Question

What is Fehlings test, and why is it used especially for determining aldehydes and not ketones. please do not spam​

Answer 1

A Fehling test :- An alkaline solution of CuSO4 .

I have Rochelle salt ; (KNaC4H4O6·4H2O ) + Alkaline solution. [Fehling B]

Fehling B + aqueous solution of CuSo4 ➝

Blue PPt of Cu(OH)2 ----(i)

(i) dissolved in clear drop of blue solution.

Then, an aliphatic aldehyde + Fehling Solution ---(heated)-> Red PPT of cupuros oxide.

RCHO + 2 cu²+ + 5 OH- ---(heat)-> RCOO- + Cu2O ⬇ + 3 H2O

Aldehyde + Fehling Solution ---(heat)-> Carboxylate ion + Cuprous Oxide (Red PPT) + water

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Answer 2

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⸙ Fehling’s test is a chemical test that is used to differentiate between reducing and non-reducing sugars.

⸙ The Fehling test is an indicator for aldehyde. Ketones cannot be oxidised using the Fehling reagent. This is because the aldehydes tend to get oxidized and give positive result. Ketones apart from alpha-hydroxy-ketones do not react.

$\large\colorbox{orange}{Happy\:learning.✌️}$

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