Triacylglycerols Many soft margarines stick margarines and solid shortenings are produced by the partial hydrogenation of vegetable oils Learning Goal Draw the condensed or lineangle structural formula for the products of a triacylglycerol that undergoes hydrogenation hydrolysis or s ID: 597216
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Slide1
17.4 Chemical Properties of
Triacylglycerols
Many soft margarines, stick margarines, and solid shortenings are produced by the partial hydrogenation of vegetable oils.
Learning Goal Draw the condensed or line-angle structural formula for the products of a triacylglycerol that undergoes hydrogenation, hydrolysis, or saponification.
General, Organic, and Biological Chemistry: Structures of Life,
5/eKaren C. Timberlake
© 2016 Pearson Education, Inc.Slide2
Triacylglycerols, Hydrogenation
In hydrogenation reactions, double bonds in unsaturated fatty acids react with hydrogen gas to produce carbon–carbon single bonds.
hydrogen gas is bubbled through the heated oil typically in the presence of a nickel catalyst.Core Chemistry Skill Identifying the Products for the Hydrogenation, Hydrolysis, and Saponification of a Triacylglycerol Slide3
Hydrogenation Reactions
In commercial hydrogenation,the addition of hydrogen is stopped before all the double bonds in a liquid vegetable oil become completely saturated.
the partial hydrogenation of a liquid vegetable oil changes it to a soft, semisolid fat.the more saturated product has a higher melting point.Slide4
Study Check
What product or products are obtained from the complete hydrogenation of glyceryl trioleate?A. glycerol and three oleic acids
B. glyceryltristearateC. glycerol and three stearic acidsSlide5
Solution
What product or products are obtained from the complete hydrogenation of glyceryl trioleate?B. glyceryltristearateSlide6
Chemistry Link to Health:
Hydrogenation and
Interesterification
Unsaturated fatty acids can be cis, with bulky groups on the same side of C C.
trans, with bulky groups on opposite sides of
C C.
General, Organic, and Biological Chemistry: Structures of Life,
5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.Slide7
Hydrogenation, Trans Fatty Acids
During hydrogenation, double bonds are converted to C — C single bonds.a small number of the cis double bonds are converted to more stable trans double bonds, causing a change in the overall structure of the fatty acids.
In the body, trans fatty acids behave like saturated fatty acids.are estimated to be 2–4% of our total calories.raise LDL-cholesterol and lower HDL-cholesterol.Slide8
Hydrogenation, Trans Fatty AcidsSlide9
Trans Fatty Acids in Foods
Foods containing naturally occurring trans fatty acids include milk, eggs, and beef.Foods that contain trans fatty acids from the hydrogenation process include deep-fried foods.bread, baked goods, and cookies.
crackers and chips.stick and soft margarines.vegetable shortening.Slide10
Study Check
Which of the following statements are true and which are false?A. There are more unsaturated fats in vegetable oils.
B. Vegetable oils have higher melting points than fats.C. Hydrogenation of oils converts some cis double bonds to trans double bonds.D. Animal fats have more saturated fats.Slide11
Solution
Which of the following statements are true and which are false?A. True
There are more unsaturated fats in vegetable oils.B. False Vegetable oils have higher melting points than fats.C. True Hydrogenation of oils converts some cis double bonds to trans double bonds.D.
True Animal fats have more saturated fats.Slide12
Study Check
Draw the condensed structural formula for the product of a glyceryl tripalmitoleate that undergoes hydrogenation
.Slide13
Solution
Draw the condensed structural formula for the product of a glyceryl tripalmitoleate that undergoes hydrogenation.
glyceryl tripalmitoleate Slide14
Interesterification
Interesterification
is a newer process used to change unsaturated vegetable oils into products that have the properties of solid and semisolid saturated fats.are used to hydrolyze ester bonds in triacylglycerols of vegetable oils using lipase enzymes so that glycerol and fatty acids are formed.The saturated fatty acids then recombine with glycerol.Slide15
Interesterification
During
interesterification, an unsaturated oleic acid in a vegetable oil could be replaced by a saturated stearic acid, which results in a more saturated fat with a higher melting point. Slide16
Hydrolysis
Triacylglycerols are hydrolyzed (split by water) in the presence of strong acids such as HCl or H2SO4
, or digestive enzymes called lipases. The products of ester hydrolysis are glycerol and three fatty acids.The polar glycerol is soluble in water, but the fatty acids with their long hydrocarbon chains are not.Slide17
HydrolysisSlide18
Saponification and Soap
Saponificationis the reaction of a fat with a strong base such as NaOH in the presence of heat.
splits triacylglycerols into glycerol and the sodium salts of fatty acids.is the process of forming “soaps” (salts of fatty acids).gives solid soaps that can be molded into different shapes when mixed with NaOH.gives softer, liquid soaps when mixed with KOH.Slide19
Saponification and SoapSlide20
Organic and Lipid ReactionsSlide21
Study Check
Write the equation for the reaction catalyzed by the enzyme lipase that hydrolyzes glyceryl trilaurate
(trilaurin) during the digestion process.Slide22
Solution
Write the equation for the reaction catalyzed by the enzyme lipase that hydrolyzes glyceryl trilaurate (trilaurin
) during the digestion process. glyceryl trilaurate