Question:

A sugar ‘X’ dehydrates very slowly under acidic conditions to give furfural which on further reaction with resorcinol gives the coloured product after some time. Sugar ‘X’ is

Updated On: Dec 31, 2025

Aldopentose
Aldotetrose
Oxalic acid
Ketotetrose

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The Correct Option is A

Solution and Explanation

To solve this question, we need to understand the dehydration reaction that leads to the formation of furfural.

The question states that sugar ‘X’ dehydrates very slowly under acidic conditions to form furfural, which is indicative of a specific type of sugar. Let's analyze the options given:

Aldopentose: An aldopentose is a monosaccharide containing five carbon atoms and an aldehyde group. Under acidic conditions, aldopentoses can dehydrate to form furfural. This is a typical reaction for sugars like arabinose and xylose.
Aldotetrose: An aldotetrose contains four carbon atoms and an aldehyde group. These sugars do not typically dehydrate to form furfural.
Oxalic acid: This is not a sugar but a dicarboxylic acid, and it does not form furfural.
Ketotetrose: A ketotetrose is a monosaccharide with four carbon atoms and a ketone group. These do not typically form furfural under acidic conditions.

From the analysis above, the correct answer is aldopentose since it aligns with the dehydration reaction forming furfural.

Conclusion: Thus, the correct answer is Aldopentose as it can dehydrate to form furfural, which further reacts to give the colored product.

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Concepts Used:

Biomolecules

Biomolecules are the most essential organic molecules, which are involved in the maintenance and metabolic processes of living organisms. These non-living molecules are the actual foot-soldiers of the battle of sustenance of life.

There are four major classes of Biomolecules – Carbohydrates, Proteins, Nucleic acids and Lipids.

Carbohydrates are chemically defined as polyhydroxy aldehydes or ketones or compounds which produce them on hydrolysis.
Proteins are another class of indispensable biomolecules, which make up around 50per cent of the cellular dry weight. Proteins are polymers of amino acids arranged in the form of polypeptide chains. The structure of proteins is classified as primary, secondary, tertiary and quaternary in some cases.
Nucleic acids refer to the genetic material found in the cell that carries all the hereditary information from parents to progeny. There are two types of nucleic acids namely, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The main function of nucleic acid is the transfer of genetic information and synthesis of proteins by processes known as translation and transcription.
Lipids are organic substances that are insoluble in water, soluble in organic solvents, are related to fatty acids and are utilized by the living cell.