Textbook Question
Predict the major products of the following reactions, including stereochemistry where appropriate.
a. 2,2-dimethylxirane + H+/H218O (oxygen labeled water)
b. 2,2-dimethylxirane + H18O–/H218O (oxygen labeled water)
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Ch. 14 - Ethers, Epoxides, and Thioethers
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 14, Problem 26d,e,f
Predict the major product when each reagent reacts with ethylene oxide.
(d) PhNH2 (aniline)
(e) KCN (potassium cyanide)
(f) NaN3 (sodium azide)
Verified step by step guidance1
Step 1: Understand the structure and reactivity of ethylene oxide. Ethylene oxide is a three-membered cyclic ether (epoxide) with significant ring strain, making it highly reactive towards nucleophiles. The nucleophile will attack the less sterically hindered carbon of the epoxide, leading to ring opening.
Step 2: Analyze the reagent in part (d), PhNH2 (aniline). Aniline is a nucleophile due to the lone pair on the nitrogen atom. The nitrogen will attack the less hindered carbon of ethylene oxide, opening the ring and forming a β-amino alcohol. The product will have the structure PhNH-CH2-CH2OH.
Step 3: Analyze the reagent in part (e), KCN (potassium cyanide). The cyanide ion (CN⁻) is a strong nucleophile. It will attack the less hindered carbon of ethylene oxide, opening the ring and forming a β-cyano alcohol. The product will have the structure HO-CH2-CH2-CN.
Step 4: Analyze the reagent in part (f), NaN3 (sodium azide). The azide ion (N3⁻) is a nucleophile. It will attack the less hindered carbon of ethylene oxide, opening the ring and forming a β-azido alcohol. The product will have the structure HO-CH2-CH2-N3.
Step 5: Summarize the general mechanism for all three reactions. In each case, the nucleophile attacks the less hindered carbon of the epoxide, leading to ring opening and the formation of a β-substituted alcohol. The specific substituent depends on the nucleophile used (PhNH for aniline, CN for potassium cyanide, and N3 for sodium azide).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Epoxide Reactivity
Epoxides, such as ethylene oxide, are three-membered cyclic ethers that are highly reactive due to the strain in their ring structure. They can undergo nucleophilic ring-opening reactions, where a nucleophile attacks the less hindered carbon atom, leading to the formation of alcohols or other functional groups. Understanding the mechanism of this reaction is crucial for predicting the products formed when different nucleophiles react with epoxides.
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General properties of epoxidation.
Nucleophiles
Nucleophiles are species that donate an electron pair to form a chemical bond in a reaction. In the context of the question, aniline (PhNH2), potassium cyanide (KCN), and sodium azide (NaN3) act as nucleophiles that will attack the epoxide. The strength and nature of the nucleophile influence the reaction pathway and the final product, making it essential to consider their reactivity and sterics when predicting outcomes.
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Product Prediction
Predicting the major product of a reaction involves understanding the regioselectivity and stereochemistry of the nucleophilic attack on the epoxide. Factors such as the nucleophile's structure, the reaction conditions, and the stability of the resulting intermediates play a significant role in determining which product is favored. Analyzing these aspects allows for accurate predictions of the major products formed in the reactions with ethylene oxide.
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Related Practice
Textbook Question
Give the expected products of the following reactions. Include a protonation step where necessary.
(a) 2,2-dimethyloxirane + isopropylmagnesium bromide
(b) propylene oxide + n-butyllithium
(c) cyclopentyloxirane + ethyllithium
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Textbook Question
Predict the major product when each reagent reacts with ethylene oxide.
(a) NaOCH2CH3 (sodium ethoxide)
(b) NaNH2 (sodium amide)
(c) NaSPh (sodium thiophenoxide)
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Textbook Question
Show the rest of the mechanism for formation of the cyclized intermediate in Figure 14-6.
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Textbook Question
Cellosolve® is the trade name for 2-ethoxyethanol, a common industrial solvent. This compound is produced in chemical plants that use ethylene as their only organic feedstock. Show how you would accomplish this industrial process.
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Textbook Question
Predict the major products of the following reactions, including stereochemistry where appropriate.
(c) (2S,3R)-2-ethyl-2,3-dimethyloxirane + CH3O– / CH3OH
(d) (2S,3R)-2-ethyl-2,3-dimethyloxirane + H+ / CH3OH
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