Formation of acetals, imines and enamines

27 questions on Formation of acetals, imines and enamines from the Organic Reaction Mechanisms I: Nucleophiles and Carbonyl Addition chapter: 5 NEET level, 11 JEE Main, 11 JEE Advanced. Each one opens with its answer and solution.

• Acetone is heated with ethylene glycol, HOCH2CH2OH, in the presence of dry HCl. The main product is NEET level
• Acetaldehyde reacts with methylamine, CH3NH2, under mild acid catalysis with loss of water. The product is NEET level
• Cyclohexanone is heated with pyrrolidine (a secondary amine) and a trace of acid with removal of water. The product is NEET level
• Acetals and ketals are readily hydrolysed back to the carbonyl compound by NEET level
• The rate of imine formation from an aldehyde and a primary amine is greatest at about NEET level
• Cyclohexanone reacts with methylamine, CH3NH2, under mild acid catalysis (water removed). The isolated product is JEE Main level
• A secondary amine and a ketone give an enamine, not an imine, because in the intermediate iminium ion JEE Main level
• Imine formation between benzaldehyde and aniline becomes very slow at pH about 1 mainly because JEE Main level
• In acid-catalysed formation of an acetal from an aldehyde and methanol, the species that is attacked by the second molecule of CH3OH is the JEE Main level
• Benzaldehyde reacts with aniline, C6H5NH2, with a trace of acid and removal of water. The product is JEE Main level
• 1-(Cyclohex-1-en-1-yl)pyrrolidine is stirred with dilute aqueous HCl. The organic products after the reaction are JEE Main level
• Which of the following forms an acetal with methanol and dry HCl most readily (all other conditions identical)? JEE Main level
• Ketone protection is carried out more efficiently with ethylene glycol than with two molecules of methanol. The main reason is that JEE Main level
• Which of the following statements about acetals (R-CH(OR')2) are correct? JEE Main level
• Which of the following reactions give a compound containing a C=N bond as the stable, isolated product (acid catalyst, water removed)? JEE Main level
• Which of the following, on heating with pyrrolidine and a trace of acid with water removed, can give an enamine? JEE Main level
• Methyl 4-formylbenzoate, p-OHC-C6H4-COOCH3, is treated in sequence with (i) one equivalent of ethylene glycol, dry HCl (aldehyde selectively protected); (ii) Li... JEE Advanced level
• Cyclohexanone is treated with (i) CH3NH2, trace acid, water removed; (ii) NaBH4, CH3OH; (iii) aqueous work-up. The product is JEE Advanced level
• Cyclohexanone is treated in sequence with (i) pyrrolidine, trace acid, water removed; (ii) CH3I; (iii) H3O+. The final organic product is JEE Advanced level
• 2,2-Dimethoxypropane is hydrolysed in aqueous acid made with H2^18O (water enriched in oxygen-18). Where does the ^18O end up? JEE Advanced level
• For the reaction of a ketone with a primary amine, the rate is measured as a function of pH. Above about pH 6, the rate falls as pH rises. The step that is rate... JEE Advanced level
• 4-Acetylbenzaldehyde, p-CH3CO-C6H4-CHO, is treated in sequence with (i) one equivalent of ethylene glycol, dry HCl; (ii) CH3MgBr (1 equiv), dry ether; (iii) dil... JEE Advanced level
• 5-Hydroxypentanal, HO-CH2CH2CH2CH2-CHO, is dissolved in methanol containing a catalytic amount of dry HCl. The product is JEE Advanced level
• Cyclohexanone is treated in sequence with (i) pyrrolidine, trace acid, water removed; (ii) CH3COCl; (iii) H3O+. The final organic product is JEE Advanced level
• The enamine of cyclohexanone with pyrrolidine is treated with each of the following, then with H3O+. Which give a new C-C bond at the alpha carbon of the ketone... JEE Advanced level
• Which of the following statements about acetal formation from an aldehyde and an alcohol are correct? JEE Advanced level
• Which of the following statements about enamines and imines are correct? JEE Advanced level