Unit 4 Aldehydes and ketones AD
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What is the general formula of a Aldehyde?
RCHO
What is the general formula of a Ketone
RCR’O
What is the difference between the melting point of a carbonyl group and a Alkane of similar relative molecular mass?
Higher due to the dipole-dipole forces between the c=o bond
Are aldehydes and ketones soluble in water?
Yes short chain aldehydes and ketones are soluble in water as they can form hydrogen bonds between water and the carbonyl group, but as the chain length increases over 4 carbons the alkyl group prevent the formation of hydrogen bonds.
Draw the structure of but-2-one
H. H. H.H |. |. |. | H-C-C-C-C-H |. |. ||. | H. H O H
Give the result of the Fehlings and silver mirror test for a ketone
Fehiling’s solution will stay blue and no sliver mirror will form as the ketone won’t react with either
An aldehydes can be reduced to what?
A primary alcohol
What is a ketone reduced to?
A secondary alcohol
Write the equation showing structural formula for the reduction of a aldehyde?
R R H + R H I :H I I H I I C=O —> C —-> C I I I + I I H H O H H OH
What type of reaction is the reduction of a Ketone and explain why?
The reduction of a ketone is called Nucleophilic addition, this is because the H- ion is classified as a nucleophile
Give two examples of reducing agents that reduce aldehydes and Ketones to an alcohol?
H and NABH ( sodium tetrahydridoborate) 2 4
Aldehydes can be oxidised using …. to an …. under ….
Acidified potassium di-chromate, COOH, reflux
What is the colour change when acidified potassium dichromate is oxidised?
orange to green
Where does the aldehyde group occur
at the end of the chain
Draw the structure of benzenecarbaldehyde
O II (Benzene ring)- C- H