Grignard reagents and carbon chain extensionEdexcel International A Level Chemistry: Mind map

Exam questions on Grignard reagents and carbon chain extension

1. A research student prepares ethylmagnesium bromide, C₂H₅MgBr, from bromoethane and magnesium. The first attempt is carried out in apparatus that has been washed and left to drain, and the student is told that this is a poor choice for this reaction.
   Explain why the apparatus and the ether must be completely dry for this preparation.2 marks
2. A student plans to convert 1-bromopropane into butanoic acid in two stages. In stage 1 the haloalkane is turned into a Grignard reagent. In stage 2 the Grignard reagent is added to an excess of crushed solid carbon dioxide, and the mixture is then treated with dilute hydrochloric acid.
   Explain why the Grignard reagent attacks the carbon atom of carbon dioxide.2 marks
3. A chemist has a bottle of methylmagnesium bromide, CH₃MgBr, in dry ethoxyethane. She wants to make three different alcohols by reacting separate portions of the reagent with three different carbonyl compounds, each followed by dilute acid: methanal, ethanal and propanone.
   Deduce the name of the alcohol formed from each carbonyl compound, and state whether it is a primary, secondary or tertiary alcohol.3 marks