Textbook Question
For each of the following pairs of compounds, identify one IR absorption band that could be used to distinguish between them:
i.
j.
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Ch. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis Spectroscopy
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
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Bruice 8th EditionCh. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis SpectroscopyProblem 48
Bruice 8th EditionCh. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis SpectroscopyProblem 48Chapter 14, Problem 48
Norlutin and Enovid are ketones that suppress ovulation, so they have been used clinically as contraceptives. For which of these compounds would you expect the infrared carbonyl absorption (C=O stretch) to be at a higher frequency? Explain.
Verified step by step guidance1
Step 1: Analyze the chemical structures of Norlutin and Enovid. Both compounds contain a ketone functional group (C=O) and other structural features such as hydroxyl groups and alkynes.
Step 2: Understand the factors affecting the infrared absorption frequency of the carbonyl group. The stretching frequency of the C=O bond in IR spectroscopy is influenced by resonance effects, inductive effects, and hydrogen bonding.
Step 3: Compare the resonance effects in Norlutin and Enovid. In Enovid, the ketone is conjugated with a double bond, which allows for resonance delocalization of electrons. This resonance reduces the double bond character of the C=O bond, lowering its stretching frequency.
Step 4: Consider the ketone in Norlutin. The ketone in Norlutin is not conjugated with a double bond, so it retains a stronger double bond character. This results in a higher stretching frequency for the C=O bond in Norlutin compared to Enovid.
Step 5: Conclude that the infrared carbonyl absorption (C=O stretch) would be at a higher frequency for Norlutin than for Enovid due to the lack of resonance stabilization in Norlutin's ketone group.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Infrared Spectroscopy
Infrared (IR) spectroscopy is a technique used to identify functional groups in organic compounds by measuring the absorption of infrared light. Different bonds absorb IR radiation at characteristic frequencies, allowing chemists to determine the presence of specific functional groups, such as carbonyls (C=O). The position of these absorptions can provide insights into the molecular environment and structure of the compound.
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Carbonyl Group Characteristics
The carbonyl group (C=O) is a functional group found in ketones, aldehydes, and other compounds. The frequency of the C=O stretching vibration in IR spectroscopy is influenced by the electronic environment surrounding the carbonyl carbon. Factors such as steric hindrance, conjugation, and the presence of electron-withdrawing or donating groups can shift the absorption frequency, with more electron-withdrawing groups typically leading to higher frequencies.
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Steric and Electronic Effects
Steric effects arise from the spatial arrangement of atoms in a molecule, which can influence the reactivity and properties of functional groups. Electronic effects involve the influence of nearby atoms or groups on the electron density of a functional group. In the case of Norlutin and Enovid, the presence of bulky groups or electron-withdrawing substituents can affect the carbonyl absorption frequency, making it essential to analyze these factors when comparing the two compounds.
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Related Practice
Textbook Question
a. How could you use IR spectroscopy to determine whether the following reaction had occurred?
b. After purifying the product, how could you determine whether all the NH2NH2 had been removed?
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Textbook Question
A compound gives a mass spectrum with essentially only three peaks at m/z = 77 (40%), 112 (100%), and 114 (33%). Identify the compound.
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Textbook Question
What hydrocarbons that contain a six-membered ring will have a molecular ion peak at m/z = 112?
Textbook Question
Assuming that the force constant is approximately the same for C–C, C–N, and C–O bonds, predict the relative positions of their stretching vibrations in an IR spectrum.
Textbook Question
A mass spectrum shows significant peaks at m/z = 87, 115, 140, and 143. Which of the following compounds is responsible for that mass spectrum?
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