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Are there any tesrs to distinguish glucose & fructose?

Are there any tesrs to distinguish glucose & fructose?

Grade:12

4 Answers

Arun
25750 Points
6 years ago
Dear Yash
 
Glucose and fructose can be distinguished by a number of chemical tests such as:
Seliwanoff’s test- It is a chemical test that distinguishes between aldose (glucose) and ketose (fructose) sugars.  This test is based on the fact that, when heated, ketoses are more rapidly dehydrated than aldoses. Acid hydrolysis of sugars is followed by adding resorcinol and concentrated HCl. The dehydrated ketose then reacts with the resorcinol to produce a deep cherry red colour. Aldoses may react slowly to produce a faint pink colour.
Furfural test- The sugar is treated with an alcoholic solution of alpha-naphthol and concentrated HCl and the mixture is boiled. An immediate violet colour is produced with fructose. Whereas, the colour appears after a few minutes with glucose. 
Ammonium Molybdate test- Freshly prepared 4% aqueous solution of ammonium molybdate is added to an equal volume of 1% solution of sugar in a boiling tube, followed by 4-5 drops of glacial acetic acid. As the boiling tube is heated, fructose gives a greenish-blue coloration within 3-4 minutes whereas, glucose gives only a very faint coloration after 10 minutes. 
 
Regards
Arun (askIITians forum expert)
E.Nandhini ketha
115 Points
6 years ago
the chemical tests to distinguish between glucose and fructose are,
1.Seliwanoff's test
2.amonium molybdate test
3.furfural test
Aditya
13 Points
5 years ago
Glucose is dextrorotary but fructose is levorotatory The structure of glucose is differ from fructose because in glucose oh group is present but in case of fructose CHO group is present
Kushagra Madhukar
askIITians Faculty 628 Points
3 years ago
Dear student,
Please find the answer to your question below.
 
Glucose and fructose can be distinguished by a number of chemical tests such as:
 
Seliwanoff’s test- It is a chemical test that distinguishes between aldose (glucose) and ketose (fructose) sugars.  This test is based on the fact that, when heated, ketoses are more rapidly dehydrated than aldoses. Acid hydrolysis of sugars is followed by adding resorcinol and concentrated HCl. The dehydrated ketose then reacts with the resorcinol to produce a deep cherry red colour. Aldoses may react slowly to produce a faint pink colour.
 
Furfural test- The sugar is treated with an alcoholic solution of alpha-naphthol and concentrated HCl and the mixture is boiled. An immediate violet colour is produced with fructose. Whereas, the colour appears after a few minutes with glucose. 
 
Ammonium Molybdate test- Freshly prepared 4% aqueous solution of ammonium molybdate is added to an equal volume of 1% solution of sugar in a boiling tube, followed by 4-5 drops of glacial acetic acid. As the boiling tube is heated, fructose gives a greenish-blue coloration within 3-4 minutes whereas, glucose gives only a very faint coloration after 10 minutes.
 
Thanks and regards,
Kushagra

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