Experiment 10 - Saponification fats, soaps and detergents

Experiment 10 - Saponification fats, soaps and detergents -...

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Experiment 10 A. Saponification of esters B. Fats, soaps and detergents Lut Ming Cheng, 4957880, CHM2123, Section C Talal Zafar, 4827101, CHM2123, Section C TA: Wendy Campbell Due Date: December 1, 2008 1 – Theory and Mechanism Ester hydrolysis reaction can be conducted in acidic and basic conditions. When the reaction is accomplished under acidic condition, the yield of product is not efficient due to the presence of equilibrium distribution. On the other hand, the basic condition (also called the saponification reaction) is more advantageous in forming carboxylate and alcohol via an irreversible mechanism. In the first part of the experiment, saponification is conducted with an unknown ester. The basic mechanism is shown as follows, The neutralization equivalent of a saponification reaction is based on the quantity of ester that reacts with an equivalent amount of base. In the second part of the experiment, saponification of triacylglycerols is conducted. Triacylglycerols are heated with potassium hydroxide, its ester functions are then cleaved to produce glycerol and potassium salt of the carboxylic acid. R O O O O R 2 O O R 1 + O H - K + R O O O O R 2 O - O R 1 OH R O O O O - O R 1 R 2 O O H R O O O OH O R 1 R 2 O O - K + Neutralization equivalent (g/mol) = mass of ester (g) Equivalents of the base (moles) R O O R 1 O H - Na + R O - O R 1 O H R O O H + + O - R 1 R O O - + O H R 1 R O OH H O + H H O H R 1 + + O H 2
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Repeat saponification with the 2 remained ester groups O H OH OH R O O - K + + + + R 1 O O - K + R 2 O O - K + The potassium salts are soluble in water. They are called soft soaps with a syrupy-like liquid state. In order to obtain hard soap from a soft soap solution, sodium chloride is added to make the sodium soap to precipitate. R CO 2 K + NaCl R CO 2 Na + KCl Addition of calcium can also reduce the effectiveness of soap. The calcium salts of soap- forming carboxylic acid generally have low solubility in water. However, precipitation can be observed under the use of hard water. 2RCO 2 - + Ca 2+ (RCO 2 ) 2 Ca Soaps are also ineffective in strongly acidic conditions. An acid-base reaction produces the long chain carboxylic acid which is insoluble in water. The soaps are mixtures of carboxylate salts and acid, the product is usually a semi-solid or an oily mass which has no detergency. RCO 2 - + H 3 O + RCO 2 H H 2 O + Synthetic detergent is used in the last part of the experiment to compare the detergency of soaps. The synthetic detergent is the salts of alkylbenzenesulfonic acids, which express detergency in both hard and soft water. 2 – Table of Reagents A. Saponification of esters Compound Molar Mass (g/mol) Quantity Density (g/mL) mmol equiv. 9M NaOH 40.00 12.00 mL 2.10 630 1.0 95% ethanol 46.068 100.00 mL 0.789 1712.69 2.7 0.5 N Sulfuric acid 98.078 44.03 mL 1.84 826.03 1.3 Unknown ester - 1.30 g - - - B. Fats, soaps and detergents Compound Molar Mass (g/mol) Quantity Density (g/mL) mmol equiv.
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Experiment 10 - Saponification fats, soaps and detergents -...

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