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Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds
Bruice - Organic Chemistry 8th Edition
Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook
All textbooksBruice 8th EditionCh. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing CompoundsProblem 70(8)
Chapter 11, Problem 70(8)

a. Draw the product or products that will be obtained from the reaction of cis-2-butene and trans-2-butene with each of the following reagents. If a product can exist as stereoisomers, show which stereoisomers are formed.
8. CH3OH + H2SO4
b. With which reagents do the two alkenes react to form different products?

Verified step by step guidance
1
Step 1: Understand the reaction conditions. The reaction involves the addition of methanol (CH₃OH) in the presence of sulfuric acid (H₂SO₄). This is an acid-catalyzed electrophilic addition reaction, where the alkene reacts with the proton (H⁺) from H₂SO₄ to form a carbocation intermediate, followed by nucleophilic attack by methanol.
Step 2: Analyze the structure of the starting materials. Cis-2-butene and trans-2-butene are geometric isomers of 2-butene. Both have the same molecular formula (C₄H₈) but differ in the spatial arrangement of substituents around the double bond. Cis-2-butene has both methyl groups on the same side of the double bond, while trans-2-butene has them on opposite sides.
Step 3: Predict the carbocation intermediate. When the double bond reacts with H⁺, the proton adds to one of the carbons in the double bond, forming a carbocation on the other carbon. Due to Markovnikov's rule, the proton will add to the carbon with more hydrogens, resulting in the more stable carbocation intermediate.
Step 4: Determine the product(s). Methanol (CH₃OH) acts as a nucleophile and attacks the carbocation, forming an ether product. For both cis-2-butene and trans-2-butene, the product will be 2-methoxybutane. However, the stereochemistry of the starting material may influence the stereochemistry of the product. Since the reaction proceeds through a planar carbocation intermediate, the product will not retain the stereochemistry of the starting material.
Step 5: Address part (b) of the question. Both cis-2-butene and trans-2-butene will form the same product (2-methoxybutane) with CH₃OH and H₂SO₄. To form different products, the reagents must be stereospecific or involve a mechanism that retains stereochemistry, such as a syn-addition or anti-addition reaction. Examples of such reagents include bromine (Br₂) or osmium tetroxide (OsO₄).

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Alkene Reactivity

Alkenes are unsaturated hydrocarbons characterized by at least one carbon-carbon double bond. Their reactivity is primarily due to this double bond, which can undergo various addition reactions. Understanding how alkenes react with different reagents, such as acids or alcohols, is crucial for predicting the products formed in these reactions.
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Stereochemistry

Stereochemistry refers to the study of the spatial arrangement of atoms in molecules and how this affects their chemical behavior. In the context of alkenes, the configuration around the double bond can lead to different stereoisomers, such as cis and trans forms. Recognizing how reagents can influence stereochemical outcomes is essential for accurately depicting the products of reactions involving alkenes.
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Electrophilic Addition

Electrophilic addition is a fundamental reaction mechanism for alkenes, where an electrophile reacts with the electron-rich double bond. In the presence of reagents like sulfuric acid and methanol, the double bond opens up, allowing for the formation of new bonds. This mechanism is key to understanding how different reagents can lead to distinct products, especially when considering the stereochemical implications of the reaction.
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Related Practice
Textbook Question

What product would be formed if the four-membered ring alcohol in Problem 70 were heated with an equivalent amount of HBr rather than with a catalytic amount of H2SO4?

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Textbook Question

Fill in each box with the appropriate reagent:

a.

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Textbook Question

Using the given starting material, any necessary inorganic reagents, and any carbon-containing compounds with no more than two carbons, indicate how the following syntheses could be carried out:

a.

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Textbook Question

Fill in each box with the appropriate reagent:

c.

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Textbook Question

Which of the following ethers would be obtained in greatest yield directly from alcohols?

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Textbook Question

Explain why (S)-2-butanol forms a racemic mixture when it is heated in sulfuric acid.