교과서 질문
cis-3,4-Dimethylcyclobutene undergoes thermal ring opening to form the two products shown. One of the products is formed in 99% yield, the other in 1% yield. Which is which?
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Ch. 28 - Pericyclic Reactions
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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TOC.tableOfContents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding31
- Ch. 2 - Acids and Bases: Central to Understanding Organic Chemistry84
- Ch. 3 - An Introduction to Organic Compounds: Nomenclature, Physical Properties, and Structure183
- Ch. 4 - Isomers: The Arrangement of Atoms in Space121
- Ch. 5 - Alkenes: Structure, Nomenclature, and an Introduction to Reactivity • Thermodynamics and Kinetics83
- Ch. 6 - The Reactions of Alkenes • The Stereochemistry of Addition Reactions175
- Ch. 7 - The Reactions of Alkynes • An Introduction to Multistep Synthesis119
- Ch. 8 - Delocalized Electrons: Their Effect on Stability, pKa, and the Products of a Reaction • Aromaticity and Electronic Effects: An Introduction to the Reactions of Benzene148
- Ch. 9 - Substitution and Elimination Reactions of Alkyl Halides212
- Ch. 10 - Reactions of Alcohols, Ethers, Epoxides, Amines, and Sulfur-Containing Compounds131
- Ch. 11 - Organometallic Compounds60
- Ch. 12 - Radicals90
- Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy62
- Ch. 14 - NMR Spectroscopy95
- Ch. 15 - Reactions of Carboxylic Acids and Carboxylic Acid Derivatives123
- Ch. 16 - Reactions of Aldehydes and Ketones • More Reactions of Carboxylic Acid Derivatives141
- Ch. 17 - Reactions at the Alpha-Carbon101
- Ch. 18 - Reactions of Benzene and Substituted Benzenes144
- Ch. 19 - More About Amines • Reactions of Heterocyclic Compounds49
- Ch. 20 - The Organic Chemistry of Carbohydrates80
- Ch. 21 - Amino Acids, Peptides, and Proteins57
- Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions35
- Ch. 23 - The Organic Chemistry of the Coenzymes—Compounds Derived from Vitamins1
- Ch. 28 - Pericyclic Reactions58
24장, 문제 39
Explain why two different products are formed from disrotatory ring closure of (2E,4Z,6Z)-octatriene, but only one product is formed from disrotatory ring closure of (2E,4Z,6E)-octatriene.
검증된 단계별 안내1
Understand the concept of disrotatory ring closure: In a disrotatory ring closure, the terminal p orbitals of the conjugated system rotate in opposite directions (one clockwise and the other counterclockwise) to form a new sigma bond. The stereochemistry of the substituents on the terminal carbons determines the stereochemistry of the product.
Analyze the stereochemistry of (2E,4Z,6Z)-octatriene: The (2E,4Z,6Z) configuration means that the substituents on C2 and C6 are on opposite sides of the double bonds. This configuration allows for two possible stereochemical outcomes during the disrotatory closure, depending on the direction of rotation of the terminal p orbitals.
Explain why two products are formed for (2E,4Z,6Z)-octatriene: During the disrotatory closure, the substituents on C2 and C6 can either both end up on the same side of the newly formed ring (cis) or on opposite sides (trans). This is because the initial stereochemistry allows for two distinct ways the p orbitals can rotate to form the ring, leading to two different stereoisomers.
Analyze the stereochemistry of (2E,4Z,6E)-octatriene: The (2E,4Z,6E) configuration means that the substituents on C2 and C6 are on the same side of the double bonds. This configuration restricts the possible outcomes of the disrotatory closure, as only one stereochemical arrangement is possible due to the initial geometry of the molecule.
Explain why only one product is formed for (2E,4Z,6E)-octatriene: In this case, the disrotatory closure leads to a single stereoisomer because the substituents on C2 and C6 are already aligned in a way that only one stereochemical outcome is possible. The geometry of the molecule does not allow for the formation of a second stereoisomer.
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주요 개념
질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.
Disrotatory and Conrotatory Mechanisms
Disrotatory and conrotatory mechanisms refer to the two types of stereochemical outcomes that can occur during cyclization reactions involving conjugated systems. In disrotatory closure, the substituents on the ends of the conjugated diene rotate in opposite directions, leading to the formation of stereoisomers. Understanding these mechanisms is crucial for predicting the products of ring closures in organic reactions.
추천 영상:
04:32
General Mechanism
Stereochemistry of Dienes
The stereochemistry of dienes, particularly in terms of their geometric isomers (E/Z configurations), plays a significant role in determining the products of cyclization reactions. The specific arrangement of substituents around the double bonds influences the spatial orientation during the ring closure, which can lead to different stereochemical outcomes, as seen in the case of (2E,4Z,6Z)-octatriene versus (2E,4Z,6E)-octatriene.
추천 영상:
가이드 코스
1:38Polymer Stereochemistry Concept 1
Product Stability and Selectivity
The stability of the products formed during a reaction can greatly influence the selectivity of the reaction pathway. In the case of (2E,4Z,6Z)-octatriene, the formation of two different products suggests that both are relatively stable, allowing for their coexistence. Conversely, the formation of only one product from (2E,4Z,6E)-octatriene indicates that this product is more stable or favored, leading to a selective reaction outcome.
추천 영상:
05:58Determining Carbocation Stability
관련 실천
교과서 질문
Propose a mechanism for the following reaction:
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교과서 질문
Draw the product of each of the following sigmatropic rearrangements:
d.
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교과서 질문
b. What would be the product if trans-2-butene were used instead of ethene?
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교과서 질문
Draw the product of each of the following sigmatropic rearrangements:
c.
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