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

Reactions of Aldehydes and Ketones Experiment 18 Reactions of Aldehydes and Ketones

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

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

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

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

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

Hydrazone formation

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

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

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

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

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

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