Structural Biochemistry/Lipids/Detergents

Chemical Structures

Detergents are primarily made up of surfactants, or “surface active agents” of which reduce the surface tension of water by adsorbing at the common boundary between liquid and gas or one liquid and another. Surfactants form into aggregates known as micelles, formations of amphiphilic lipids. In micelles, the amphiphilic lipid has a tail that forms a core that encapsulates an oil droplet or dirt particle and a head that maintains contact with the surrounding water environment. To work effectively, the chemical formation of micelles is not enough to remove oil or grease; mechanical energy (scrubbing or water flow) is often required.

Surfactants can be formed from petrochemical or oleochemicals, chemical products made from raw materials such as petroleum or other hydrocarbon substances (olefin or aromatics). Alkalis and oxidizing agents are other components of detergents. Alkalis provide positively charged cations that can trigger chemical reactions. Oxidizing agents can act as a source of energy for chemical reactions and include sulfuric acid and ethylene dioxide.

Detergents can also be composed of substances that can modify pH of other components, as well as water softeners (compounds that reduce metal ion concentration) and enzymes that digest proteins or fats. In addition, detergents can comprise of ingredients that modify the presence of foam or stabilize the viscosity of a solution.

CH₃(CH₂)₁₄-CO-O-(CH₂-C-OH)₃

Properties

•Nonionic detergents, which form electrically neutral colloidal particles in solution, contain non-ionic emulsifiers, amplifying the ability to remove oily residues. These nonionic surfactants are low-foaming and have defoaming properties that improve wetting, rinsing and particle removal while not hindering with mechanical labor. A common nonionic detergent is Liquinox used to clean glassware and does not react with hard water ions; this is due to the fact that no ionic groups exist to do so. In addition, it foams less than ionic detergents but has some polar portions to provide necessary water solubility.

•Cationic detergents often come in powder foam and have a long cationic chain that is responsible for surfactant properties. However, cationic detergents are poor detergents even though they have adequate emulsifying properties. Instead, there are often used in bacterica/germ free environments due to their antiseptic properties.

•Anionic detergents are based on sulfate or carboxylate anions and are of the most common modern synthetic detergents producing negative charged colloidal ions in solution.

•Bile salts in the stomach have emulsifying properties in the digestive system, reacting with fats and oils as a detergent to form smaller particles of the consumed compounds. In addition, the same amphipathic properties that allow bile acids to emulsify using lipids also make them membrane-disruptive mediums.

Sources

• http://www.elmhurst.edu/~chm/vchembook/558detergent.html. Elmhurst College. 2003.
• http://chemistry.about.com/od/howthingswork/f/detergentfaq.htm. About.com. Anne Marie Helmenstine, Ph.D. 2009
• http://www.chemistry.co.nz/surfactants.htm. LA & HA Campbell. 1999