A Brief History of Synthetic Dyes
In 1856, teenager William Perkin accidentally discovered a dye he called mauve while trying to make quinine in his home lab. This accident spawned a new synthetic dye industry that changed the course of the textile industry turning them away from the use of natural dyes to producing dyes from coal tar.
Perkin was trying to convert an artificial base into the natural alkaloid quinine. Instead of getting a colorless quinine, he ended up with a reddish powder. This intrigued him and he decided to experiment further. He tried adding aniline – a different base with a simpler construction. This created a perfectly black product. After purification, drying and washing with alcohol, Perkin had a mauve dye.
At the time, no one realized that this simple experiment would be a catalyst for a new spirit of cooperation between science and industry.
By the time Perkin discovered mauve, aniline was already linked to colorants and color producing reactions for the past 30 years. Unfortunately, these colors had no practical use.
Perkin filed his patent in August of 1856 and a new dye industry was born. He initially called his discovery Tyrian purple to give it more value.
Most of the dyes we use today are Synthetic Organic Chemicals that are cracked from crude oil, they are Aromatic organic compounds. These are the ones used to color everything in our world today from the pills we take to the clothes we wear. What a dull world it would be if that young scientist had not made his accidental discovery over 150 years ago!
Aromatic compounds are substances that consist of one or more rings that contain alternating single and double bonds. In the ring of an aromatic compound, electrons are delocalized, meaning that they spread out over the entire ring and are not attached to a specific atom.
Most dye molecules contain two parts:
- The first part is a single benzene ring or a substituted benzene ring. This part could also contain a system of either two rings fused together (naphthalene) or three rings fused together (anthracene).
Think of this as either a one, two, or three ring circus.
- And the second part, a chromophore. This is the part of a molecule which when exposed to visible light will absorb and reflect color.
You can increase the intensity and change the color in a dye molecule by the addition of compounds that contain lone pairs of electrons to the benzene ring:
These compounds are called auxochromes.
Auxochromes are a group of atoms that can give color to a chromophore. It cannot do this when it is on its own. Auxochromes are commonly called color helpers or ‘color intensifiers’.
The whole molecule can be called a chromogen (dye).
There are many types of dyes (classes) that are made today. Dyes can even be manufactured for a specific use. We have come a long way since the experiments of Perkin and others. If you’re interested in reading the sequel of this blog post, A Brief History of Natural Dyes, click the picture below!