition–Elimination Was Confirmed
16.13
Fats and Oils Are Triglycerides
16.14
Reactions of Carboxylic Acids
16.15
Reactions of Amides
16.17
THE GENERAL MECHANISM FOR NUCLEOPHILIC ADDITIONAL - ELIMINATION REACTIONS
16.18
The Hydrolysis of an Imide: A Way to Synthesize Primary Amines
16.19
Nitriles
16.2
The Structures of Carboxylic Acids and Carboxylic Acid Derivatives
16.21
Dicarboxylic Acids
16.22
How Chemists Activate Carboxylic Acids
16.4
Fatty Acids Are Long-Chain Carboxylic Acids
16.5
How Carboxylic Acids and Carboxylic Acid Derivatives React
16.6
The Relative Reactivities of Carboxylic Acids and Carboxylic Acid Derivatives
16.9
The Reactions of Esters
17
Reactions of Aldehydes and Ketones, More Reactions of Carboxylic Acid Derivatives, Reactions of A,B-Unsaturated Carbonyl Compounds
17.1
The Nomenclature of Aldehydes and Ketones
17.11
The Reactions of Aldehydes and Ketones with Water
17.12
The Reactions of Aldehydes and Ketones with Alcohols
17.13
Protecting Groups
17.15
The Reactions of Aldehydes and Ketones with a Peroxyacid
17.17
Disconnections, Synthons, and Synthetic Equivalents
17.18
Nucleophilic Addition to a, b-Unsaturated Aldehydes and Ketones
17.19
Nucleophilic Addition to a, b-Unsaturated Carboxylic Acid Derivatives
17.2
The Relative Reactivities of Carbonyl Compounds
17.4
The Reactions of Carbonyl Compounds with Grignard Reagents
17.5
The Reactions of Carbonyl Compounds with Acetylide Ions
17.6
The Reactions of Aldehydes and Ketones with Cyanide Ion
17.7
The Reactions of Carbonyl Compounds with Hydride Ion
17.8
More About Reduction Reactions
17.9
Chemoselective Reactions
18
Reactions at the a-Carbon of Carbonyl Compound
18.1
The Acidity of an a-Hydrogen
18.11
The Dehydration of Aldol Addition Products Forms a,b-Unsaturated Aldehydes and Ketones
18.12
A Crossed Aldol Addition
18.13
A Claisen Condensation Forms a b-Keto Ester
18.14
Other Crossed Condensations
18.15
Intramolecular Condensations and Intramolecular Aldol Additions
18.16
The Robinson Annulation
18.17
Carboxylic Acids with A Carbonyl Group at the 3-Position Can Be Decarboxylated
18.18
The Malonic Ester Synthesis: A Way to Synthesize a Carboxylic Acid
18.19
The Acetoacetic Ester Synthesis: A Way to Synthesize a Methyl Ketone
18.2
Keto–Enol Tautomers
18.21
Reactions at the a-Carbon in Living Systems
18.3
Keto–Enol Interconversion
18.4
Halogenation of the a-Carbon of Aldehydes and Ketones
18.5
Halogenation of the a-Carbon of Carboxylic Acids: The Hell–Volhard–Zelinski Reaction
18.6
Forming an Enolate Ion
18.7
Alkylating the a-Carbon of Carbonyl Compounds
18.8
Alkylating and Acylating the a-Carbon using an Enamine Intermediate
18.9
Alkylating the b-Carbon: The Michael Reaction
19
Reactions of Benzene and Substituted Benzenes
19.1
The Nomenclature of Monosubstituted Benzenes
19.12
How Some Substituents on a Benzene Ring Can Be Chemically Changed
19.13
The Nomenclature of Disubstituted and Polysubstituted Benzenes
19.14
The Effect of Substituents on Reactivity
19.15
The Effect of Substituents on Orientation
19.16
The Effect of Substituents on pKa
19.18
Additional Considerations Regarding Substituent Effects
19.19
The Synthesis of Monosubstituted and Disubstituted Benzenes
19.2
How Benzene Reacts
19.21
The Synthesis of Substituted Benzenes Using Arenediazonium Salts
19.22
The Arenediazonium Ion as an Electrophile
19.23
