Preparation of Ketones from Nitriles (using Grignard Reagents)
Ketones are prepared by the reaction of nitriles with Grignard reagents, followed by hydrolysis.
What is Preparation of Ketones from Nitriles (using Grignard Reagents)?
An organic compound containing a cyano group (-C≡N).
Key formula / rule: General Reaction of Nitrile with Grignard Reagent
Key points
- To explain the mechanism of ketone formation from nitriles and Grignard reagents.
- To predict the product of a reaction between a given nitrile and Grignard reagent.
- To identify the necessary reagents and conditions for this synthesis.
Common exam trap
Using wet solvents or reagents, which destroys the Grignard reagent.
Definitions
- Term
Nitrile
- Meaning
An organic compound containing a cyano group (-C≡N).
- Term
Grignard Reagent
- Meaning
An organomagnesium halide (R-MgX) used as a nucleophile in organic synthesis.
- Term
Imine
- Meaning
A compound containing a carbon-nitrogen double bond (C=N).
Learning objectives
To explain the mechanism of ketone formation from nitriles and Grignard reagents.
To predict the product of a reaction between a given nitrile and Grignard reagent.
To identify the necessary reagents and conditions for this synthesis.
Formulae
- Name
General Reaction of Nitrile with Grignard Reagent
- Note
Formation of magnesium salt of imine
- Expression
R-C≡N + R'-MgX → [R-C(=NMgX)-R']
- Name
Hydrolysis of Imine Salt to Ketone
- Note
Acidic hydrolysis yields the ketone
- Expression
[R-C(=NMgX)-R'] + H3O+ → R-CO-R' + Mg(OH)X + NH4+X-
Prerequisites
Understanding of Grignard reagents and their reactivity.
Knowledge of nitrile structure and nomenclature.
Familiarity with hydrolysis reactions.
Common mistakes
Using wet solvents or reagents, which destroys the Grignard reagent.
Over-hydrolysis leading to carboxylic acids (though less common with imine salts).
Incorrect stoichiometry, leading to incomplete reaction or side products.
Keywords
Ketone synthesis
Nitrile
Grignard reagent
Organometallic chemistry
Hydrolysis
Imine salt
Practice preview
When benzonitrile reacts with phenylmagnesium bromide followed by hydrolysis, the product formed is:…
medium
Which of the following reactions can be used to prepare a ketone from a nitrile?…
easy
What is the product formed when acetonitrile reacts with methylmagnesium bromide followed by hydrolysis?…
easy