SYNTHESIS OF SOAP AND DETERGENT Ciara Maye A. Morales, John Ian V. Nacino, Dean Xavier C. New, Jason A. Ong, Mark Kenneth F. Ong and Leah Kristine C. Reyes Group 7 2B Medical Technology Organic Chemistry Laboratory
ABSTRACT Grease, oil and other non-polar substances are hard to clean with water alone. Soaps and detergents, however, can help in the cleaning due to their ampiphatic properties. This experiment then aims to synthesize soaps and detergents, as well as compare their behaviour in hard water. In order to synthesize soaps, the group used cooking oil and diluted NaOH which produced soap and glycerol molecules. On the other hand, dodecanol was added with sulfuric acid in order to synthesize detergents. The results from these synthesis yielded a white precipitate, which means that the reactions were completed and the salts were formed. The synthesized soap was an alkaline (sodium) salt while the detergent was a sodium dodecylsulfate, which is another sodium salt. When added to 1% CaCl2 and 1% MgCl2, the soap was insoluble and formed precipitates since it cannot interact with hard water which contains Ca 2+ and Mg2+ ions while the detergent was soluble due to its structure that enables it to interact with the hard water.
INTRODUCTION Soap is a salt of a compound known as a fatty acid. A soap molecule consists of a long hydrocarbon chain (composed of carbons and hydrogens) with a carboxylic acid group on one end which is ionic bonded to a metal ion, usually a sodium or potassium. The hydrocarbon end is non-polar and is soluble in non-polar substances (such as fats and oils), and the ionic end (the salt of a carboxylic acid) is soluble in water.
Figure 1. molecule
Condensed
structure
of
a
Figure 2. Condensed structure of a sodium alkylbenzene sulfonate (example of detergent)
soap
Soaps for cleansing are obtained by treating vegetable or animal oils and fats with a strongly alkaline solution. Fats and oils are composed of triglycerides; three molecules of fatty acids are attached to a single molecule of glycerol. The alkaline solution, often called lye, brings about a chemical reaction known as saponification. In saponification, the fats are first hydrolyzed into free fatty acids, which then combine with the alkali to form crude soap. Glycerol (glycerine) is liberated and is either left in or washed out and recovered as a useful byproduct, depending on the process employed. xujDetergents are structurally similar to soaps, but differ in the water-soluble portion. These substances are usually alkylbenzenesulfonates, a family of compounds that are similar to soap but are more soluble in hard water, because the polar sulfonate (of detergents) is less likely than the polar carboxyl (of soap) to bind to calcium and other ions found in hard water.
Figure 3. Condensed structure of a glycerol nonionic detergent
Figure 4. Condensed structure of a sodium alkyl sulfate Detergents, like soaps, work because they are amphiphilic: partly hydrophilic (polar) and partly hydrophobic (non-polar). Their dual nature facilitates the mixture of hydrophobic compounds (like oil and grease) with water. Because air is not hydrophilic, detergents are also foaming agents to varying degrees.
The cleaning action of both soaps and detergents results from their ability to emulsify or disperse water-insoluble materials (dirt, oil, grease, etc.) and hold them in suspension in water. This ability comes from the molecular structure of soaps and detergents. When a soap or detergent is added to water that contains oil or other water-insoluble materials, the soap or detergent molecules surround the oil droplets. The oil or grease is “dissolved” in the alkyl groups of the soap molecules while the ionic end allows the micelle to dissolve in water. As a result, the oil droplets are dispersed throughout the water (this is referred to as emulsification) and can be rinsed away.
Figure 5. A diagram of a soap micelle surrounded by water molecules. The lines in the center represent grease and oil. Soaps, will react with metal ions in the water and can form insoluble precipitates. The precipitates can be seen in the soapy water and are referred to as “soap scum”. This soap scum can form deposits on clothes causing them to be gray or yellow in color. To eliminate the metal ions in water, washing aids such as washing soda (sodium carbonate) and borax (sodium tetraborate) were added to the wash water. These compounds would precipitate the metal ions, eliminating most of the soap scum. With the discovery of synthetic detergents, much of the need for washing aids was reduced. A detergent works similar to a soap, but does not form precipitates with metal ions, reducing the discoloration of clothes due to the precipitated soap.
dodecanol (C12H25OH), (coconut oil)
ice,
vegetable oil
B. Procedure 1. Preparation of Soap Prepare a mixture of 30 mL of 6MNaOH and 50 mL of distilled water. Transfer these into a 500 mL beaker, heat using a small flame, and stir frequently. Add a total amount of 15 mL coconut oil in the mixture gradually and heat for about 15 to 20 minutes with stirring, just to ensure that water is replaced via evaporation. To test if the saponification is complete, add a drop of the mix into a milliliter of water. If the mix still exhibits a presence of coconut oil, heat again for 15 to 20 minutes along with stirring. Stir until the mixture is homogenous. Pour it into a 50 mL of cold, saturated solution of NaCl while still hot. As the soap forms, filter the precipitated soap through cheesecloth. The filtrate, a liquid, is now ready for glycerol test. Wash the collected soap in 5 mL ice cold water twice. Squeeze again to remove excess water. Dissolve in an evaporating dish, add 10 to 20 mL of water to dissolve soap, and evaporate into a jelly-like consistency. Cool and pour into a mold, and use this formed soap in hard water behavioral test. 2. Extraction of Glycerol Neutralize the filtrate, the liquid collected from a repeated squeezing of the soap, with diluted HCl. If it’s not clear, filter it. Evaporate it into small volume or a syrupy consistency and allow cooling down. Extract the syrup and add 95% ethanol then filter again. Evaporate the alcoholic extract in a water bath and now the residue that remained has glycerol.
