Textbook Question
Suggest an arrow-pushing mechanism for each of the following acid–base reactions.
(d) [an intramolecular reaction]
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Ch. 4 - Acids and Bases: Electron Flow
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
Chapter 3, Problem 75
BCl3 has an empty p orbital, so it is a strong Lewis acid. Would you expect an amide to react with BCl3 at nitrogen or oxygen?
Verified step by step guidance1
Step 1: Understand the nature of BCl3 as a Lewis acid. BCl3 has an empty p orbital, making it electron-deficient and capable of accepting electron pairs from Lewis bases.
Step 2: Analyze the amide structure. An amide contains both a nitrogen atom with a lone pair and an oxygen atom with lone pairs. Both atoms can act as Lewis bases and donate electron pairs.
Step 3: Compare the electronegativity of oxygen and nitrogen. Oxygen is more electronegative than nitrogen, meaning its lone pairs are held more tightly and are less available for donation compared to nitrogen's lone pairs.
Step 4: Consider steric factors. The nitrogen atom in the amide is less sterically hindered compared to the oxygen atom, making it more accessible for interaction with BCl3.
Step 5: Conclude that the nitrogen atom is more likely to react with BCl3 due to its less tightly held lone pair and greater accessibility compared to the oxygen atom.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Lewis Acids and Bases
Lewis acids are substances that can accept an electron pair, while Lewis bases are those that can donate an electron pair. In this context, BCl₃ acts as a Lewis acid due to its empty p orbital, allowing it to interact with electron-rich species. Understanding this interaction is crucial for predicting the reactivity of amides with BCl₃.
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The Lewis definition of acids and bases.
Amides Structure and Reactivity
Amides are organic compounds characterized by a carbonyl group (C=O) bonded to a nitrogen atom (N). The nitrogen in amides is typically a Lewis base due to its lone pair of electrons, while the oxygen can also participate in reactions. Recognizing the functional groups and their electron-donating or accepting abilities is essential for determining the site of reaction with Lewis acids like BCl₃.
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Nucleophilicity
Nucleophilicity refers to the ability of a species to donate an electron pair to an electrophile. In the case of amides, the nitrogen atom is generally more nucleophilic than the oxygen atom due to its less electronegative nature and the presence of a lone pair. This concept is vital for predicting whether the reaction with BCl₃ will occur at the nitrogen or oxygen site.
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Related Practice
Textbook Question
One of the more reactive species we will study in organic chemistry is the carbene (molecular formula of CH2). The carbene can react as both a Lewis acid and a Lewis base. Explain these properties.
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Textbook Question
Imidazole has two potentially basic sites (a and b). Of the two, where would you expect a proton to add preferentially?
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Textbook Question
Consider the following drugs used to treat the indicated diseases. Would you expect the activity of these drugs to be impacted by a patient taking other medicines for acid reflux disease?
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Textbook Question
Suggest an arrow-pushing mechanism for each of the following acid–base reactions
(c)
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Textbook Question
In addition to radicals, anions, and cations, a fourth class of reactive intermediates is carbenes. A neutral species, the simplest carbene has a molecular formula of CH2.
(c) Carbenes are Lewis acids. Based on your answers to (a) and (b), explain this observation.
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