Nucleophilic addition to aldehydes and ketones

55 questions on Nucleophilic addition to aldehydes and ketones from the Organic Reaction Mechanisms I: Nucleophiles and Carbonyl Addition chapter: 11 NEET level, 22 JEE Main, 22 JEE Advanced. Each one opens with its answer and solution.

• Which of the following carbonyl compounds is the most reactive towards nucleophilic addition of HCN? NEET level
• Acetaldehyde is treated with (i) CH3MgBr in dry ether; (ii) H3O+. The product is NEET level
• Formaldehyde reacts with C2H5MgBr followed by acid hydrolysis. The product is NEET level
• Acetone is reduced with NaBH4 in ethanol. The organic product is NEET level
• The reagent that converts R2C=O into R2CH2 under strongly basic conditions is NEET level
• In the formation of a cyanohydrin from a ketone with HCN and a trace of base, the species that attacks the carbonyl carbon is NEET level
• During nucleophilic addition to a carbonyl group, the hybridisation of the carbonyl carbon changes from NEET level
• Acetone reacts with hydroxylamine, NH2OH, in weakly acidic medium. The product is NEET level
• Which of the following does NOT form a crystalline bisulphite addition product with saturated aqueous NaHSO3? NEET level
• Acetaldehyde is warmed with excess methanol containing a little dry HCl gas. The product is NEET level
• Acetone gives an orange-yellow precipitate with Brady's reagent. The precipitate is NEET level
• The correct order of reactivity of the following towards nucleophilic addition of HCN is JEE Main level
• The correct order of reactivity towards nucleophilic addition (e.g. HCN) for the following benzaldehydes is JEE Main level
• Imine formation from a ketone and a primary amine is fastest at about pH 4-5 and slower both in strongly acidic and in basic solution. Which statement explains ... JEE Main level
• Cyclohexanone is heated with piperidine and a trace of p-toluenesulphonic acid, with removal of water. The main organic product is JEE Main level
• Ethyl acetate is treated with (i) excess CH3MgBr in dry ether; (ii) H3O+. The final product is JEE Main level
• One equivalent of CH3MgBr is added to 4-hydroxybutanal, HO-CH2CH2CH2-CHO, in ether. The main immediate process is JEE Main level
• Ethyl 3-oxobutanoate is treated with NaBH4 in ethanol at 0 degC, followed by dilute acid work-up. The main product is JEE Main level
• Chloral, Cl3C-CHO, forms an isolable crystalline hydrate, but acetaldehyde does not. The main reason is that JEE Main level
• The cyclic acetal formed from cyclohexanone and ethylene glycol is stable towards which of the following? JEE Main level
• Methyl 4-oxopentanoate, CH3-CO-CH2CH2-COOCH3, is treated in sequence with (i) ethylene glycol, H+; (ii) LiAlH4, ether; (iii) H3O+ (aqueous work-up). The final p... JEE Main level
• Acetaldehyde is treated with (i) NaCN / H2SO4 (aq, cold); (ii) H3O+, heat. The final product is JEE Main level
• 4-Methylacetophenone, p-CH3-C6H4-CO-CH3, is heated with NH2NH2 and KOH in ethylene glycol. The product is JEE Main level
• The rate of cyanohydrin formation from acetone and HCN is very small in pure HCN but increases when a few drops of NaOH are added; it falls again if strong acid... JEE Main level
• 1,4-Dioxaspiro[4.5]decan-8-one (cyclohexane-1,4-dione mono(ethylene ketal)) is heated with NH2NH2 and KOH in ethylene glycol at 200 degC. The product is JEE Main level
• 5-Hydroxypentanal in solution exists largely as JEE Main level
• In semicarbazide, H2N-NH-CO-NH2, only the NH2 attached to the NH of the hydrazine unit takes part in semicarbazone formation because JEE Main level
• Phenylmagnesium bromide is added to acetone and the mixture is hydrolysed with aqueous NH4Cl. The product is JEE Main level
• 4-Nitrobenzaldehyde is treated with NaBH4 in ethanol, then dilute acid. The product is JEE Main level
• Cyclohexanone is refluxed with ethylene glycol and p-toluenesulphonic acid in toluene using a Dean-Stark trap. The function of the trap is to JEE Main level
