Explain the steriochemisty of gyceraldehyde and glycerol, give reasons for absence of anomeric forms in sucrose.
1. In the monosaccharide derivatives known as sugar alcohols, the carbonyl oxygen is reduced to a hydroxyl group. For example, D-glyceraldehyde can be reduced to glycerol. However, this sugar alcohol is no longer designated D or L. Why?
2. Lactose exists in two anomeric forms; though, no anomeric forms of sucrose have been reported. Why?