1. Experimental Reports Today is the final practical
Get dry weights for % yield, melting points by next week
All reports must be handed up to your demonstrators no later than one week from today – otherwise marks will be lost

2. Reactions of Aldehydes and Ketones
Experiment 18
Reactions of Aldehydes and Ketones

3. Introduction Aldehydes and ketones are carbonyl compounds
Undergo similar types of reactions – addition, condensation and substitution reactions
Aldehydes more reactive then ketones

4. Introduction Aldehydes can be oxidized, ketones can not be oxidized
Fehlings test uses this principle to distiguish between the two types of compound
Accompanied by formation of a red precipitate

5. Fehlings Test Aldehydes oxidized to carboxylic acids
Ketones not oxidized
Precipitate due to formation of insoluble Cu+1 as Cu2O – indicates presence of aldehyde

6. Derivative Formation
One derivative of each class of compound will be prepared
A semicarbazone derivative of a ketone will be formed
A phenylhydrazone derivative of an aldehyde will be formed

7. Nucleophilic Addition Reaction
Addition of semicarbazine/hydrazine reagent to the carbonyl compound results in semicarbazone/hydrazone formation
Imine functional group is formed

8. Hydrazone formation

9. Experimental – Fehlings Test
To 6 drops of Fehlings solution in a test tube add 3 drops of propanal
Heat in the water bath for 2 mins
Red precipitate indicated oxidation of aldehyde
Repeat with butanone – record observations & comment on the results

10. Experimental – Semicarbazone Formation
Dissolve 2.0 g of semicarbazide hydrochloride and 2.0 g of sodium acetate in 10 ml water
Add 2 ml butanone and heat for 15 min on the water bath
Cool to room temperature & collect the crude crystals

11. Experimental – Semicarbazone Formation
Wash with water
Recrystallise from aqueous ethanol
Allow to dry on the Hirsch funnel
Record the yield in g, the melting point, and % yield of the dry crystals
Include a mechanism for the reaction in your experimental report

12. Experimental – hydrazone formation
To 1.0 ml of propanal add 10 ml ethanol and 25 ml of the 2,4-dinitrophenylhydrazine solution
Heat for 5 mins and allow to cool
Isolate the crystals on the Hirsch funnel
Allow to dry, record the yield in g, the melting point and % yield of crystals

13. Report
Introduction
Observsations & conclusions from Fehlings tests & derivative formation
% yield & mp of semicarbazone
Mechanism of semicarbazone formation
% yield & mp of phenylhydrazone
Discussion of all results and reactions

14. Experimental Reports Today is the final practical
Get dry weights for % yield, melting points by next week
All reports must be handed up to your demonstrators no later than one week from today – otherwise marks will be lost