Question 7 - Chemistry CBSE Class 12 Sample Paper for 2022 Boards [Term 2] - Solutions to CBSE Sample Paper - Chemistry Class 12

An alkene ‘A’ (Mol. formula C ₅ H ₁₀ ) on ozonolysis gives a mixture of two compounds ‘B’ and ‘C’. Compound ‘B’ gives positive Fehling’s test and also forms iodoform on treatment with I ₂ and NaOH. Compound ‘C’ does not give Fehling’s test but forms iodoform. Identify the compounds A, B and C. Write the reaction for ozonolysis and formation of iodoform from B and C. 

Answer

A is an Alkene with the chemical formula: C 5 H 10

Its structure can be drawn as any of the following:

Compound A is an alkene, so, on ozonolysis it will give carbonyl compounds B and C.

We know that, 

• B gives positive Fehling’s test : so it is an aldehyde .

It gives positive Iodoform tes t so it has CH3C=O group . This means the aldehyde is acetaldehyde .

Also, 

• C does not give Fehling’s test : it is a ketone . 
• It gives positive iodoform test so it is a methyl ketone.  

• A methyl ketone must have at least three carbon atoms .

Based on ozonolysis mechanism, 

Only A= satisfies this condition.