Textbook Question
Looking ahead in Chapter 4, we explain that molecules like CH3+ are Lewis acids or electron pair acceptors. Into which orbital would the new electron pair go?
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Ch. 2 - General Chemistry Translated: Finding the Electrons
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471
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Table of contents
- Ch. 2 - General Chemistry Translated: Finding the Electrons114
- Ch. 3 - Alkanes and Cycloalkanes: Properties and Conformational Analysis109
- Ch. 4 - Acids and Bases: Electron Flow144
- Ch. 5 - Chemical Reaction Analysis: Thermodynamics and Kinetics118
- Ch. 6 - Stereoisomerism: Arrangement of Atoms in Space112
- Ch. 7 - Principles of Green (Organic) Chemistry3
- Ch. 8 - Alkenes I: Properties and Electrophilic Additions158
- Ch. 9 - Alkenes II: Oxidation and Reduction150
- Ch. 10 - Alkynes: Electrophilic Addition and Redox Reactions101
- Ch. 11 - Properties and Synthesis of Alkyl Halides: Radical Reactions108
- Ch. 12 - Substitution and Elimination: Reactions of Haloalkanes172
- Ch. 13 - Alcohols, Ethers and Related Compounds: Substitution and Elimination239
- Ch. 14 - Structural Identification I: Infrared Spectroscopy and Mass Spectrometry54
- Ch. 15 - Structural Identification II: Nuclear Magnetic Resonance Spectroscopy93
- Ch. 16 - Metals in Organic Chemistry48
- Ch. 17 - Carbonyl Addition Reactions: Aldehydes and Ketones45
- Ch. 18 - Nucleophilic Acyl Substitution I: Carboxylic Acids18
- Ch. 19 - Nucleophilic Acyl Substitution II: Carboxylic Acid Derivatives39
- Ch. 20 - Enolates: Carbonyl Addition and Substitution13
- Ch. 21 - Conjugated Systems I: Stability and Addition Reactions56
- Ch. 22 - Conjugated Systems II: Pericyclic Reactions54
- Ch. 23 - Benzene I: Aromatic Stability and Substitution Reactions64
- Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring62
- Ch. 25 - Amines: Structure, Reactions, and Synthesis27
- Ch. 26 - Amino Acids, Proteins, and Peptide Synthesis9
- Ch. 27 - Carbohydrates, Nucleic Acids, and Lipids54
Mullins1st EditionOrganic Chemistry: A Learner Centered ApproachISBN: 9780137566471Not the one you use?Change textbook
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Mullins 1st EditionCh. 2 - General Chemistry Translated: Finding the ElectronsProblem 81
Mullins 1st EditionCh. 2 - General Chemistry Translated: Finding the ElectronsProblem 81Chapter 1, Problem 81
In propene, the indicated C―C bond length is 1.51 Å. In the allyl cation, the indicated C―C bond length is 1.41 Å. Explain.
Verified step by step guidance1
In propene, the indicated C―C bond is a single bond between a sp3-hybridized carbon and a sp2-hybridized carbon. Single bonds typically have longer bond lengths due to less overlap of orbitals. The bond length is measured as 1.51 Å.
In the allyl cation, the indicated C―C bond is part of a conjugated system where resonance occurs. Resonance allows delocalization of electrons across the π-system, leading to partial double bond character in the indicated C―C bond.
Double bonds are shorter than single bonds because they involve greater orbital overlap (π and σ bonds). The delocalization in the allyl cation reduces the bond length to 1.41 Å, giving it a bond length closer to that of a double bond.
The allyl cation is stabilized by resonance, which distributes the positive charge over the molecule. This delocalization affects the bond lengths, making them intermediate between single and double bonds.
In summary, the shorter bond length in the allyl cation compared to propene is due to resonance and partial double bond character, while the longer bond length in propene is due to the single bond nature of the indicated C―C bond.
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Bond Length and Strength
Bond length refers to the distance between the nuclei of two bonded atoms. Generally, shorter bond lengths indicate stronger bonds due to increased overlap of atomic orbitals. In the case of propene and the allyl cation, the C―C bond in the allyl cation is shorter, suggesting a stronger bond compared to the C―C bond in propene.
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Single bonds, double bonds, and triple bonds.
Resonance Stabilization
Resonance stabilization occurs when a molecule can be represented by multiple valid Lewis structures, leading to a delocalization of electrons. In the allyl cation, the positive charge can be delocalized over the adjacent carbon atoms, which stabilizes the cation and results in a shorter C―C bond length due to increased bond strength from this electron delocalization.
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Hybridization
Hybridization is the concept of mixing atomic orbitals to form new hybrid orbitals that can accommodate bonding. In propene, the carbon atoms are sp² hybridized, while in the allyl cation, the positive charge leads to a change in hybridization that can affect bond lengths. The sp² hybridization in propene allows for a longer bond length compared to the more effective overlap in the allyl cation, resulting in a shorter bond length.
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Related Practice
Textbook Question
The C―H σ bond length in ethane is 1.09 Å. The C―H σ bond in ethene is 1.07 Å. Explain.
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Textbook Question
There is free rotation around the C―C bond in ethane. There is an extremely high barrier to rotation around the C=C bond in in ethene. Explain.
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Textbook Question
The C―N bond in the following amide is much stronger than the C―N bond in the amine. Explain.
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Textbook Question
Carbon dioxide (CO2) has no dipole moment (μ = 0 D). The related molecule sulfur dioxide (SO2) does have a dipole moment (μ = 1.6 D) Explain this observation.
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Textbook Question
In comparison to CH3+ in Assessment 2.82, the related molecule H3O+ is not a Lewis acid at oxygen. Why?
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