91Ó°ÊÓ

The S_N1 mechanism involves the following two steps:

• The formation of a carbocation intermediate: The leaving group moves from the alkyl halide and leads to the formation of an intermediate carbocation.
• The carbocation intermediate is planar in structure, due to which the nucleophile can attack either side of the carbocation. This results in the formation of a racemic mixture of the products.

The S_N1 reactions are always favored by the polar protic solvents such as water, ethanol, etc.

The reaction of 1-bromo-hex-2-ene with ethanol takes place in the following way:

The above reaction proceeds in the following steps:

Formation of resonance stabilized carbocation

The 1-bromo-hex-2-ene is a primary alkyl halide, but it reacts with the weak nucleophile under the S_N1 reaction conditions because of the formation of the resonance stabilized carbocation.

The nucleophilic attack on the carbon atoms is shown below:

The nucleophilic attack on carbon 1

The nucleophilic attack on carbon 2