Textbook Question
Show how you would make each compound, beginning with an alcohol of your choice.
(d)
(e)
(f)
1
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Ch.11 - Reactions of Alcohols
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 11, Problem 46a,b,c
Show how you would convert (S)-hexan-2-ol to
(a) (S)-2-chlorohexane.
(b) (R)-2-bromohexane.
(c) (R)-hexan-2-ol.
Verified step by step guidance1
Step 1: To convert (S)-hexan-2-ol to (S)-2-chlorohexane, perform a substitution reaction. First, protonate the alcohol group (-OH) using a strong acid like HCl to form a good leaving group (water). Then, the chloride ion (Cl⁻) from HCl will attack the carbon attached to the leaving group, resulting in (S)-2-chlorohexane. Ensure the stereochemistry is retained since the reaction proceeds via an SN2 mechanism.
Step 2: To convert (S)-hexan-2-ol to (R)-2-bromohexane, first convert the alcohol group (-OH) into a better leaving group by reacting it with PBr₃ (phosphorus tribromide). This reaction proceeds via an SN2 mechanism, which inverts the stereochemistry at the chiral center, yielding (R)-2-bromohexane.
Step 3: To convert (S)-hexan-2-ol to (R)-hexan-2-ol, perform a two-step process. First, oxidize (S)-hexan-2-ol to hexan-2-one using an oxidizing agent like PCC (pyridinium chlorochromate). This removes the stereochemistry by converting the alcohol to a ketone. Then, reduce hexan-2-one back to an alcohol using a chiral reducing agent like (R)-CBS catalyst to selectively produce (R)-hexan-2-ol.
Step 4: For each transformation, carefully monitor reaction conditions to ensure stereochemical control. For example, SN2 reactions invert stereochemistry, while chiral catalysts can selectively produce desired enantiomers.
Step 5: Verify the stereochemistry of the products using techniques like polarimetry or chiral chromatography to confirm the desired enantiomer has been obtained.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Stereochemistry
Stereochemistry is the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In this question, understanding the stereochemistry of (S)-hexan-2-ol and its derivatives is crucial, as the conversion processes must preserve or invert the stereochemistry of the chiral center.
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Nucleophilic Substitution Reactions
Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule by a nucleophile. In the context of converting (S)-hexan-2-ol to (S)-2-chlorohexane and (R)-2-bromohexane, recognizing whether to use an SN1 or SN2 mechanism is essential, as it influences the stereochemical outcome of the reaction.
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01:47Nucleophiles and Electrophiles can react in Substitution Reactions.
Reagents and Reaction Conditions
Different reagents and reaction conditions can significantly affect the outcome of organic reactions. For example, using thionyl chloride (SOCl2) for chlorination or phosphorus tribromide (PBr3) for bromination can lead to different stereochemical products. Understanding how these reagents interact with (S)-hexan-2-ol is key to achieving the desired transformations.
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Related Practice
Textbook Question
Predict the esterification products of the following acid/alcohol pairs.
(d)
(e)
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Textbook Question
Both cis- and trans-2-methylcyclohexanol undergo dehydration in warm sulfuric acid to give 1-methylcyclohexene as the major alkene product. These alcohols can also be converted to alkenes by tosylation using TsCl and pyridine, followed by elimination using KOC(CH3)3 as a strong base. Under these basic conditions, the tosylate of cis-2-methylcyclohexanol eliminates to give mostly 1-methylcyclohexene, but the tosylate of trans-2-methylcyclohexanol eliminates to give only 3-methylcyclohexene. Explain how this stereochemical difference in reactants controls a regiochemical difference in the products of the basic elimination, but not in the acid-catalyzed elimination.
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Textbook Question
Predict the major products (including stereochemistry) when cis-3-methylcyclohexanol reacts with the following reagents.
(a) PBr3
(b) SOCl2
(c) Lucas reagent
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Textbook Question
Predict the esterification products of the following acid/alcohol pairs.
(a) CH3CH2CH2COOH + CH3OH
(b) CH3OH + HNO3
(c) 2 CH3CH2OH + H3PO4
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Textbook Question
Show how you would make each compound, beginning with an alcohol of your choice.
(g)
(h)
1
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