colour of solutions with complex ions Flashcards
What’s the functional group of both ketones and aldehydes and their named ending
Aldehydes = al /-CHO
Ketones = one /-CO
State the oxidation equations of both carbonyls
Ketones –> cant be oxidised
Aldehydes + [O] —> carboxylic acid
over reflux
Kr2CrO7 and dilute sulfuric acid
Reduction of carbonyls
reagents and conditions
Reagents : NaBH4 - sodiumtetrahydridoborate
Conditions : Room temperature and pressure
aldehyde + 2[H] –> primary alcohol
ketone + 2[H] –> secondary alcohol
Why cant carbonyls undergo nucleophilic addition
The carbon is electron deficient as the electrons are closer to the O in the
C=O bond , the O is slightly negatively charged.
The positive charge on the electrophile would repel the slightly positive carbon
What is a nucleophile
electron pair donor
What is the overall equation for carbonyls when they react with cyanide ions.
what are the reagents and conditions
carbonyl + CN- –> hydroxytnitrile
Reagents: KCN/NaCN and dilute sulfuric acid
Conditions : Room temperature and pressure
How do you make tollens reagent
- add AgNO3
- add drops NaOH –> brown precipitate
- add drops of NH4OH –> until colourless
How do you use the simple test for carbonyls:
What are the results
- add tollens reagent ( agno3 + naoh (brown)+nh4oh(colourless))
2.aldehyde = silver grey mirror ketone = no colour change
Explain the redox in the simple carbonyl test
REUCTION - silver Ag+ + e- –> Ag
OXIDATION : aldehyde + [O] –> carboxylic acid
ketones don’t oxidise so ne redox reaction occurs
What’s the test for carbonyls ( which isn’t the simple test)
Reagents and conditions
Bradys reagent - 2,4DNP/2,4DNPH (dinitrophenylhydrazine)
Dissolve in methanol/sulfuric acid
1.React with 2,4DNP ( green to orange - crystals may appear)
2.Purify by recrystallisation
3.Check the melting point against known melting points
