Grignard formation

Overview

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

Transformation

Chloroalkanes → Grignard reagents

Equation

R-Cl + Mg -> R-MgCl

Reagents

Mg

Environment

dry ether

Reaction class

organometallic formation

Mechanism

organomagnesium formation

Evidence level

textbook core

Scope and limitations

Scope

Chloroalkanes form Grignard reagents with magnesium under dry ether conditions.

Limitations

Strictly anhydrous ether is required because water destroys Grignard reagents; alkyl chlorides are less reactive than the corresponding bromo/iodoalkanes, so this is recorded as a scoped route rather than a general reactivity guarantee and is not a displayed electron-flow mechanism.

Related reactions

• Chlorination: Alcohols → Chloroalkanes

  Alcohols can be converted into chloroalkanes to create a better leaving group for downstream substitution.

• Chlorination with thionyl chloride: Alcohols → Chloroalkanes

  Thionyl chloride converts alcohols into chloroalkanes with sulfur dioxide and hydrogen chloride as by-products.

• Hydrochlorination: Alkenes → Chloroalkanes

  Addition of hydrogen chloride across an alkene can form a chloroalkane.

• Hydrolysis: Chloroalkanes → Alcohols

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

• Cyanation: Chloroalkanes → Nitriles

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

• Amination: Chloroalkanes → Amines

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

• Elimination: Chloroalkanes → Alkenes

  Base-promoted elimination removes HCl to form an alkene.

• Free radical chlorination: Alkanes → Chloroalkanes

  Photochemical chlorination can convert alkanes into chloroalkanes.

• Grignard formation: Bromoalkanes → Grignard reagents

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

• Grignard formation: Iodoalkanes → Grignard reagents

  Iodoalkanes 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.