A. Samples of compounds, solvents and solutions used
3. Test for Glycerol To the residue, add a pinch of potassium bisulfate (KHSO4). Heat the mixture strongly or at high temperatures. Take note of the odor released.
20% of NaOH, 6M NaOH, concentrated H2SO4, 1% CaCl2, 1% MgCl2, solid NaCl, saturated NaCl, phenolphthalein,
4. Preparation of Detergent In preparing the detergent, place 5 mL of dodecanol (C12H25OH) into a 100 mL
EXPERIMENTAL
beaker. Add gradually a total amount of 2 mL concentrated H2SO4 while stirring for about a minute after the acid is completely added and let stand for an additional of ten minutes.
Figure 6. Adding 5 mL of dodecanol in a 100 mL beaker Mix well 5 mL 6M NaOH with 10 mL of water and add four drops of phenolphthalein which may begin to fade in the presence of a strongly basic solution. After ten minutes have passed, add it now to the dodecanol-sulfuric acid mixture and stir until the tinge of phenolphthalein disappears. There should be a large amount of detergent formed.
excess water and prepare for hard water behavioural tests. 5. Behavior in Hard Water Place 5 mL of both soap solution and the detergent solution into two test tubes each sample. Add 2 mL 1% CaCl2 to detergent solution and soap solution. Do the same to the rest of the test tubes with 2 mL 1% MgCl2. Mix but do not shake the mixtures and note any precipitate formed if it does so. Add four drops of cooking oil to each tube, put a stopper and vigorously shake the four tubes. Observe and record any emulsifying ability of the soap and detergent in each tube. Indicate whether if formed suds as heavy, light, few, or none at all.
RESULTS AND DISCUSSION Upon performing the experiment, the following observations were noted and are summarized into table. Table 1. Properties of Soap and Detergent Color & Appearance Solubility in 1% CaCl2 Solubility in 1% MgCl2 Emulsifying Ability
Figure 7. The mixture attained a pink color due to the addition of phenolphthalein Fill a 250 mL of one third of ice and 10 g of NaCl and thoroughly mix. Add water until it reaches a total amount of 75 mL. Pour the detergent mixture to make it lump on the cold NaCl ice mixture. Then filter it in a three layered cheese cloth. Wash the collected detergent in two portions of water with10 mL each portion. Then finally squeeze to take off any
Soap White gelatin (solid) insoluble
Detergent White, amorphous (solid) Soluble
insoluble
Soluble
Slightly Emulsified (less suds)
Slightly Emulsified (more suds)
The table above shows that both the soap and detergent appeared as white solid. Their appearance is due to their chemical nature, in which soaps are alkaline salts, and detergents are sodium dodecyl sulfate.
Figure 8. Saponification
Reaction
Sequence
for
The reaction sequence shows that fats or oil underwent alkaline hydrolysis with NaOH and yielded glycerol and soap. The soap molecule contained sodium salts which accounted to its appearance and solubility in water. Its interaction with hard water showed formation of precipitates. Hard water contains Ca2+ and Mg2+ ions, which are both insoluble in water, and as sodium salts are water-soluble, their interaction yielded insoluble solids. Glycerol, the by-product, was determined by adding a pinch of powdered potassium bisulphate and heating the mixture. This reaction yielded a sweet, butter-like odor due to the presence of a fatty acid derivative in the mixture.
Figure 8. Reaction Sequence for the preparation of detergent. By reacting dodecyl alcohol (dodecanol) with sulfuric acid, dodecyl sulfate and water were formed. The product dodecyl sulfate was further converted to a sodium salt by alkaline hydrolysis with the use of NaOH. The resulting salt was a sodium dodecylsulfate, which attributes to its appearance as well as solubility in water. Detergents, when added to a 1% CaCl 2 and 1% MgCl2, were more soluble than soap. Both soaps and detergents displayed their emulsifying ability. Though the detergents produced more suds than soaps, the emulsified products proved that the oil was dissolved in their respective alkyl groups while their ionic ends made the molecules dissolve in water.
REFERENCES [1] Bayquen, A.P., Cruz, C.T., De Guia, R.M., Lampa, F.F., Peña, G.T., Sarile, A.S., Torres, P.C. (2009). Laboratory Manual in Organic Chemistry. Quezon City, Philippines: C & E Publishing, Inc. [2] David, K.A. (2000). The science of soaps and detergents. Retrieved on April 27, 2007 and September 21, 2012 from the World Wide Web. http://www.scribd.com/doc/61766809/Soap-andDetergent. [3] Detergents. Retrieved on September 21, 2012 from the World Wide Web. http://en.wikipedia.org/wiki/Detergent.
[4] Soap. Retrieved on September 21, 2012 from the World Wide Web. http://en.wikipedia.org/wiki/Soap.