CHEM 208 Lecture Notes - Lecture 6: Glycerol, Lanolin, Shampoo
28 Jun 2018
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* Chapter 6: Household Products *
Soap, Detergents and our Health
-these chemicals help make our surroundings cleaner, healthier
(removing germs) and more pleasant
-in order to make it more effective in the process of cleaning, the water
must be made to spread and thus wet surfaces effectively (its surface
tension must be reduced)
-this is achieved by using compounds called surfactants
What are surfactants?
-soaps and detergents are composed of surfactants
- surfactants are water-soluble and surface-active agents
-soaps are anionic surfactants
-composed of a hydrophilic (water-soluble) head and a hydrophobic
(fat-soluble, water-hating) tail.
-hydrophilic end is stable when solubilized in water
- the hydrophobic end consists of a long chain hydrocarbon that is more
stable when surrounded by other organic groups
Classes of Surfactants
-different classes of surfactants categorized by the charge of the
hydrophilic component of the surfactant molecule after dissociation in
water:
-anionic surfactants have a negative charge
-cationic surfactants have a positive charge
-non-ionic surfactants have no charge
-amphoteric surfactants have both positive and negative charges
-All About Soap-
Composition and Limitations of Soap
-soaps (anionic surfactants) consist of the long hydrocarbon tails of
fatty acids and the polar heads of sodium or potassium salts of fatty
acids (found in fats and oils of animals and plants )
find more resources at oneclass.com
find more resources at oneclass.com
-traditionally, soap was made form animal fat and wood ash )composed
of potassium hydroxide and potassium carbonate )
Advantages
-soap manufactured from combinations of natural and renewable
resources
-soaps are biodegradable and do not pollute bodies of water
Disadvantages
-formation of soap (or scum) in water containing Ca2+ and Mg 2+ ions
(hard water) (hard water contains certain alkaline earth cations)
-the calcium and magnesium ions react with soap molecules to
produce calcium and magnesium salts of fatty acids. These salts are
insoluble in water and impair the surfactant properties of soap because
the amount of soap available for cleaning is reduced. Soap scum is
difficult to rinse away and can be visible (on fabrics, bathtubs and sinks)
-poor adaptability to diversity of fibers, washing temperatures and
water conditions
-tendency to clog sewage systems due to their gelling properties
-All about Detergent-
Composition
-detergents (containing a variety of engineered anionic or non-ionic
surfactants) are made from petrochemicals
find more resources at oneclass.com
find more resources at oneclass.com
Advantages
-detergents are less affected by calcium and magnesium ions in water,
thus acting as better cleaning agents and almost eliminating the film
formation
-detergents perform well under diverse conditions such as adaptability
to diversity of fibers, washing temperatures and water conditions
Disadvantages
-detergents are made form non-renewable petroleum- based oils
-majority of detergents are not biodegradable
The Cleaning Process
Soap/ Detergent Chemical Interaction
-in the cleaning process, the polar ends of the surfactant molecule
interacts with water (polar molecule) and the non-polar end is attracted
to oil or grease (non-polar molecules)
Step 1
-chemical interaction (with soap or detergent) traps the oily and greasy
soil molecules. In aqueous solution, surfactants cluster near the surface
Step 2
-the hydrophobic tails are attracted to grease and the hydrophilic heads
to the water, thereby forcing the grease away from the soiled surface
Step 3
-the grease is then surrounded by the individual surfactant molecules
and removed from the soiled surface
Finally…
-Thermal Interaction (with hot water) helps dissolve oil and grease
molecules. Mechanical Interaction (machine agitation or hand
rubbing) releases oily and greasy soil from the fabric
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
These chemicals help make our surroundings cleaner, healthier (removing germs) and more pleasant. In order to make it more effective in the process of cleaning, the water must be made to spread and thus wet surfaces effectively (its surface tension must be reduced) This is achieved by using compounds called surfactants. Composed of a hydrophilic (water-soluble) head and a hydrophobic (fat-soluble, water-hating) tail. Hydrophilic end is stable when solubilized in water. The hydrophobic end consists of a long chain hydrocarbon that is more stable when surrounded by other organic groups. Different classes of surfactants categorized by the charge of the hydrophilic component of the surfactant molecule after dissociation in water: Amphoteric surfactants have both positive and negative charges. Soaps (anionic surfactants) consist of the long hydrocarbon tails of fatty acids and the polar heads of sodium or potassium salts of fatty acids (found in fats and oils of animals and plants )
