Q. Glucose (C6H12O6) can survive as both an open-chain form and a closed-ring form. Before 1900, glucose was only thought to happen as an open chain. Now we know that over 99 percent of the time, glucose occurs in the closed-ring form. What probable difference between these forms would give chemists a clue that the open-chain form was not present?

a) Open-chain molecules could form polymers and glucose does not.

b) Only open-chain forms might undergo condensation, which does not happen with glucose.

c) An open chain presents ends with functional groups (in this case aldehyde), and glucose failed to undergo typical aldehyde reactions; phenomenon that could be explained by having no end functional group in a ring structure.

d) Since glucose is solid at room temperature, it should have saturated hydrocarbon chains.

e) Glucose might not be “denatured” so it must be a tight chain.