How do you make aldehyde?

1 Answer
Mar 28, 2016

With difficulty; usually by oxidation of alcohol.

Explanation:

We start with a primary alcohol, #RCH_2OH#; (why can't we start with a secondary alcohol?).

#RCH_2OH + [O] rarr RC(=O)H rarr RC(=O)OH#

Now, there a variety of oxidizing agents, metal oxides, oxygen, chlorates for instance. The problem is that they tend to be indiscriminant. I have known very experienced organic chemists to use #K_2Cr_2O_7# to oxidize primary alcohols to aldehydes, but they would strictly monitor the reaction by #TLC#, and stop the oxidation at the aldehyde stage.