Chapter Sixteen Carboxylic Acids, Esters, and Other Acid Derivatives

Chapter 16 | Slide 2 of 52 Carboxylic acid: An organic compound with carboxyl functional group Carboxyl group: A carbonyl group (C=O) with a hydroxyl group (— OH) bonded to the carbonyl carbon atom A general structural representation for a carboxyl group is shown below Carboxylic acid Carbonyl group

Chapter 16 | Slide 3 of 52 Fig The three simplest carboxylic acids: methanoic acid, ethanoic acid, and propanoic acid. Carboxylic Acids

Chapter 16 | Slide 4 of 52 →Fig Benzoic acid molecule Carboxylic Acids

Chapter 16 | Slide 5 of 52 Carboxylic acids always contain the carboxyl group on __________ ____. 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 52 IUPAC Rules for Naming Monocarboxylic Acids Rule 1: Select the longest carbon chain that includes the carbon atom of the carboxyl group as the parent chain. Rule 2: Name the parent chain by changing the “-e” ending of the corresponding alkane to “-oic” acid. Rule 3: Number the parent chain by assigning the #1 to the carboxyl carbon atom. Rule 4: Determine the identity and location of any substituents in the usual manner, and append this information to the front of the parent chain name.

Chapter 16 | Slide 7 of 52 Identify longest chain containing the ___________ group (IUPAC) Number ____________ carbon as 1 (Common) Assign , ,  to carbon atoms adjacent to ____________ carbon CH 3 | CH 3 — CH—CH 2 —COOH IUPAC 3-methylbutanoic acid Common  -methylbutryic acid Naming Rules

Chapter 16 | Slide 8 of 52 Formula IUPAC Common alkan -oic acid prefix – ic acid HCOOH methanoic acid formic acid CH 3 COOH ethanoic acid acetic acid CH 3 CH 2 COOH propanoic acid propionic acid CH 3 CH 2 CH 2 COOH butanoic acid butyric acid Naming Carboxylic Acids

Chapter 16 | Slide 9 of 52 First Six Unbranched Monocarboxylic Acids

Chapter 16 | Slide 10 of 52 First Six Unbranched Dicarboxylic Acids

Chapter 16 | Slide 11 of 52 Aromatic Carboxylic Acids Benzoic Acid is the ______________ 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 12 of 52 Common Acids Acetic Acid: CH 3 COOH –Vinegar is 4%-8% (v/v) acetic acid solution –Colorless liquid with sharp odor Oxalic acid: HOOC-COOH - found in spinach and cabbage –Harmful at high concentrations –Used to remove rust, bleach straw, and leather and ink stains

Chapter 16 | Slide 13 of 52 PCAs contain at least one or more functional groups other than carboxyl group PCAs are commonly found in living organisms an play an important role in human body –Occur in many fruits –Used in over the counter skin care products and prescription drugs Common types of PCAs: –Unsaturated acids –Hydroxy acids –Keto acids Polyfunctional Carboxylic Acids

Chapter 16 | Slide 14 of 52 Unsaturated Acids Contain at least one carbon-carbon double bond (C=C): Two types of monounsaturated carboxylic acids: –Trans - unsaturated carboxylic acids –Cis – unsaturated carboxylic acids Examples: –Propenoic acid (acrylic acid) used in the manufacture of polymeric materials. –Futenedioic acid - has two forms Fumaric acid : trans-form Maleic acid: cis-form

Chapter 16 | Slide 15 of 52 Hydroxy Acids Contain at least one hydroxyl group and are naturally present in many foods Examples: –Glycolic acid: present in juice from sugar cane and sugar beets –Lactic acid: Present sour milk, sauerkraut, and dill pickles –Malic acid and tartaric acid occur naturally in fruits

Chapter 16 | Slide 16 of 52 Keto Acids Contain a carbonyl (C=O) group within a carbon chain. Example: –Pyruvic acid - simplest keto acid with odor resembling that of vinegar (acetic acid) and it is also a metabolic acid

