Question

Write the mechanism of the following reaction:
 $ nBuBr+KCN\xrightarrow{EtOH-{{H}_{2}}O}nBuCN $

Answer 1

Hint :We know that the nucleophiles generally takes part in the nucleophilic substitution reactions and during this reaction nucleophile becomes attracted towards a partial or full positive charge rather than this neutral nucleophilic reactions with solvents like water is known by the name solvolysis.

Complete Step By Step Answer:
The substitution of the existing nucleophile by the incoming and more reactive nucleophile is known as the nucleophilic substitution reaction. The acetate ion is a fairly good nucleophile. It pushes out the chloride from the compound and acquires its position. The nucleophilic substitution may proceed through the bimolecular or unimolecular pathways. The leaving group leaves as a neutral molecule. The nucleophiles are the electron-rich species, and have an affinity towards the positive charge. The substitution of one nucleophile by the more reactive nucleophile is the nucleophilic substitution reaction. The nucleophilic substitution reaction follows two types of mechanism:
-Substitution nucleophilic bimolecular $ ~\left( {{S}_{{{N}^{2}}}} \right). $
-Substitution nucleophilic unimolecular $ ~\left( {{S}_{{{N}^{1}}}} \right). $
Nucleophilic substitution reaction is a type of organic reaction where one nucleophile is replaced by others. It is quite the same as the displacement reactions that we find in chemistry. In a displacement reaction, a less reactive element gets replaced by a more reactive element from its salt solution. The group that takes electron pairs and displaces them from the carbon is known as the leaving group, and the substitution takes place on a molecule known as substrate.
This is an example of bimolecular nucleophilic substitution reaction $ ~{{S}_{{{N}^{2}}}}. $ Cyanide ion acts as a nucleophile and bromide ion acts as leaving group. It is one step reaction and the mechanism is as:
 $ \underset{n\text{ }butyl\text{ }bromide}{\mathop{C{{H}_{3}}-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{2}}-Br}}\,\text{ }\xrightarrow[{{S}_{{{N}^{2}}}}]{Ethanol/water}\underset{Pentanenitrile}{\mathop{N\equiv C-C{{H}_{2}}-C{{H}_{2}}-C{{H}_{3}}}}\,+KCN $

Note :
Remember that the nucleophilic substitution reactions, nucleophilicity are the term used for describing the reactivity and strength of nucleophiles. In a nucleophilic substitution reaction, a stronger nucleophile replaces a weaker nucleophile in its compound.