Increasing carbon chain length

how to increase chain length of halogenoalkane using cyanide ion

halogenoalkane —→ (CN-) Nitrile

Nucleophilic subsitution

reaction of carbonyl with cyanide ion

• Porduce Nitrile

• Nucleophilic addition

Friedel crafts reactions of benzene to increase chain length

• Benzene + CH3C—→ (halogen carrier ALCL3) methyl benzene Alkylation

• Benzene+ CH3COCl (R-COCl)—> phenylethanone Acylation

how to make girgnard reagent

• Halogenoalkanes are heated under reflux with magnesium in dry ether

• If water is present the Grignard reagent will not form

R-Mg-X + H2O—> R-H + HOMgX

• 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]

reaction of grignard reagents with CO2

• Produces a carboxylic acid

• CH₃CH₂MgI  + CO₂ CH₃CH₂COOH + Mg(OH)I see book

Reaction of grignard with aldehydes

• 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)CH₃ + Mg(OH)I

• Grignard reagents react with methanal to produce a primary alcohol 

RMgI + HCHO RCH₂OH + Mg(OH)I

with aldehydes they produce secondary alcohol + HOMgBr

Reaction of grignard with ketones

• 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