Chem 1152: Ch. 15 Carboxylic Acids and Esters

Carboxylic Acids Produce sour tastes in foods Acetic Acid (vinegar) Citric acid (lemons) Malic acid (apples) C O OH COOHCO 2 H C O O C Esters Esters are responsible for fragrant odors in fruits and flowers Used as flavoring agents and scents (perfume, deodorant)

Naming Carboxylic Acids Identify the longest C chain including the carboxyl group. Number the parent chain so that carboxyl C has lowest number. So for monocarboxylic acids, this will be 1, and does not need to be numbered in naming. Drop final –e (or –ene from benzene) from parent chain and replace with –oic acid.

Know common name and characteristics/uses of highlighted carboxylic acids Sweat! Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011

Physical Properties of Carboxylic Acids Solubility Highly-soluble at low MW (H-bonds with HOH) Insoluble at high MW (7+ carbons) Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 General order of Solubility Hydrocarbons < ethers < aldehydes and ketones < alcohols < carboxylic acids

Physical Properties of Carboxylic Acids Boiling Points Higher BP than alcohols due to formation of 2 H- bonds vs. 1 H-bond between like molecules. Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 alcohol Carboxylic acid

Carboxylic Acids: Acidity Carboxylic acids weak acids: Only about 5% of acetic acid dissociates compared to ~100% for mineral acid (e.g., HCl) Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 H+H+ HCl + H 2 O  H 3 O + + Cl - Reaction is reversible for carboxylic acids (not HCl)

Acidity/Basicity 0714 pH basicneutralacidic pH = -log[H + ] H+H+ OH -  The pH of solution determines form of carboxylic acid  Ex. Carboxylate ion predominates at pH 7.4 (physiological pH) Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011

Carboxylic Acid Salts Reaction with base produces salt and water HCl + NaOH  H 2 O + NaCl Sodium carboxylate Naming carboxylic salts  Name the metal first  Change the –ic acid ending of the acid name to -ate sodium ethanoate (sodium acetate) potassium benzoateLithium 2-methylbenzoate

Useful Carboxylic Acid Salts Sodium stearate  Important component of soap  produced by hydrolysis of triglycerides (esters of fatty acids)  How soap is made from animal fat Sodium benzoate  Food preservative Zinc 10-undecylenate  Used to treat athletes foot

Carboxylic Esters  Esterification: Carboxylic acids can react with alcohols to form esters  -OR’ group of alcohol forms ester linkage Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Ester linkage H +, heat Ex. 1 Ex. 2

Ester Reaction Products Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 Relatively Poor Yields

Important Esters Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011  Polyesters: Polymers of esters  Formed by condensation polymerization (joining monomers, water byproduct) Symmetrical monomers

Polyester Leisure Suits: Yeah…

Better Yield Reactions to Create Esters Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011  More reactive than carboxylic acids  Non-reversible  Still use alcohol

Specific Reactions with Acid Chlorides/Anhydrides Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011

Naming Esters  Esters may have common or IUPAC names  The first word of the name of an ester is the name of alkyl or aromatic group (R)  Change the –ic acid ending of the acid name to –ate (like naming carboxylic acid salts)  Parent contains the –COO group methyl ethanoate phenyl butanoateethyl benzoate isopropyl methanoate methyl benzoate

Ester Products/Names Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011 ethyl benzoate ethyl propanoate methyl benzoate isopropyl propanoate Carboxylic acid chloride

Ester Reactions: Hydrolysis Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011  Reaction of ester with water to break ester linkage and produce alcohol and carboxylic acid  Reverse of esterification  Catalyzed by strong acids

Ester Reactions: Saponification Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011  Reaction of ester with water to break ester linkage and produce alcohol and carboxylic acid  Reverse of esterification  Done in solutions containing strong bases  Carboxylic acid converted to salt

Saponification Products Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011  Reaction of ester with water to break ester linkage and produce alcohol and carboxylic acid isopropyl propanoatesodium propanoate ethyl benzoate potassium benzoate

Esters of Inorganic Acids Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011  Alcohols can form esters by reaction with strong, inorganic acids (sulfuric, nitric and phosphoric)

Production of Phosphoric Anhydrides Seager SL, Slabaugh MR, Chemistry for Today: General, Organic and Biochemistry, 7 th Edition, 2011  Alcohols can form esters by reaction with strong, inorganic acids (sulfuric, nitric and phosphoric)  Phosphoric most important  Forms linkage for DNA/RNA, ATP/ADP ADP