Textbook Question
Predict the compound in each pair that will undergo the SN2 reaction faster.
(a)
(b)
1
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Ch.6 - Alkyl Halides; Nucleophilic Substitution
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
Chapter 6, Problem 30c
Show how you would convert (in one or two steps) 1-phenylpropane to the three products shown below. In each case, explain what unwanted reactions might produce undesirable impurities in the product.
Verified step by step guidance1
Step 1: Analyze the starting material, 1-phenylpropane, and the target product, 2-phenylbutanenitrile. The transformation involves the addition of a nitrile group (-C≡N) to the carbon adjacent to the phenyl group, which requires a nucleophilic substitution reaction.
Step 2: Perform bromination of 1-phenylpropane using bromine (Br₂) in the presence of light or heat (radical halogenation conditions). This will selectively brominate the benzylic position (the carbon adjacent to the phenyl group) due to the stability of the benzylic radical intermediate. The product will be 1-bromo-2-phenylpropane.
Step 3: React 1-bromo-2-phenylpropane with sodium cyanide (NaCN) in a polar aprotic solvent like DMSO or acetone. This will result in an SN2 reaction, where the bromine atom is replaced by the cyanide group (-C≡N), forming 2-phenylbutanenitrile.
Step 4: Consider potential side reactions. During bromination, over-bromination (e.g., dibromination) or bromination at non-benzylic positions could occur, leading to impurities. During the SN2 reaction, elimination reactions (E2) might compete, forming alkenes as side products.
Step 5: To minimize impurities, ensure controlled reaction conditions: use excess bromine for selective benzylic bromination and avoid strong bases during the SN2 reaction to suppress elimination pathways.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nitrile Formation
Nitriles are organic compounds containing a cyano group (-C≡N). To convert 1-phenylpropane to 2-phenylbutanenitrile, a common method is to perform a nucleophilic substitution or addition reaction, where a suitable reagent, such as a cyanide ion, is introduced to form the nitrile. Understanding the mechanism of this transformation is crucial for predicting the reaction pathway and the conditions required.
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Unwanted Side Reactions
In organic reactions, unwanted side reactions can lead to impurities in the final product. For instance, during the conversion of 1-phenylpropane to 2-phenylbutanenitrile, side reactions such as elimination or rearrangement may occur, resulting in by-products. Identifying these potential side reactions helps in optimizing reaction conditions to minimize impurities.
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Reagent Selection
The choice of reagents is critical in organic synthesis, as it influences both the efficiency and selectivity of the reaction. In the case of converting 1-phenylpropane to 2-phenylbutanenitrile, selecting a suitable cyanide source and reaction conditions (like temperature and solvent) is essential to ensure a high yield of the desired product while reducing the formation of undesired by-products.
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Related Practice
Textbook Question
A reluctant first-order substrate can be forced to ionize by adding some silver nitrate (one of the few soluble silver salts) to the reaction. Silver ion reacts with the halogen to form a silver halide (a highly exothermic reaction), generating the cation of the alkyl group.
Give mechanisms for the following silver-promoted rearrangements.
(b)
Textbook Question
Draw the structures of the following compounds.
a. sec-butyl chloride
b. isobutyl bromide
5
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Textbook Question
Predict the compound in each pair that will undergo the SN2 reaction faster.
(c)
(d)
1
views
Textbook Question
Show how you would convert (in one or two steps) 1-phenylpropane to the three products shown below. In each case, explain what unwanted reactions might produce undesirable impurities in the product.
2
views
Textbook Question
A reluctant first-order substrate can be forced to ionize by adding some silver nitrate (one of the few soluble silver salts) to the reaction. Silver ion reacts with the halogen to form a silver halide (a highly exothermic reaction), generating the cation of the alkyl group.
Give mechanisms for the following silver-promoted rearrangements.
(a)
3
views