Why aldehyde group is easy to oxidize than hydroxyl groups of glucose

In all the reactions i had Seen I pointed out that aldehyde groups of a compound like glucose are easy to oxidize than the hydroxyl groups. I had also read some similar answers but I was unable to find any reason. Can anyone help?

• Can you help us out with a few more details? Which reactions have you seen and which answers are you referring to? What exactly do you mean by "easy"? Nov 27 '21 at 20:38
• It is an experimental result. One big drop of benzaldehyde on a ceramics plate gets oxidized simply by contact with air. After one or two minutes, you will see solid needles of benzoic acid at the surface of the drop. Nothing similar is formed with corresponding alcohol. Nov 27 '21 at 21:30
• Are you sure it is the aldehyde group and not the hemiacetal that is being oxidized? What is the oxidant? Nov 28 '21 at 0:31

Yeah, that's a good question. I like your reasoning. It's sort of like the question, "why is the $$\mathrm{p}K_\mathrm{a}$$ of a carboxylic acid $$(\mathrm{p}K_\mathrm{a} \approx 3)$$ lower than a primary alcohol $$(\mathrm{p}K_\mathrm{a} \approx 15)$$?" The answer is simple. Let's compare the structures of aldehydes, carboxylic acids, and primary alcohols.