Textbook Question
Show how you would accomplish the following conversions.a. cis-hex-3-ene to meso-hexane-3,4-diol
Ch.8 - Reactions of Alkenes
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 8, Problem 7
a. Propose a mechanism for the following reaction.
b. Give the structure of the product that results when this intermediate is reduced by sodium borohydride.
Verified step by step guidance1
Step 1: Analyze the reaction conditions. The reaction involves an alkene (CH3C(CH3)=CHCH3) undergoing oxymercuration in the presence of mercuric acetate (Hg(OAc)2) and ethanol (CH3CH2OH). This is a typical oxymercuration reaction where the alkene reacts with Hg(OAc)2 to form a mercurinium ion intermediate.
Step 2: Propose the mechanism for the formation of the intermediate. The alkene reacts with Hg(OAc)2, leading to the formation of a cyclic mercurinium ion. The positive charge is stabilized by the mercury atom. Ethanol (CH3CH2OH) then acts as a nucleophile, attacking the more substituted carbon of the mercurinium ion, leading to the opening of the ring and forming the intermediate (CH3)2C(CH3CH2O)CH(Hg(OAc))CH3.
Step 3: Explain regioselectivity. The nucleophilic attack by ethanol occurs at the more substituted carbon of the mercurinium ion due to Markovnikov's rule, which states that the nucleophile will add to the carbon with more alkyl substituents.
Step 4: Describe the reduction step. When the intermediate is treated with sodium borohydride (NaBH4), the Hg(OAc) group is replaced by a hydrogen atom. This reduction step leads to the formation of the final product, which is an alcohol with the ethoxy group attached to the more substituted carbon.
Step 5: Consider stereochemistry. The reaction produces a racemic mixture (both enantiomers) because the attack by ethanol on the mercurinium ion can occur from either side of the planar intermediate, leading to two stereoisomers.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Oxymercuration-Demercuration
Oxymercuration-demercuration is a two-step reaction used to convert alkenes into alcohols. In the first step, an alkene reacts with mercuric acetate (Hg(OAc)2) in the presence of water or alcohol, leading to the formation of a mercurinium ion intermediate. This intermediate is then attacked by a nucleophile, resulting in the formation of an alcohol. The second step involves the reduction of the mercurial intermediate, typically using sodium borohydride (NaBH4), to yield the final alcohol product.
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General properties of oxymercuration-reduction.
Mechanism of Oxymercuration
The mechanism of oxymercuration involves the electrophilic addition of the mercuric ion to the double bond of the alkene, forming a cyclic mercurinium ion. This intermediate is stabilized by the positive charge on the mercury, allowing for nucleophilic attack by water or an alcohol at the more substituted carbon. This regioselectivity leads to Markovnikov addition, where the nucleophile adds to the more substituted carbon, resulting in a product with a hydroxyl group and a mercuric acetate group.
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Sodium Borohydride Reduction
Sodium borohydride (NaBH4) is a common reducing agent used in organic chemistry to convert carbonyl compounds and certain organometallic intermediates into alcohols. In the context of oxymercuration, NaBH4 reduces the mercurial intermediate formed during the reaction, replacing the mercury group with a hydrogen atom. This reduction is crucial for obtaining the final alcohol product, which retains the stereochemistry of the original alkene, leading to the formation of enantiomers if the starting material is chiral.
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Related Practice
Textbook Question
Predict the products of the following hydration reactions.
b. 2-phenylpropene + dilute acid
c. 1-phenylcyclohexene + dilute acid
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Textbook Question
Predict the products of the following hydration reactions.
a. 1−methylcyclopentene + dilute acid
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Textbook Question
Propose a mechanism to show how 3,3-dimethylbut-1-ene reacts with dilute aqueous H2SO4 to give 2,3-dimethylbutan-2-ol and a small amount of 2,3-dimethylbut-2-ene.
HINT: When predicting products for electrophilic additions, first draw the structure of the carbocation (or other intermediate) that results from electrophilic attack.
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Textbook Question
Show how you would accomplish the following conversions.d. trans-hex-3-ene to (d,l)-hexane-3,4-diol
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Textbook Question
Predict the major products of the following reactions.
a. 1-methylcyclohexene+ aqueous Hg(OAc)2
b. the product from part (a), treated with NaBH4
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