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Carboxylic Acids and Carboxylic Acid Derivatives. Chapter 15 Pages 408-438. Structure of Carboxylic Acids. The carboxyl group is shown in red and may be written in the condensed form: -COOH.
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Carboxylic Acids and Carboxylic Acid Derivatives Chapter 15 Pages 408-438
Structure of Carboxylic Acids • The carboxyl group is shown in red and may be written in the condensed form: -COOH. • The term carboxylic is taken from the terms carbonyl and hydroxyl, the two structures that make up the carboxyl group.
Properties of Carboxylic Acids • Very polar compounds • Can hydrogen bond to one another and to water • Boil at higher temperatures than aldehydes, ketones, or alcohols • Smaller carboxylic acids are soluble in water • Lower molecular weight acids have sharp, sour tastes and unpleasant aromas • Longer chain carboxylic acids are called fatty acids and are important components of biological membranes
Naming Carboxylic Acids - IUPAC • Determine the name of the parent compound, the longest continuous chain containing the carboxyl group. • Replace the –e ending with the suffix –oic acid. If there are two carboxyl groups, the suffix is –dioic acid. • Number the chain so the carboxyl carbon is number 1. • Name and number substituents.
Naming carboxylic acids of cycloalkanes • Add the suffix carboxylic acid to the name of the cycloalkane or substituted cycloalkane. • The carboxyl group is always numbered 1. • Other substituents are named and numbered as usual. Cyclopentanecarboxylic acid
Name the following. 2,4-dimethylpentanoic acid 2-ethylcyclopentanecarboxylic acid 3-methylcyclohexanecarboxylic acid 2,4-dichlorobutanoic acid
Draw structures for the following. • 2,3-dihydroxybutanoic acid • 2-bromo-3-chloro-4-methylhexanoic acid • 1,4-cyclohexanedicarboxylic acid • 4-hydroxycyclohexanecarboxylic acid • Formic acid • Acetic acid
Naming Aromatic Carboxylic Acids • These are usually named as derivatives of benzoic acid. • Generally, the –oic acid or –ic acid suffix is attached to the appropriate prefix. o-bromobenzoic acid
Naming Aromatic Carboxylic Acids • Often, the phenyl group is treated as a substituent. 2-phenylethanoic acid 4-phenylpentanoic acid
Draw structures for the following. • 2,4,6-tribromobenzoic acid • 2,2,2-triphenylethanoic acid • 3-phenylhexanoic acid • 3-phenylcyclohexanecarboxylic acid
Preparation of Carboxylic Acids • As discussed in Ch 14, carboxylic acids can be prepared from the oxidation of primary alcohols and/or aldehydes. 1º alcohol Aldehyde Carboxylic acid Examples: • 1-propanol • 2-methylbutanal
Carboxylic acid - ACID • Carboxylic acids act as acids because they are proton (H+) donors. They are weak acids that dissociate to form a carboxylate ion and a hydrogen ion as shown: carboxylic acid carboxylate anion hydrogen ion
Acid/Base Reaction • Since a carboxylic acid acts as an acid, it will neutralize a strong base like NaOH or KOH to form water and the salt of the carboxylic acid. Acid Base Salt water
Acid/Base Reaction • Naming the Salt of the Carboxylic Acid: • Replace the –ic acid suffix with –ate • Place the name of the metal cation from the base first EX: CH3COOH + KOH CH3COO -K+ + H2O ethanoic acid potassiumethanoate
Examples Write a balanced equation and name the products that are formed. Acetic acid + sodium hydroxide Benzoic acid + potassium hydroxide
YOU TRY THESE! • Propanoic acid + potassium hydroxide • Ethanol • Butanedial • Hexanoic acid + sodium hydroxide
Structure of Esters • Esters are carboxylic acid derivatives. • They are formed from the reaction of a carboxylic acid with an alcohol.
Formation of an Ester“Esterification” H+, heat Carboxylic acid alcohol Ester Water
Properties of Esters • Mildly polar • Have pleasant aromas • Found in natural foodstuffs (banana oil, pineapples, raspberries, etc.) • Boil at approximately the same temperature as aldehydes or ketones of similar molecular weights • Simpler ones are somewhat soluble in water
Naming Esters • Use the alkyl portion of the alcohol as the first name. • Remove the –ic acid ending of the carboxylic acid and replace it with –ate. • The same naming rules apply if the common name of the carboxylic acid is used.
Examples of Ester Names Methyl ethanoate (methyl acetate) Propyl ethanoate (propyl acetate) Methyl benzoate Methyl m-bromobenzoate
Answers to You Try These! • Cyclopentyl ethanoate • (cyclopentyl acetate) • Ethyl cyclohexanecarboxylate • Methyl p-nitrobenzoate • Methyl butanoate
Esterification Reactions H+, heat Ethanoic acid ethanol (Acetic Acid) Ethyl ethanoate (Ethyl acetate)
Esterification • Butanoic Acid + Methanol • How would you make ethyl propanoate from only alcohols?
Esterification • Fats and oils are triesters of the alcohol glycerol. • Carboxylic acid + alcohol ester + water
Formation of Soap - Saponification • When esters are hydrolyzed by saponification, the products are soaps.
Saponification • Base-catalyzed hydrolysis of esters • Ester + water OHC.A. salt + alcohol • SOAP is a salt of long-chain carboxylic acids AKA Fatty Acid Salts • Lower molecular weight salts (<12 carbons) have high water solubility and large bubbles • K+ salts are more water soluble than Na+ salts
Saponification • Ester + waterbase C.A. salt + alcohol O O CH3CH2COCH3 + H2O KOH CH3CH2COK Methyl ethanoatepotassium ethanoate + CH3OH methanol
Acid Chlorides IUPAC name - Replace the –oic acid ending of the IUPAC name with –oyl chloride. Common name – Replace the –ic acid ending of the common name with –yl chloride.
Examples of Acid Chlorides Ethanoyl chloride (acetyl chloride) 3-bromopropanoyl chloride p-chlorobenzoyl chloride (4-chlorobenzoyl chloride)
Properties of Acid Chlorides • Noxious, irritating chemicals • Slightly polar • Boil at approximately the same temperature as aldehydes or ketones of similar molecular weights • React violently with water
Formation of Acid Chlorides Carboxylic acid Acid Chloride (+ inorganic products) Ethanoic acid Ethanoyl chloride (acetic acid) (acetyl chloride)
Hydrolysis of Acid Chlorides Acid chloride water Carboxylic acid + Hydrochloric acid Ethanoyl chloride ethanoic acid (acetyl chloride) (acetic acid)
Acid Anhydrides An acid anhydride is two carboxylic acids with a water molecule removed. “Anhydride” means without water.
Formation of Acid Anhydrides Carboxylic acid Carboxylic acid Water Acid anhydride