17. Organometallic Compounds
🎯 Learning outcomes
By the end of the chapter, students should be able to:
- Briefly describe the general formula and examples of organolithium, organocopper, and organocadmium compounds.
- Explain the nature of the Metal-Carbon bond.
- Define a Grignard reagent.
- Show the preparation of a Grignard reagent (using haloalkane and haloarene).
- Explain the reaction of a Grignard reagent with water, aldehydes, and ketones (preparation of primary, secondary, and tertiary alcohols), carbon dioxide, HCN, RCN, ester, and acid chloride.
Compounds in which a metal is bonded to carbon atoms of the alkyl (organic) group.
- R-LiAlkyllithium
- R2CuLiLithium dialkyl cuprate
- R2CdDialkyl cadmium
Grignard reagent: It has the general formula RMgX; its general name is alkylmagnesium halide, a well-known example of an organometallic compound.
Highly polar covalent bonds
RMgXAlkyl magnesium halide
17.3.1 Preparation (using haloalkane and haloarene)
Haloalkanes or haloarenes react with magnesium metal in the presence of dry ether, forming alkyl magnesium halide or the Grignard’s reagent.
Precaution: While preparing Grignard’s reagent, the conditions must be dry or moisture-free. If water is present, it reacts with Grignard’s reagent, resulting in an alkane, an undesired product.
1. With Aldehydes and Ketones (formation of 10,20 and 30 alcohol)
The addition of Grignard’s reagent to aldehydes and ketones gives addition products, which, on hydrolysis, produce alcohols.
Formaldehyde gives primary alcohols.
Other aldehydes give secondary alcohols.
Ketones give tertiary alcohols.
2. With carbon dioxide (formation of carboxylic acids)
Carbon dioxide gas, if passed through a dry ether solution of Grignard’s reagent, produces an addition product. The addition product undergoes hydrolysis with mineral acid to giving carboxylic acid.
3. With HCN
4. With RCN
5. Ester
6. Acid chloride
Test your understanding
Take a short quiz on organometallic compounds.