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Experiment 24:

Experiment 24:. SYNTHESIS AND GC ANALYSIS OF FATTY ACID METHYL ESTERS. Objectives:. To synthesize fatty acid methyl esters through transesterification of an unknown vegetable oil. To purify your product using column chromatography.

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Experiment 24:

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  1. Experiment 24: SYNTHESIS AND GC ANALYSIS OF FATTY ACID METHYL ESTERS

  2. Objectives: • To synthesize fatty acid methyl esters through transesterification of an unknown vegetable oil. • To purify your product using column chromatography. • To identify and analyze the purity of your compound using TLC and GC analysis. • To identify the unknown oil based on fatty acid methyl ester composition.

  3. CHEMICAL EQUATION(Hydrolysis of a fat)

  4. CHEMICAL EQUATION(Transesterification of vegetable oil)

  5. COMMON FATTY ACIDS Saturated= NO double bonds! Monounsaturated= ONE double bond! Polyunsaturated= >one double bond!

  6. SHAPES OF FATTY ACIDS More cis double bonds = more “bent” shape

  7. EXPERIMENTAL PROCEDURE(Synthesis) • Add 10 dropsofunknown oil and methanol to vial with stir bar. • Add 1M KOH/methanol. • Stir in heat block. • Attach reflux condenser. • Heat to reflux. Maintain temperature b/n 70-80oC for 30 minutes. • Cool flask.

  8. EXPERIMENTAL PROCEDURE(Purification and Isolation) • DO NOT add Saturated NaCl to vial. • Extract product • 2X with hexane • 1X with 9:1 hexane: diethyl ether. • After each extraction step, pass organic layer through SiO2 column into a small test tube. • Proceed to PRODUCT ANALYSIS. MODIFICATION

  9. EXPERIMENTAL PROCEDURE(Product Analysis) • TLC Analysis • Perform analysis of product along with provided standards of the unknown oil and FAMEs solutions. • Must use 10% H2SO4 stain with heat in order to visualize spots. • Have stained TLC plate inspected by lab instructor. • GC Analysis • With instructor permission, prepare sample for GC analysis.

  10. GC ANALYSIS OF FAMES STANDARD SOLUTION • Once returned, identify and quantify FAMEs present in your unknown oil. • Compare these results to table on p. 201 in order to identify your unknown oil.

  11. Table 24.1 Be sure to give CENTIMETER measurements for ALL spots and give measurement for SOLVENT FRONT on this diagram!

  12. Table 24.2

  13. RELATIVE COMPOSITION OF OILS

  14. Table 24.3

  15. SAFETY CONCERNS CAUTION: • SULFURIC ACID and POTASSIUM HYDROXIDE are very corrosive! • HEXANE and DIETHYL ETHER are extremely flammable! • METHANOL is very flammable and toxic!

  16. WASTE MANAGEMENT • All liquid waste in container labeled “ORGANIC WASTE (FAMEs). • Leave TLC plates with instructor. • Place filter papers in the yellow SOLID WASTE can. • Place used TLC capillaries, SiO2 columns, and glass Pasteur pipets in broken glass container.

  17. CLEANING • Rinse all glassware with wash acetone ONLY! • DO NOT return any glassware to lab drawer dirty or wet!

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