Answer to Question #186015 in Organic Chemistry for Sam

Question

reaction mechanism types:

• Addition e.g. aldehyde or ketone with HCN

• Substitution e.g. halogenoalkane with aqueous NaOH

• Elimination e.g. halogenoalkane with ethanolic NaOH

• Addition-elimination e.g. aldehyde or ketone with 2,4-dinitrophenylhydrazine

This section must explore and interpret the similarities and differences between each of the four mechanisms

Answer 1

Nucleophilic Addition.

The atoms of HCN add to the carbon-oxygen double bond of the ketone by nucleophilic attack of the cyanide anion on the electrophilic carbon of the carbonyl.

Substitution Reaction

The halogenoalkane is heated under reflux with a solution of sodium or potassium hydroxide. Heating under reflux means heating with a condenser placed vertically in the flask to prevent loss of volatile substances from the mixture.

The solvent is usually a 50/50 mixture of ethanol and water, because everything will dissolve in that. The halogenoalkane is insoluble in water. If you used water alone as the solvent, the halogenoalkane and the sodium hydroxide solution wouldn't mix and the reaction could only happen where the two layers met.