The Chemistry behind how hand washing with soap helps fight coronavirus- Pall thordarson

- March 20, 2020

Hand washing.

By: Shofu Babalola Theophilus
Washing your hands with soap is one of the simplest and most effective ways of killing off any viruses you may have come into contact with.
Alcohol-based disinfectants are also effective, but soap is a highly efficient way of killing the virus when it’s on your skin.
Viruses can be active outside the body for hours, even days. Disinfectants, liquids, wipes, gels and creams containing alcohol are all useful at getting rid of them – but they are not quite as good as normal soap.
Soap is one of the most effective ways to get rid of COVID-19.

It dissolves the fatty layer that coats coronaviruses.
The RNA, proteins and lipids self-assemble to form the virus.
The viral self-assembly is based on "non-covalent" interactions between the proteins, lipid and RNA. It difficult to split up the self-assembled viral particle but can be splitted by using soap and water.
Most viruses, including the coronavirus, are between 50-200 nanometers – so they are truly nanoparticles. Nanoparticles have complex interactions with surfaces they are on. Same with viruses. Skin, steel, timber, fabric, paint and porcelain are very different surfaces. When you cough, or especially when you sneeze, tiny droplets from the airways can fly up to 10 meters (30 ft)! The larger ones are thought to be main coronavirus carriers and they can go at least 2 m (7 ft).
These tiny droplets end on surfaces and often dry out quickly. But the viruses are still active! What happens next is all about supramolecular chemistry and how self-assembled nanoparticles ( viruses) interact with their environment. Wood, fabric and not to mention skin interact fairly strongly with viruses.
Contrast this with steel, and at least some plastics, e.g. teflon. The surface structure also matter – the flatter the surface the less the virus will “stick” to the surface. Rougher surfaces can actually pull the virus apart.
So why are surfaces different? The virus is held together by a combination of hydrogen bonds (like those in water) and what we call hydrophilic or “fat-like” interactions. The surface of fibres or wood for instance can form a lot of hydrogen bonds with the virus, but steel, Teflon materials do not form a lot of hydrogen bond with the virus. So the virus is not strongly bound to these surfaces. The virus can stay active on favourable surfaces as stated earlier for hours. Sunlight, moisture and heat can make it less stable.
The skin is an ideal surface for a virus! It is “organic” and the proteins and fatty acids in the dead cells on the surface interact with the virus through both hydrogen bonds and the “fat-like” hydrophilic interactions.

Washing your hands with water alone will not help wash the virus away from your hands because the virus is quite sticky. Soapy water is more better, soap contains fat-like substance known as amphiphiles which is similar structurally to the lipids in the virus membrane, Also the soap molecules also competes with the non-covalent bonds that help the proteins, RNA and the lipids to stick together. It dissolves the glue that holds the virus together. Ethanol and other alcohols do not only readily form hydrogen bonds with the virus material but as a solvent, are more lipophilic than water. Hence alcohol do also dissolve the lipid membrane and disrupt other supramolecular interactions in the virus. You need a high concentration (60- 80)% of the alcohol to get a rapid dissolution of the virus.
Water is not effective alone in washing the virus off our hands. Alcohol based Products work better. But soap detaches the virus from the skin and falls apart.