Sunday, August 28, 2011

Ethanol in Mouthwash

"A company that makes oral cancer detection tests is suing Listerine-maker Johnson & Johnson over claims the company stymied sales of the tests to protect the image of its mouthwash.
....... Some studies have linked mouthwashes with high alcohol content to cancer ... "
(http://www.smh.com.au/lifestyle/beauty/listerine-cancer-claim-triggers-court-battle-20110829-1jh63.html)

At concentrations above 60% by volume, ethanol is an antiseptic that kills bacteria, fungi and some viruses by denaturing their proteins and dissolving their lipids. The ethanol content of a mouthwash can be around 20% by volume, which is substantially greater than the alcohol content of most wines at around 12% v/v, but less than that required to act as an antiseptic.

One of the antiseptic agents present in mouthwash is thymol, shown to the right.
The concentration of thymol in mouthwash can be about 0.0063% w/v.
Thymol is only slightly soluble in water, but it is very soluble in ethanol.

Typically, a person will use 20mL of mouthwash twice a day to rinse the mouth, and will spit out the mouthwash rather than swallowing it.

Further reading:
Lipids
Proteins
Functional Groups
Molecular Mass Calculations
Weight/Volume Concentration

Study Questions:
  1. Give the molecular and structural formula for ethanol.
  2. Explain what Chemists mean when they refer to the denaturing of a protein.
  3. What is a lipid?
  4. What are the elements that are present in all proteins?
  5. What are the elements that are present in all lipids?
  6. Give the molecular formula for thymol.
  7. On the structural formula of thymol, circle the functional groups present.
  8. What is the molecular mass (formula weight) of thymol?
  9. What mass of thymol would be present in 20mL of mouthwash?
  10. How much ethanol would be present in a 750mL bottle of mouthwash?
  11. How much ethanol would be present in a 750mL bottle of wine?
  12. In Australia, a standard drink is defined as one that contains 10g of pure ethanol. How many standard drinks are present in:
    • 750mL bottle of wine?
    • 750mL bottle of mouthwash?

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