The Mechanism for the Reaction of Amines with Nitrous Acid
19.24
Nucleophilic Aromatic SubstitutioNucleophilic Aromatic Substitution: An Addition–Elimination Reaction
19.25
The Synthesis of Cyclic Compounds
19.4
The Halogenation of Benzene
19.5
The Nitration of Benzene
19.6
The Sulfonation of Benzene
19.7
The Friedel–Crafts Acylation of Benzene
19.8
The Friedel–Crafts Alkylation of Benzene
20
More About Amines, Reactions of Heterocyclic Compounds
20.1
More About Amine Nomenclature
20.2
More About the Acid–Base Properties of Amines
20.3
Amines React as Bases and as Nucleophiles
20.5
Aromatic Five-Membered-Ring Heterocycles
20.6
Aromatic Six-Membered-Ring Heterocycles
20.7
Some Amine Heterocycles Have Important Roles in Nature 1
21
The Organic Chemistry of Carbohydrates
21.1
Classification of Carbohydrates
21.11
Glucose is the Most Stable Aldohexose
21.12
Formation of Glycosides
21.14
Reducing and Nonreducing Sugars
21.15
Disaccharides
21.16
Polysaccharides
21.17
Some Naturally Occurring Compounds Derived from Carbohydrates
21.18
Carbohydrates on Cell Surfaces
21.2
The D and L Notation
21.3
The Configurations of the Aldoses
21.4
The Configurations of the Ketoses
21.5
The Reactions of Monosaccharides in Basic Solutions
21.6
The Oxidation–Reduction Reactions of Monosaccharides
21.7
Lengthening the Chain: The Kiliani–Fischer Synthesis
21.8
Shortening The Chain: The Wohl Degradation
21.9
The Stereochemistry of Glucose: The Fischer Proof
22
The Organic Chemistry of Amino Acids, Peptides, and Proteins
22.1
The Nomenclature of Amino Acids
22.11
Automated Peptide Synthesis
22.13
How to Determine the Primary Structure of a Polypeptide or Protein
22.14
Secondary Structure
22.15
Tertiary Structure
22.16
Quaternary Structure
22.2
The Configuration of Amino Acids
22.3
The Acid–Base Properties of Amino Acids
22.4
The Isoelectric Point
22.5
Separating Amino Acids
22.6
The Synthesis of Amino Acids
22.7
The Resolution of Racemic Mixtures of Amino Acids
22.8
Peptide Bonds and Disulfide Bonds
22.9
Some Interesting Peptides
23.10
The Mechanism for an Enzyme-Catalyzed Reaction That Involves Two Sequential SN2 Reactions
23.11
The Mechanism for an Enzyme-Catalyzed Reaction That Is Reminiscent of the Base-Catalyzed Enediol Rearrangement
23.12
The Mechanism for an Enzyme-Catalyzed Reaction that Is Reminiscent of an Aldol Addition
23.2
Acid Catalysis
23.3
Base Catalysis
23.5
Metal-Ion Catalysis
23.6
Intramolecular Reactions
23.7
Intramolecular Catalysis
23.9
The Mechanisms for Two Enzyme-Catalyzed Reactions That Are Reminiscent of Acid-Catalyzed Amide Hydrolysis
24
The Organic Chemistry of the Coenzymes, Compounds Derived from Vitamins
24.1
Niacin: The Vitamin Needed for Many Redox Reactions
24.2
Riboflavin: Another Vitamin Used in Redox Reactions
24.3
Vitamin B1: The Vitamin Needed for Acyl Group Transfer
24.5
Vitamin B6: The Vitamin Needed for Amino Acid Transformations
24.6
Vitamin B12: The Vitamin Needed for Certain Isomerizations
24.7
Folic Acid: The Vitamin Needed for One-Carbon Transfer
24.8
Vitamin K: The Vitamin Needed for Carboxylation of Glutamate
25
The Organic Chemistry of the Metabolic Pathways, Terpene Biosynthesis
25.10
The Citric Acid Cycle
25.11
Oxidative Phosphorylation
25.12
Anabolism
25.15
Amino Acid Biosynthesis
25.16
Terpenes Contain Carbon Atoms in Multiples of Five
25.17
How Terpenes are Biosynthesized
25.18
How Nature Synthesizes Cholesterol
25.4
The “High-Energy” Character of Phosphoanhydride Bonds
25.6
The Catabolism of Fats
25.7
The Catabolism of Carbohydrates
25.8
The Fate of Pyruvate
25.9
The Catabolism of Proteins
26
The Chemistry of the Nucleic Acids
26.1
Nucleosides and Nucleotides
26.12
How the Base Sequence of DNA is Determined
26.2
Other Important Nucleotides
26.3
Nucleic Acids Are Composed of Nucleotide Subunits
26.5
The Biosynthesis of DNA Is Called Replication
26.7
The Biosynthesis of RNA Is Called Transcription
26.9
The Biosynthesis of Proteins Is Called Translation
27
Synthetic Polymers
27.10
Biodegradable Polymers
27.2
Chain-Growth Polymers
27.4
Polymerization of Dienes, The Manufacture of Rubber
27.7
Classes of Step-Growth Polymers
27.8
Physical Properties of Polymers
28
Pericyclic Reactions
28.2
Molecular Orbitals and Orbital Symmetry
28.3
Electrocyclic Reactions
28.4
Cycloaddition Reactions
28.5
Sigmatropic Rearrangements
28.6
Pericyclic Reactions in Biological Systems
28.9
Classes of Step-Growth Polymers
Textbook Solutions for Organic Chemistry
Chapter 4.1 Problem 25
Question
A solution prepared by mixing 10 mL of a 0.10 M solution of the R enantiomer of a compound and 30 mL of a 0.10 M solution of the S enantiomer was found to have an observed specific rotation of +4.8 . What is the specific rotation of each of the enantiomers? ( Hint: mL * M = millimole, abbreviated as mmol) Solution One mmol (10 mL * 0.10 M) of the R enantiomer is mixed with 3 mmol (30 mL * 0.10 M) of the S enantiomer; 1 mmol of the R enantiomer plus 1 mmol of the S enantiomer will form 2 mmol of a racemic mixture, so there will be 2 mmol of S enantiomer left over. Because 2 out of 4 mmol is excess S enantiomer, the solution has a 50% enantiomeric excess. Knowing the enantiomeric excess and the observed specific rotation allows us to calculate the specific rotation. enantiomeric excess = observed specificrotation specific rotation of the pure enantiomer * 100% 50% = +4.8 x * 100% 50 100 = +4.8 x 1 2 = +4.8 x x = 21+4.82 x = 9.6 The S enantiomer has a specific rotation of +9.6 , so the R enantiomer has a specific rotation of -9.6 .
Solution
The first step in solving 4.1 problem number 3 trying to solve the problem we have to refer to the textbook question: A solution prepared by mixing 10 mL of a 0.10 M solution of the R enantiomer of a compound and 30 mL of a 0.10 M solution of the S enantiomer was found to have an observed specific rotation of +4.8 . What is the specific rotation of each of the enantiomers? ( Hint: mL * M = millimole, abbreviated as mmol) Solution One mmol (10 mL * 0.10 M) of the R enantiomer is mixed with 3 mmol (30 mL * 0.10 M) of the S enantiomer; 1 mmol of the R enantiomer plus 1 mmol of the S enantiomer will form 2 mmol of a racemic mixture, so there will be 2 mmol of S enantiomer left over. Because 2 out of 4 mmol is excess S enantiomer, the solution has a 50% enantiomeric excess. Knowing the enantiomeric excess and the observed specific rotation allows us to calculate the specific rotation. enantiomeric excess = observed specificrotation specific rotation of the pure enantiomer * 100% 50% = +4.8 x * 100% 50 100 = +4.8 x 1 2 = +4.8 x x = 21+4.82 x = 9.6 The S enantiomer has a specific rotation of +9.6 , so the R enantiomer has a specific rotation of -9.6 .
