Cl*Mg

Do you mean Grignard reagents formed from an alkyl/aryl chloride with magnesium (R-Cl + Mg → RMgCl)? If yes, here’s a quick refresher you can use for exams.

Key ideas (Grignard reagents RMgX, with X = Cl in your case)

• Preparation: R-Cl + Mg in dry ether (diethyl ether or THF) under inert atmosphere. Initiation can be slow; sometimes small activators (I2, 1,2-dibromoethane) are used.
• Solvent role: Ethers stabilize Mg via coordination (O-lone pairs on ethers to Mg).
• Reactivity order: RI > RBr > RCl (RCl is the least reactive; slower initiation and consumption).
• Workup: RMgX + H2O or (NH4)Cl → RH + Mg(OH)X; RMgX + CO2 → RCO2MgX, then acidic workup gives carboxylic acid; RMgX + aldehyde/ketone → secondary/ tertiary alcohol after hydrolysis.
• Typical reactions (high-yield exam concepts):
  • With formaldehyde (H2C=O): R-CH2OH after workup (primary alcohol with one extra carbon).
  • With aldehydes: RMgX adds to give secondary alcohols after workup.
  • With ketones: RMgX adds to give tertiary alcohols after workup.
  • With CO2: carboxylic acid after acidic workup (R-CO2H).
  • With epoxides: nucleophilic opening to give alcohols with chain extension (R–CH2–CH2OH type product, depending on conditions).

A quick example

• Ethyl chloride (EtCl) + Mg → EtMgCl (in dry THF or diethyl ether)
• EtMgCl + CO2 → EtCO2MgCl
• Acid workup → propionic acid (EtCO2H)

If you meant something else by "Cl*Mg" (for example a different notation, or a specific intermediate), please clarify and I’ll tailor the explanation. Do you want me to work through a concrete exam-style problem? If so, tell me the exact setup (e.g., which R-Cl and which reagent or which product you need).