Re: Why are chemicals like ethyl acetate needed in nail polish?

Dear No Name Entered =Þ ,

Ethyl acetate (ethyl ethanoate) and butyl acetate (butyl ethanoate) and the like are known as esters. These are made by reacting a carboxylic acid with an alcohol. As you know, a carboxylic acid has the -COOH functional group and alcohols have the -OH functional group. They react to form an ester and water. Esters have the general formula R-COO-R', where R comes from the carboxylic acid and the R' comes from the alcohol.

Most esters have a fruity odour. For example, amyl acetate (pentyl ethanoate) smells like pears. You are right, ethyl ethanoate is quite harmful, but that's only if it is inhaled or ingested in excessive amounts or comes into contact with sensitive parts of the body, e.g. the eyes. Handle it with care, like with all chemicals. A material safety data sheet (MSDS) for ethyl ethanoate can be found here. However, the precautions to be taken make the previous document seem a bit alarming. Here (link defunct as of 8/21/2006: http://www.worksafe.gov.au/databases/exp/az/Ethyl_acetate.htm) is an Australian government site which briefly goes through the effects of ethyl acetate on humans. As you can see, it is not really as dangerous as you suppose, causing only some measure of irritation. Esters can be found in use in the flavoring and perfume industries, so we could logically assume that they are safe enough in small amounts.

Ethyl ethanoate and the like are used as solvents. As you know, the substance found in nail polish is organic, and also insoluble in water. Going by the principle of like-dissolves-like, ethyl acetate and other organic solvents are more suitable. It also dries fairly fast, so application of nail polish is easy. In fact, its smell is most often associated with nail polish, something I noted when my students do experiments with esters during class. Note that ethyl acetate is also used in nail polish remover, so it works both ways. Acetone (propanone) is another solvent used, however, it is more harmful to the environment than ethyl ethanoate. Flammability of the substance is more of a concern than its toxic effects.

There are some interesting sites I found while researching your answer. Here is a project done by a schoolkid on which solvent is a better nail polish remover. Here is a page detailing the structure and some synonyms of the chemical. You can also read up more about the chemical and physical properties of the substance from the above site. Finallly, I also found a rather interesting write up on nail care with the medical perspective.

I hope this helps answer your question. Keep up your interest in science!

Thiam Hock "Iron Nails" Tan

Other References:
Ho, Mabel, Chemistry Potpourri. S'pore, S'pore Science Centre. 1st ed., 1988.
Solomons, G. & Fryhle, C., Organic Chemistry. New York, John Wiley. 7th ed., 2000.