Look at the one with the highest number - OH is D on the right

Number of optical isomers n is the number of chiral carbons

Write the Fisher form of the hemiacetal form

Write the six-membered ring of epoxy in the upper right corner and number it in sequence

Write the hydroxyl groups in the Fisher formula in the corresponding numbered positions according to the "upper left, lower right" rule.

C5: D type is on the top, L type is on the bottom

Morich reaction (purple ring reaction)

Silevanov reaction

Anthrone reaction

D-glucose can be obtained by treating D-glucose with dilute alkali to obtain D-mannose and D-fructose.

All monosaccharides are reducing

Reduction of monosaccharides to form polyols

Monosaccharide phenylhydrazine-phenylhydrazone, α hydroxyl group continues to react to form uracil (yellow crystal)

Esterification

into ether