Nature Brings

GENERAL PROPERTIES OF CARBOHYDRATES

Carbohydrates can easily be divided into THREE main groups called monosaccharides, 

disaccharides and polysaccharides. The GENERAL properties of these groupings are found below. 

1. MONOSACCHARIDE - These are crystalline compounds, soluble in water, sweet to taste, and needs 

digestion in order to be absorbed into the blood stream. They may contain either five carbons (pentose) 

or six carbons (hexose). 

2. DISACCHARIDES -These are crystalline, water-soluble, sweet to the taste, and must be digested to 

monosaccharides before they can be absorbed and used for energy. These are a combination of two 

monosaccharides. 

3. POLYSACCHARIDES -These are not water soluble and are not crystalline. They form colloidal 

suspensions instead of solutions. They are not sweet and must be digested before being absorbed. 

They are made up of many polysaccharides joined together. 

The water solubility obviously depended on the molecular weight of carbohydrates in water.

SPECIAL TEST FOR SACCHARIDES

1. NItro-Chromic Acid Test

–> detection of primary and secondary alcohol with special reference to saccharides

2HNO3 + K2CrO4 —> H2CrO4 + 2KNO3

H2CrO4 – acid +chromium salt

– strong acid for oxidizing alchol ->ketones -> carboxylic acid

– made through the reaction

primary alcohol oxidizes to carboxylic

secondary alcohol oxidizes to ketone

aldehyde oxidizes to carboxylic

H2CrO4 + reducing sugars —> HCrO3

>reduced state

> color blue

Chromium VI is reduced to Chromium IV

3. Mucic Acid Test

–> test for identifying galactose

–> aldehyde and primary groups are oxidized to carboxyl group in reaction of galactose with           HNO3 forming saccharic acid

–> saccharic acid is insoluble

Mucic acid is another name of galactaric acid which is an example of saccharic acid

4. Reduction Test

a. Fehling’s test

Fehling’s reagent–> CuSO4 + KOH + Rochelle salt (sodium potassium tartrate)

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