Question

Organic Chemistry Help!

Questions and Exercises 1. In the course of reflux of the triglyceride in a sodium hydroxide solution you will notice a lot of foaming. Explain. What is left behind in the aqueous layer after filtration of the saponification product? The starting material and the product of the saponification reaction have similar melting points. How do you know you actually isolated a new product rather than just recovered the starting material? Give at least two different methods to show this. Can a triglyceride be chiral? Explain your answer. What is the structure of the original triglyceride in Crisco/margarine? What information could you obtain from the IR spectra of the isolated products? 2. 3. 4. 5. 6. Experiment s. Part l: Saponification of a Triglyceride Experimental Techniques . Reflux . Vacuum filtration Soap making imvolves hydroysis of a trigbceride (a fat) ro ids component alcohol (sbcerol) and sodism or pofassium satr of the either acid-catalyzed or base-mediated. corresponding alcohol and salt of the carboxylic acid. In order to isolate the acid, we have to acidify the carbaxpylic acld by treatment with an aqweous ase. An ester can be hydrolyzed to the corresponding alcohol and carboxylic acid. Hydrolysis can be Under basic conditions, the base is used as a stoichiometric reagent. Reaction products are the solution (Scheme 6.1) NaOH R'OH Scheme 5.2.1 The mechanism of hydrolysis involves attack of a hydroxide ion at the carbonyl carbon to form a negatively charged tetrahedral intermediate (Scheme 6.2). The intermediate eliminates alkoxide ion to produce the corresponding carboxylic acid. Finally, in an acid-base reaction, the alkoxide ion removes the acidic proton from the carboxylic acid to give alcohol and carboxylate ion. The reaction proceeds to completion because the carboxylate ion, being negatively charged, is not readily attacked by nucleophiles such as R-OH, which is the other saponification product. The carboxylic acid can be isolated upon acidification of the solution with a strong acid (for example, HC) 0 OH + ROH +ROH Scheme 5.2.2 The reaction is called saponification since it is used to convert a fat into a soap. In this experiment, your task is to saponify the triglyceride isolated and purified in the previous experiment, and to isolate, purify and identify the fatty acid (Scheme 5.2.3), The products of saponification will be glycerol and sodium salt of the corresponding acid. The acid will then be precipitated by acidification of the solution. The most common fatty acids found in natural fats contain 12 to 18 carbon atoms NaOH 0-0-R но Scheme 7.2.3 PROCEDURE Caution Sodium hydroxide solution can cause burns. On contact with skin it will produce a "soapy" feeling. In the case of skin contact, wash skin under running water for at least 15 minutes. Hydrochloric acid can cause skin burns. In the case of skin contact rinse with running water for at least 15 minutes. Diethyl ether, hexanes, methanol and ethanol are all highly volatile and flammable solvents. Use no flames in the laboratory during this experiment. I. Place 1.0 g of the triglyceride (Crisco or margarine), 25 mL of a 20% sodium hydroxide solution, 10 mL of ethanol and a stirring bar in a 100 mL round bottom flask. Attach a reflux condenser to the flask (Figure 5.2.1). Heat the mixture at reflux for 30 minutes. Remove the flask, transfer the contents to a 250 mL beaker, add 100 mL of water and cool it in an ice bath. 2. 3. 4. 5, Cautiously acidify the mixture (test with pH paper) by adding 20% hydrochloric acid in small portions, 6. Use a Büchner or a Hirsch funnel to vacuum filter the cold suspension (Figure 5.2.2), wash the solid 7. Weigh the dry product and calculate percent yield of the isolated acid. with stirring. on the funnel with a small amount of cold water, and spread it on a piece of filter paper to dry.

Answer 1

Triglyceridu, İs an ester derived from glyce rol & three Rhratii t Alkaline hydrolysis of hriglyceride (ie caponification) to form Sodium salt o long chain fatty auid (the produt cared spor Hene, duriag the sagoni fication proces lot of Foam of produei will be Formed 田曰 + 3 NaOH ㅡ스 o-t-R Triglyceride By-Produet apocat produot 2) AIhation the sod um salt f long chain faty auid Afte can be isolated by RIation The by-produut glycerol Left be hind in aquous Filtrahe, due to its sdubility in waker 3) ⓐ You can check the sap-Valuuof the produit, by classical analysis meted you will shos the sap-valu That means, unacted stains compond euill e Present. (thar kst speciolly Fur esrer compound) Neutralised the produst br usin HC1 - soluhion Then , Athtr reased wh NaH co , lot of ettervescence of co- br li Ơbserved.[if Procluer will formed] A) Yes, riglyceride can be chiral rt the RLtR3. Then the cen halcarbon of iglyceride will be chtral due h。Four different group attached. 0 o--R3 central carbon atom autom-