Textbook Question
What alkyl bromide would you use in a Gabriel synthesis to prepare each of the following amines?
b. isohexylamine
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26. Amines
Gabriel Synthesis
2:05 minutesProblem 55i
Textbook Question
Predict the product(s) of the reactions shown.
(i) 
Verified step by step guidance1
Step 1: Identify the starting material as phthalimide, which is a cyclic imide derived from phthalic acid.
Step 2: Recognize the first reagent, nBuBr (n-butyl bromide), which is an alkyl halide. This suggests an alkylation reaction where the nitrogen atom of the phthalimide will act as a nucleophile.
Step 3: Understand that the phthalimide nitrogen will attack the n-butyl bromide, displacing the bromide ion and forming N-butylphthalimide.
Step 4: Note the second step involves KOH and hydrazine (H2NNH2) under heat (Δ). This indicates a Gabriel synthesis, where the phthalimide is converted to a primary amine.
Step 5: In the Gabriel synthesis, hydrazine reacts with N-butylphthalimide to release the primary amine, n-butylamine, and form phthalhydrazide as a byproduct.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Nucleophilic Substitution Reaction
Nucleophilic substitution is a fundamental class of reactions in organic chemistry where a nucleophile selectively bonds with or attacks the positive or partially positive charge of an atom or a group of atoms to replace a leaving group. In the given reaction, nBuBr (n-butyl bromide) acts as the alkylating agent, where the bromide ion is the leaving group, and the nitrogen atom in the imide acts as the nucleophile.
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Nucleophiles and Electrophiles can react in Substitution Reactions.
Gabriel Synthesis
Gabriel synthesis is a method used to synthesize primary amines from primary alkyl halides. The reaction involves the use of phthalimide, which is deprotonated to form a nucleophilic phthalimide anion that reacts with an alkyl halide. In this reaction, the phthalimide is alkylated by nBuBr, and subsequent hydrazinolysis releases the primary amine, n-butylamine.
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Hydrazinolysis
Hydrazinolysis is a chemical reaction where hydrazine is used to cleave a bond, often in the context of removing protecting groups. In the Gabriel synthesis, hydrazinolysis is used to convert the N-alkylphthalimide intermediate into the corresponding primary amine. Here, hydrazine reacts with the alkylated phthalimide to release n-butylamine and phthalhydrazide as a byproduct.
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