Leaving Cert Chemistry - Aldehydes and Ketones

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Aldehydes and Ketones

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Aldehydes and ketones are compounds i.e. they have a carbon- double bond.
All aldehydes contain the -CHO group and are named with the ending . Aldehydes are formed by the oxidation of alcohols. Further oxidation causes the aldehyde to form a carboxylic . The simplest aldehyde is methanal.
All ketones contain a carbonyl group attached to two groups and are named with the ending . Ketones are formed by the oxidation of secondary alcohols. The simplest ketone is .
Aldehydes and ketones are found in nature and they are used as in the manufacture of polymers.
The carbonyl group contains a bond which has a significant effect on the properties of aldehydes and ketones.The smaller aldehydes and ketones have much higher points than alkanes of a similar molecular mass.This is due to the polar nature of the carbonyl group. However, aldehydes have lower boiling points than alcohols of similar relative mass. This is due to the dipole-dipole attraction between the aldehde/ketone molecules not being as strong as the bonding between the alcohol molecules.
The polar carbonyl group also causes smaller aldehydes and ketones to be with water. This is because water forms bonds with the carbonyl group.
The larger aldehydes and ketones are much less soluble in water due to the size of the hydrocarbon part of the molecule. Aldehydes and ketones are soluble in non-polar solvents such as .
An aldehyde can be to a primary alcohol, while a ketone can be reduced to a secondary alcohol. This is done by reaction with hydrogen gas over a nickel .
Aldehydes can be oxidised to acids by either acidified potassium permanganate or solution. Ketones cannot be oxidised.