Benedict Test Grading: Molisch and Benedict's Tests for Carbohydrates Quiz

Study Notes

Carbohydrate Tests

Molisch test: used to detect the presence of carbohydrates in a sample, involving the addition of Molisch's reagent and concentrated H2SO4, resulting in a purple or purplish-red ring at the point of contact.

Reducing Sugar Tests

Benedict's test: used to detect the presence of reducing sugars, involving Benedict's reagent, resulting in a brick-red precipitate.
Fehling's test: used to detect and estimate reducing sugars, consisting of Fehling's A and Fehling's B.
Tollen's test: used to differentiate reducing sugars from non-reducing sugars, involving the alkaline solution of silver nitrate and liquid ammonia, resulting in a dark grey precipitate or silver mirror.

Monosaccharide Tests

Barfoed's test: used to detect the presence of reducing monosaccharides in the presence of disaccharides, involving Barfoed's reagent, resulting in a red precipitate.
Bial's test: used to detect the presence of pentoses, involving orcinol, hydrochloric acid, and ferric chloride, resulting in a blue-green or bluish precipitate.
Mucic acid test: used to detect the presence of galactose and lactose, involving the formation of saccharic acids, resulting in crystal formation.

Sugar Classification Tests

Seliwanoff's test: used to differentiate between ketose and aldose sugars, involving resorcinol and concentrated HCl, resulting in a cherry red-colored complex.
Osazone test: used to detect and classify reducing sugars, involving phenylhydrazine in acetate buffer, resulting in yellow-colored crystals of characteristic shape, solubility, melting point, and time of formation.

Polysaccharide Tests

Iodine test: used to distinguish mono- or disaccharides from certain polysaccharides like amylase, dextrin, and glycogen, involving Lugol's iodine, resulting in a blue-black or purple color.

Description

Learn about Molisch test, which detects the presence of carbohydrates through the formation of a purple ring, and Benedict's test, which indicates the presence of reducing sugars by the formation of a color change. Understand the procedures and significance of these tests in carbohydrate analysis.