Question

Prove that Glucose have 5 OH group ?

I want chemical reaction !

Answer 1

Let us say we have 1 mole of Glucose having weight 180 gram.

After Acetylation , the weight of glucose increases by 210 gram because of attachment of 5 Acetyl groups ; each having weight of 43 gram and 5 Hydrogen atoms are also removed from the 5 -OH groups of Glucose.

The net weight gain = (43 x 5) - (1 x 5) = 210 gram

The removal of these 5 Hydrogen atoms Or the attachment of 5 Acetyl groups confirm the presence of 5 - OH groups in it.

....sry...I'm not able to send image of reaction...so kindly refer to the link

https://socratic.org/questions/how-can-we-prove-glucose-contain-five-oh-groups#

Answer 2

Explanation :

As we know that glucose is a monoaccharide molecule that has five free hydroxyl groups and 1 aldehyde group.

Acetylation of glucose with acetic anhydride :

When the glucose react with the acetic anhydride to gives a penta ester. From this we conclude that it has 5 hydroxyl groups.

That means the presence of 5 hydroxyl group is confirmed by the acetylation of glucose with acetic acid which gives glucose pentaacetate.

The acetylation of glucose with acetic acid reaction is shown below.