6.1.2 Carbonyls Flashcards
What are carbonyl compounds?
Carbonyl compounds contain a C=O bond and can be classified as either aldehydes or ketones
How do you identify an aldehyde from it’s structure?
In an aldehyde, the C=O group is at the end of the chain, attached to at least 1 hydrogen atom, ends in “-al”
How do you identify a ketone from it’s structure?
In a ketone, C=O group is in the middle of the carbon chain, with no attached hydrogen and the name ends in “-one”
Why are smaller carbonyl compounds soluble in water?
Why are larger carbonyl compounds not soluble in water?
Smaller carbonyls like propanone and ethanal can form hydrogen bonds with water
As the non-polar hydrocarbon part disrupts hydrogen bonding with water so solubility decreases with size
Why do carbonyls have permanent dipole forces?
The C=O bond is polar, allowing dipole-dipole interactions.
Describe the oxidation reaction for primary alcohols?
Primary alcohols are oxidised to aldehydes and then to carboxylic acids
How does Tollen’s reagent test for aldehyde?
Tollen’s reagent oxidises aldehydes to carboxylic acids, reducing silver ions to metallic silver creating a “silver mirror”
What is a reaction of 2,4-dinitrophenylhydrazine with carbonyl compounds?
2,4 DNP reacts with both aldehydes and ketones to form an orange precipitate, which can be used to detect carbonyl groups
How can the melting point of a 2,4-DNP derivative help in identifying a carbonyl compound?
The melting point of the orange crystals formed from 2,4 - DNP can be compared with known values to identify the specific carbonyl compound
How do you distinguish between an aldehyde and a ketone using chemical tests?
Use Tollens reagent
Aldehydes give a silver mirror
ketones don’t react
What reagents are used to reduce carbonyl compounds to alcohols?
NaBH4 or LiAlH4
What type of alcohols are produced from the reduction of aldehydes and ketones?
Aldehydes are produced to primary alcohols, while ketones are reduced to secondary alcohols
How does HCN- react with carbonyl compounds like aldehydes and ketones
HCN- reacts with carbonyl compounds
in a nucleophilic addition reaction
The CN- attacks the carbon
in the C=O bind
breaking the double bond
A H+ attaches to the oxygen = forms OH
hydroxynitrile forms final product
this has OH group and CN group attatched
What conditions are required for the reaction of hydrogen cyanide addition to a carbonyl compound?
Sodium cyanide (NaCN)
Sulfuric Acid (H2SO4)
RTP
What reaction occurs for the reaction of hydrogen cyanide to carbonyl compounds?
undergoes nucleophilic addition
to form hydroxynitrile
