Methyl orange

Methyl orange is a synthetic pH indicator commonly used in acid-base titrations, especially between strong acids and weak bases. It changes color from red in acidic solutions (pH < 3.1) to yellow in basic solutions (pH > 4.4), with a sharp transition at pKa ≈ 3.47.
🧪 Chemical Properties and Use
• Color change: Red → Orange → Yellow (as pH increases)
• Effective pH range: 3.1 – 4.4
• Type: Azobenzene derivative
• Application: Ideal for titrating strong acids vs. weak bases
• Color mechanism: Protonation of the azo group (–N=N–) alters light absorption
🏭⚗️ Synthesis
Methyl orange is synthesized by coupling diazotized sulfanilic acid with dimethylaniline, forming an azo compound through electrophilic substitution and rearomatization.
⚠️ Safety
Methyl orange is considered mutagenic. Under oxidative stress or microbial action, it may degrade into harmful compounds such as aniline derivatives and reactive oxygen species. Always handle with proper lab safety precautions.