What is N-bromo succinimide or NBS and What is the use of N-bromo succinimide or NBS ?

What is N-bromo succinimide  or NBS ?

N-bromo succinimide  or NBS is a very important  chemical reagent  which is used in radical substitution , electrophilic addition and electrophilic substitution reactions  in organic chemistry . It is used mainly as a allylic and benzylic  bromination . The structure of N-bromo succinimide  or NBS is as follows,

 Preparation of N-bromo succinimide  or NBS .

N-bromo succinimide is prepared from succinic acid. When succinic acid is reacts with ammonia it forms diammonium succinate which on heating gives succinamide . On further heating succinamide convert into succinimide .This succinimide reacts with bromine gives   N-bromo succinimide  or NBS .

What is the use of N-bromo succinimide  or NBS ?

N-bromo succinimide  or NBS is a very important  chemical reagent  , which is used in the preparation of aliphatic and aromatic halo alkane and halo arenes .

N-bromo succinimide or NBS is a good reagent for allylic and benzylic bromination . For example,

when NBS reacts with propene in the presence of sunlight and peroxide , 3-bromoprop-1-ene is the product which obtained in large extent .

Again , when NBS reacts with ethyl benzene in the presence of sunlight and  little peroxide, 1-bromo-1-phenyl ethane is obtained .

In both cases the reaction proceed through free radical substitution method .

Besides the above reaction  NBS is used  in bromination of carbonyl derivatives and also in Hofmann rearrangement  reaction .

Why  SOCl₂ is more suitable than PCl₅ to prepare chloro alkane from alcohol ?

To prepare chloro alkane from SOCl₂ is more suitable reagent than PCl₅ , because if we use SOCl₂ , the side products are SO₂ and HCl . Both they are in gaseous state. So they are easily eliminated from the product mixtures . As a result , we can get about pure chloro alkane.

On the other hand if we used PCl₅ instead of SOCl₂ ,the side products are POCl₃ and HCl . Although HCl is in gaseous form , but POCl₃ can not be separated from the products mixture .

Consequently, pure chloro alkane is not available. 

Summary :

What is N-bromo succinimide  or NBS ?

Preparation of N-bromo succinimide  or NBS .

What is the use of N-bromo succinimide  or NBS ?

Why  SOCl₂ is more suitable than PCl₅ to prepare chloro alkane from alcohol ?

Why the dipole moment of CH3F is less than CH3Cl .Click here