From the textbook chapter Cis–Trans Isomers Result From Restricted Rotation you will find a few key concepts needed to solve this.
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Title
Organic Chemistry 7
Author
Paula Yurkanis Bruice
ISBN
9780321803221
A solution prepared by mixing 10 mL of a 0.10 M solution of the R enantiomer of a
Chapter 4.1 textbook questions
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Chapter 4: Problem 2 Organic Chemistry 7
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Chapter 4: Problem 3 Organic Chemistry 7
a. Which of the following compounds can exist as cistrans isomers? b. For those compounds that can exist as cis and trans isomers, draw and label the isomers. 1. CH3CH 2. CH3CH2C CHCH2CH2CH3 CHCH3 CH2CH3 4. CH3CH2CH CH2 3. CH3CH CHCH3
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Chapter 4: Problem 4 Organic Chemistry 7
Draw skeletal structures for all the compounds in Problem 3 , including any cistrans isomers.
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Chapter 4: Problem 5 Organic Chemistry 7
Draw three compounds with molecular formula C5H10 that have carboncarbon double bonds but do not have cistrans isomers.
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Chapter 4: Problem 6 Organic Chemistry 7
Which of the following compounds have a dipole moment of zero? H H C Cl C H B Cl H C Cl C H C Cl Cl C H C H A H Cl C Cl C H
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Chapter 4: Problem 23 Organic Chemistry 7
( + )-Mandelic acid has a specific rotation of +158 . What would be the observed specific rotation of each of the following mixtures? a. 50% ( - )-mandelic acid and 50% ( + )-mandelic acid b. 25% ( - )-mandelic acid and 75% ( + )-mandelic acid c. 75% ( - )-mandelic acid and 25% ( + )-mandelic acid
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Chapter 4: Problem 24 Organic Chemistry 7
Naproxen, a nonsteroidal anti-inflammatory drug that is the active ingredient in Aleve (page 118 ) , has a specific rotation of +66 . One commercial preparation results in a mixture with a 97% enantiomeric excess. a. Does naproxen have the R or the S confi guration? b. What percent of each enantiomer is obtained from the commercial preparation?
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Chapter 4: Problem 25 Organic Chemistry 7
A solution prepared by mixing 10 mL of a 0.10 M solution of the R enantiomer of a compound and 30 mL of a 0.10 M solution of the S enantiomer was found to have an observed specific rotation of +4.8 . What is the specific rotation of each of the enantiomers? ( Hint: mL * M = millimole, abbreviated as mmol) Solution One mmol (10 mL * 0.10 M) of the R enantiomer is mixed with 3 mmol (30 mL * 0.10 M) of the S enantiomer; 1 mmol of the R enantiomer plus 1 mmol of the S enantiomer will form 2 mmol of a racemic mixture, so there will be 2 mmol of S enantiomer left over. Because 2 out of 4 mmol is excess S enantiomer, the solution has a 50% enantiomeric excess. Knowing the enantiomeric excess and the observed specific rotation allows us to calculate the specific rotation. enantiomeric excess = observed specificrotation specific rotation of the pure enantiomer * 100% 50% = +4.8 x * 100% 50 100 = +4.8 x 1 2 = +4.8 x x = 21+4.82 x = 9.6 The S enantiomer has a specific rotation of +9.6 , so the R enantiomer has a specific rotation of -9.6 .
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