Question

How do you make aldehyde from the carboxylic acid?

Answer 1

Hint:In order to make the aldehyde from the carboxylic acid, we must have an idea about what an aldehyde and carboxylic acid is. Aldehyde is an organic compound which is having a functional group of – CHO group, while carboxylic acid is an organic compound which is having a functional group of -COOH group.

Complete answer:
Let us first understand what an aldehyde and carboxylic acid is.
> Aldehyde is an organic compound which has a carbonyl group as the functional group. The carbonyl group present in the aldehyde is -CHO group.
> Carboxylic acid is an organic compound which is also having carbonyl group as the functional group. The carbonyl group present in the carboxylic acid is the -COOH group.
> The carboxylic acid will be having an extra oxygen compared to the aldehyde.
> In order to obtain aldehyde from the carboxylic acid, we have to use a reducing agent. The reducing agent which is used in the conversion of the acid into aldehyde is $$LiAl{H}_4$$ or $$NaB{H}_4$$. It will be very difficult to reduce the acid into aldehyde without further reducing that aldehyde into alcohol. This is because $$NaB{H}_4$$ is less reactive but $$LiAl{H}_4$$ is more reactive. So, all we have to do is to reduce the acid with $$LiAl{H}_4$$to produce primary alcohol and further partially oxidizing that alcohol back to aldehyde using the PCC (Pyridinium chlorochromate). The reaction is given below:

Note:
- We have to remember that we can also prepare the aldehyde by oxidation of the primary alcohol. The oxidizing agent which is used for converting the primary alcohol into the aldehyde is the potassium dichromate.
- We can further convert this aldehyde into a carboxylic acid by oxidation process with the same oxidizing agent.