FUN EXPERIMENT 5: Lipid

Abstract:

Saponification number primarily serves to determine the proportion of fatty acid esters in the sample. Saponification number also used as an indicator to fatty acid chain length in triglyceride. This number can be measured by the concentration of KOH used to complete the hydrolysis of one gram of fat or oil. Triglycerides containing high fatty acid number will have a lower saponification number than triglycerides with low fatty acids number. In this experiment, corn oil were used as a sample of triglycerides. From the experiment, corn oil shows higher saponification number which is meant corn oil have lower fatty acid chain in triglycerides.The application of using lipid is by making soap. Soap is known as an excellent emulsifier due to its amphipathic structures molecules where it has hydrophilic head group and hydrophobic portion group. This structure becomes nonpolar hydrocarbon portion of the micelled that will break up the nonpolar dirt/grease molecule. 

Introduction:

Triglyceride is an ester composed glycerol and three fatty acids. It is a blood lipid that helps bidirectional transference of adipose fat and blood glucose from liver. There two categories of triglycerides; saturated and unsaturated. Saturated compounds contain high amount of hydrogen in the molecule. Meanwhile unsaturated compounds contain double bonds between the carbon atoms (C=C) which reduce the number of places where hydrogen atoms can bond to carbon atoms. Saponification is the process of making soap. Meanwhile, saponification number which  also referred as “sap” shows the number of potassium hydroxide required in milligrams to saponify 1 g of fat under specified condition.

1) Saponification of triglycerides

Procedure:

Results: 

Discussion:

           Saponification number is a measure of the total free and combined acids especially in a fat, wax, or resin expressed as the number of milligrams of potassium hydroxide required for the complete saponification of one gram of substance. Throughout this experiment, corn oli have higher saponification number compared to palm oil. According to Lewkowitsch (1922), the actual saponification number of palm oil is higher than the number of saponification in corn oil. The actual saponification of corn oil is between 188-193 mg while saponification number of palm oil is in range between 196-205 mg. The high saponification number of corn oil is due to the large proportion of lauric acid and myristic acid that they contain. According to Niir Board (2002), oleic acid and linoleic acid usually comprise over 80% of the fatty acids in a ratio 1:2 – 1:3. Linoleic acid is either absent or present in traces. Palmitic acid is the main saturated fatty acid (10%). The triglycerides are mainly di- and triunsaturated. 
         In this experiment, The difference in the molar amount of HCl used to neutralize the control and the amount of HCl used to neutralize the sample equivalent to the molar amount of KOH used to saponify the test sample because one mole of HCl reacts with one mole of KOH. Thus, the test sample requires more acid to neutralize it because it contains more alkali than the control. Since the ratio concentration of HCL and KOH is 1:1 reaction, so the moles of KOH and HCl are equivalent.

Conclusions:

In a conclusion, the highest saponification number in corn oil indicates its fatty acid chain length in triglyceride is lower.




2) Application: Making soap


Procedure: 

Corn Oil weighted

NaOH added

Results:

Soap 1

Soap 2

Discussion: 

            In this experiment, we used corn oil to make soap. Soaps are mixtures of sodium or potassium salts of fatty acids which can be derived from oils or fats by reacting them with an alkali (such as sodium or potassium hydroxide) at 80°–100 °C in a process known as saponification. Each soap molecule has a long hydrocarbon chain, sometimes called its 'tail', with a carboxylate 'head'. In water, the sodium or potassium ions float free, leaving a negatively-charged head.

Soap is known as an excellent cleanser because of its ability to act as an emulsifying agent. An emulsifier is capable of dispersing one liquid into another immiscible liquid. This means that while oil (which attracts dirt) doesn't naturally mix with water, soap can suspend oil/dirt in such a way that it can be removed. Soap can act to disperse dirt/grease by its amphipathic molecules structure because it has a hydrophilic head group and hydrophobic portion. The organic part of a natural soap is a negatively-charged, polar molecule. Its hydrophilic (water-loving) carboxylate group (-CO₂) interacts with water molecules via ion-dipole interactions and hydrogen bonding. The hydrophobic (water-fearing) part of a soap molecule, its long, nonpolar hydrocarbon chain, does not interact with water molecules. The hydrocarbon chains are attracted to each other by dispersion forces and cluster together, forming structures called micelles. In these micelles, the carboxylate groups form a negatively-charged spherical surface, with the hydrocarbon chains inside the sphere. Because they are negatively charged, soap micelles repel each other and remain dispersed in water.

Grease and oil are non polar and insoluble in water. When soap and soiling oils are mixed, the non polar hydrocarbon portion of the micelles break up the nonpolar oil molecules. A different type of micelle then forms, with non polar soiling molecules in the center. Thus, grease, oil and the 'dirt' attached to them are caught inside the micelle and can be rinsed away.

           In saponification, boiling the oil (triglycerides) will react with alkali (potassium hydroxide) to produce glycerol and fatty acids salts. Triglycerides exist in the organic phase while the hydroxide exists in the aqueous phase. By increase stirring, the reactants will happen to be in the same phase. Therefore, the oils can be hydrolyzed to form glycerol and fatty acid salts. So, glycerol and fatty acid salts which having distance different solubility in both phases can be formed. The reagent will increase in concentration in the phase which is most favored by the other as the reaction progress.

Conclusion:

Soap can act to disperse dirt/grease by its amphipathic molecules structure where it has a hydrophilic head group and hydrophobic portion. This structure becomes nonpolar hydrocarbon portion of the micelled that will break up the nonpolar dirt/grease molecule. 

Reference:

1. Anne Marie Helmenstine. How Soap Cleans, Soap is an Emulsifier. Retrieved from   

             http://chemistry.about.com/od/cleanerchemistry/a/how-soap-cleans.htm

2. Structure of Lipids. Retrieved from http://dwb.unl.edu/Teacher/NSF/C10/C10Links/mills.edu/RESE 

           ARCH/FUTURES/JOHN B/struct urefunction/724.html

3.  Soap. Retrieved from http://www.chemistryexplained.com/Ru-Sp/Soap.html

4. Lewkowlts, J.(1922). Chemical Technology and Analysis of Oils,Fats and Waxes. London, Macmillan. 

             Retrieved from http://www.journeytoforever.org/biofuel_library/fatsoils/fatsoils2.html

5. Niir Board (2002). Oils, Fats & Its Derivatives. Delhi : Asia Pacific Business Press Inc. Retrieved from      http://books.google.com.my/booksid=rChwMIJHdE8C&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

6. Triglycerides. Retrieved from http://en.wikipedia.org/wiki/Triglyceride

7. Saponification value. Retrieved from http://en.wikipedia.org/wiki/Saponification_value