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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
How are soaps made?
This reaction is basically the opposite of an esterification Esterification – remove HOH to connect molecules Saponification – Add Na. OH to break molecules Esterification H HO Saponification Na HO
What is a soap? Because a soap molecule has a long carbon chain, it is partially nonpolar. Nonpolar - + Polar Na Attracts oil Attracts water 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)
If oil is added to water, the two liquids do not mix. Because of this, grease stains can be difficult to remove during washing. Soaps are compounds which act as emulsifiers. soap molecule water This means that they help the oil to mix with the water. oil
How do soaps work?
Saponification Making Soap “Soaponification”
Saponification Reaction: Fat + Lye Soap + Glycerol
Lye - Caustic solution made from ashes. Soda Lye = Na. OH Potash Lye = KOH Combining potash K 2 CO 3 with slaked lime Ca(OH)2 yields KOH and Ca. CO 3 Na. OH obtained from reacting sodium compounds.
• 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.
Determination of Saponification Number On refluxing with alkali, triacylglycerols (fatty acid esters) are hydrolyzed to give glycerol and potassium salts of fatty acids (soap). Such process is known as, Saponification.
Determination of Saponification Number H 2 O Δ
Determination of Saponification Number • The saponification value is the number of milligrams of KOH required to neutralize the fatty acids resulting from the complete hydrolysis of 1 g of fat.
Determination of Saponification Number ■ The saponification value gives an indication of the nature of the fatty acids constituent of fat and thus, depends on the average molecular weight of the fatty acids constituent of fat. • The greater the molecular weight (the longer the carbon chain), the smaller the number of fatty acids is liberated per gram of fat hydrolyzed and therefore, the smaller the saponification number and vice versa.
Materials: 1 - Fats and oils (olive oil, coconut oil, sesame oil, and butter) 2 - Fat solvent (equal volumes of 95% ethanol and ether) 3 -Alcholic KOH (0. 5 mol/liter) 4 -Reflux condenser. 5 -Boiling water bath. 6 -Phenolphethalein. 7 -Hydrochloric acid (0. 5 mol/liter) 8 -Burettes (10 ml and 25 ml) 9 -Conical flasks (250 ml)
0. 5 mol/L HCL Phenolphthalein (Ph. ph) 25 ml alcoholic KOH 3 ml fat solvent 1 ml fat Heat flask on a boiling water bath for 30 min. Leave to cool to room temperature
Calculations: • The difference between the blank and the test reading gives the number of milliliters of KOH required to saponify 1 g fat. • You can use this formula to calculate the saponification value: 1 ml (0. 5 N HCl ) = 28. 05 mg KOH ( B-T ) = S ■ Saponification value (S) = ( B-T ) x 28. 05 = mg KOH/1 g Wt. of fat (1 g)
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