NCERT Class XI Chemistry Organic Chemistry Some basic principles and Techniques Solutions
© examsnet.com
Question : 14
Total: 40
Classify the following reactions in one of the reaction type studied in this unit.
(a)C H 3 C H 2 B r + H S – C H 3 C H 2 S H + B r –
(b)( C H 3 ) 2 C = C H 2 + H C l ( C H 3 ) 2 C l C – C H 3
(c)C H 3 C H 2 B r + H O – C H 2 = C H 2 + H 2 O + B r –
(d)( C H 3 ) 3 C – C H 2 O H + H B r ( C H 3 ) 2 C B r C H 2 C H 3 + H 2 O
(a)
(b)
(c)
(d)
Solution:
(a) C H 3 C H 2 B r + H S – C H 3 C H 2 S H + B r –
Here, –SH, a nucleophile displaces Br– from the bromoalkane. Since, the reaction is brought about by a nucleophile and substitution occurs thereafter, the reaction will be termed as a nucleophilic substitution reaction.
(b)( C H 3 ) 2 C = C H 2 + H C l ( C H 3 ) 2 C l C – C H 3
In the given reaction we see that theH + C l –
(c)C H 3 C H 2 B r + H O – C H 2 = C H 2 + H 2 O + B r –
Here there is no atom which is displaced or substituted. Although the reaction is brought about by a nucleophile – OH it is not a nucleophilic substitution. An HBr molecule has been removed from the reactant and hence, it is an elimination reaction.
(d)( C H 3 ) 3 C – C H 2 O H + H B r ( C H 3 ) 2 C B r C H 2 C H 3 + H 2 O
This is an example of a rearrangement followed by nucleophilic substitution. Initially, a 1° carbocation is formed which rearranges to produce a more stable 3° carbocation. Finally, Br– attacks the carbocation and product is formed.
Here, –SH, a nucleophile displaces Br– from the bromoalkane. Since, the reaction is brought about by a nucleophile and substitution occurs thereafter, the reaction will be termed as a nucleophilic substitution reaction.
(b)
In the given reaction we see that the
(c)
Here there is no atom which is displaced or substituted. Although the reaction is brought about by a nucleophile – OH it is not a nucleophilic substitution. An HBr molecule has been removed from the reactant and hence, it is an elimination reaction.
(d)
This is an example of a rearrangement followed by nucleophilic substitution. Initially, a 1° carbocation is formed which rearranges to produce a more stable 3° carbocation. Finally, Br– attacks the carbocation and product is formed.
© examsnet.com
Go to Question: