Glucose (C6H12O6) can exist as both an open-chain form and a closed-ring form. Before 1900, glucose was only thought to occur as an open chain. Now we know that over 99 percent of the time, glucose occurs in the closed-ring form. What possible difference between these forms would give chemists a clue that the open-chain form was not present?
a) Open-chain molecules can form polymers and glucose does not.
b) Only open-chain forms can undergo condensation, which does not occur with glucose.
c) An open chain presents ends with functional groups (in this case aldehyde), and glucose failed to undergo typical aldehyde reactions; a phenomenon that could be explained by having no end functional group in a ring structure.
d) Because glucose is solid at room temperature, it must have saturated hydrocarbon chains.
e) Glucose could not be "denatured" so it must be a tight chain.