Carbonyl Compounds Flashcards
Describe the oxidation of a secondary alcohol
Add acidified potassium dichromate, and heat under reflux. A ketone will form and the solution will turn from orange to green
Describe the oxidation of a primary alcohol
Add acidified potassium dichromate, and heat under reflux. The solution will change from orange to green. If distilled immediately an aldehyde will be formed. If the compound is continually heated under reflux, a carboxylic acid will form
Describe the oxidation of aldehydes
Add acidified potassium dichromate and heat under reflux, a carboxylic acid will form
Describe the reduction of aldehydes
Add NaBH4, and warm in aqueous ethanol, a primary alcohol will form
Describe the reduction of ketones
Add NaBH4, and warm in aqueous ethanol, a secondary alcohol will form
Describe the mechanism for a nucleophilic addition reaction
A dipole is formed at the C=O. The pair of electrons from one of the double bonds is given to the O atom. The lone pair on the H- ion is given to the C. The O- ion now has a lone pair, which is given to an H atom in an H2O molecule. The electrons from the O-H bond is given to the O atom in H2O. An OH- ion is formed
What test is used to identify the presence of a carbonyl group?
Add 2,4-DNPH, a yellow precipitate is formed. Can only be used to identify a ketone or aldehyde
How can a compound be identified as a specific ketone or aldehyde using 2,4-DNPH?
The solid formed when 2,4-DNPH is added it slightly impure. It is filtered and recrystallised. The melting point of this pure sample is measured and recorded, which is then compared to a database to identify the original aldehyde or ketone
How can the presence of an aldehyde group be detected?
Ammonical silver nitrate us added, if an aldehyde is present, a silver mirror forms. This is an oxidation reaction and both silver and a carboxylic acid form. Ketones will not be oxidised by the solution
