Question

Reagent used to detect sugar (glucose) in urine is.
A. Tollen’s reagent
B. Fehling’s reagent
C. Baeyer’s reagent
D. Benedict’s reagent

Answer 1

Hint: Benedict solution is a mixture of copper sulphate, sodium carbonate and sodium citrate. Sucrose breaks down when heated with benedict's solution and hydrochloric acid.


Step by step answer: The non-reducing sugars do not react with Tollen, Fehling, Baeyer and Benedict reagent.

Glucose is a reducing sugar which reacts with Tollen, Fehling, Baeyer and Benedict reagent.
The Benedict reagent is used to detect sugar (glucose) in the urine.
Benedict reagent reacts with the carbonyl group of glucose as follows:
\[{\text{C}}{{\text{u}}^{{\text{2 + }}}}\,{\text{ + }}\,{\text{RCHO}}\, \to \,{\text{RCOOH}}\,{\text{ + }}\,{\text{CuS (s)}}\]

The copper ion of Benedict reagent reacts with carbonyl functional group of sugar and convert it
Into acid and forms copper sulphide. Copper sulphide is insoluble so, it precipitates that
indicates the reaction between Benedict's reagent and sugar.

The Tollen reagent is not used to detect sugar in urine so, option (A) is incorrect.
The Fehling reagent is not used to detect sugar in urine so, option (B) is incorrect.
The Baeyer reagent is not used to detect sugar in urine, so option (C) is incorrect.
The Benedict reagent is not used to detect sugar in urine so, option (D) is incorrect.

Additional information: The sugars that have a free carbonyl group (aldehyde or ketone) are known as reducing sugars such as glucose. All monosaccharides are reducing sugar. The sugars that do not have a free carbonyl group (aldehyde or ketone) are known as non-reducing sugars such as sucrose.

Note: Glucose reacts with all these reagents, Tollen, Fehling, Baeyer and Benedict reagent but Benedict reagent is used to detect sugar in the urine.