Phenol is the most basic family member of a group of compounds involving an –OH group attached to a benzene ring. It has the molecular formula C6H5OH, and is mildly acidic. It used to be made from Benzene, using sulfuric acid and sodium hydroxide in a multi-stage process. Now it is mainly manufactured from benzene and propene, with a reaction yield of 86% phenol. It is mainly used for the synthesis of plastics, but is also essential for the production of many other things, including some pharmaceutical drugs.
Before the mid 1800s, surgery was very dangerous and often led to a lot of deaths. However, Sir Joseph Lister used phenol as an antiseptic for the first time in the 1960s. Lister was aware of the germ killing properties of phenol, which had been discovered previously by the work of Louis Pasteur and others, so decided to use it in surgery as an antiseptic. It is reputed that phenol’s germ-killing power first came to notice in a bizarre way. Sailors who underwent amputations at sea appeared to have a higher survival rate than patients in hospital. This seemed to be due to the practice at sea of dipping the stump into molten tar to seal the wound. Tar contains, among other things, phenol, so it was investigated further to test its antiseptic properties.
Although phenol is effective at killing germs, it also has some drawbacks. There are some side effects with using phenol. Because phenol is absorbed relatively quickly through the skin, poisoning can occur as well as nasty chemical burns. Although the burns can be treated and decontaminated by washing with polyethylene glycol, isopropyl alcohol, or perhaps even copious amounts of water, the side effects aren’t ideal and can cause discomfort for the patient. There has been work on making safer phenols for antiseptic purposes, with fewer side effects. It has been found that the more electronegative a substituent, the less harmful it is to the skin and also, the more methyl groups attached to the benzene ring, the better the germ-killing power. Although phenol on its own is already an effective germicide, stronger germ-killing phenols with more methyl groups attached such as 4-chloro-3,5-dimethylphenol shown below (small numbers showing relative germ-killing power), are being used as the greater efficiency means that smaller concentrations can be used and fewer side effects will be expected.
Because Phenol has a good penetrating power into organic matter, and is a strong germ-killer, it is mainly used today as a disinfecting agent for equipment or organic materials that are to be destroyed. Due to its corrosive properties and tendency for burns, it is rarely used as an antiseptic anymore, but is only really used today as an antiseptic for cauterising infected areas. It is also incorporated into cutaneous applications for pruritus, stings, bites, burns, etc, because of its local anaesthetic and antibacterial properties to relieve itching and control infections.