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 45c,d
Bruice 8th EditionCh. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis SpectroscopyProblem 45c,dChapter 14, Problem 45c,d
For each of the following pairs of compounds, identify one IR absorption band that could be used to distinguish between them:
c. CH3CH2CH2OH and CH3CH2OCH3
d. 
Verified step by step guidance1
Step 1: Analyze the functional groups present in the compounds in pair I. The first compound contains a hydroxyl (-OH) group, while the second compound contains a methoxy (-OCH3) group. These functional groups have distinct IR absorption bands.
Step 2: Identify the characteristic IR absorption band for the hydroxyl (-OH) group in the first compound. The -OH group typically shows a broad absorption band around 3200-3600 cm⁻¹ due to O-H stretching.
Step 3: Identify the characteristic IR absorption band for the methoxy (-OCH3) group in the second compound. The C-O stretching in ethers typically appears in the range of 1000-1300 cm⁻¹.
Step 4: Analyze the functional groups present in the compounds in pair II. The first compound contains an amide functional group (-CONH2), while the second compound contains an ester functional group (-COOCH3). These functional groups have distinct IR absorption bands.
Step 5: Identify the characteristic IR absorption bands for the amide and ester groups. The amide group typically shows a strong absorption band around 1650-1700 cm⁻¹ due to C=O stretching and a band around 3200-3500 cm⁻¹ due to N-H stretching. The ester group typically shows a strong absorption band around 1735-1750 cm⁻¹ due to C=O stretching and a band around 1000-1300 cm⁻¹ due to C-O stretching.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Infrared (IR) Spectroscopy
Infrared spectroscopy is a technique used to identify functional groups in organic compounds by measuring the absorption of infrared light. Different bonds absorb characteristic frequencies of IR radiation, leading to distinct absorption bands in the IR spectrum. This allows chemists to distinguish between compounds based on their functional groups and molecular structure.
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General Features of IR Spect
Functional Groups
Functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. In the provided compounds, functional groups such as hydroxyl (-OH), carbonyl (C=O), and ester (-O-) play a crucial role in determining the IR absorption bands. Identifying these groups helps in distinguishing between similar compounds.
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Characteristic Absorption Bands
Each functional group has a characteristic absorption band in the IR spectrum, which corresponds to the vibrational transitions of the bonds within that group. For example, alcohols typically show a broad O-H stretch around 3200-3600 cm⁻¹, while carbonyl groups exhibit a strong C=O stretch around 1700 cm⁻¹. Recognizing these bands is essential for differentiating between compounds in IR spectroscopy.
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Related Practice
Textbook Question
In the mass spectrum of the following compounds, which is the tallest—the peak at m/z = 57 or the peak at m/z = 71?
a. 3-methylpentane
b. 2-methylpentane
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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
What would be the difference in the colors of the compounds at pH = 3?
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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.
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Textbook Question
Rank the following compounds in order of increasing lmax:
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