Benzene formed nitrobenzene at temperature of 60$^0$C when it reacts with mixture of concentrated trioxonitrate(V) acid and concentrated

Analysis

The question asks for the specific reagent used alongside concentrated trioxonitrate(V) acid ($HNO_3$) to facilitate the nitration of benzene at 60°C. This is a classic electrophilic substitution reaction in organic chemistry.

Concept: Nitration of Benzene

The nitration of benzene involves the substitution of a hydrogen atom on the benzene ring with a nitro group ($-NO_2$).

1. The Reagents: To generate the active electrophile, the nitronium ion ($NO_2^+$), benzene must react with a mixture of concentrated trioxonitrate(V) acid ($HNO_3$) and concentrated tetraoxosulphate(VI) acid ($H_2SO_4$).
2. The Role of $H_2SO_4$: Concentrated tetraoxosulphate(VI) acid acts as a catalyst and a dehydrating agent. It protonates the nitric acid, causing it to lose a water molecule and form the highly reactive nitronium ion ($NO_2^+$), which then attacks the benzene ring.
3. Conditions: This reaction is typically carried out at a controlled temperature of about 50°C to 60°C to prevent further nitration (which would produce dinitrobenzene).

Step-by-Step Solution

• Step 1: Identify the reaction type: Electrophilic aromatic substitution (Nitration).
• Step 2: Recall the "nitrating mixture": The standard laboratory mixture for nitration is concentrated $HNO_3$ and concentrated $H_2SO_4$.
• Step 3: Evaluate the options: • A. Phosphoric acid is not the standard catalyst for this reaction. • B. Hydrochloric acid does not facilitate the formation of the nitronium ion. • C. Tetraoxosulphate(VI) acid ($H_2SO_4$) is the correct reagent used to generate the nitronium ion. • D. Hydrogen iodide is a reducing agent and is not involved in this substitution.

Conclusion

The reaction of benzene with concentrated trioxonitrate(V) acid requires concentrated tetraoxosulphate(VI) acid to produce nitrobenzene.

Exam Tip: Always remember the "Nitrating Mixture" mnemonic: "Nitric and Sulphuric". If you see "nitration" in an exam question, look for $H_2SO_4$ as the partner acid!