9701 MCQ Solution 27

Question 27: [Organic > Carbonyl Compounds]:

Burnt sugar has a characteristic smell caused partly by the following compound. It has two functional groups indicated by Q and R.

When this compound is tested in a laboratory with 2,4-dinitrophenylhydrazine and Fehling’s reagent, which functional groups are responsible for positive tests?

	2,4-dinitrophenylhydrazine	Fehling’s reagent
A	Q and R	Q and R
B	R only	Q and R
C	Q and R	R only
D	Q only	R only

Reference: Past Exam Paper – November 2002 Paper 1 Q27

Solution 27:

Answer: C.

Both carbonyl groups will react with 2,4 DNPH due to the presence of the C=O bond. Thus options B and D are eliminated. 

Fehling’s reagent is a solution which reacts only with the aldehyde group, the CHO. 

Thus option A is eliminated leaving C as the correct answer.