IMO Practice Test — Aldehydes, Ketones and Carboxylic Acids
14 Questions • 15 min • Olympiad level
15:00
Question 1 of 14
In nucleophilic addition to a carbonyl, the geometry change at the attacked carbon is:
sp2 → sp3
sp3 → sp2
sp → sp2
no change
Explanation: The planar sp2 carbon becomes tetrahedral sp3 as the nucleophile adds.
Question 2 of 14
Which pair will both give a positive iodoform test?
ethanol and propanal
acetone and ethanal
methanol and acetone
propanal and benzaldehyde
Explanation: Both acetone and ethanal carry the CH3CO– group.
Question 3 of 14
A compound C3H6O gives a silver mirror with Tollens. It is:
propan-1-ol
acetone
propanal
propylene oxide
Explanation: Only the aldehyde (propanal) reduces Tollens reagent; acetone (also C3H6O) does not.
Question 4 of 14
Increasing order of acidity: I CH3COOH, II ClCH2COOH, III FCH2COOH, IV CH3CH2COOH:
II < III < IV < I
I < II < III < IV
III < II < I < IV
IV < I < II < III
Explanation: Propanoic acid (extra +I) is weakest, then acetic acid, then ClCH2COOH, and FCH2COOH strongest (F most electronegative).
Question 5 of 14
X gives Cannizzaro but not aldol. X could be:
HCHO
CH3COCH3
CH3CH2CHO
CH3CHO
Explanation: HCHO has no α-H, so it cannot do aldol but undergoes Cannizzaro.
Question 6 of 14
Cross-aldol of benzaldehyde and acetaldehyde gives mainly:
but-2-enal
cinnamaldehyde (C6H5CH=CHCHO)
benzoic acid
acetophenone
Explanation: Benzaldehyde has no α-H; the enolate of ethanal adds, then dehydration gives cinnamaldehyde.
Question 7 of 14
A carbonyl compound that does NOT undergo nucleophilic addition with NaHSO3 readily is:
acetaldehyde
acetone
di-tert-butyl ketone
methanal
Explanation: The very bulky tert-butyl groups block the carbon sterically, so the bulky bisulphite cannot add.
Question 8 of 14
Identify the reagent: CH3COCH3 → CH3CH2CH3 in basic medium:
Zn-Hg/HCl
LiAlH4
NaBH4
NH2NH2, KOH/glycol
Explanation: Full reduction of C=O to CH2 in base is the Wolff–Kishner reaction.
Question 9 of 14
An acid C2H4O2 liberates CO2 with NaHCO3 and gives no iodoform. It is:
acetic acid
glycolaldehyde
methyl formate
ethanol
Explanation: Acetic acid (CH3COOH) is acidic (CO2 with bicarbonate) and has no CH3CO– oxidisable to iodoform.
Question 10 of 14
On ozonolysis, an alkene gives only propanone. The alkene is:
2-methylbut-2-ene
2,3-dimethylbut-2-ene
but-2-ene
propene
Explanation: (CH3)2C=C(CH3)2 cleaves into two molecules of propanone.
Question 11 of 14
Which conversion needs Grignard + CO2 rather than simple oxidation?
ethanol → acetic acid
acetaldehyde → acetic acid
CH3Br → CH3COOH
benzyl alcohol → benzoic acid
Explanation: Going from a halide to an acid with one extra carbon requires CH3MgBr + CO2.
Question 12 of 14
In the Hell–Volhard–Zelinsky reaction, the halogen is introduced at the:
carbonyl carbon
β-carbon
oxygen
α-carbon
Explanation: HVZ replaces an α-hydrogen of the acid with a halogen.
Question 13 of 14
Which will react fastest with HCN?
acetone
methanal
acetaldehyde
acetophenone
Explanation: Methanal is the least hindered and most electrophilic, so it adds HCN fastest.
Question 14 of 14
Esterification of a carboxylic acid with an alcohol is catalysed by H+ and is best driven forward by:
adding water
lowering temperature
removing water or using excess alcohol
adding base
Explanation: Esterification is reversible; removing water (or excess alcohol) shifts equilibrium to the ester.