Textbook Question
Match four of the following UV absorption maxima (λmax) with the corresponding compounds: (1) 232 nm; (2) 256 nm; (3) 273 nm; (4) 292 nm; (5) 313 nm; (6) 353 nm.
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Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy
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
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Wade 9th EditionCh. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet SpectroscopyProblem 24
Wade 9th EditionCh. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet SpectroscopyProblem 24Chapter 15, Problem 24
Classify the following dienes and polyenes as isolated, conjugated, cumulated, or some combination of these classifications.
(a) cycloocta-1,4-diene
(b) cycloocta-1,3-diene
(c) cyclodeca-1,2-diene
(d) cycloocta-1,3,5,7-tetraene
(e) cyclohexa-1,3,5-triene (benzene)
(f) penta-1,2,4-triene
Verified step by step guidance1
Step 1: Understand the classifications of dienes and polyenes. Isolated dienes have double bonds separated by more than one single bond. Conjugated dienes have alternating single and double bonds. Cumulated dienes have adjacent double bonds. Some molecules may exhibit combinations of these classifications.
Step 2: Analyze structure (a) cycloocta-1,4-diene. The double bonds are separated by two single bonds, making them isolated dienes.
Step 3: Analyze structure (b) cycloocta-1,3-diene. The double bonds are separated by one single bond, forming a conjugated diene.
Step 4: Analyze structure (c) cyclodeca-1,2-diene. The double bonds are adjacent, making this a cumulated diene.
Step 5: Analyze structure (d) cycloocta-1,3,5,7-tetraene and (e) cyclohexa-1,3,5-triene (benzene). Both structures exhibit alternating single and double bonds throughout the ring, classifying them as conjugated polyenes. For structure (f) penta-1,2,4-triene, the molecule contains both cumulated and conjugated double bonds, as the first two double bonds are adjacent (cumulated), and the second and third double bonds are separated by one single bond (conjugated).
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Diene Classification
Dienes are classified based on the arrangement of their double bonds. Isolated dienes have double bonds separated by more than one single bond, conjugated dienes have alternating double and single bonds, and cumulated dienes have two or more double bonds directly adjacent to each other. Understanding these classifications is essential for predicting reactivity and stability in organic reactions.
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Structural Classification
Conjugation
Conjugation occurs when p-orbitals overlap across adjacent double bonds, allowing for delocalization of electrons. This delocalization stabilizes the molecule and can affect its reactivity and color. Conjugated systems often exhibit unique properties, such as lower energy transitions, which are important in fields like organic electronics and photochemistry.
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Cycloalkenes
Cycloalkenes are cyclic compounds that contain one or more double bonds. The geometry and strain of these rings can influence the stability and reactivity of the compound. For example, smaller rings may experience angle strain, while larger rings can accommodate multiple double bonds, leading to various classifications of dienes and polyenes based on their structure.
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Related Practice
Textbook Question
Predict the products of the following reactions.
(b) cyclopentadiene + anhydrous HCl
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Textbook Question
Predict the products of the following reactions.
(c) 2-methylpropene + NBS, light
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Textbook Question
Phenolphthalein is an acid–base indicator that is colorless below pH 8 and red above pH 8. Explain briefly why the first structure is colorless and the second structure is colored.
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Textbook Question
One milligram of a compound of molecular weight 160 is dissolved in 10 mL of ethanol, and the solution is poured into a 1-cm UV cell. The UV spectrum is taken, and there is an absorption at λmax = 247 nm. The maximum absorbance at 247 nm is 0.50. Calculate the value of e for this absorption.
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Textbook Question
Predict the products of the following reactions.
(a) allyl bromide + cyclohexyl magnesium bromide
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