The Color of Methyl Orange in Strong Acidic Solution is ________
Methyl orange is an intensely colored compound used in dyeing and printing textiles. It is also known as C.I. Acid Orange 52, C.I. 13025, helianthine B, Orange III, Gold orange, and Tropaeolin D .
Chemists use methyl orange as an indicator in the titration of weak bases with strong acids. It changes from red (at pH 3.1) to orange-yellow (at pH 4.4)
pH-related color changes result from changes in the way electrons are confined in a molecule when hydrogen ions are attached or detached. Here is the structure of methyl orange in acidic solution
How is methyl orange made?
Methyl orange is synthesized by reaction of sulfanilic acid, sodium nitrite, and dimethylaniline. First, sulfanilic acid is dissolved in dilute aqueous acid. Sodium nitrite is added to produce adiazonium salt
This reaction is called diazotization and it is extremely useful in organic synthesis. The nitrous acid provides NO+ which replaces a hydrogen on the -NH3+ group to produce -NH2NO+ and water; a second water is eliminated to produce the -N2+ group.
The diazonium salt is then coupled with dimethylaniline. The coupling takes place in the opposite (“para”) position from the -N(CH3)2 group: