This chapter is crucial because it links core reaction patterns (oxidation–reduction, nucleophilic addition, aldol/Cannizzaro, haloform, enol/enolate chemistry) with real exam-scoring skills. In CBSE boards and competitive exams (JEE/NEET), most questions test concept clarity via choice of correct product, reaction selectivity (e.g., vs stronger reducers), and understanding why particular pathways (aldol vs Cannizzaro, 1,2 vs 1,4 reduction) dominate under given conditions.
15
Minutes
10
Questions
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Marking
Q1. Among the following carbonyl compounds, which will be reduced most rapidly by sodium borohydride () in ethanol, considering electronic and steric factors?
(acetone)
(benzophenone)
(acetaldehyde)
(benzaldehyde)
Q2. Crotonaldehyde () is treated with in methanol. Which is the major organic product after aqueous work-up?
(saturated aldehyde from 1,4‑reduction)
(allylic alcohol; 1,2‑reduction product)
(butan‑1‑ol, over‑reduction product)
cis- (allylic alcohol; minor E/Z outcome)
Q3. When benzaldehyde () and acetone () in molar ratio 2:1 are treated with dilute followed by acidification, the major organic product obtained is:
(benzyl alcohol)
(benzoin)
Benzaldehyde remains unchanged
(dibenzalacetone)
Q4. Assertion (A): When benzaldehyde () is mixed with acetaldehyde () and treated with dilute , the Cannizzaro reaction of benzaldehyde is largely suppressed and the crossed aldol condensation product predominates.
Reason (R): Acetaldehyde is readily enolized under base to give an enolate which rapidly attacks benzaldehyde; this fast enolate‑electrophile reaction consumes benzaldehyde before significant hydride transfer (Cannizzaro) can occur, thus favoring crossed aldol.
Both A and R are true and R is the correct explanation of A
Both A and R are true but R is not the correct explanation of A
A is true but R is false
A is false but R is true
Q5. An unknown aromatic carbonyl compound A (molecular formula ) gives a positive 2,4‑DNP test, a negative Tollen's test, produces a yellow precipitate with in (haloform test), and on vigorous oxidation with yields benzoic acid. Which of the following is compound A?
(benzaldehyde)
(phenylacetaldehyde)
(acetophenone)
(propiophenone)
Q6. Which of the following carbonyl compounds will undergo the Cannizzaro reaction when treated with concentrated NaOH?
Q7. Among the following, which compound will form the most stable enolate (i.e., has the most acidic ‑hydrogen)?
Q8. 2‑Methylcyclohexanone on treatment with LDA at followed by methyl iodide gives predominantly:
‑Dimethylcyclohexanone
‑Dimethylcyclohexanone
A 1:1 mixture of ‑ and ‑dimethylcyclohexanones
No alkylation; only enolate formation is observed
Q9. A mixture of benzaldehyde () and acetaldehyde () is treated with dilute NaOH at room temperature. The major isolated organic product after workup will be:
Benzoic acid and benzyl alcohol (Cannizzaro products)
Crotonaldehyde () from self‑aldol of acetaldehyde
Cinnamaldehyde () — the crossed aldol condensation product
Ethyl benzoate (from Tishchenko reaction)
Q10. Which one of the following compounds gives a positive Tollens’ test but a negative iodoform test?