Case Study Question on Amines
Read the passage given below and answer the following questions:
Reductive alkylation is the term applied to the process of introducing alkyl groups into ammonia or a primary or secondary amine by means of an aldehyde or ketone in the presence of a reducing agent. The present discussion is limited to those reductive alkylations in which the reducing agent is hydrogen and a catalyst or “nascent” hydrogen, usually from a metal- acid combination; most of these reductive alkylations have been carried out with hydrogen and a catalyst. The principal variation excluded is that in which the reducing agent is formic acid or one of its derivatives; this modification is known as the Leuckart reaction. The process of reductive alkylation of ammonia consists in the addition of ammonia to a carbonyl compound and reduction of the addition compound or its dehydration product. The reaction usually is carried out in ethanol solution when the reduction is to be effected catalytically
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Since the primary amine is formed in the presence of the aldehyde it may react in the same way as ammonia, yielding an addition compound, a Schiff’s base (RCH= NCH2R) and finally, a secondary amine. Similarly, the primary amine may react with the imine, forming an addition product which also is reduced to a secondary amine. Finally, the secondary amine may react with either the aldehyde or the amine to give products which are reduced to tertiary amines.
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Similar reactions may occur when the carbonyl compound employed is a ketone.
(source: Emerson, W. S. (2011). The Preparation of Amines by Reductive Alkylation. Organic Reactions, 174–255. doi:10.1002/0471264180.or004.03 )
Q1. Ethanal on reaction with ammonia forms an imine (X) which on reaction with nascent hydrogen gives (Y). Identify ‘X’ and ‘Y’.
- X is CH3CH=NH and Y is CH3NH2
- X is CH3CHOHNH2 and Y is CH3CH2NH2
- X is CH3CHOHNH2 and Y is CH3NH2
- X is CH3CH=NH and Y is CH3CH2NH2
Q2. Acetaldehyde is reacted with ammonia followed by reduction in presence of hydrogen as a catalyst. The primary amine so formed further reacts with acetaldehyde. The Schiff’s base formed during the reaction is:
- CH3CH=NHCH3
- CH3CH=NHCH2CH3
- CH3=NHCH2CH3
- CH3CH2CH=NHCH3
Q3. The reaction of ammonia and its derivatives with aldehydes is called:
- Nucleophilic substitution reaction
- Electrophilic substitution reaction
- Nucleophilic addition reaction
- Electrophilic addition reaction
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The compound Q is:
- (CH3CH2CH2)3N
- (CH3CH2CH2)2N(CH2CH3)
- (CH3CH2)3N
- (CH3CH2)2NH
Q5. Reductive alkylation of ammonia by means of an aldehyde in presence of hydrogen as reducing agents results in formation of:
- Primary amines
- Secondary amines
- Tertiary amines
- Mixture of all three amines
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