The oxidation of glucose with Fehling reactive

Irimia Diana, Gherghisan Cristina, Alexandrescu Isabela
“Vasile Alecsandri” High School, Galati, Romania

The necessary Fehling reactive is prepared using:
1) Fehling 1 solution-we dissolve 7g of copper sulphate in 100ml water
2) Fehling 2-we dissolve 35g Seighette salt and 26g potassium hydrate in 100ml water
In the experiment we use equal parts of both solutions.


We introduce in a clean test tube 2-3 ml Fehling reactive and we boil it; meanwhile we drip in the test tube washy glucose solution 20-25% until the blue color of the blend disappears and a red copper oxide precipitate appears.

CuSO₄ + 2 KOH = Cu(OH)₂ + K₂SO₄

C₆H₁₂O₆ + 2 Cu(OH)₂ = C₆H₁₂O₇ + Cu₂O + 2 H₂O
Glucose --> Gluconic acid

Colage

By Irimia Diana and Cristina Gherghisa
“Vasile Alecsandri” High School, Galati, Romania