Qualitative Tests For Carbohydrates s4f45

BS (Hons) 2nd Semester

Organic Chemistry Practical Manual

Experiment Title: Qualitative tests for carbohydrates. Carbohydrates are defined as the polyhydroxy aldehydes or polyhydroxy ketones or substances which form such compounds upon hydrolysis. Experiments Organic compound + conc. H2SO4 + heat

Observations Blacking of colour

Inferences Carbohydrate indicated

Molisch’s test: 2-3 mL of aqueous solution of organic compound + few drops of freshly A violet ring at the prepared 10% α-naphthol solution in Carohydrate present junction alcohol (Molisch reagent) + conc. H2SO4 along the side of test tube (carefully). Anthrone Test: 1mL of aqueous solution of Green or bluish green Carbohydrate organic compound + 1mL of anthrone colouration present solution shake and warm. Tests for Reducing Sugars (Such as glucose fructose, maltose, lactose etc.) Fehling’s test: 1mL of aqueous solution of Reducing sugars organic compound + 1mL Fehling’s solution Red ppt. (Carbohydrates) + boil present Benedict’s test: 1mL of aqueous solution of Reducing sugars organic compound + 1mL of Benedict’s Red ppt. (Carbohydrates) solution + boil present. Tollen’s test: 1mL of aqueous solution of Silver mirror is Reducing sugars organic compound + 1mL of ammonical produced. (Carbohydrates) AgNO3 solution (Tollen’s reagent) + warm present. on water bath for 20-30 minutes. Mixture turns yellow Reducing sugars Organic compound + NaOH solution + heat then brown with the (Carbohydrate) smell of burnt sugar present Special Tests 1 mL of aqueous solution of organic Blue colouration Starch present compound + dilute iodine solution 1 mL of aqueous solution of organic compound + few drops of ammonium Blue colouration Fructose present molybdate + warm Cobalt nitrate solution + NaOH + organic Violet colouration Sucrose present compound

1 Dr. Muhammad Aslam Assistant Professor-Chemistry University of Education, Township Campus, Lahore.