The Many Uses of Phenol(s)

Phenol

     Phenol, the first completely man-made polymer, was created about 25 years prior to Du Pont's nylon. This compound kicked off what is known as the Age of Plastics. Phenol is known to have links to orchids, surgical practices, endangered elephants, and photography. It has played an important role in advancements that would change the world.

     In 1860, hospitals were very dark and unsanitary, and people would only agree to surgery as a last resort. A large portion (40 percent) of amputees would die from "hospital disease", and in army hospitals it was 70 percent. The lack of sterilization in hospitals caused the majority of wounds to become infected, and bacteria could easily spread from patient to patient. The miasma theory was supported at the time, which was a belief that toxic gases from drains and sewers would carry through the air to other patients after a patient becomes infected. Treatments prescribed for miasma gases included salicylic acid, thymol, carbon dioxide gas, bitters, zinc sulfate, boracic acid, and raw carrot poultices. These treatments were rarely effective, and their occasional success could not be replicated.

     

Joseph Lister was born in Yorkshire in 1827, and received his medical degree from the University College in London. He was a surgeon at the Royal Infirmary in Glasgow in 1861, and he was also a professor of surgery at the University of Glasgow. Lister believed the hospital disease was caused by something microscopic in the air rather than poisonous gases. He found that "The Germ Theory of Diseases" by Louis Pasteur applied to his ideas. Pasteur considered germs to be everywhere, and his experiments showed that germs could be killed by boiling. Lister knew that he couldn't boil the doctors and patients, so he settled on carbolic acid to sanitize surfaces. One day, an eleven year old boy came to the hospital with a compound fracture, which posed high risks for infection. Lister cleaned the area around the broken bone with lint covered in carbolic acid. He used a surgical dressing made of layers of linen soaked in carbolic solution, then he covered it with a metal sheet to reduce evaporation of the carbolic acid. The boy's wound healed quickly, without any occurrence of infection. Lister later performed the same procedures on other patients, producing the same results. This convinced Lister that carbolic acid was effective at preventing infections. He began using it as an antiseptic in all of his surgical procedures in August 1867. Crude carbolic acid burned the skin, but Lister managed to obtain phenol, the main constituent of carbolic acid, in the form of white crystals.

Phenol Structure

    

     Phenol contains a benzene ring with an attached OH group. It is a simple aromatic molecule, and while it is very soluble in oil, it is only somewhat water soluble. Lister formed a "carbolic putty poultice" by mixing phenol with linseed oil and whitening. He would then spread the resulting paste over a wound to provide a barrier to the bacteria. A solution of phenol in water was used to clean the surgical tools, the skin around a wound, and the surgeon's hands. It was even sprayed onto incisions during operations. Although it was evident that the carbolic acid had a positive effect on patient recovery, Lister believed that he had yet to achieve complete antiseptic conditions during surgeries. In order to sanitize every particle in the air, he created a machine to constantly spray a mist of carbolic acid solution. Although this machine helped prevent contamination from airborne germs, it had harmful effects on the people in the operating room. Phenol is toxic, and it caused bleaching, numbing, and cracking of the skin. Inhalation of the phenol spray led to illness. By 1878, these techniques were used worldwide. However, phenol is no longer used as an antiseptic due to its toxicity and harmful effects.
     Phenol refers to a group of related molecules that have a benzene ring with an OH group, not just Lister's antiseptic. Although there is only one "phenol" itself, there are hundreds of thousands of phenols. Man-made phenols can be used as antiseptics, and picric acid, once used as dye, is explosive. Phenols also occur naturally. Molecules such as capsaicin, zingerone, eugenol, and isoeugenol (from the spices chapter) are classified as phenols. Other natural phenols include vanillin (from vanilla) and tetrahydrocannabinol (THC) in marijuana, and they usually have at least two OH groups. Gossypol is toxic and it is considered a polyphenol because it has six OH groups and four benzene rings. Epigallocatechin-3-gallate is a phenol found in green tea, and it has even more OH groups.
     Although there are many phenols in the world, the one with the most impact is the parent molecule, phenol itself. At the time of Lister's carbolic acid experiments, ivory was becoming a common material for combs, piano keys,cutlery, buttons, and more. The problem with this is that many elephants were being killed for their tusks, making ivory scarce and expensive. The decreasing elephant population caused concern, because the game of billiards was becoming very popular. The balls for this game must be cut from flawless animal tusk, because they require high-quality ivory in order to roll properly. In the late 19th century, billiard balls were made from other materials- bone dust, wood pulp, cotton paste with a hard cellulose-based resin, and eventually celluloid.
     A Belgian immigrant to the United States, Leo Baekeland, created the first synthetic version of what we now know as plastic in the early 1900s. This invention sparked the beginning of the Age of Plastics. Baekeland received his doctorate at the University of Ghent at the age of 21. His decision to emigrate to the New World appeared to be a mistake at first, and he was almost bankrupt in 1893. Baekeland saved himself by meeting with George Eastman, the founder of Eastman Kodak, a photographic company. Baekeland offered to sell Eastman a new type of photographic paper he created, which would allow people to easily develop their photos. Eastman was so impressed that he paid $750,000, which allowed Baekeland to open a lab next to his home. Baekeland then turned his focus to making a synthetic form of shellac, which is used to preserve wood. His approach was to react phenol with formaldehyde, which produced bad results when combined in previous attempts. In 1907, Baekeland created a reaction where he could control pressure and heat, and he produced a liquid that hardened into a transparent, amber-colored solid in the shape of the mold it was poured into. He called this substance Bakelite, and it was able to hold its shape when exposed to high temperatures. This material was very superior when used as an electrical insulator, and it did not react with water, sunlight, salt air, or ozone. It did not easily become degraded or cracked. Bakelite was the perfect material for billiard balls, although it was not Baekeland's intended purpose. All billiard balls that were not made of ivory were made of Bakelite by 1912, and the material was later applied to many other everyday items- telephones, plates, fountain pens, radios, pipe stems, glasses, kitchen equipment, decorations, etc.
     Demand for vanillin has exceeded the supply produced by the vanilla orchid, so a synthetic vanillin is manufactured. It comes from the "waste pulp liquor" from treatment of wood pulp when making paper. This waste liquor is mainly composed of lignin, which, when broken up, can form vanillin. Although synthetic vanillin is pure vanillin that is from a natural source, it lacks the traces of other compounds that the vanilla bean has, which help produce the flavor of true vanilla.
     Phenol has had a major role in shaping the world we live in today. It has made antiseptic surgery possible, improving chances of survival for people with serious injuries, and allowing the advanced surgeries that are performed today. Baekeland's photographic paper allowed people to pursue photography as a hobby, and allowed George Eastman to offer better film. Baekeland's first synthetic material from the Age of Plastics improved insulators used in the electrical industry. The large variety of phenols are likely to continue shaping our way of life.