Organic Chemistry,5th Edition L.G.Wade,Jr. Chapter 25 Lipids Jo Blackburn Richland College,Dallas,TX Dallas County Community College District ©2003，Prentice Hall
Chapter 25 Lipids Jo Blackburn Richland College, Dallas, TX Dallas County Community College District © 2003, Prentice Hall Organic Chemistry, 5th Edition L. G. Wade, Jr
Introduction Classified by solubility,not structure. Can be extracted from cells by nonpolar organic solvents. Complex lipids are easily hydrolyzed. >Waxes >Triglycerides Simple lipids are not easily hydrolyzed. >Steroids >Prostaglandins >Terpenes Chapter 25 => 2
Chapter 25 2 Introduction • Classified by solubility, not structure. • Can be extracted from cells by nonpolar organic solvents. • Complex lipids are easily hydrolyzed. ➢Waxes ➢Triglycerides • Simple lipids are not easily hydrolyzed. ➢Steroids ➢Prostaglandins ➢Terpenes =>
Examples of Lipids Examples of complex lipids Examples of simple lipids u-oCH)nct CH-O-C-(CH2)16CH3 -0-C(CHioCH HO tristearin,a fat cholesterol,a steroid ae-o&anm spermaceti(cetyl palmitate),a wax a-pinene,a terpene => Chapter 25
Chapter 25 3 Examples of Lipids =>
Waxes Esters of long-chain fatty acids with long-chain alcohols. Spermaceti is found in the head of the sperm whale and is probably used to control buoyancy. Most natural waxes are protective coats for plants'leaves,insects'exoskeleton, mammals'fur,and birds'feathers. => Chapter 25
Chapter 25 4 Waxes • Esters of long-chain fatty acids with long-chain alcohols. • Spermaceti is found in the head of the sperm whale and is probably used to control buoyancy. • Most natural waxes are protective coats for plants’ leaves, insects’ exoskeleton, mammals’ fur, and birds’ feathers. =>
Triglycerides Fatty acid esters of glycerol. ·Fats >Solid at room temperature >Most are derived from mammals 。Oils >Liquid at room temperature >Most are derived from plants or cold- blooded animals. => Chapter 25 5
Chapter 25 5 Triglycerides • Fatty acid esters of glycerol. • Fats ➢Solid at room temperature ➢Most are derived from mammals • Oils ➢Liquid at room temperature ➢Most are derived from plants or coldblooded animals. =>
Fatty Acids Unbranched carboxylic acids with 12-20 carbons. Most contain an even number of carbons because they are built from acetic acid units. Melting points increase with increasing molecular weights. Unsaturation greatly lowers the melting point. => Chapter 25 6
Chapter 25 6 Fatty Acids • Unbranched carboxylic acids with 12-20 carbons. • Most contain an even number of carbons because they are built from acetic acid units. • Melting points increase with increasing molecular weights. • Unsaturation greatly lowers the melting point. =>
Melting Points A cis double bond bends the molecule so it cannot pack efficiently. A trans double bond has less effect. COOH COOH stearic acid,mp 70C oleic acid.mp 4C > Chapter 25 7
Chapter 25 7 Melting Points • A cis double bond bends the molecule so it cannot pack efficiently. • A trans double bond has less effect. =>
Fats and Oils Most fats have saturated fatty acids. Most oils have unsaturated fatty acids. CH,-0-C CHO CH2-0一C tristearin,mp 72C CH2O CH,一0 => triolein,mp-4C Chapter 25 8
Chapter 25 8 Fats and Oils • Most fats have saturated fatty acids. • Most oils have unsaturated fatty acids. =>
Saponification ·“Soap-making' ● Base-catalyzed hydrolysis of ester linkages in fats and oils. 0 CH2-OH -o-(CHCH CH-OH H-0-C-CH6CH3】 CH2-OH +3 NaOH 0 CH2-0-C一(CH2)16CH3 +3Na+0-C-(CH2)16CH => Chapter 25 A soap 9
Chapter 25 9 Saponification • “Soap-making” • Base-catalyzed hydrolysis of ester linkages in fats and oils. CH O C O (CH2 )16CH3 CH2 O C O (CH2 )16CH3 CH2 O C O (CH2)16CH3 + 3 NaOH CH2 CH CH2 OH OH OH + 3 Na+ - O C O (CH2 )16CH3 A soap =>
Soap Structure Ionic head CO boundary of water into structure Hydrocarbon tail => Chapter 25 10
Chapter 25 10 Soap Structure =>