Oils and Fats Major Component (%95-99) Triglycerides Minor Components (%1-5) Triglyceride Derivatives Glycerol Free Fatty Acids Mono- and Diglycerides Non-Triglyceride Derivatives Phospholipids Sterols Pigments Vitamins Antioxidants Oxidation Products Trace Metals Hydrocarbons

Triglyceride Structure O C - R1 triacylglycerol = - R2 - R3 HC H2C OH glycerol HC H2C HO - C O - R1 3 fatty acids + - R3 - R2 +3H20 O R One chiral carbon with 1-3 acyl groups simpler stereochemistry than sugars - C more possible substituents acyl

Saponification General reaction Fat + Base  Soap + glycerine Base = chemical that contains OH at the end Creating soap from fats or oils. Soaps are usually made from vegetable fats and oils. These consist of 3 fatty acid chains, held together by a glycerol molecule. Fatty acid glycerine

Triglycerides differ from each other in regard to Number of Carbon Atoms in fatty acid chains Number of double bonds Isomerization Distribution of FA on glycerol backbone

How are soaps made?

This reaction is basically the opposite of an esterification Esterification – remove HOH to connect molecules Saponification – Add NaOH to break molecules Esterification Saponification H HO Na HO

The sodium part has a + and – charge, so it’s polar at this end. What is a soap? Because a soap molecule has a long carbon chain, it is partially nonpolar. The sodium part has a + and – charge, so it’s polar at this end. On end can attract polar molecules like water (hydrophilic), the other end can attract nonpolar molecules like oil (hydrophobic) Nonpolar + Polar Na Attracts oil Attracts water

Saponification Reaction: Fat + Lye  Soap + Glycerol

Lye - Caustic solution made from ashes. Soda Lye = NaOH Potash Lye = KOH Combining potash K2CO3 with slaked lime Ca(OH)2 yields KOH and CaCO3 NaOH obtained from reacting sodium compounds.

O H C17H35-C-O-C-H + NaOH  O H Fat Lye (Triglyceride)

O H C17H35-C-ONa H-C-OH O C17H35-C-ONa + H-C-OH H Soap! Glycerol

How does it happen?? O Break the ester linkages C – O- by hydrolyzing the bonds between the carbon backbone and the fatty acid chains. (Reversal of esterification reaction) Form the sodium salt of a fatty acid (soap) and a trihydroxy alcohol (glycerol).

The Chemistry http://en.wikipedia.org/wiki/Saponification

If oil is added to water, the two liquids do not mix. Because of this, grease stains can be difficult to remove during washing. soap molecule Soaps are compounds which act as emulsifiers. This means that they help the oil to mix with the water. water oil

How do soaps work?

Organic Reaction: Slow! Must break covalent bonds. Refluxing: Technique which allows a volatile solvent to boil, condense and return to the reaction vessel. It helps to maintain a fairly constant temperature throughout the reaction period.

Strange but true… Fat in cadavers: saponifies if conditions are right. Alkalai environment, moist, minimal oxygen. Adipocere or grave wax is formed.

Saponification Value Saponification - hydrolysis of ester under alkaline condition. The saponification value of an oil or fat is defined as the number of mg of potassium hydroxide (KOH) required to neutralize the fatty acids resulting from the complete hydrolysis of 1 g of the sample.

Saponification Value Determination Saponification # --mgs of KOH required to saponify 1 g of fat. 1. 5 g in 250 ml Erlenmeyer. 2. 50 ml KOH (0.5 N) in Erlenmeyer. 3. Boil for saponification. 4. Titrate with HCl (0.5 N) using phenolphthalein. Conduct blank determination. B - ml of HCl required by Blank. S - ml of HCl required by Sample. N- Factor of 0.5 N HCL.