Reduction of carbonyl compounds

Introduction -Reduction is defined in chemistry as loss of oxygen, gain of hydrogen or gain of electrons -Carbonyl group is consisting of a carbon (C) and an oxygen (O) atom connected by a double bond.

Introduction The difference between the electronegativities of carbon and oxygen is large enough to make the C=O bond moderately polar.

Carbonyl compounds Ester Carboxylic acid ketone aldehyde Compound Structure RCOOR' RCOOH RCOR' RCHO General formula

1\ Reduction of aldehydes and ketones

1\ Reduction of aldehydes and ketones e.g.1: e.g.2:

2\ Reduction of carboxylic acids Most reductions of carboxylic acids lead to the formation of primary alcohols. These reductions are normally carried out using a strong reducing agent, such as lithium aluminum hydride (LiAlH4).

2\ Reduction of carboxylic acids Examples : (1° alcohol) (1° alcohol)

3\ Reduction of esters A pair of alcohols ( with at least one being 1ry ) results from the reduction of an ester. They can be reduced by LiAlH4, NaBH4

3\ Reduction of esters Example :

Reduction of benzaldehyde 2

Reduction of benzaldehyde Procedure : 1- dissolve 13.5g of KOH in 13ml of H2O then add it in ice bath. 2-add the solution in glass bottle and add 15ml of benzaldehyde, close the bottle and shake will, then leave it for 24h. 3-after 24h, add 50ml of H2O and shake until the solution dissolve.

Reduction of benzaldehyde 4- transfer the solution to separating funnel, wash the remain with 15ml of ether and add it to the solution. 5-shake the solution in the separating funnle to separate benzyl alcohol, collect the ether layer, and repeat the process twice more (each with 12ml ether). (keep the aqueous layer) When used with an aqueous solution, the organic layer(ether) is on top as the diethyl ether has a lower density than the water

Reduction of benzaldehyde 6-pass the collected solution (ether layer) in to ordinary funnel lined with filter paper and saturated sodium sulphate powder. 7- add 5ml of 10% sodium carbonate and separate it , then wash it with 5ml H2O. 8-leave to dry, then collect the powder and calculate the % of benzyl alcohol. Sometimes the organic layer, when derived from an acidic solution, should be washed with sodium carbonate, which is a base. A salt is formed in this reaction that is soluble in water and will be flushed out with the aqueous phase.

Reduction of benzaldehyde 9- to the aqueous layer add 40ml conc HCl , 40ml of H2O and 50g of ice. 10-filter the benzoic acid by vacum filtration. 11-wight the powder and calculate the % of benzoic acid.

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