《有机化学》课程PPT教学课件（Official PPT of Organic Chemistry 6th LG Wade by Prentice Hall，L. G. Wade, Jr.）Chapter 20 Carboxylic Acids

Organic Chemistry,6th Edition L.G.Wade,Jr. Chapter 20 Carboxylic Acids Jo Blackburn Richland College,Dallas,TX Dallas County Community College District ©2006，Prentice Hall

Chapter 20 Carboxylic Acids Jo Blackburn Richland College, Dallas, TX Dallas County Community College District © 2006, Prentice Hall Organic Chemistry, 6th Edition L. G. Wade, Jr

Introduction Carbonyl (-C=O)and hydroxyl (-OH)on the same carbon is carboxyl group. Carboxyl group is usually written-COOH. Aliphatic acids have an alkyl group bonded to -COOH. Aromatic acids have an aryl group. Fatty acids are long-chain aliphatic acids. R-C-0-H+H,0:→ +H,O+ pK,=5 (K≡105) acid => 2 carboxylate

Chapter 20 2 Introduction • Carbonyl (-C=O) and hydroxyl (-OH) on the same carbon is carboxyl group. • Carboxyl group is usually written -COOH. • Aliphatic acids have an alkyl group bonded to -COOH. • Aromatic acids have an aryl group. • Fatty acids are long-chain aliphatic acids. =>

Common Names Many aliphatic acids have historical names. Positions of substituents on the chain are labeled with Greek letters. 0 -C-C-C-C-C-C-0H NH, CH3-CH一C一OH CH2一CH2-CH2-C一OH a-chloropropionic acid y-aminobutyric acid => Chapter 20 3

Chapter 20 3 Common Names • Many aliphatic acids have historical names. • Positions of substituents on the chain are labeled with Greek letters. =>

IUPAC Names Remove-e from alkane (or alkene) name,add -oic acid. The carbon of the carboxyl group is #1. CIO H CHCH-CHC-OH CC、 H COOH 2-chlorobutanoic acid trans-3-phenyl-2-propenoic acid (cinnamic acid) => Chapter 20 4

Chapter 20 4 IUPAC Names • Remove -e from alkane (or alkene) name, add -oic acid. • The carbon of the carboxyl group is #1. CH3 CH2 CHC Cl OH O 2-chlorobutanoic acid Ph C H C H COOH trans-3-phenyl-2-propenoic acid (cinnamic acid) =>

Naming Cyclic Acids Cycloalkanes bonded to -COOH are named as cycloalkanecarboxylic acids. Aromatic acids are named as benzoic acids. COOH COOH CH(CH3)2 OH 2-isopropylcyclopentanecarboxylic acid -hydroxybenzoic acid (salicylic acid) => Chapter 20 5

Chapter 20 5 Naming Cyclic Acids • Cycloalkanes bonded to -COOH are named as cycloalkanecarboxylic acids. • Aromatic acids are named as benzoic acids. COOH CH(CH3 ) 2 2-isopropylcyclopentanecarboxylic acid COOH OH o-hydroxybenzoic acid (salicylic acid) =>

Dicarboxylic Acids Aliphatic diacids are usually called by their common names (to be memorized). For IUPAC name,number the chain from the end closest to a substituent. Two carboxyl groups on a benzene ring indicate a phthalic acid. COOH Br HOOCCH2CHCH2CH2COOH COOH 3-bromohexanedioic acid 1,3-benzenedicarboxylic acid β-bromoadipic acid m-phthalic acid => Chapter 20 6

Chapter 20 6 Dicarboxylic Acids • Aliphatic diacids are usually called by their common names (to be memorized). • For IUPAC name, number the chain from the end closest to a substituent. • Two carboxyl groups on a benzene ring indicate a phthalic acid. HOOCCH2 CHCH2 CH2 COOH Br 3-bromohexanedioic acid -bromoadipic acid COOH COOH 1,3-benzenedicarboxylic acid m-phthalic acid =>

Structure of Carboxyl Carbon is sp2 hybridized. ·Bond angles are close to120°. ·O-H eclipsed with C=O,to get overlap ofπ orbital with orbital of lone pair on oxygen. :O :0 major very minor minor Copyright 2005 Pearson Prentice Hall,Inc. Chapter 20

Chapter 20 7 Structure of Carboxyl • Carbon is sp2 hybridized. • Bond angles are close to 120. • O-H eclipsed with C=O, to get overlap of  orbital with orbital of lone pair on oxygen. =>

Boiling Points Higher boiling points than similar alcohols, due to dimer formation. C一R OH0 hydrogen-bonded acid dimer Copyright 2005 Pe on Prentice Hall,In Acetic acid,b.p.118C Chapter 20 8

Chapter 20 8 Boiling Points Higher boiling points than similar alcohols, due to dimer formation. Acetic acid, b.p. 118C =>

Melting Points Aliphatic acids with more than 8 carbons are solids at room temperature. Double bonds (especially cis)lower the melting point.Note these 18-C acids: >Stearic acid (saturated):72C >Oleic acid (one cis double bond):16C >Linoleic acid (two cis double bonds):-5C => Chapter 20 9

Chapter 20 9 Melting Points • Aliphatic acids with more than 8 carbons are solids at room temperature. • Double bonds (especially cis) lower the melting point. Note these 18-C acids: ➢Stearic acid (saturated): 72C ➢Oleic acid (one cis double bond): 16C ➢Linoleic acid (two cis double bonds): -5C =>

Solubility Water solubility decreases with the length of the carbon chain. Up to 4 carbons,acid is miscible in water. More soluble in alcohol. Also soluble in relatively nonpolar solvents like chloroform because it dissolves as a dimer. Chapter 20 10

Chapter 20 10 Solubility • Water solubility decreases with the length of the carbon chain. • Up to 4 carbons, acid is miscible in water. • More soluble in alcohol. • Also soluble in relatively nonpolar solvents like chloroform because it dissolves as a dimer. =>