• Consider the following carbonyl compounds: HCHO, CH3CHO, Cl3C-CHO, (CF3)2C=O (hexafluoroacetone), (C6H5)2C=O, (CH3)3C-CO-C(CH3)3 and CH3-CO-CH3. Counting aceton... JEE Main level
• Which of the following give an appreciable yield of a cyanohydrin on treatment with HCN in the presence of a catalytic amount of base? JEE Main level
• Which of the following reactions give a SECONDARY alcohol after (i) reaction with CH3MgBr (1 equiv, dry ether); (ii) H3O+? JEE Main level
• Cyclohexanone is subjected to (i) CH3MgBr, dry ether; (ii) H3O+; (iii) conc. H2SO4, heat. The major final product is JEE Advanced level
• Ethyl benzoate is treated with (i) excess C2H5MgBr, dry ether; (ii) H3O+. The product is JEE Advanced level
• 4-Oxopentanal, CH3-CO-CH2CH2-CHO, is treated with exactly one equivalent of CH3MgBr at -78 degC, followed by aqueous NH4Cl. The major product is JEE Advanced level
• Cyclohexanone is treated with (i) pyrrolidine, H+ cat., remove water; (ii) CH3I; (iii) aqueous H3O+. The final product is JEE Advanced level
• Cyclohexanone is treated with (i) CH3NH2, mild acid (pH about 5-6); (ii) NaBH3CN. The product is JEE Advanced level
• Benzaldehyde is treated with (i) NaCN, H+ (aq); (ii) LiAlH4, ether; (iii) aqueous work-up. The final product is JEE Advanced level
• What is the minimum number of moles of LiAlH4 required to reduce completely 1 mol of ethyl 4-oxopentanoate to the corresponding diol (assume all four Al-H bonds... JEE Advanced level
• Which statement about the pH dependence of the reaction of a ketone with a primary amine to give an imine, R2C=O + R^primeNH2 -> R2C=NR^prime + H2O, is correct? JEE Advanced level
• Ethyl formate, HCOOC2H5, is treated with excess CH3MgBr in ether, then H3O+. The product is JEE Advanced level
• Diethyl carbonate, (C2H5O)2C=O, is treated with excess C2H5MgBr followed by H3O+. The product is JEE Advanced level
• In the acid-catalysed formation of a dimethyl acetal from an aldehyde RCHO and methanol, the species that is attacked by the second molecule of methanol is JEE Advanced level
• Ethyl 4-oxopentanoate is treated with (i) ethylene glycol, H+ (cat.), remove water; (ii) excess CH3MgBr, ether; (iii) dilute H3O+ work-up. The final product is JEE Advanced level
• Select the correct statement(s) about the reaction of Grignard reagents with carbonyl compounds followed by acid hydrolysis. JEE Advanced level
• Under the usual laboratory conditions, which of the following reagents convert a ketone R2C=O into the corresponding secondary alcohol R2CH-OH? JEE Advanced level
• Which of the following halides CANNOT be converted into a stable Grignard reagent by reaction with Mg in dry ether? JEE Advanced level
• Which of the following form a crystalline addition product with saturated aqueous sodium hydrogen sulphite under the usual textbook conditions (aldehydes, methy... JEE Advanced level
• For hydration in water at 298 K, K = [gem-diol]/[carbonyl] has the values 2000 for HCHO, 1.0 for CH3CHO and 0.0014 for CH3COCH3. Which statements follow? JEE Advanced level
• Which of the following carbonyl compound / amine pairs give an ENAMINE as the isolable condensation product (with acid catalysis and water removal)? JEE Advanced level
• Which of the following statements about the Wolff-Kishner reduction (R2C=O with NH2NH2, KOH, ethylene glycol, heat) is/are correct? JEE Advanced level
• Which of the following nucleophilic additions to the carbonyl group are essentially IRREVERSIBLE under the reaction conditions (before work-up)? JEE Advanced level
• Which structural changes INCREASE the reactivity of a carbonyl compound towards nucleophilic addition? JEE Advanced level
• An aldehyde RCHO is dissolved in water to a total concentration (free aldehyde plus hydrate) of 0.20 M. At equilibrium K = [hydrate]/[RCHO] = 2.3 (the concentra... JEE Advanced level