14 ORGANIC CHEMISTRY Carboxylic Acids and Carboxylic Acid

14 ORGANIC CHEMISTRY Carboxylic Acids and Carboxylic Acid Derivatives General, Organic, and Biochemistry 9 th Edition Katherine J. Denniston Joseph J. Topping Danaè R. Quirk Dorr Robert L. Caret Copyright © 2017 Mc. Graw-Hill Education. Permission required for reproduction or display

Functional Group Formulas Ar= Aromatic hydrocarbon R = Aliphatic hydrocarbon

14. 1 Carboxylic Acids Structure • Carboxylic acid groups consist of two very polar functional groups 1 – Carbonyl group – Hydroxyl group • Carboxylic acid groups are very polar Carboxylic acid Ester – Carboxylic Acid Derivative Copyright © 2017 Mc. Graw-Hill Education. Permission required for reproduction or display

14. 1 Carboxylic Acids Physical Properties • Low molar mass carboxylic acids – Sharp, sour taste – Unpleasant aromas • High molar mass carboxylic acids – Fatty acids important in biochemistry • Low molar mass carboxylic acids are water soluble due to hydrogen bonding with: – Water – Each other Copyright © 2017 Mc. Graw-Hill Education. Permission required for reproduction or display

14. 1 Carboxylic Acids Boiling Points Due to carboxylic acids forming intermolecular hydrogen bonds, boiling points are at higher temperatures than those of any other functional group studied

14. 1 Carboxylic Acids Nomenclature 2 • Determine the parent compound: 4 C – butane • Number the chain so that the carboxyl carbon is carbon 1: from right to left • Replace the –e ending with –oic acid – Butanoic acid – If two carboxyl groups are present use –dioic acid • Complete naming as usual – bromine on C-3 4 3 2 1

14. 1 Carboxylic Acids Carboxylic Acid Naming Examples

14. 1 Carboxylic Acids Common Names • Use Latin or Greek prefixes • Suffix is –ic acid • Greek letters indicate the position of the substituents

14. 1 Carboxylic Acids Names and Structures of Some Common Carboxylic Acids

14. 1 Carboxylic Acids Benzoic Acid Derivatives

14. 1 Carboxylic Acids with a Phenyl Substituent • The phenyl group is benzene with one hydrogen removed:

14. 1 Carboxylic Acids Common Dicarboxylic Acids 3

14. 1 Carboxylic Acids Some Important Carboxylic Acids 3 • More complex carboxylic acids are found in a variety of foods • Citric Acid is found in citrus fruits • Bacteria in mild produce lactic acid as a product of fermentation of sugars • Tartaric acid is used in baking powder because it will react with carbonates in the dough • Malic acid gives the sour taste to green apples • Fatty acids are long chain carboxylic acids found in plant and animal sources

14. 1 Carboxylic Acids Found in Food 3

14. 1 Carboxylic Acids Reactions Involving Carboxylic Acids • Carboxylic acids are prepared by oxidation of primary alcohols and aldehydes 4

14. 1 Carboxylic Acids Carboxylate Anion Formation 5 • Carboxylic acids behave as acids because when they are dissolved in water they will deprotonate to form a carboxylate ion and the hydronium ion • Carboxylic acids are weak acids with dissociations of less than 5% Copyright © 2017 Mc. Graw-Hill Education. Permission required for reproduction or display

14. 1 Carboxylic Acids Neutralization Reactions • Carboxylic acids DO react with strong bases to form carboxylate salts – A process of neutralization – Acid protons are removed by the –OH- to form H 2 O and carboxylate ion – Equilibrium shifts to the right with removal of H+

14. 1 Carboxylic Acids Acid-Base Reactions Copyright © 2017 Mc. Graw-Hill Education. Permission required

14. 1 Carboxylic Acids Salts of Carboxylic Acids • Nomenclature – First add the cation’s name • Sodium – Then drop the –oic acid and add –ate • Sodium benzoate • Uses of carboxylic acids • • Soaps like sodium stearate Preservatives Anti-fungal medicines Used to control food p. H

14. 1 Carboxylic Acids Esterification • Carboxylic acids react with alcohols to form: –

14. 2 Esters 7 Structure and physical properties • Esters are mildly polar, somewhat water soluble • Frequently found in natural foodstuffs • Many have pleasant aromas – Isoamyl acetate = banana oil 3 -methylbutyl ethanoate – Ethyl butanoate = pineapple aroma Ethyl butanoate – Isobutyl formate = raspberry aroma Isobutyl methanoate • Boil at approximately the same temperature as carbonyls with comparable molecular weight

14. 2 Esters Ester IUPAC Nomenclature 8 Form from the reaction of a carboxylic acid with an alcohol, which is reflected in the naming 1. Use the alkyl group as the first name (Alcohol part of the ester) 2. Base the name for the acid part of the structure from the longest chain ending in the C=O (Carboxylic acid part of the ester) 3. Change the –oic acid of the acid name to –oate Copyright © 2017 Mc. Graw-Hill Education. Permission required for reproduction or display

