Question

Account for the following:

There are 5 OH groups in glucose

Answer 1

Acetylation of glucose with acetic anhydride gives glucose pentaacetate which confirms the presence of five –OH groups. Since it exists as a stable compound, five –OH groups should be attached to different carbon atoms.

\[\begin{array}{cc}
\phantom{...}\ce{CHO}\phantom{...................}\ce{CHO}\phantom{....}\phantom{}\ce{O}\phantom{.........}\\
\phantom{..}|\phantom{.......................}|\phantom{}\phantom{........}||\phantom{........}\\
\phantom{}\ce{(CHOH)4 ->[Acetic anhydride] (CH-O-C-CH3)4}\\
\phantom{..........................}\ce{O}\\
\phantom{..}|\phantom{.......................}|\phantom{.}\phantom{........}||\phantom{........}\\
\phantom{}\ce{CH2OH}\phantom{................}\ce{CH2-O-C-CH3}\phantom{}
\end{array}\]