ethanal with fehling and acidified potassoim and ammonical silve ntrate

Theory

Study how ethanal reacts with the compounds: acidified potassium permangenate and ammonical silver nitrare

Acidified potassium permangenate

• ethabal and ppp placed in a tube

• heat and observe colour change

• purple to colourless

• ethanol to ethanoic acid

• if were to use ketone nothing would happen as ketones cant be oxidised

conclusion

Aldehydes can be oxidised to carboxylic acids but ketones cannot

Fehlings reagent

A mixture in equal amounts of fehlings a and fehlings b

• Must always be freshly made before use

Fehlings A

copper sulfate in water (blue)

Fehlings B

potassium sodium tartare and sodium hydroxide (coloulress

WHat happents when equal quantities are added

a royal blue solutions is formed this solution formed is known as felings reagent

Felings reagent

• An oxidising agent used to distinguish between aldehydes and ketones

• When felings solution is warmed with an aldehyde brick red percipitate is formed

CU2+ + e-======== CU+

what are aldehydes said to be good at

Aldehydes are said to be good reducing agents since they reduce CU2+ to CU

since ketonea are too diffiuclt to oxidise no colour change is observed at all

• Fehlings reagents is very weak oxidising agent to weak to oxidise ketone

method

• make up fehlins reagent by adding felings a and felings b together

• Place ethana; and fehlings (oxidisation) together in a test tube

• Heat and observe colour change

Colour change

royal blue to brick red

EThanal is oxidised to ethanoic acid by feelings reagent

Ammonical silver nitrate

Ammonical silver nitrate

Aldehydes reudce a solution of silver ions in dilute amonia to silver metal

• Silver oxide dissolves in ammonia to form a solution called ammonical silver nitrate

Ammonical silver nitrate

Tollens reagent: if amonium silver nitrate is added to a test tube containing ethanal and the test tube is warmed a reaction takes [lace and a silver mirror is deposited on the side of the test tube

Method

• add silver nitrate to sodium hydroxide and ammonia makr up a solution called tollens reagent

• PLace tollens reganet in a clean dry test tube then add ethanal

• Heat and obcerve colour change

chnage

silver mirror forms on the inside of the test tube ethanal is being oxidised to form ethanoic acid