CM8001

a) C6H12O6 = C6(H2O)6

b) D-Fructose and L-Fructose

c)No. The difference in structures will have different binding affinity to sweetness (taste) receptors, which elicits different neural response.

In reality, everything we eat, whether healthy or not, are composed of chemicals.
Even if the food is grown in organic/pesticides-free condition, there are chemicals brought about by rain may still contaminate these food. (e.g. pesticides flushed down from non-organic farms to organic farms by rain)
Packaging such as plastics containers can cause chemicals to be transferred to the food.