SAPONIFICATIONSHEANNEN NICOLE L. TAN11DEPARTMENT OF CHEMICAL ENGINEERING, COLLEGE OF UNIVERSITY OF THE PHILIPPINES, DILIMAN, QUEZON CITY 1101, PHILIPPINES DATE SUBMITTED: 7 April 2015 DATE PERFORMED: 13 April 2015

ANSWERS TO QUESTIONS

Discuss:

1. Show and briefly discuss the mechanism of saponification.

The reaction mechanism is based on nucleophilic acyl substitution. Attack of the hydroxyl anion on the carbonyl group of the ester gives an orthoester:

The carbonyl group reforms with generation of a carboxylic ester and an alkoxide:

This alkoxide is less acidic than the acid and proton transfer takes place in step three.

2. Why does the curing process take a long time?

3. What is a surfactant? Why are surfactants used in manufacturing soaps?Surfactant means surface active agent. They are used in making soaps because they reduce the surface tension of water, they adsorb at the liquid gas interface, allowing lathering to take place. Lathering is desired in soaps.

4. How do soaps act as cleansing agents?Soaps dissolve in water. They loosen, emulsify (dispersing in water) and hold soil in suspension until it can be rinsed away. Soaps have both hydrophobic and hydrophilic ends. Hydrophilic part of the molecule is attracted to water while non-polar ends connects with fat/dirt. Mechanical rubbing of hands loosen the dirt and allows the soap micelle to trap the dirt. Micelle form, a spherical structure with the polar portions of molecules on the surface with a non-polar center is attracted to water and carried away from the surface.

5. Why is it not advisable to use carboxylate-containing soaps. (e.g. soaps with stearate salts) with hard water?It is not advisable to use carboxylate-containing soaps with hard water because hard water contains magnesium and calcium ions. These ions will react with the carboxylate and form white or grey precipitates with the reaction shown below.

When these precipitates form, there will be no lather that will form unless all calcium and magnesium ions have reacted. The soap will be wasted and drains will be clogged by water insoluble precipitates.

6. Give atleast two examples of water-softening soap additives.EDTA will make the calcium and magnesium ions into complexes which will not react with the carboxylate, therefore it can lather freely. Another example is sodium carbonate, these will react with calcium and magnesium ions to form calcium carbonate and magnesium carbonate. These products form readily than carboxylates, therefore may prevent reaction with soap.

REFERENCEShttp://www.tutorvista.com/content/chemistry/chemistry-iii/hydrogen/hard-and-soft-water.phphttp://www.chagrinvalleysoapandsalve.com/idascorner/soap/why-do-handmade-soap-and-shampoo-bars-need-to-cure