• If we need to increase the chain length we can use?Grignard reagents

Preparing Grignard reagents?

• A halogenoalkane is dissolved in dry ether and reacted with magnesium to produce the reactive Grignard reagent
• If 1-iodoethane is reacted with magnesium,?ethyl magnesium iodide?is produced
• This is an example of a Grignard reagent

CH3CH2I + Mg → CH3CH2MgI

• These compounds are highly reactive and the alkyl group (R group) can be considered to have a negative charge, therefore it can behave as a nucleophile
  • R-[+MgI]

Reactions of Grignard with carbonyl compounds

• Grignard reagents react with?methanal?to produce a?primary alcohol

RMgI + HCHO ?RCH2OH + Mg(OH)I

• For example, methanal can react with ethyl magnesium iodide to produce?propanol

CH3CH2MgI ?+ HCHO ?CH3CH2CH2OH + Mg(OH)I

• They also can react with longer chain aldehydes?to produce?secondary alcohols
• For example, ethanal can react with ethyl magnesium iodide to produce butan-2-ol

CH3CH2MgI ?+ CH3CHO? ?CH3CH2CH(OH)CH2?+ Mg(OH)I

• Ketones?are also able to react with Grignard reagents producing a tertiary alcohol
• For example, propanone can react with ethyl magnesium iodide to produce?2-methylbutan-2-ol

CH3CH2MgI ?+ CH3COCH3 ?CH3CH2C(CH3)(OH)CH3?+ Mg(OH)I

Reactions of Grignard reagents with carbon dioxide?

• This reaction will produce a carboxylic acid

CH3CH2MgI ?+ CO2 ?CH3CH2COOH + Mg(OH)I