Chapter 16 | Slide 17 of 52 Metabolic acids: Polyfunctional acids formed as intermediates of ________________ reactions in the human body. There are eight such acids that will appear repeatedly in the biochemistry chapters Metabolic acids are derived from: −Propionic acid, (C 3 mono acids): lactic, glyceric, and pyruvic acids −Succinic acid (C 4 diacid): fumaric, oxaloacetic, and malic acids −Glutaric acid (C 5 diacid):  -ketoglutaric and citric acids

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Chapter 16 | Slide 19 of 52 At Room Temperature and Pressure Straight chain carboxylic acids with 1-9 carbon atoms are liquids and strong odors Straight chain carboxylic acids with >10 C atoms are waxy solids with no odor. Aromatic and dicarboxylic acids: Odorless solids

Chapter 16 | Slide 20 of 52 Properties of Carboxylic Acids Like alcohols, carboxylic acids form ___________ intermolecular hydrogen bonds. Most carboxylic acids exist as ___________. –Boiling points higher than alkanes of similar MW. –Small carboxylic acids (1-4 carbons) are soluble in water

Chapter 16 | Slide 21 of 52 Boiling Points

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Chapter 16 | Slide 23 of 52 Synthesis of Carboxylic Acids Synthesized from aromatic rings, primary alcohols and aldehydes. Oxidizing Agents: K 2 Cr 2 O 7 / H 2 SO 4 or KMnO 4 Carboxylic Acid

Chapter 16 | Slide 24 of 52 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 25 of 52 Oxidation of Aromatic Compounds with KMnO 4

Chapter 16 | Slide 26 of 52 Oxidation of primary alcohols and aldehydes:

Chapter 16 | Slide 27 of 52 Oxidation of alcohols to carboxylic acids.

Chapter 16 | Slide 28 of 52 Carboxylic acids are ________ acids –Stronger acids than alcohols In water they dissociate to release ___________ (H + ) and form carboxylate ion (RCOO - ) -- equilibrium reactions and equilibrium lies towards the left indicating that small amount of acid is ionized 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 29 of 52 Monocarboxylic acids release ______ H + to form carboxylate ion with _______ negative charge Dicarboxylic acids release ______ H + ions to form carboxylate ion with _____ negative charges and so on

Chapter 16 | Slide 30 of 52 Carboxylic acids are obviously _________. Stronger acids than alcohols, but __________ than mineral acids. Will react with _________ to give metal carboxylates. There is a large range of acidities depending on the substituents on a carboxylic acid.

Chapter 16 | Slide 31 of 52 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 32 of 52 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 33 of 52 Uses of Carboxylic Acid Salts Good antimicrobial and antifungal agents Benzoate salts: Effective (0.1%, m/m) against yeast and mold in beverages, jams and jellies, etc. Sodium sorbate: Inhibits mold and yeast in dairy products, dried fruits, some meat and fish products Propionate: Used in preservation of baked goods Benzoate and sorbate can’t be used in yeast leavened baked goods as they inhibit mold and yeast

Chapter 16 | Slide 34 of 52 Carboxylic Acids

Chapter 16 | Slide 35 of 52 ←Fig Methyl and ethyl esters of acetic acid. Esters

Chapter 16 | Slide 36 of 52 In an ester, the _______ in the carboxyl group is replaced with an ________ 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 37 of 52 The name for the alcohol part of the ester appears _________ and is _____________ by a separate word giving the name for the acid part of the ester. The name for the alcohol part of the ester is simply the name of the R group (alkyl, cycloalkyl, or aryl) present in the —OR portion of the ester. The name for the acid part of the ester is obtained by dropping the “-ic” acid ending for the acid’s name and adding the suffix “-ate.”

Chapter 16 | Slide 38 of 52 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

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Chapter 16 | Slide 40 of 52 Esters

Chapter 16 | Slide 41 of 52 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 42 of 52 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 43 of 52 Hydrolysis

Chapter 16 | Slide 44 of 52 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 45 of 52 Soaps Carboxylate salts

Chapter 16 | Slide 46 of 52 The following figure represents soap. Which end of the anion is hydrophobic?

Chapter 16 | Slide 47 of 52 How does soap interact with grease?

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Chapter 16 | Slide 51 of 52 Dicarboxylic Acids

Chapter 16 | Slide 52 of 52 The C 2 dicarboxylic acid, oxalic acid, contributes to the tart taste of rhubarb stalks.