Question

How can aldehydes and ketones be prepared in the laboratory?

Answer 1

They are both oxidation product of alcohols.

Explanation:

We make a distinction between primary and secundary alcohols:

A primary alcohol has its `-OH` group at the end of a carbon chain, so it looks like `-CH_2OH` (with two `H`'s at the same `C`)
After oxidation this will look like `-CH=O` and is called aldehyde , which can further oxidize to a carboxylic acid `-COOH`

A secundary alcohol has the `-OH` group in the middle of a chain, so the `C` has only one extra `H`: `-CHOH-`
After oxidation this will be a ketone : `-C=O`

How to make them in the lab: You can make use of `Cr(VI)` compounds, like potassium dichromate. In the case of making aldehydes, the amount must be carefully mastered, or too much of the carboxylic acid will form.