Textbook Question
Rationalize the ranking of increasing reaction rate of the benzylic halides shown.
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Ch. 24 - Benzene II: Reactions Influenced by the Aromatic Ring
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. 24 - Benzene II: Reactions Influenced by the Aromatic RingProblem 52
Mullins 1st EditionCh. 24 - Benzene II: Reactions Influenced by the Aromatic RingProblem 52Chapter 23, Problem 52
A chemist attempted to oxidize a primary alcohol to a carboxylic acid using chromic acid. The product shown was obtained as a major component in the mixture. Suggest an arrow-pushing mechanism that accounts for its formation. [Think about what chromic acid would normally do to a phenol and make a list of bonds formed and bonds broken.]
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Identify the starting material: The primary alcohol is the substrate that will undergo oxidation. Chromic acid is a strong oxidizing agent typically used to convert primary alcohols to carboxylic acids.
Consider the role of chromic acid: Chromic acid (H₂CrO₄) is known to oxidize alcohols by first converting them to aldehydes, which can further oxidize to carboxylic acids. However, in the presence of phenolic groups, chromic acid can lead to different pathways.
Analyze the reaction conditions: In the presence of phenolic groups, chromic acid can lead to the formation of quinones or other oxidized products. Consider how the phenolic group might interact with chromic acid, potentially leading to a different major product.
List bonds formed and broken: During the oxidation process, the C-H bond of the alcohol is broken, and a C=O bond is formed. If a phenolic group is involved, additional C-O bonds may form, and aromatic C=C bonds may rearrange.
Propose an arrow-pushing mechanism: Begin with the alcohol oxygen attacking the chromium center, forming a chromate ester. This intermediate can undergo a series of electron transfers, leading to the formation of a carbonyl group and potentially rearranging the aromatic system if phenolic groups are involved.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Oxidation of Alcohols
Oxidation of alcohols involves the conversion of primary alcohols to aldehydes and further to carboxylic acids using oxidizing agents like chromic acid. Chromic acid is a strong oxidizing agent that facilitates the removal of hydrogen atoms from the alcohol, forming a carbonyl group. Understanding this process is crucial for predicting the outcome of the reaction.
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Strong oxidizing agents
Arrow-Pushing Mechanism
Arrow-pushing is a technique used to illustrate the movement of electrons during chemical reactions. It involves drawing arrows to show how electron pairs move from nucleophiles to electrophiles, forming and breaking bonds. This concept helps in visualizing the step-by-step transformation of reactants to products, essential for understanding complex organic reactions.
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Reactivity of Phenols with Chromic Acid
Phenols react differently with chromic acid compared to alcohols due to the stability of the aromatic ring. Chromic acid can oxidize phenols to quinones, involving the formation of new carbon-oxygen bonds and the breaking of carbon-hydrogen bonds. Recognizing this reactivity is key to predicting the products formed when phenols are subjected to oxidation.
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Related Practice
Textbook Question
The following steps were used in the synthesis of the antimalarial thiaplakortone A. Identify the missing reagents, (a) and (b),
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Textbook Question
Identify the aromatic product that would result from the oxidation of the triol with an excess of PCC.
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Textbook Question
In Chapter 23, we learned about the electrophilic aromatic nitration reaction. When phenol is subjected to these conditions with a large excess of nitric acid, a molecule called picric acid is produced. Predict the product of this reaction and explain why the pKa value of this compound is 0.38.
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Textbook Question
Rationalize the fact that 1,4-dihydroxybenzene melts at a significantly higher temperature than 1,2-diydroxybenzene.
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Textbook Question
In light of your answers to Assessments 24.54 and 24.55, rank the following based on the rate of protonation of the alkene (1 = most basic, 6 = least basic). [Ignore the fact that the alkene may not be the most basic site in the molecule.]
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