Textbook Question
Which of the following compounds reacts with HBr more rapidly?
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Ch. 18 - Reactions of Benzene and Substituted Benzenes
Bruice8th EditionOrganic ChemistryISBN: 9780135213711
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Table of contents
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 1)31
- Ch. 1 - Remembering General Chemistry: Electronic Structure and Bonding (Part 2)65
- 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
Chapter 19, Problem 64
An aromatic hydrocarbon with a molecular formula of C13H20 has an 1H NMR spectrum with a signal at ~7 ppm that integrates to 5H. It also has two singlets; one of the singlets has 1.5 times the area of the second. What is the structure of the aromatic hydrocarbon?
Verified step by step guidance1
Analyze the molecular formula C13H20: This indicates the compound is an aromatic hydrocarbon. Aromatic hydrocarbons typically contain a benzene ring (C6H6) as part of their structure. The remaining carbons and hydrogens must account for the substituents attached to the benzene ring.
Interpret the 1H NMR signal at ~7 ppm: A signal in this region is characteristic of aromatic protons. The integration of 5H suggests that the benzene ring is monosubstituted, leaving five hydrogens on the ring to contribute to the signal.
Examine the two singlets: Singlets in the 1H NMR spectrum indicate protons that are not coupled to neighboring protons. The fact that one singlet has 1.5 times the area of the other suggests a ratio of 3:2 for the protons contributing to these signals. This is consistent with a tert-butyl group (C(CH3)3, contributing 9H) and an isopropyl group (CH(CH3)2, contributing 6H).
Propose the substitution pattern: A tert-butyl group and an isopropyl group are likely attached to the benzene ring. The tert-butyl group contributes 9H (appearing as a singlet due to symmetry), and the isopropyl group contributes 6H (appearing as a singlet for the two equivalent methyl groups).
Construct the structure: Combine the benzene ring with a tert-butyl group and an isopropyl group as substituents. The substitution pattern should be consistent with the integration of the aromatic protons (5H) and the singlets (3:2 ratio). Verify the molecular formula (C13H20) and the NMR data to confirm the structure.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Aromatic Hydrocarbons
Aromatic hydrocarbons are compounds that contain one or more benzene rings, characterized by their stability and unique electronic structure due to resonance. They follow Huckel's rule, which states that a cyclic, planar molecule with a certain number of pi electrons (4n + 2) is aromatic. Understanding the structure and properties of aromatic compounds is essential for interpreting NMR data.
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Aromaticity of Hydrocarbons
Nuclear Magnetic Resonance (NMR) Spectroscopy
NMR spectroscopy is a powerful analytical technique used to determine the structure of organic compounds. In 1H NMR, the chemical environment of hydrogen atoms is revealed through shifts in resonance frequency, measured in parts per million (ppm). The integration of signals indicates the relative number of protons contributing to each signal, which helps deduce the molecular structure.
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Integration and Signal Patterns in NMR
In NMR, the area under each signal (integration) corresponds to the number of protons contributing to that signal. Singlets indicate that the protons are not coupled to neighboring protons, while the ratio of the areas can provide insight into the relative number of different types of protons in the molecule. Understanding these patterns is crucial for deducing the structure of the compound based on the given NMR data.
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Related Practice
Textbook Question
Why is anisole nitrated more rapidly than thioanisole under the same conditions?
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Textbook Question
Describe two ways to prepare anisole from benzene.
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Textbook Question
Show how the following compounds can be synthesized from benzene:
g. p-dideuteriobenzene
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Textbook Question
Show how the following compounds can be synthesized from benzene:
h. p-nitro-N-methylaniline
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Textbook Question
Show how the following compounds can be synthesized from benzene:
a. N,N,N-trimethylanilinium iodide
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