Question

An organic compound answers Molisch’s test as well as Benedict’s test. But it does not answer Scliwanoff’s test. Most probably, it is:
A. Sucrose
B. Protein
C. Fructose
D. Maltose

Answer 1

Hint: Molisch’s test is used to detect the presence of carbohydrates. Benedict’s test is used to detect the presence of reducing sugars. Scliwanoff’s test is used to differentiate the aldose and ketose sugars.

Complete step by step answer:
The carbohydrates (sugars) give a positive result for Molisch’s test. Reducing sugars give a positive result for Benedict’s test and ketose sugars give a positive result for Scliwanoff’s test.
1. The organic compound gives a positive result for Molisch’s test as well as Benedict’s test. So, the organic compound is a carbohydrate and in carbohydrate, it is a reducing sugar.
2. But the organic compound gives a negative result for Scliwanoff’s test, so the reducing sugar is not a ketose sugar.

a. Sucrose is a disaccharide composed of two monosaccharides glucose and fructose. The sucrose is non-reducing sugar but the organic compound is a reducing sugar, so option (A) is incorrect.

b. Molisch’s test as well as Benedict’s test, both tests for carbohydrates, and the protein is not a carbohydrate so, option (B) is incorrect.

c. Fructose is sugar so it will give a positive result for Molisch’s test and it is a monosaccharide, so it has a free ketone functional group, so it will have a positive result for Benedict’s test. The fructose is a ketose sugar, so it will give a positive result for Scliwanoff’s test but the organic compound does not give a positive result for Scliwanoff’s test, so option (C) is incorrect.

d. Maltose is disaccharides composed of two units of glucose that are monosaccharides and it is a reducing sugar, so maltose will give a positive test for Molisch’s test as well as Benedict’s test. The maltose is an aldose sugar, so it will give a negative result for Scliwanoff’s test, so option (D) is correct.

Therefore, option (D) Maltose, is correct.

Note:
The molecules consist of carbon, hydrogen and oxygen are known as carbohydrates.
The sugar has a ketone function group known as ketose and the sugar having aldehyde. The functional group is known as aldose sugar. The sugar has a free aldehyde or ketone group known as reducing sugars. All monosaccharides and some disaccharides are reducing sugars