Grignard formation

Overview

Iodoalkanes can react with magnesium in dry ether to form Grignard reagents.

Transformation

Iodoalkanes → Grignard reagents

Equation

R-I + Mg -> R-MgI

Reagents

Mg

Environment

dry ether

Reaction class

organometallic formation

Mechanism

organomagnesium formation

Evidence level

textbook core

Scope and limitations

Scope

Iodoalkanes form Grignard reagents with magnesium under dry ether conditions.

Limitations

Strictly anhydrous ether is required because water destroys Grignard reagents; this is recorded as a synthetic extension rather than a displayed arrow-pushing mechanism.

Related reactions

• Iodination: Alcohols → Iodoalkanes

  Iodine and red phosphorus conditions convert alcohols into iodoalkanes.

• Hydroiodination: Alkenes → Iodoalkanes

  Addition of hydrogen iodide across an alkene can form an iodoalkane.

• Cyanation: Iodoalkanes → Nitriles

  Cyanide substitution forms a nitrile and extends the carbon chain by one carbon.

• Amination: Iodoalkanes → Amines

  Ammonia substitutes iodide to form a primary amine; excess ammonia limits further alkylation.

• Hydrolysis: Iodoalkanes → Alcohols

  The C-I bond can be displaced by hydroxide to form an alcohol.

• Elimination: Iodoalkanes → Alkenes

  Base-promoted elimination removes HI to form an alkene.

• Grignard formation: Chloroalkanes → Grignard reagents

  Chloroalkanes can react with magnesium in dry ether to form Grignard reagents.

• Grignard formation: Bromoalkanes → Grignard reagents

  Bromoalkanes can react with magnesium in dry ether to form Grignard reagents.

• Carbonyl addition: Grignard reagents → Primary alcohols

  Grignard addition to methanal gives primary alcohols after work-up.

• Carbonyl addition: Grignard reagents → Secondary alcohols

  Grignard addition to aldehydes gives secondary alcohols after work-up.

• Carbonyl addition: Grignard reagents → Tertiary alcohols

  Grignard addition to ketones gives tertiary alcohols after work-up.

• Carboxylation: Grignard reagents → Carboxylic acids

  Grignard carboxylation gives carboxylic acids after acidic work-up.

References

1. Organic Chemistry: Reactions of Alkyl Halides: Grignard ReagentsJohn McMurry · OpenStax Organic Chemistry · 2023

   Supports alkyl chlorides, bromides, or iodides reacting with magnesium in ether or THF to form Grignard reagents; also notes chloroalkanes are less reactive than bromo/iodo analogues and that moisture destroys Grignard reagents.