Ammonolysis of Alkyl Halides
Synthesis of primary, secondary, tertiary amines, and quaternary ammonium salts by the reaction of alkyl halides with ammonia.
What is Ammonolysis of Alkyl Halides?
A chemical reaction in which a compound is broken down by ammonia, typically with ammonia acting as a nucleophile.
Key formula / rule: General Reaction
Key points
- Understand the mechanism of ammonolysis of alkyl halides.
- Identify the products formed in this reaction.
- Recognize the issue of over-alkylation.
- Learn methods to favor primary amine formation.
Common exam trap
Assuming only primary amine is formed.
Definitions
- Term
Ammonolysis
- Meaning
A chemical reaction in which a compound is broken down by ammonia, typically with ammonia acting as a nucleophile.
- Term
Nucleophile
- Meaning
An atom or molecule that donates an electron pair to form a chemical bond in reactions.
- Term
Electrophile
- Meaning
An atom or molecule that accepts an electron pair to form a chemical bond in reactions.
- Term
Over-alkylation
- Meaning
The process where a product molecule reacts further with the alkylating agent, leading to a mixture of products with increasing degrees of alkylation.
- Term
Quaternary Ammonium Salt
- Meaning
An organic salt where the positively charged nitrogen atom is bonded to four alkyl or aryl groups.
Learning objectives
Understand the mechanism of ammonolysis of alkyl halides.
Identify the products formed in this reaction.
Recognize the issue of over-alkylation.
Learn methods to favor primary amine formation.
Compare ammonolysis with other amine synthesis methods.
Formulae
- Name
General Reaction
- Note
Where R is an alkyl group and X is a halogen.
- Expression
R-X + NH3 → RNH2 + R2NH + R3N + R4N+X-
- Name
Formation of Primary Amine
- Note
Favored by a large excess of ammonia.
- Expression
R-X + NH3 (excess) → RNH2
- Name
Formation of Secondary Amine
- Note
Occurs due to reaction of primary amine with alkyl halide.
- Expression
RNH2 + R-X → R2NH
- Name
Formation of Tertiary Amine
- Note
Occurs due to reaction of secondary amine with alkyl halide.
- Expression
R2NH + R-X → R3N
- Name
Formation of Quaternary Ammonium Salt
- Note
Occurs due to reaction of tertiary amine with alkyl halide.
- Expression
R3N + R-X → R4N+X-
Prerequisites
Alkyl halides
Ammonia
Nucleophilic substitution reactions (SN2)
Basicity and nucleophilicity of amines.
Common mistakes
Assuming only primary amine is formed.
Not using excess ammonia, leading to lower yields of primary amine.
Incorrectly identifying the nucleophile and electrophile.
Ignoring the possibility of quaternary salt formation.
Keywords
Ammonolysis
Alkyl Halides
Ammonia
Primary Amine
Secondary Amine
Tertiary Amine
Quaternary Ammonium Salt
Nucleophilic Substitution
SN2
Over-alkylation
Practice preview
Which of the following is the primary product when ethyl bromide is heated with excess alcoholic ammonia?…
easy
The reaction of an alkyl halide with ammonia to form amines is known as:…
easy
When methyl bromide is treated with ammonia, the product mixture contains primary amine, secondary amine, tertiary amine, and a quaternary ammonium salt. To maximize the yield of the primary amine, one should:…
easy