Example: Naming Esters 14. 2 Esters Name the following esters: • Alkyl portion = first name ethyl • Parent carboxylic acid = butanoic acid • Change suffix to reflect ester = Ethyl butanoate • Alkyl portion = first name proply • Parent carboxylic acid = ethanoic acid • Change suffix to reflect ester = Propyl ethanoate

Naming Esters 14. 2 Esters Naming esters is much like naming the salts of carboxylic acids: • Alkyl portion = first name ethyl • Parent carboxylic acid = ethanoic acid • Change suffix to reflect ester = Ethyl ethanoate

14. 2 Esters Preparing Esters • • 6 Carboxylic acids react with alcohols to produce esters The reaction is catalyzed by strong mineral acid Heat is required A molecule of water is also released as a product: reaction is a dehydration Copyright © 2017 Mc. Graw-Hill Education. Permission required for reproduction or display

14. 2 Esters Ester Formation Reaction Example Copyright © 2017 Mc. Graw-Hill Education. Permission

Hydrolysis of Esters 14. 2 Esters • The main reaction of esters is hydrolysis, reaction with water – This reaction is also called hydration = cleavage of any bond by the addition of a water molecule • However, the uncatalyzed reaction is slow and requires heat • The reaction can be either acid or base catalyzed 9

14. 2 Esters Acid hydrolysis of Esters Acid hydrolysis products are: • Acid •

14. 2 Esters Base Hydrolysis of Esters The base catalyzed hydrolysis of an ester: • Saponification or soap-making • Products are: 10 – Acid salt – Alcohol • Acid can’t exist in basic conditions, so the product is the salt of the carboxylic acid using the cation of the base catalyst Copyright © 2017 Mc. Graw-Hill Education. Permission required for reproduction or display

Saponification • Saponification (soap-making) is: – Base-catalyzed hydrolysis of fats (glycerol triesters)

14. 2 Esters Simplified Action of Soap • The wiggly lines represent the long carbon chains of each soap molecule • Particles of oil and grease are surrounded by soap molecules to form a micelle

14. 2 Esters Condensation Polymers • Polyesters are condensation polymers • They are formed by eliminating a small molecule (e. g. , H 2 O) when combining: – Diacid – Diol • Each of the combining molecules has two reactive functional groups, highlighted in red

Polethylene terphthalate, PETE 1, 2 -ethanediol PETE is used in: • Mylar • Plastic bottles • Polyester fabric Continued condensation at each end Repeating unit of the polymer

14. 3 Acid Chlorides and Acid Anhydrides • Acid chlorides are derivatives of carboxylic acids having the general formula: • Are named: – by replacing the –oic acid ending of the IUPAC name with –oyl chloride 11

Acid Anhydrides 14. 3 Acid Chlorides and Acids Chlorides 11 Acid chlorides • Noxious, irritating chemicals requiring great care in handling • Slightly polar, boiling near the corresponding carbonyl’s temperature • React violently with water • Are good acyl group transfer reagents

• Acid anhydrides have the formula: Acid Anhydrides 14. 3 Acid Chlorides and Acid Anhydrides 12 • The molecule is 2 carboxylic acid molecules with a water molecule removed – Anhydride means without water • Symmetrical anhydrides are those with both acyl groups the same • Symmetrical anhydrides are named by replacing the -acid ending of the acid with –anhydride

Anhydrides 14. 3 Acid Chlorides and Acid Formation of Acid Anhydrides • Acid anhydrides are not typically formed in a reaction between the parent carboxylic acids 13

• One reaction used to form acid anhydrides is the combination of a(n): 13 Anhydrides 14. 3 Acid Chlorides and Acid Chlorides in the Formation of Acid Anhydrides – Acid chloride – Carboxylate anion

• Acid anhydride reacts with alcohol to produce: Anhydrides 14. 3 Acid Chlorides and Acid Types of Acid Anhydride Reactions With Alcohols – Ester – Carboxylic acid – An acyl group transfer reaction

Anhydrides 14. 3 Acid Chlorides and Acid Anhydride Reaction With Alcohol

14. 4 Nature’s High Energy Compounds: Phosphoesters and Thioesters 14 • Phosphoric acid reacts with alcohols to produce a phosphate ester or phosphoester • The ester can then react with a second or third acid to give phosphoric acid anhydrides • ADP and ATP of biochemistry fame are important examples of phosphate esters

Thioesters 14. 4 Nature’s High Energy Compounds: Phosphoesters and ATP – Adenosine Triphosphate Copyright

• In biochemistry, acetyl coenzyme A (acetyl Co. A-SH) reacts with acyl groups to “activate” them for further biological reaction by forming a thioester Thioesters 14. 4 Nature’s High Energy Compounds: Phosphoesters and Thioesters

Reaction Schematic

Types of Reactions: Summary 1. Carboxylic acids a. Preparation b. Dissociation c. Neutralization d. Esterification 2. Esters a. Acid hydrolysis b. Saponification 3. Acid chloride synthesis 4. Acid anhydride synthesis 5. Phosphoester formation

Summary of Reactions Equations