Molish test

CARBOHYDRATES
Carbohydrates are polyhydroxy aldehyde or ketone, or compounds that yield these derivatives on hydrolysis.
They are classified into monosaccharides (single unit), disaccharides (two units), oligosaccharides (3 to 10
units) or polysaccharides (more than ten units). Monosaccharides can be further classified into trioses, tetroses,
pentoses, hexoses, and so on, depending on the number of carbon atoms.
To 2 ml of sample solution, add 1drop of a-naphthol
in alcohol and 2 ml conc. H2SO4 slowly and carefully
along the side of the test tube
A purple ring develops The sample contains carbohydrates
i. A strong dehydrating agent like conc. H2SO4 converts sugars to hydroxymethyl furfural. The furfural
condenses with phenolic compounds like a-naphthol to give the coloured ring.
Molish test is given by at least five carbons.
iii. a-naphthol in alcohol should be freshly prepared.
iv. Water-acid interaction produces heat and can cause charring of carbohydrates, resulting in formation of