Greetings,
This series on colloidal matter now continues with a discussion on the action of detergents. When a detergent is "in action", an emulsion is produced. The reader may recall the description of an emulsion in my last post, Colloidal Matter, Part 1.
A detergent is essentially a salt of a fatty acid. A fatty acid is a long hydrocarbon chain with an acid group (such as sulfuric acid) on one end. The hydrocarbon chain is often conjugated, meaning that there are alternating single and double bonds along the entire length of the structure. This has the effect of producing straight and rigid hydrocarbon chains. A detergent is produced when a fatty acid is reacted with an alkali metal base, such as potassium hydroxide; commonly known as "potash" or "lye". Here is the reaction for the production of Potassium Lauryl Sulfate:
C16H32SO4H (aq) + KOH (aq) --> C16H32SO4K (aq) + H2O
When mixed with water, detergent molecules arrange themselves into molecular spheres called micelles. The hydrophobic hydrocarbon chain "tails" attract each other by way of London Dispersion Forces. When enough detergent molecules are present (i.e. a critical concentration has been reached) complete micelles form. Each micelle consists of an inner part "filled" with hydrocarbon chains and a surface layer consisting of the anion ends of each detergent molecule. If oil and/or dirt is present in the detergent solution, it is broken up into tiny particles or droplets, in the case of oil. These particles and/or droplets are attracted to the hydrocarbon "tails" inside each micelle and so they become trapped inside the micelles. The dirt and oil can then be washed away because of the dipole-dipole attractive forces between the hydrophilic micelle surfaces and water molecules. The following diagram explains the process graphically.
Detergents are also known as "surfactants" because they reduce the surface tension of "dirty" water. This surface tension reduction causes larger aggregates of dirt and oil to break up into tiny particles. When the dirt and/or oil becomes dispersed enough, the droplets are captured within micelle spheres.
Common detergents are examples of the emulsion type of colloidal matter. The Chemistry of their actions is fascinating, indeed!
As always, thank you for reading!
This series on colloidal matter now continues with a discussion on the action of detergents. When a detergent is "in action", an emulsion is produced. The reader may recall the description of an emulsion in my last post, Colloidal Matter, Part 1.
A detergent is essentially a salt of a fatty acid. A fatty acid is a long hydrocarbon chain with an acid group (such as sulfuric acid) on one end. The hydrocarbon chain is often conjugated, meaning that there are alternating single and double bonds along the entire length of the structure. This has the effect of producing straight and rigid hydrocarbon chains. A detergent is produced when a fatty acid is reacted with an alkali metal base, such as potassium hydroxide; commonly known as "potash" or "lye". Here is the reaction for the production of Potassium Lauryl Sulfate:
C16H32SO4H (aq) + KOH (aq) --> C16H32SO4K (aq) + H2O
When mixed with water, detergent molecules arrange themselves into molecular spheres called micelles. The hydrophobic hydrocarbon chain "tails" attract each other by way of London Dispersion Forces. When enough detergent molecules are present (i.e. a critical concentration has been reached) complete micelles form. Each micelle consists of an inner part "filled" with hydrocarbon chains and a surface layer consisting of the anion ends of each detergent molecule. If oil and/or dirt is present in the detergent solution, it is broken up into tiny particles or droplets, in the case of oil. These particles and/or droplets are attracted to the hydrocarbon "tails" inside each micelle and so they become trapped inside the micelles. The dirt and oil can then be washed away because of the dipole-dipole attractive forces between the hydrophilic micelle surfaces and water molecules. The following diagram explains the process graphically.
Detergents are also known as "surfactants" because they reduce the surface tension of "dirty" water. This surface tension reduction causes larger aggregates of dirt and oil to break up into tiny particles. When the dirt and/or oil becomes dispersed enough, the droplets are captured within micelle spheres.
Common detergents are examples of the emulsion type of colloidal matter. The Chemistry of their actions is fascinating, indeed!
As always, thank you for reading!
No comments:
Post a Comment
Comments or Questions? Feedback is always welcome!