Question

Aniline is reacted with bromine water and the resulting product is treated with an aqueous solution of sodium nitrite in the presence of dilute HCl. The compound so formed is converted into tetrafluoroborate which is subsequently heated dry. The final product is:
А. 2.4 – Tribromo fluorobenzene
B. 1,3,5-tribromobenzene
C. p - bromoaniline
D. o – bromo fluorobenzene

Answer 1

Hint: To solve this question, we need to move step by step and understand the products that are formed at every step of the reaction. Each product formed would act as a reactant in the next reaction. Hence, it is important to understand the chemical characteristics of these products formed.

Complete Step-by-Step Answer:
Before we move forward with the solution of the given question, let us first understand some important basic concepts.
The molecular structure of aniline is formed by adding an amino group on a benzene ring at the position 01 carbon atom. Aniline reacts with bromine water to cause bromination reaction. since aniline is a weak leaving group, it would not get substituted. Instead, the bromine atoms would substitute the hydrogen atoms present at the ortho and para positions. The chemical reaction for the same can be given as:

This tribromo aniline is now reacted with sodium nitrate and HCl. This causes a substitution reaction with respect to the amino group present. The chlorine atoms from HCl substitute the Hydrogen atoms present in the Amino group. This would result in the formation of tribromo diazonium chloride. The chemical reaction for the same can be given as:

This tribromo diazonium salt is now reacted with tetrafluoroborate which is subsequently heated dry. This causes the fluorine to substitute the unstable diazonium chloride group. This results in the formation of o, p – tribromo fluorobenzene. The chemical reaction for the same can be given as:

Hence, Option A is the correct option

Note: To solve these types of questions, it is very important to remember the chemical characteristics like valency, electronegativity, acidity, basicity, leaving group tendency, etc. Solid fundamentals of these concepts help in solving these questions.