tailieunhanh - Lecture Organic chemistry: Chapter 25 - L. G. Wade, Jr.

After studying this chapter you will be able to understand: Classify simple and complex lipids. Identify waxes, triglycerides, phospholipids, steroids, prostaglandins, and terpenes; explain how unsaturations affect the properties of fats and oils. Compare the properties of saturated fats with those of polyunsaturated oils and partially hydrogenated vegetable oils; predict the reactions of lipids under basic hydrolysis and with standard organic reagents. | Chapter 25 Copyright © 2010 Pearson Education, Inc. Organic Chemistry, 7th Edition L. G. Wade, Jr. Lipids Chapter 25 Introduction Lipids are compounds that can be extracted from cells by nonpolar organic solvents. Complex lipids are easily hydrolyzed. Long-chain esters called fatty acids. Simple lipids are not easily hydrolyzed in acid or base. Steroids Prostaglandins Terpenes Chapter 25 Examples of Lipids Chapter 25 Waxes Esters of long-chain fatty acids with long-chain alcohols. Commonly found in nature. Spermaceti is found in the head of the sperm whale. Beeswax is a mixture of waxes, hydrocarbons, and alcohols that bees used to make their honeycomb. Carnauba wax is a mixture of waxes of high molecular weights. Chapter 25 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 . | Chapter 25 Copyright © 2010 Pearson Education, Inc. Organic Chemistry, 7th Edition L. G. Wade, Jr. Lipids Chapter 25 Introduction Lipids are compounds that can be extracted from cells by nonpolar organic solvents. Complex lipids are easily hydrolyzed. Long-chain esters called fatty acids. Simple lipids are not easily hydrolyzed in acid or base. Steroids Prostaglandins Terpenes Chapter 25 Examples of Lipids Chapter 25 Waxes Esters of long-chain fatty acids with long-chain alcohols. Commonly found in nature. Spermaceti is found in the head of the sperm whale. Beeswax is a mixture of waxes, hydrocarbons, and alcohols that bees used to make their honeycomb. Carnauba wax is a mixture of waxes of high molecular weights. Chapter 25 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 Glycerides Fatty acid esters of the triol glycerol. Tryglycerides are the most common glycerides and they are used for long-term energy storage in plants and animals. Fats Solid at room temperature. Most are derived from mammals. Oils Liquid at room temperature. Most are derived from plants or cold-blooded animals. Melting Points of Fatty Acids Chapter 25 Figure: Title: Structures and Melting Points of Some Common Fatty Acids Caption: Saturated fatty acids have melting points that increase gradually with their molecular weight. Notes: The presence of cis double bonds lowers the melting point. Chapter 25 Melting Points The cis double bond in oleic acid lowers the melting point by 66°C. A cis double bond bends the molecule, so it cannot pack efficiently. A trans double bond has less effect. Chapter 25 Fats and Oils Unsaturated triglycerides have lower melting points because their unsaturated fatty acids do .