Chemistry - Biomolecules Question with Solution | TestHub
A hexose sugar is the most abundant ketohexose found in nature. It undergoes the following tests and chemical transformations:
1. [S] gives a positive Molisch’s test and produces a red color in Seliwanoff’s test within 2 minutes of heating.
2. On treatment with excess phenylhydrazine, [S] forms an osazone [Z] that is identical to the osazone obtained from D-glucose.
3. When heated with concentrated H2SO4 acid, [S] undergoes dehydration to yield [P] (5- hydroxymethylfurfural), which further reacts with 1-naphthol to produce a violet-colored compound.
4. Reduction of [S] with sodum borohydride (NaBH4 ) produces a mixture of two epimeric hexitols, [A] and [B].
Based on the above observations, choose the correct statement:
Options:
Answer:
Solution:
[S] is the most abundant ketohexose in nature, hence it is D-Fructose.
It gives a rapid red color in Seliwanoff’s test because ketoses dehydrate faster than aldoses to form hydroxymethylfurfural.
It forms the same osazone as D-Glucosesince osazone formation involves only C-1 and C-2 atoms. On heating with concentrated acid, fructose forms 5-Hydroxymethylfurfural by loss of three molecules of water.
Reduction of fructose yields two epimeric hexitols Sorbitol and Mannitol.