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Experiment #8: Making Soap: Base-Catalyzed Hydrolysis of a TriglycerideAnnie HallChemistry 106 Lab APartner: Julianne DarceyNovember 12, 2012
Abstract: The purpose of this experiment was to perform a saponification reaction to prepare a simple soap from a vegetable oil. The emulsifying properties of the soap were tested and what happens to soap in hard or acidic water was investigated. The properties of the prepared soap were studied and comparisons were made between the soaps produced from different types of oils. The oil used in this experiment was grape seed oil. The primary fatty acid in grape seed oil is linoleic acid. The soap made from this oil was a light yellow color and had a flakey, but soft, look to it. This was a good emulsifier because oil and water were able to mix in the presence of the soap, whereas they are not able to mix by themselves. When the hard water mineral, CaCl2, was added to the soap, the solution turned into a white, solid precipitate. This product was insoluble. When the hard water mineral, MgCl2, was added to the soap, the solution turned to a cloudy white mixture. When an acidic mineral, such as FeCl3, was added to the soap the solution turned into a peach colored liquid. Background: A fatty carboxylic acid has a carboxylic acid group that contains a long carbon chain that varies in length and may contain double bonds. A fatty acid that contains only single bonds is a saturated fatty acid, whereas a fatty acid that contains one or more double bonds is an unsaturated fatty acid. Triglycerides are the main ingredients of vegetable oils (unsaturated) and animal fats (saturated). A triglyceride is an ester formed from glycerol and three fatty acids. Triglycerides are mechanisms in humans used to storeunused calories. Their high blood concentration correlates with the consumption of starchy and other high carbohydrate foods. Saponification will be used in this experiment in order to make a triglyceride in common vegetable oil into soap. In order for saponification to work the three ester bonds in the triglyceride must break through exposure to heat under basic conditions. An alcohol and a carboxylic acid are produced from the breaking of an ester bond. The carboxylic acid is deprotonated under basic conditions so that there is a negative charge
on the oxygen. This negatively charged oxygen is attracted to positively charged ions in the solution, such as sodium. The end result is a carboxylate salt of the fatty acid, or soap.