Textbook Question
Which of the following pairs of compounds could be separated by recrystallization or distillation?
a. meso-tartaric acid and (±)-tartaric acid (HOOC—CHOH—CHOH—COOH)
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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 23c
Which of the following pairs of compounds could be separated by recrystallization or distillation?
(c) 
Verified step by step guidance1
Analyze the chemical structures provided: The two compounds are diastereomers, as they have the same molecular formula and connectivity but differ in the spatial arrangement of their bromine substituents.
Understand the physical properties of diastereomers: Diastereomers typically have different physical properties, such as melting points and boiling points, which makes them separable by physical methods.
Consider recrystallization: Recrystallization is effective for separating compounds with different solubilities in a given solvent. Check if the diastereomers have significantly different solubilities in a suitable solvent.
Consider distillation: Distillation is effective for separating compounds with different boiling points. Check if the diastereomers have sufficiently different boiling points to allow separation by this method.
Choose the appropriate method: Based on the analysis of solubility and boiling point differences, determine whether recrystallization or distillation is the more suitable method for separating these diastereomers.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Recrystallization
Recrystallization is a purification technique used to separate compounds based on their solubility differences. In this process, a solid compound is dissolved in a hot solvent and then allowed to cool, leading to the formation of pure crystals. The impurities remain dissolved in the solvent, allowing for the isolation of the desired compound. This method is particularly effective for separating compounds with different melting points.
Distillation
Distillation is a separation technique that exploits differences in boiling points of compounds. In this process, a mixture is heated to vaporize the more volatile component, which is then condensed back into a liquid and collected separately. This method is commonly used for purifying liquids and can effectively separate compounds that have significantly different boiling points, making it suitable for mixtures of liquids.
Stereoisomers
Stereoisomers are compounds that have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of their atoms. This category includes enantiomers and diastereomers, which can exhibit different physical properties. Understanding stereoisomerism is crucial for separation techniques like recrystallization and distillation, as these methods can exploit differences in the physical properties of stereoisomers to achieve effective separation.
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Related Practice
Textbook Question
Which of the following pairs of compounds could be separated by recrystallization or distillation?
(b)
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1
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Textbook Question
For each structure,
1. star (*) any asymmetric carbon atoms.
2. label each asymmetric carbon as (R) or (S).
3. draw any internal mirror planes of symmetry.
4. label the structure as chiral or achiral.
5. label any meso structures.
(a)
(b)
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1
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Textbook Question
(a) Give the products expected when (+)@glyceraldehyde reacts with HCN.(b) What is the relationship between the products? How might they be separated?(c) Are the products optically active? Explain.
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Textbook Question
The following four structures are naturally occurring optically active compounds. Star (*) the asymmetric carbon atoms in these structures.
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Textbook Question
To show that (R)-2-butyl (R,R)-tartrate and (S)-2-butyl (R,R)-tartrate are not enantiomers, draw and name the mirror images of these compounds.
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