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.

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