Question

Primary amines can be converted into secondary amines by reaction with haloalkanes. This reaction is difficult to achieve in the lab because of the large number of byproducts. Select the possible products/ byproducts of the following reaction.

Answer 1

Concepts and reason

The concept used to solve this problem is the knowledge of nucleophilic substitution reaction. The \(\mathrm{S}_{\mathrm{N}} 2\) reaction or the bimolecular nucleophilic substitution reaction is a concerted type reaction followed by the trigonal bipyramidal shaped transition state which results in the formation of the product of inverted stereochemistry.

Fundamentals

Nucleophilic substitution reaction involves the primary attack of a nucleophile to the \(\sigma^{*}\) antibonding orbital of the carbon of alkyl halide, which on effect attach the nucleophile on that carbon and the removal of the halogen as a leaving group.

 

Attack of lone pair of nitrogen of substituted ammonia to the carbon- halogen bond of the halogen alkane. The initial attack is shown below:

The lone pair of substituted ammonia initially attack the \(\sigma^{*}\) antibonding orbital of the carbon of alkyl halide which results in the removal of the halide group from the alkane chain while the nitrogen group gets attached to the ring results in the formation of salt alkyl ammonium halide.

Attack of the substituted ammonia acts as a base and abstracts proton from the alkyl ammonium halide salt to form the secondary amine. The attack of substituted ammonia is shown below:

As each of the intermediates are stable and the product again acts as a nucleophile and hence several byproducts are possible.

The possible products and the byproducts formed are A, B, C, F, H, and K.

The alkyl ammonium salt is further attacked by the substituted ammonia which acts as a base and abstracts proton to form primary amine or secondary amine. This product can again act as a nucleophile and attack again to the alkyl halide to give several products.

 

 

 

The possible products and the byproducts formed are A, B, C, F, H, and K.