carbonyls - aldehydes and ketones Flashcards
aldehyde functional group and suffix
-al
-CHO
Ketone functional group and suffix
-one
-CO
Oxidation of an aldehyde
conditions + reagents + products
aldehyde + [O] –> Carboxylic acid
[O] = K2Cr2O7 –> Cr2O72-
Reflux
Oxidation of a ketones
conditions + reagents + products
Ketones cant undergo oxidation as they don’t have any hydrogen atoms attached to their carboxyl group
Whats the simple test for carbonyls also known as
Tollens reagent
How do you prepare tollens reagent
- Add AgNo3
- Add NaOH until Brown ppt forms
3.Add NH4OH til colourless ( ammoniahydroxide)
Why can you only carry out tollens reagent on an aldehyde
Tollens reagent oxidises the carbonyl group and ketones don’t have nay hydrogens to be oxidised , unlike aldehydes
How do you use tollens reagent
If you add tollens reagent to both aldehydes and ketones what colour would you see
Heat gently over a waterbath
Aldehydes : silver mirror
Ketones : no colour change
What is the tollens reagent test use for
to distinguish between carbonyls
What does 2,4DNP /2,4DNPH stand for
what colour does it appear
2,4 dinitrophenylhydrazine
Green
What is the other name or 2,4DNP
Bradys reagent
Whats the purpose of the Bradys reagehnt test
To test for a carbonyl
What order do you carry out the test
- Bradys reagent
- tollens reagent
How do yo carry out the Bradys reagent test
dissolve 2,4DNP in sulfuric acid
1. React the substance with 2,4DNP ( orange colour should form)
2.Puridy by recrystallisation
3.Check the melting points against known data
What’s the reducing agent to reduce a carbonyl
NaBH4 - sodium tetrahydridoborate
