Molisch's test
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2008-04-09T02:28:03Z
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'''Molisch's Test''' is a [[chemical test]] for the presence of [[carbohydrate]]s, based on the dehydration of the carbohydrate by sulfuric acid to produce an aldehyde.
The test solution is combined with a small amount of Molisch's reagent (α-[[naphthol]] dissolved in ethanol) in a [[test tube]]. After mixing, a small amount of concentrated [[sulfuric acid]] is slowly added down the sides of the sloping test-tube, without mixing. A positive reaction is indicated by a purple ring forming at the interface between the acid and test layers.
All carbohydrates -- [[monosaccharide]]s, [[disaccharide]]s, and [[polysaccharide]]s -- should give a positive reaction. [[Glycoprotein]]s also give a positive reaction. [[Pentose]]s are dehydrated to [[furfural]]; [[hexose]]s are dehydrated to [[hydroxymethylfurfural]]. Either of these aldehydes, if present, will condense with two molecules of naphthol to form a purple-colored product.all carbohydrate give positive molish test
>O<sub>2</sub> (furfural) +
Reactions:
:1. C<sub>5</sub>H<sub>10</sub>O<sub>5</sub> (pentose) + (conc.) H<sub>2</sub>SO<sub>4</sub> → C<sub>5</sub>H<sub>4</sub>O<sub>2</sub> + 3 H<sub>2</sub>O
:2. C<sub>5</sub>H<sub>4</sub> + 2 C<sub>10</sub>H<sub>8</sub>OH (α-naphthol) → colored product
[[Category:Chemical tests]]
[[es:Reacción de Molisch]]