LipidsBy Group 35I. ObjectivesTo be able to:Determine properties of lipids.Determine solubility of substances given in water and organic compounds.
II. Data results and discussion A. Solubility testSampleSolvent UsedResultExplanationCottonseed oilDistilled water- Not solubleDistilled water is not soluble in cottonseed oil because water is a polar substance while cottonseed is a non-polar substance.Ethyl alcohol- Not solubleEthyl alcohol is not soluble in cottonseed oil because ethyl alcohol is a polar substance while cottonseed is a non-polar substance.Ether- Soluble - 2 secondsEther is soluble in cottonseed oil because both of them are non-polar substances.Chloroform- Soluble- 5 secondsChloroform is soluble in cottonseed oil because both of them are non-polar substances.Benzene- Soluble- 8 secondsBenzene is soluble in cottonseed oil because both of them are non-polar substances.5% HCl- Not solubleHCl is not soluble in cottonseed oil because HCl is a polar substance while cottonseed is a non-polar substance.5% NaOH- Soluble- 4 secondsNaOH is soluble in cottonseed oil because both of them are non-polar substances.discussionSolubility test is used to determine if cottonseed oil are soluble or insoluble in both organic and inorganic compounds. Such as water, ethyl alcohol, ether, chloroform, benzene, HCl and NaOH.
B.Test for UnsaturationTest SolutionsReagents AddedResultExplanationOleic Acid- Br2 in CCl4The faint orange color appeared after 4 mins. and 10 sec. with 20 drops.The result was positive because there was no white precipitate formed.Palmitic Acid- CHCl3- Haus IodineColor did not disappearThe result shows a negative result because it did not react.Oleic Acid- CHCl3- Haus IodineColor did not disappearThe result shows a negative result because it did not react.Cottonseed Oil- CHCl3- Haus IodineColor did not disappearThe result shows a negative result because it did not react.DiscussionC.Acrolein TestTest SolutionsReagents AddedResultExplanationGlycerolKHSO4 (s)Burned odorThe result was positive because it gave off a pungent odor.Cottonseed OilKHSO4 (s)Pungent irritating odorThe result was positive because it gave off a pungent odor.discussionD.Rancidity TestTest SolutionsReagents addedResultExplanationFresh coconut oilPhenolphtalein-Insoluble- did not mix -looks like oilMethyl orange-insoluble-orange and oilpH paper-blue litmus paper turned to redRancid coconut oilPhenolphtalein-formed an orange colorMethyl orange- Orange but circlepH paper-blue litmus paper turned to reddiscussionE.SaponificationTest SolutionsReagents AddedResultExplanationCoconut oil10% KOHFormed a gelatinous massdiscussionF.Properties of SoapName of TestTest SolutionsReagents AddedResultExplanationSalting-outSoap solution10% HCl-formed a white substance-smells like coconutFormation of Fatty AcidsSoap solution5% CaCl2-formed into a cloudy white solution with bubble on the wall of the test tubeInsoluble SoapsSoap solution-cloudy solution with white precipitate formedDetergent- white precipitate was formed in the cloudy solutiondiscussionG.Liebermann- Burchard TestTest SolutionsReagent AddedResultExplanationCholesterol-2mL chloroform-10 drops of acetic anhydride-2-3 drops of concentrated sulfuric acidFirst, it turned to orange then it changed to very dark blue then blue then green and lastly it changed to blue green.discussionH.Emulsifying ActionTest SolutionsReagents AddedResultExplanation2% AlbuminCholesterol-dissolved in albuminCholesterol- lecithin-formed no layer. No formation of solid like fatty acid.discussionAnswers to questions1. Why are fatty acids insoluble in water?Fatty acids consist of long, unbranched hydrocarbons with a carboxylic acid group at one end. Fatty acids made up of ten or more carbon atoms are nearly insoluble in water.
2. Explain why the cis-form is the predominant configuration of unsaturated fatty acids.If the double bond is a cis bond the carbon atoms are on the same side this causes a kink in the chain allowing different and more rigid shapes to be formed. A trans bond has the carbon atoms on opposite sides leaving the structure similar to the saturated form, with just a bit more rigidity. trans fatty acids are generally a product of processing (hydrogenation) not normally found naturally making them difficult to digest properly.
3. What type of rancidity occurs in vegetable shortenings? How can it be prevented?The type of rancidity that occurs in vegetable shortenings is oxidative rancidity. It can be prevented thru keeping it clean.
4. Show the structure of the parent compound of cholesterol. OHCH3CH3
5. Explain the cooperative effect of lecithin and albumin.Lecithin is an emulsifier consisting of a variety of ingredients, the active components being phospholipids - these are long chain polar lipids. The emulsifying properties of lecithin result from this combination of a polar (hydrophilic) group attached to a non-polar (hydrophobic) lipid chain, and means that they can help disperse an oil phase into an aqueous solution or vice versa, creating an emulsion (oil-in-water or water-in-oil respectively). These emulsions are not solutions, but rather are very well dispersed micro-droplets of the secondary phase, and this explains why emulsions are opaque rather than completely transparent (think of a vinaigrette). Albumins are water-soluble proteins - massive polar molecules - and I expect work by a similar mechanism.
conclusionI therefore conclude that lipids possess different properties that can be determined through different tests or experiments. For instance, solubility test using cottonseed as the solvent in the experiment. It showed that lipids are insoluble in water but is soluble in organic compounds such as in ether and alcohol. Another experiment performed was a test to determine the unsaturation of a substance. This test shows how unsaturated a lipid is, to show how much double bonds it has and the more halogens it can absorb. Acrolein test is a test used to determine the formation of acrolein which is observable through a smell that is a pungent irritating odor. A product that was released thru dehydration is glycerol. Rancidity test is a test that indicates the presence of lipids. A positive test is shown if it gave off a rancid odor which can be smelled when exposed to air at room temperature.