Textbook Question
Predict the carbenoid addition products of the following reactions.
(a) cyclohexene + CHCl3, 50% NaOH/H2O
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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 24a
One of the principal components of lemongrass oil is limonene, C10H16. When limonene is treated with excess hydrogen and a platinum catalyst, the product is an alkane of formula C10H20. What can you conclude about the structure of limonene?
Verified step by step guidance1
Identify the molecular formula of limonene, which is C10H16. This indicates that limonene is an unsaturated hydrocarbon, as it has fewer hydrogens than the corresponding alkane (C10H22).
Recognize that treating limonene with excess hydrogen and a platinum catalyst results in hydrogenation, a process that adds hydrogen atoms to double bonds or triple bonds in the molecule.
Note that the product of the reaction has the formula C10H20, which is an alkane. This suggests that limonene originally contained two double bonds, as the addition of hydrogen converts each double bond into a single bond, increasing the hydrogen count by two for each double bond.
Conclude that limonene is likely a diene (a compound with two double bonds) based on the molecular formula and the reaction outcome. The double bonds are responsible for the unsaturation in the original molecule.
Consider the possibility that limonene has a cyclic structure, as many terpenes (like limonene) are cyclic hydrocarbons. The presence of double bonds in a cyclic structure would further explain its reactivity during hydrogenation.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Hydrogenation
Hydrogenation is a chemical reaction that involves the addition of hydrogen (H2) to an unsaturated compound, typically in the presence of a catalyst. In the case of limonene, which contains double bonds, hydrogenation converts these unsaturated sites into saturated ones, resulting in the formation of an alkane. This process is crucial for understanding how the structure of limonene changes when treated with hydrogen.
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The definition of hydrogenation.
Alkene vs. Alkane
Alkenes are hydrocarbons that contain at least one carbon-carbon double bond, while alkanes are saturated hydrocarbons with only single bonds. The transformation of limonene (an alkene) into an alkane (C10H20) through hydrogenation indicates that limonene must have at least one double bond in its structure. Recognizing this distinction helps in deducing the structural features of limonene.
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Structural Isomerism
Structural isomerism occurs when compounds have the same molecular formula but different structural arrangements of atoms. Limonene, with the formula C10H16, can exist in various isomeric forms, including different placements of double bonds and branching. Understanding structural isomerism is essential for analyzing the possible configurations of limonene and predicting its reactivity during hydrogenation.
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Related Practice
Textbook Question
Give the expected major product for each reaction, including stereochemistry where applicable.
(a) but-1-ene + H2/Pt
(b) cis-but-2-ene + H2/Ni
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Textbook Question
The chiral BINAP ligand shown in Figure 8-8 contains no asymmetric carbon atoms. Explain how this ligand is chiral.
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Textbook Question
Show how you would accomplish the following synthetic conversions.
c. 1-methylcyclopentanol → 2-chloro-1-methylcyclopentanol
Problem-Solving Hint: The opening of a halonium ion is driven by its electrophilic nature. The weak nucleophile attacks the carbon bearing more positive charge.
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Textbook Question
Predict the carbenoid addition products of the following reactions.
a. trans-hex-3-ene + CH2I2, Zn(Cu)
b. cis-hex-3-ene + CH2I2, Zn(Cu)
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Textbook Question
Give the expected major product for each reaction, including stereochemistry where applicable.
(c)
(d)
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