Fat and oil are names for the same class of compounds, calledtriglycerides, whic
ID: 689705 • Letter: F
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Fat and oil are names for the same class of compounds, calledtriglycerides, which contain three ester groups where R, R', and R'' represent long hydrocarbon chains. (a) Suggest a reaction that leads to the formation of atriglyceride molecule, starting wwith glycerol and carboxylicacids. Refer to the structure of glycerol: (b) In the old days, soaps were made by hydrolyzing animal fatwith lye (a sodium hydrozide solution). Write an equation for thisreaction. (c) The difference between fats and oils is that at roomtemperature, the former are solids and the latter are liquids. Fatsare usually produced by animals, wheras oils are commonly found inplants. The melting points of these substances are determined bythe number of C=C bonds (or the extent of unsaturation) present -the larger the number of C=C bonds, the lower the melting point andthe more likely that the substance is a liquid. Explain. (d) One way to convert liquid oil to soild fat is thehydrogenate the oil, a process by which some or all of the C=Cbonds are converted to C-C bonds. This procedure prolongs shelflife of the oil by removing the more reactive C=C group andfacilitates packaging. How would you carry out such a process (thatis, what reagents and catalyst would you employ?) (e) The degree of unsaturation of oil can be determined byreacting the oil with iodine, which reacts with the C=C bond asfollows: The procedure is to add a known amount of iodine to the oiland allow the reaction to go to completion. The amount of excess(unreacted) iodine is determined by titrating the remaining iodinewith a standard sodium thisulfate(Na2S2O3) solution: I2 + 2Na2S2O3--> Na2S4O6 + 2NaI The number of grams of iodine that react with 100 grams of oilis called the iodine number: In one case, 43.8 grams ofI2 were treated with 35.3 grams of corn oil. The excessiodine required 20.6 mL of a 0.142 MNa2S2O3 for neutralization.Calculate the iodine number of the corn oil.Explanation / Answer
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