In Glucose, how will you prove the presence of the following? [closed]








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1. One carbonyl group
2. 5 hydroxyl groups
3. One primary alcholic group




***1. Reaction with $\ce{HCN}$, or with hydroxlyamine ($\ce{NH2OH}$)***


Glucose reacts with $\ce{HCN}$ to give a cyanohydrin, or with a schiffs base to give an oxime. This shows the presence of a carbonyl group.


***2. Reaction with acetic anhydride $\ce{(CH3CO)2O}$***


Glucose gives a penta ester with acetic anhydride, revealing that it has 5 hydroxyl groups. 


***3. Reaction with Nitric acid***


On oxidation with Nitric acid ($\ce{HNO3}$),glucose as well as gluconic acid both yeild a dicarboxylic acid (saccharic acid). This indicates the presence of a primary alcoholic group in glucose.


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**To prove the presence of $\ce{-CHO}$ group:**


When glucose reacts with **hydroxylamine**, **oxime** is formed and ***cyanohydrins are formed*** on the addition of hydrogen cyanide to it. This reaction can confirm the presence of carbonyl group in glucose. And also on the reaction of glucose with a mild oxidising agent like bromine water, the glucose gets oxidised to carboxylic acid containing six carbon atoms. This indicates that the carbonyl group is present (as an aldehyde group).


**To prove the presence of $\ce{-OH}$ groups:** 


The presence of $\ce{-OH}$ group is confirmed after the ***acetylation of glucose with acetic anhydride***, which gives glucose pentaacetate.


Hope this helps


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