Textbook Question
How can you use UV spectroscopy to distinguish between the compounds in each of the following pairs?
b.
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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 71a
Bruice 8th EditionCh. 13 - Mass Spectrometry; Infrared Spectroscopy; UV/Vis SpectroscopyProblem 71aChapter 14, Problem 71a
Each of the IR spectra shown below is the spectrum of one of the following compounds. Identify the compound that produced each spectrum.
a. <IMAGE>
Verified step by step guidance1
Step 1: Analyze the IR spectrum provided. The broad peak around 3300 cm⁻¹ indicates the presence of an N-H or O-H bond, which is characteristic of amines or alcohols. The absence of a sharp peak around 1700 cm⁻¹ suggests that there is no carbonyl group (C=O) in the compound.
Step 2: Compare the IR spectrum with the functional groups in the given compounds. Compound (i) contains an amine group (-NH₂) attached to a cyclohexane ring, which matches the broad peak around 3300 cm⁻¹. Compound (ii) contains both an amine group and a carbonyl group, but the IR spectrum does not show a strong peak around 1700 cm⁻¹, ruling out this compound.
Step 3: Compound (iii) contains an aromatic amine group (-NH₂) attached to a benzene ring. Aromatic compounds typically show peaks in the region of 1500-1600 cm⁻¹ due to C=C stretching, which is not prominent in the IR spectrum provided. This suggests that compound (iii) is not the correct match.
Step 4: Compound (iv) contains a carboxylic acid group (-COOH), which would show a broad O-H stretch around 3000 cm⁻¹ and a sharp C=O stretch around 1700 cm⁻¹. Since the IR spectrum lacks a sharp peak at 1700 cm⁻¹, compound (iv) is not the correct match.
Step 5: Based on the analysis, the IR spectrum corresponds to compound (i), which contains an amine group (-NH₂) attached to a cyclohexane ring. The broad peak around 3300 cm⁻¹ is consistent with the N-H stretching vibration of the amine group.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Infrared Spectroscopy (IR)
Infrared spectroscopy is a technique used to identify and study chemicals based on their absorption of infrared light. Molecules absorb specific wavelengths of IR radiation, causing vibrations in their bonds. The resulting spectrum displays transmittance versus wavenumber, revealing characteristic peaks that correspond to functional groups within the molecule.
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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. Common functional groups include hydroxyl (-OH), carbonyl (C=O), and carboxylic acid (-COOH). Identifying these groups in an IR spectrum helps in determining the structure of the compound being analyzed.
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Peak Interpretation
In an IR spectrum, peaks represent the frequencies at which a molecule absorbs infrared light, indicating the presence of specific functional groups. The position and intensity of these peaks provide information about bond types and molecular structure. For example, a broad peak around 3200-3600 cm⁻¹ typically indicates the presence of an -OH group, while sharp peaks in the 1700-1750 cm⁻¹ range suggest a carbonyl group.
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Related Practice
Textbook Question
Give approximate wavenumbers for the major characteristic IR absorption bands that would be given by each of the following compounds:
e.
f.
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Textbook Question
How can you use UV spectroscopy to distinguish between the compounds in each of the following pairs?
a.
2
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Textbook Question
Each of the IR spectra shown below is the spectrum of one of the following compounds. Identify the compound that produced each spectrum.
b. <IMAGE>
Textbook Question
Give approximate wavenumbers for the major characteristic IR absorption bands that would be given by each of the following compounds:
a.
b.
8
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Textbook Question
Phenolphthalein is an acid–base indicator. In solutions of pH < 8.5, it is colorless; in solutions of pH > 8.5, it is deep red-purple. Account for the change in color.
1
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