Textbook Question
The following compound reacts with a hot, concentrated solution of NaOH (in a sealed tube) to give a mixture of two products. Propose structures for these products, and give a mechanism to account for their formation.
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Ch. 17 - Reactions of Aromatic Compounds
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 17, Problem 58d
Show the products you expect when each compound reacts with NBS with light shining on the reaction.
(d) 
Verified step by step guidance1
Step 1: Recognize the reaction conditions. NBS (N-Bromosuccinimide) in the presence of light is used for allylic or benzylic bromination. This reaction selectively replaces a hydrogen atom at the allylic or benzylic position with a bromine atom.
Step 2: Identify the benzylic position in the given compound. The structure contains a benzene ring attached to a propyl group. The benzylic position is the carbon atom directly attached to the benzene ring in the propyl chain.
Step 3: Determine the radical intermediate. Under light, the reaction proceeds via a radical mechanism. The benzylic hydrogen is abstracted to form a benzylic radical, which is stabilized due to resonance with the benzene ring.
Step 4: Add bromine to the benzylic radical. The bromine atom from NBS reacts with the benzylic radical to form the brominated product. The bromine is added at the benzylic position.
Step 5: Verify the product structure. The final product will have a bromine atom attached to the benzylic position, replacing one of the hydrogens. The rest of the molecule remains unchanged.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
NBS (N-Bromosuccinimide)
NBS is a reagent commonly used in organic chemistry for bromination reactions, particularly in the presence of light. It generates bromine radicals under photolytic conditions, which can abstract hydrogen atoms from alkenes or alkanes, leading to the formation of brominated products. Understanding how NBS functions is crucial for predicting the products of reactions involving this compound.
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Radical Mechanism
The radical mechanism involves the formation and reaction of free radicals, which are highly reactive species with unpaired electrons. In the context of NBS reactions, light initiates the homolytic cleavage of the N-Br bond, generating bromine radicals that can abstract hydrogen from the substrate. This mechanism is essential for understanding how products are formed in radical bromination reactions.
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Substitution vs. Addition Reactions
In organic chemistry, substitution reactions involve replacing one atom or group in a molecule with another, while addition reactions involve adding atoms or groups to a molecule. When reacting with NBS, the process typically leads to substitution of hydrogen atoms with bromine, particularly at allylic positions. Recognizing the type of reaction occurring helps in predicting the structure of the final products.
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Related Practice
Textbook Question
Electrophilic aromatic substitution usually occurs at the 1-position of naphthalene, also called the a position. Predict the major products of the reactions of naphthalene with the following reagents.
(d) isobutylene and HF
Textbook Question
Give the structures of compounds A through C in the following series of reactions.
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Textbook Question
Give the structures of compounds C through D in the following series of reactions.
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Textbook Question
α-Tetralone undergoes Birch reduction to give an excellent yield of a single product. Predict the structure of the product, and propose a mechanism for its formation.
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Textbook Question
Electrophilic aromatic substitution usually occurs at the 1-position of naphthalene, also called the a position. Predict the major products of the reactions of naphthalene with the following reagents.
(a) HNO3, H2SO4
(b) Br2, FeBr3
(c) CH3CH2COCl, AlCl3
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