[POST LAB] EXPT 7: Saponification

Saponification

• process by which soaps are made from the base hydrolysis of a fat or an oil

• known and adopted method for soap making

Soaps

• carboxylate salts with very long hydrocarbon chains

• traditionally made with animal fat or lye (NaOH)

Esters treated with sodium hydroxide

converted into carboxylate salts which upon neutralization yield carboxylic acids

Base (NaOH or KOH) used for hydrolysis

• fatty acids produced are deprotonated and are present as its corresponding carboxylate salt

• because the carboxylate salts are charged, they become more soluble in water than the uncharged fatty acids

carboxylate salts

• have long nonpolar tail

• compatible with nonpolar greases and oils

Sodium palmitate

common soap ingredient

Irreversible

saponification under basic conditions is…

Micelles

soaps are able to emulsify fats and oils by forming … around oil droplets

Dispersion of oil droplets

enough soap molecules surrounding oil droplets facilitate the … in water where they can easily be washed away

Other methods of breaking down fat or oil molecules

• using lots of soap

• using hot water

• agitation

using lots of soap

could accommodate more fat molecules

Using hot water

can melt solid fats

Agitation

breaks down fats and oils into smaller droplets

Fats and oils

triesters of glycerol and three fatty acids

Fats, oils, and fatty acids

generally insoluble in water because of the presence of long hydrophobic tails

Methodology

• soap preparation (coconut oil + 15ml EtOH + 15ml 20% NaOH + heating & stirring + 50ml 30% NaCI solution)

• vacuum filtration

• comparison to distilled water (negative control) and commercial soap (positive control)

Vacuum filtration

• principle: formation of negative pressure at the outlet of the filtrate and using it as the driving force of filtration

  • accelerates the filtration process

• use: to obtain a filter residue with low moisture content

• used to create solid soap sample with as low moisture content as possible

expected result of soap

after being subjected to vacuum filtration, it should form white solid clumps with little to no moisture

Possible sources of error

• too much coconut oil was added

• a portion of the NaOH solution was not dispensed properly

• inadequate mixing

4 weeks

• curing time for soaps where they lose more water and become milder

• soaps become physically harder and longer lasting

pH 7-10

homemade or laboratory made soap should have this pH level range

Soaps with pH level greater than 10

considered lye heavy and can irritate or burn the skin

24 hours

saponification reaction takes around … and continues to become milder with time

Colloidal

when shaking the soap mixed with water, it is expected that the soap solution becomes … in nature

Agitation (by mixing)

concentrated the solution on the surface which causes foaming

Height of the foam

comparison of the foaming capacity of the soap samples is usually based on the … created after agitation

Soaps

• are surfactants

• reduces surface tension of the water making the water molecules less likely to stick together and more likely to interact with oil or grease

Surfactant

substances that reduce the surface tension in the liquid

Soaps

surround fat molecules

Hydrophilic part of soap molecules

interact with the water molecules in solution forming the outer surface of the micelle

Hydrophobic part of soap molecules

interacts with the oil trapping the oil in the center

As the soapy water is rinsed away

the oil/grease goes along with it

Soaps

less effective in hard water

Hard water

water that contains a significant concentration of Mg2+ and Ca2+ ions

Soap scum

Mg2+ and Ca2+ ions form precipitates with soap molecules which is often characterized as a gray line on a bathtub or sink called …

Mg2+ and Ca2+

• as the soap molecules form precipitates with these ions, most of the soap molecules are no longer present in solution

• result: less emulsification capacity and less foam formed

Soft water

• water that contains very few or no ions that precipitate with soap

• more soap molecules are available in solution that can interact with oil molecules, making soaps much more effective in soft water than hard water

Detergents

• similar to soap in that they also have a charged head group and a long hydrocarbon tail

• not prepared form natural fats or oils

• advantage: they work effectively both in soft and hard water as they do not form precipitates with Mg2+ and Ca2+

Sodium lauryl sulfate

a typical ingredient found in commercial shampoos and other cleaning products

Nonbiodegradable detergent

it was found out that they were not broken down in sewage treatment plants due to sodium lauryl sulfate being a …

Sodiumlaurylbenzenesulfonate

biodegradable detergents were developed substituting sodium lauryl sulfate with other biodegradable compounds like

Phosphate free

• some commercial detergents are also being advertised as being …

• advantageous for the environment as excessive amounts of phosphate in bodies of water accelerates the growth of algae which consumes too much of the dissolved O2 in water

• because of this, the ecosystem in these bodies of water are disturbed, also negatively affecting the species that inhibit these ecosystems

Lipid

• enter the body from the food that we eat

• broken down into small component for absorption

Lipid emulsification

primarily facilitated by bile salts

Amphipathic nature of bile salts

aid in the digestion of fat droplets in the body, preventing their reaggregation

Bile salts

stored in the gallbladder which is stimulated to contract and secrete the bile when food passes from the stomach into the duodenum

Bile salts

• steroidal detergents

• form mixed micelles with lipids, fats, and/or cholesterol and this enable the digestion and absorption of fats and fat soluble vitamins in the intestine