Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 13 Lecture Outline Prepared by Jennifer N. Robertson-Honecker West Virginia University

Carboxylic Acids, Esters, Amines, and Amides Carboxylic acids and esters are two families of organic molecules that contain a carbonyl group (C=O) singly bonded to an oxygen atom. A carboxylic acid contains a carboxyl group (COOH). An ester contains an alkoxy group (OR) bonded to the carbonyl carbon. 2

Nomenclature Naming a Carboxylic Acid (RCOOH) To name a carboxylic acid using the IUPAC system: Number the chain to put the COOH group at C1, but omit “1” from the name. Apply all other nomenclature rules. CH 3 CHCHCH 2 CH 2 CH 3 C O hexane  hexanoic acid 145 Answer: 2,3-dimethylhexanoic acid 3 Find the longest chain containing the COOH group, and change the “-e” ending of the parent alkane to “-oic acid”. OH

Nomenclature Naming a Carboxylic Acid (RCOOH) Many simple carboxylic acids are referred to by their common names. A common name uses the suffix -ic acid. formic acidacetic acidbenzoic acid 4

Nomenclature Naming an Ester (RCOOR’) To name an ester using the IUPAC system: Name the R' group bonded to the oxygen atom as an alkyl group. Name the RCO– group by changing the “-ic acid” ending of the parent carboxylic acid to the suffix “-ate”. 5

Nomenclature Naming an Ester (RCOOR′) Give the IUPAC name for the following ester: CH 3 CH 2 CH 2 OCH 3 C O Step [1] Name the R’ group bonded to the O atom as an alkyl group. methyl group Sample Problem 13.2 CH 3 CH 2 CH 2 OCH 3 C O 6

Nomenclature Naming an Ester (RCOOR′) Step [2] Name the acyl group (RCO-) by: Change the “-ic acid” ending of the parent carboxylic acid to “-ate”. This becomes the second part of the name. derived from butanoic acid  butanoate Answer: methyl butanoate Sample Problem 13.2 CH 3 CH 2 CH 2 OCH 3 C O 7

Carboxylic acids and esters are polar compounds. Only carboxylic acids can undergo intermolecular hydrogen bonding. Physical Properties of Carboxylic Acids and Esters 8

Physical Properties Carboxylic acids also have higher boiling points than esters because esters are incapable of intermolecular hydrogen bonding. Increasing boiling point methyl acetatepropanoic acid 9

Physical Properties Carboxylic acids have higher boiling points than similar alcohols because there are more hydrogen bonding interactions possible than alcohols. Increasing boiling point 10

Interesting Carboxylic Acids Simple carboxylic acids have foul or biting odors. Formic acid (HCO 2 H) is responsible for the sting of some types of ants. Acetic acid (CH 3 CO 2 H) is the sour-tasting component of vinegar; it can be made by air oxidation of ethanol when wine “goes bad”. 11

Focus On Health & Medicine Skin Care Products Several skin care products purported to smooth fine lines contain  -hydroxy acids. General structure of an  -hydroxy acid: These acids work by removing the outer, older layer of skin cells, revealing the healthier looking, new cells underneath. 12

Focus On Health & Medicine Aspirin and Anti-Inflammatory Agents Common pain relievers that are also anti- inflammatory agents contain a carboxyl group: aspirinibuprofen 13

Interesting Carboxylic Acids Aspirin and Anti-Inflammatory Agents Pain relievers work because they block the synthesis of prostaglandins, compounds responsible for pain responses in the body. 14

The Acidity of Carboxylic Acids Carboxylic acids are proton (H + ) donors: They are weak acids compared to inorganic acids like HCl or H 2 SO 4. Only a small percentage of a carboxylic acid is ionized in aqueous solution. 15

The Acidity of Carboxylic Acids Reaction with Bases Carboxylic acids react with bases such as NaOH to form water-soluble salts. A proton is removed from acetic acid to form its conjugate base, the acetate anion, which is present in solution as its sodium salt, sodium acetate. Hydroxide (OH − ) gains a proton to form neutral H 2 O. 16

The Acidity of Carboxylic Acids Carboxylate Anions—Salts of Carboxylic Acids The salts of carboxylic acids formed by acid-base reactions are water-soluble ionic solids. Thus, the reaction will turn a water-insoluble carboxylic acid into a water-soluble carboxylic acid salt. Water-insolublewater-soluble CH 3 (CH 2 ) 6 —C—O—H octanoic acid O + Na + − OH base CH 3 (CH 2 ) 6 —C—O − Na + sodium octanoate O + H—O—H 17

The Acidity of Carboxylic Acids How Does Soap Clean Away Dirt? Soap has been used by humankind for ~2000 years. Soaps are salts of carboxylic acids that have many C atoms in a long hydrocarbon chain. A soap molecule has two parts: 1.The ionic end is called the polar head. 2.The carbon chain of nonpolar C—C and C—H bonds is called the nonpolar tail. 18

The Acidity of Carboxylic Acids How Does Soap Clean Away Dirt? Structure of a soap molecule: polar head ionic end nonpolar tail nonpolar end 19

The Acidity of Carboxylic Acids How Does Soap Clean Away Dirt? In water, soap forms micelles, spherical droplets with the ionic heads on the surface and the nonpolar tails packed together in the interior. 20

The Acidity of Carboxylic Acids How Does Soap Clean Away Dirt? Nonpolar hydrocarbon tails trap nonpolar material like grease and oil. The polar head remains on the surface, sealing off the grease and oil, and washing away in the presence of water. 21

Reactions Involving Carboxylic Acids and Esters Carboxylic acids and esters undergo a common type of reaction—substitution. 22

Carboxylic acids react with alcohols to form esters. Here, the OR′ group replaces the OH group. Reactions Involving Carboxylic Acids and Esters Ester Formation 23

Formation of an ester is done by the Fisher esterification: Reactions Involving Carboxylic Acids and Esters Ester Formation 24

Treatment of an ester (RCOOR') with water in the presence of an acid catalyst forms a carboxylic acid (RCOOH) and a molecule of alcohol (R'OH). Here, the OH group replaces the OR′ group. Reactions Involving Carboxylic Acids and Esters Ester Hydrolysis 25

Reactions Involving Carboxylic Acids and Esters Ester Hydrolysis This reaction is a hydrolysis, since bonds are cleaved by reaction with water. 26

Focus on Health & Medicine Olestra, a Synthetic Fat Triacylglycerols, common naturally occurring esters, contain three ester groups, each with a long C chain. They are lipids, water-insoluble organic compounds, present in fats and oils. 27

Focus on Health & Medicine Olestra, a Synthetic Fat Animals store energy in the form of triacylglycerols. Using enzymes called lipases, the three ester bonds are hydrolyzed when the triacylglycerol is metabolized. Diets high in fat lead to obesity, so the “fake fat” olestra (Olean) was invented to replace some triacylglycerols in snack foods. The lipase enzymes cannot hydrolyze the olestra, so it passes through the body unmetabolized, providing no calories to the consumer. 28

Focus on Health & Medicine Olestra, a Synthetic Fat Hydrolysis of a triacylglycerol by lipase: C O C O C O R R’ R’’ CH 2 O CH O CH 2 O The 3 bonds that break are drawn in red. H2OH2O lipase CH 2 OH CH OH CH 2 OH glycerol C O C O C O R R’ R’’ HO 3 long-chain carboxylic acids 29

Focus on Health & Medicine Structure of Olestra 30