How do you explain the presence of an aldehydic group in a glucose molecule?

Explanation

Glucose reacts with hydroxylamine to form a monoxime and adds one molecule of hydrogen cyanide to give cyanohydrin.
`{:(" "CHO),(" |"),(" "(CH_(2)OH)_(4)),(" |"),(" "CH_(2)OH):}+NH_(2)OHrarr underset("Glucose oxime ")({:(" "CH=N-OH),(" |"),(" "(CHOH)_(4)),(" |"),(" "CH_(2)OH):})`
`{:(" "CHO),(" |"),(" "(CHOH)_(4)),(" |"),(" "CH_(2)OH):}+HCNrarr underset(" Glucose cyanohydrin")({:(" "CH(OH)CN),(" |"),(" "(CHOH)_(4)),(" |"),(" "CH_(2)OH):})`
Therefore, it contains a carbonyl group which can be an aldehyde or a ketone. On mild oxidation with bromine water, glucose gives gluconic acid which is a carboxylic acid containing six carbon atoms.
`{:(" "CHO),(" |"),(" "(CHOH)_(4)),(" |"),(" "CH_(2)OH):}+Ooverset(Br_(2),H_(2)O)rarr underset("Glucose acid")({:(" "COOH),(" |"),(" "(CHOH)_(4)),(" |"),(" "CH_(2)OH):})`
This indicates that carbonyl group present in glucose is an aldehydric group.