Question

How can you confirm the presence of aldehyde grp in glucose?

Answer 1

glucose reacts with hydroxylamine to form a monoxime and adds one molecule of hydrogen cyanide to give cyanhydren.
so it contains a carbonyl group which can be aldehyde or a Ketone
on mild oxidation with bromine water, glucose gives gluconic acid which is a six carbon carboxylic acid.
this indicates that carbonyl group is present in glucose is an aldehydic group.