Textbook Question
Identify the alkene that would react with Ti(OiPr)₄, (+) -diethyltartrate, and t-butylhydroperoxide to give the following chiral, nonracemic epoxides.
(c)
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Ch. 9 - Alkenes II: Oxidation and Reduction
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
Chapter 8, Problem 39c
Questions (a)–(d) all refer to the following reaction, which has been engineered to produce one enantiomer to the exclusion of the other.
(c) Suppose the difference in activation energy is 1.6 kcal/mol. At what temperature would you produce C in 99% ee?
Verified step by step guidance1
Step 1: Understand the concept of enantiomeric excess (ee). Enantiomeric excess is a measure of the purity of one enantiomer in a mixture of two enantiomers. It is calculated using the formula: ee = (|C - B| / (C + B)) × 100%, where C and B represent the concentrations of the two enantiomers.
Step 2: Relate the difference in activation energy (ΔEa) to the ratio of enantiomers. The ratio of enantiomers can be determined using the equation: ln(C/B) = -ΔEa / (RT), where R is the gas constant (1.987 cal/(mol·K)) and T is the temperature in Kelvin.
Step 3: Use the given enantiomeric excess (99% ee) to find the ratio of enantiomers. For 99% ee, the ratio of C to B can be expressed as: C/B = (1 + ee) / (1 - ee). Substituting ee = 0.99, calculate the ratio C/B.
Step 4: Rearrange the equation ln(C/B) = -ΔEa / (RT) to solve for temperature (T). Substitute the values for ΔEa (1.6 kcal/mol, converted to cal/mol), R (1.987 cal/(mol·K)), and the calculated ratio C/B into the equation.
Step 5: Perform the calculation to determine the temperature (T) in Kelvin. Once T is found, you can convert it to Celsius if needed by subtracting 273.15 from the Kelvin value.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Enantiomers and Enantiomeric Excess (ee)
Enantiomers are pairs of molecules that are non-superimposable mirror images of each other, often differing in their spatial arrangement. Enantiomeric excess (ee) quantifies the purity of one enantiomer over the other in a mixture, expressed as a percentage. A high ee indicates a predominance of one enantiomer, which is crucial in applications like pharmaceuticals where specific enantiomers can have different biological effects.
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Calculating Enantiomeric Excess and Observed Rotation
Activation Energy and Temperature
Activation energy is the minimum energy required for a chemical reaction to occur. It plays a significant role in determining the rate of a reaction; lower activation energy typically leads to a faster reaction. The relationship between activation energy and temperature can be described by the Arrhenius equation, which shows that increasing temperature can enhance the reaction rate, thereby influencing the formation of products, including enantiomers.
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Chiral Catalysis
Chiral catalysis involves the use of a chiral catalyst to promote a reaction that produces one enantiomer preferentially over the other. This technique is essential in asymmetric synthesis, where the goal is to create compounds with specific stereochemistry. The presence of a chiral catalyst can lower the activation energy for the formation of one enantiomer, thus increasing the yield and ee of the desired product.
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Related Practice
Textbook Question
Conjugated dienes, molecules containing two alkenes separated by one single bond, are discussed in detail in Chapter 21.
(b) How might you account for this difference in stability?
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Textbook Question
Without concerning yourself with the mechanism of the reaction, calculate the equilibrium constant for the following equilibrium processes. (Assume T = 298 K.)
(a)
1033
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Textbook Question
Identify the alkene that would react with Ti(OiPr)₄, (+) -diethyltartrate, and t-butylhydroperoxide to give the following chiral, nonracemic epoxides.
(a)
861
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Textbook Question
Identify the alkene that would react with Ti(OiPr)4, (+) -diethyltartrate, and t-butylhydroperoxide to give the following chiral, nonracemic epoxides.
(b)
585
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Textbook Question
Conjugated dienes, molecules containing two alkenes separated by one single bond, are discussed in detail in Chapter 21.
(a) Considering the observed ∆H° of hydrogenation, is hexa-1,3-diene (conjugated) or hexa-1,4-diene (unconjugated) more stable?
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