Chapter 16 | Slide 4 of 39 Carboxylic acids contain the carboxyl group on carbon 1. A carboxyl group is a carbonyl attached to a hydroxyl Acts differently than an alcohol or a carbonyl compound O CH 3 — C—OH= CH 3 —COOH carboxyl group Carboxylic Acids
Chapter 16 | Slide 6 of 39 Identify longest chain containing the carboxyl group (IUPAC) Number carboxyl carbon as 1 (Common) Assign , , to carbon atoms adjacent to carboxyl carbon CH 3 | CH 3 — CH—CH 2 —COOH IUPAC 3-methylbutanoic acid Common -methylbutryic acid Naming Rules
Chapter 16 | Slide 7 of 39 Aromatic Carboxylic Acids Benzoic Acid is the aromatic carboxylic acid Locates substituents by assigning 1 to the carbon with the carboxyl group Benzoic acid 3-chlorobenzoic acid 4-methylbenzoic acid
Chapter 16 | Slide 10 of 39 Properties of Carboxylic Acids Like alcohols, carboxylic acids form strong intermolecular hydrogen bonds. Most carboxylic acids exist as dimers. –Boiling points higher than alkanes of similar MW. –Small carboxylic acids (1-4 carbons) are soluble in water
Chapter 16 | Slide 12 of 39 Synthesis of Carboxylic Acids Synthesized from aromatic rings, primary alcohols and aldehydes. Carboxylic Acid
Chapter 16 | Slide 13 of 39 Oxidation of Aromatic Compounds Benzene does not react with KMnO 4. Alkyl groups on the ring (-R) are readily oxidized though. One product for all reactions.
Chapter 16 | Slide 14 of 39 Oxidation of Aromatic Compounds with KMnO 4
Chapter 16 | Slide 15 of 39 Oxidation of primary alcohols and aldehydes:
Chapter 16 | Slide 16 of 39 Oxidation of alcohols to carboxylic acids.
Chapter 16 | Slide 17 of 39 Carboxylic acids are weak acids –Stronger acids than alcohols CH 3 COOH + H 2 O CH 3 COO – + H 3 O + Neutralized by a base CH 3 COOH + NaOH CH 3 COO – Na + + H 2 O Properties
Chapter 16 | Slide 18 of 39 Carboxylic acids are obviously acidic. Stronger acids than alcohols, but weaker than mineral acids. Will react with NaOH to give metal carboxylates. There is a large range of acidities depending on the substituents on a carboxylic acid.
Chapter 16 | Slide 19 of 39 Carboxylate Ions The conjugate base of a carboxylic acid –Formed when a carboxylic acid loses a proton –Named by dropping the -ic acid ending and replacing it with –ate CH 3 CH 2 COO - Propionate CH 3 COO - Ethanoate (Acetate) CH 3 CH 2 CH 2 COO - Butanoate
Chapter 16 | Slide 20 of 39 Carboxylate Salts An ionic compound in which the negative ion is a carboxylate ion –Naming: the positive ion is named first, followed by a separate word giving the name of the negative ion –Converted back to a carboxylic acid by the addition of a strong acid CH 3 CH 2 COO - Na + Sodium Propionate CH 3 COO - K + Potassium Ethanoate CH 3 CH 2 CH 2 COO - Li + Lithium Butanoate
Chapter 16 | Slide 22 of 39 ←Fig. 16.12 Methyl and ethyl esters of acetic acid. Esters
Chapter 16 | Slide 23 of 39 In an ester, the H in the carboxyl group is replaced with an alkyl group O CH 3 — C—O —CH 3 = CH 3 —COO —CH 3 ester group Sulfur analogs of esters are called thioesters (sulfur replaces the hydroxyl oxygen) Ester
Chapter 16 | Slide 24 of 39 Name the alkyl from the alcohol –O- Name the acid with the C=O with –ate acidalcohol O methyl CH 3 — C—O —CH 3 Ethanoate methyl ethanoate (IUPAC) (acetate)methyl acetate (common) Naming Esters
Chapter 16 | Slide 27 of 39 Reaction of a carboxylic acid and alcohol Acid catalyst O H + CH 3 — C—OH + HO—CH 2 CH 3 O CH 3 — C—O—CH 2 CH 3 + H 2 O Esterification: Preparation of Esters
Chapter 16 | Slide 28 of 39 Esters react with water and acid catalyst Split into carboxylic acid and alcohol O H + H — C—O—CH 2 CH 3 + H 2 O O H — C—OH + HO—CH 2 CH 3 Hydrolysis: Breaking Up Esters
Chapter 16 | Slide 30 of 39 Esters react with bases Produce the salt of the carboxylic acid and alcohol O H 2 O CH 3 C—OCH 2 CH 3 + NaOH O CH 3 C—O – Na + + HOCH 2 CH 3 salt of carboxylic acid Saponification reactions produce soaps Saponification
Chapter 16 | Slide 38 of 39 The C 2 dicarboxylic acid, oxalic acid, contributes to the tart taste of rhubarb stalks.
Chapter 16 | Slide 39 of 39 Polyfunctional Carboxylic Acids Carboxylic acids that contain one or more additional functional groups –Unsaturated acids Contain a multiple bond –Hydroxy acids Contains an additional hydroxyl group –Keto acids Contains an additional carbonyl group Many monoacids and polyfunctional carboxylic acids are intermediates in metabolic reactions