Textbook Question
Rank each group of compounds in order of increasing heat of hydrogenation.
(b)
1
views
Ch. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet Spectroscopy
Wade9th EditionOrganic ChemistryISBN: 9780135213728
Not the one you use?Change textbookSelect a different textbook
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
All textbooks
Wade 9th EditionCh. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet SpectroscopyProblem 4
Wade 9th EditionCh. 15 - Conjugated Systems, Orbital Symmetry, and Ultraviolet SpectroscopyProblem 4Chapter 15, Problem 4
Draw another resonance form for each of the substituted allylic cations shown in the preceding figure, showing how the positive charge is shared by another carbon atom. In each case, state whether your second resonance form is a more important or less important resonance contributor than the first structure. (Which structure places the positive charge on the more-substituted carbon atom?)
Verified step by step guidance1
Identify the allylic cation structure. An allylic cation is a positively charged species where the positive charge is located on a carbon atom adjacent to a double bond.
Draw the initial resonance structure of the allylic cation. This involves showing the positive charge on the carbon atom that is directly adjacent to the double bond.
To draw another resonance form, move the electrons from the double bond towards the positively charged carbon atom. This will shift the positive charge to the other carbon atom that was part of the double bond.
Evaluate the stability of the new resonance form. The resonance form where the positive charge is on the more substituted carbon atom is generally more stable due to hyperconjugation and inductive effects.
Compare the importance of the resonance forms. The resonance form with the positive charge on the more substituted carbon atom is typically a more important contributor to the resonance hybrid because it is more stable.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
5mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Resonance Structures
Resonance structures are different Lewis structures for a molecule that depict the same arrangement of atoms but differ in the distribution of electrons. They are used to represent delocalized electrons within certain molecules where the bonding cannot be expressed by a single Lewis structure. Resonance structures help in understanding the stability and reactivity of the molecule.
Recommended video:
Guided course
03:04
Drawing Resonance Structures
Allylic Cations
Allylic cations are positively charged ions where the positive charge is located on a carbon atom adjacent to a carbon-carbon double bond. These cations are stabilized by resonance, as the positive charge can be delocalized over the π system of the double bond, allowing for multiple resonance structures. This delocalization increases the stability of the cation.
Recommended video:
0:52Cationic Polymerization Concept 3
Substituted Carbon Atoms
In organic chemistry, a substituted carbon atom is one that is bonded to one or more substituent groups, which can affect the stability of a molecule. In the context of resonance, placing a positive charge on a more-substituted carbon atom often results in a more stable resonance structure due to hyperconjugation and inductive effects, which help to delocalize the positive charge more effectively.
Recommended video:
Guided course
01:44The difference between atomic numbers and atomic mass.
Related Practice
Textbook Question
When 3-bromo-1-methylcyclohexene undergoes solvolysis in hot ethanol, two products are formed. Propose a mechanism that accounts for both of these products.
Textbook Question
Propose a mechanism for each reaction, showing explicitly how the observed mixtures of products are formed.
(b) 2-methylbut-3-en-2-ol + HBr → 1-bromo-3-methylbut-2-ene + 3-bromo-3-methylbut-1-ene
1
views
Textbook Question
The central carbon atom of an allene is a member of two double bonds, and it has an interesting orbital arrangement that holds the two ends of the molecule at right angles to each other.
a. Draw an orbital diagram of allene, showing why the two ends are perpendicular.
b. Draw the two enantiomers of penta-2,3-diene. A model may be helpful.
4
views
Textbook Question
Treatment of an alkyl halide with AgNO3 in alcohol often promotes ionization.
Ag+ + R–Cl → AgCl + R+
When 4-chloro-2-methylhex-2-ene reacts with AgNO3 in ethanol, two isomeric ethers are formed. Suggest structures, and propose a mechanism for their formation
6
views
Textbook Question
In a strongly acidic solution, cyclohexa-1,4-diene tautomerizes to cyclohexa-1,3-diene. Propose a mechanism for this rearrangement, and explain why it is energetically favorable.
1
views