Coupling Reaction of Diazonium Salt

- Diazonium salt is a compound that contains a positively charged nitrogen molecule.
- Sulphanilic acid is a compound that contains a diazonium group (-N=N-).
- N,N-dimethylaniline is a compound that contains a nitrogen atom and two methyl groups (-CH3).
- When the diazonium salt of sulphanilic acid is coupled with N,N-dimethylaniline, a reaction occurs that forms a new compound.
- The coupling reaction involves the substitution of the diazonium group (-N=N-) for the dimethylamino group (-N(CH3)2) in N,N-dimethylaniline.
- The resulting compound has an azo linkage (-N=N-) and is commonly used as an indicator in chemistry.

Methyl Orange as an Indicator

- Methyl orange is an azo compound that is obtained by coupling the diazonium salt of sulfanilic acid with N,N-dimethylaniline.
- Methyl orange has an orange color in acidic solutions and a yellow color in basic solutions.
- The color change of methyl orange is due to the protonation and deprotonation of the nitrogen atoms in the azo linkage.
- In acidic solutions, the nitrogen atoms are protonated, which stabilizes the azo linkage and causes the compound to have an orange color.
- In basic solutions, the nitrogen atoms are deprotonated, which destabilizes the azo linkage and causes the compound to have a yellow color.

Conclusion

- The indicator that is obtained by coupling the diazonium salt of sulphanilic acid with N,N-dimethylaniline is methyl orange.
- Methyl orange is an azo compound that has an orange color in acidic solutions and a yellow color in basic solutions.
- The color change of methyl orange is due to the protonation and deprotonation of the nitrogen atoms in the azo linkage.