Question

Diazotization of ${\text{n - Bu - N}}{{\text{H}}_{\text{2}}}$ with ${\text{NaN}}{{\text{O}}_{\text{2}}}{\text{/HCl}}$ gives ______ isomeric butene.
A.2
B.3
C.4
D.5

Answer 1

The chemical process used in converting a primary aromatic amine into the corresponding diazonium salt of the amine is commonly referred to as diazotization. This process is also known as ‘diazotization’.

Complete step-by-step answer: Here reagent given to us is ${\text{NaN}}{{\text{O}}_{\text{2}}}{\text{/HCl}}$. The reaction between ${\text{NaN}}{{\text{O}}_{\text{2}}}$ and ${\text{HCl}}$ is as follows:

${\text{NaN}}{{\text{O}}_{\text{2}}}{\text{ + HCl}} \to {\text{ NaCl + HN}}{{\text{O}}_{\text{2}}}$

The structure of ${\text{n - Bu - N}}{{\text{H}}_{\text{2}}}$ amine is as follows:

Diazotization of ${\text{n - Bu - N}}{{\text{H}}_{\text{2}}}$ with ${\text{NaN}}{{\text{O}}_{\text{2}}}{\text{/HCl}}$ gives diazonium ion as the intermediate product.

Alkyl diazonium salts are unstable so converted into carbocation. In this reaction ${{\text{N}}_{\text{2}}}$ is a good leaving group.

This primary carbocation converted into 1-butene after the loss of hydrogen as follows.

So, we can say that Diazotization of ${\text{n - Bu - N}}{{\text{H}}_{\text{2}}}$ with ${\text{NaN}}{{\text{O}}_{\text{2}}}{\text{/HCl}}$ gives 1-butene as one of the products.

Primary carbocation also shows rearrangement of the hydrogen atom and converts into secondary carbocation as follows:

This secondary carbocation converted into 2-butene after the loss of hydrogen as follows

2-butene has two types of isomers cis and trans.

Diazotization of ${\text{n - Bu - N}}{{\text{H}}_{\text{2}}}$ with ${\text{NaN}}{{\text{O}}_{\text{2}}}{\text{/HCl}}$ gives 1-butene, cis-2-butene and trans-2-butene isomers.
So, we can say that diazotization of ${\text{n - Bu - N}}{{\text{H}}_{\text{2}}}$ with ${\text{NaN}}{{\text{O}}_{\text{2}}}{\text{/HCl}}$ gives 3 isomeric butene.

Hence, the correct option is (B) 3

Note: Isomer having similar groups on the same side is known as a cis isomer. Isomers having similar groups on opposite sides are known as the trans isomer. Cis and trans isomers are known as a geometrical isomers. Alkenes having two different substituents at each end of ${\text{C = C}}$ show geometrical isomers. 1-butene does not show any isomer.