How will you prove the presence of one $(- C H O)$ group and five $(- O H)$ groups in the Glucose? Write down the chemical reactions of both the tests.

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Solution

1) Bromine water is mild oxidising agent. It oxidises glucose to gluconic acid. Decolourisation of bromine water indicates positive test and confirms presence of one $- C H O$ group in the glucose.
$H O C H_{2} - (C H O H)_{4} - C | | O - H [O] - \to H O C H_{2} - (C H O H)_{4} - C | | O - O H$
2) When glucose reacts with acetic anhydride in presence of sulfuric acid, a penta acetyl derivative of glucose is obtained. It confirms that glucose has 5-OH groups.
$H O H_{2} C (C H O H)_{4} - C H O + 5 A c_{2} O \to A c O H_{2} C (C H O A c)_{4} - C H O + 5 A c O H$

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