Carboxylic Acid Derivatives

1. Carboxylic Acid Derivatives Bettelheim, Brown, Campbell and Farrell Chapter 19

2. Derivatives of Carboxylic Acids Carboxylic acids Derivatives of carboxylic acids Anhydrides, Esters, and Amides Made by reacting a carboxyl acid group with another molecule. H2O is formed in each reaction

3. Properties of Organic Families: ACIDIC BASIC NEUTRAL carboxylic amines alcohols acids carboxylate ethers phenols ions aldehydes thiols ketones amides esters

4. Esters An ester has a carbonyl group bonded to an -OR group Ester names are derived from the names of the parent carboxylic acids Name the alkyl or aryl group bonded to oxygen first, followed by the name of the acid; replace the suffix -ic acid by -ate Cyclic ester is called a lactone

6. Making an ester Esterification Needs acid catalyst (i.e., conc H2SO4) Reversible reaction

7. Fischer Esterification Fischer esterification is commonly used to make esters Carboxylic acid is reacted with an alcohol in the presence of an acid catalyst, such as concentrated sulfuric acid Fischer esterification is reversible Can drive reaction in either direction by altering experimental conditions (Le Chatelier’s principle)

8. Fischer Esterification Alcohol adds to the carbonyl group of the carboxylic acid to form a tetrahedral carbonyl addition intermediate Intermediate then loses H2O to form an ester

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10. Hydrolysis of Esters Break ester into carboxylic acid and alcohol Add HOH to break bond Reverse of esterification Acid Hydrolysis: Carboxylic acid + alcohol Basic Hydrolysis: Carboxylate ion + alcohol Saponification

11. Hydrolysis of Esters Occurs very slowly in water Much more rapid when ester is heated in aqueous acid or base Acidic hydrolysis of esters is the reverse of Fischer esterification Large excess of water drives the equilibrium to the right to form the carboxylic acid and alcohol (Le Chatelier's principle)

12. Hydrolysis of Esters Basic hydrolysis of ester called saponification Used in the manufacture of soaps Basic hydrolysis done in hot aqueous base, such as aqueous NaOH Ester hydrolysis forms carboxylic acid and alcohol Carboxylic acid reacts with hydroxide ion to form a carboxylate ion One mole of base needed for each mole of ester

14. Phosphoric Esters Phosphoric acid forms mono-, di-, and triphosphoric esters In more complex phosphoric esters, it is common to name the organic molecule and then indicate the presence of the phosphoric ester by either the word "phosphate" or the prefix phospho- Dihydroxyacetone phosphate and pyridoxal phosphate are shown as they are ionized at pH 7.4, the pH of blood plasma

15. Amides An amide has a carbonyl group bonded to a nitrogen atom Amide names: IUPAC: Drop the suffix -oic acid and add -amide Common: Drop the suffix -ic acid and add -amide Alkyl or aryl groups attached to the N show their location with an N- followed by the name of group Two alkyl or aryl groups are shown by N,N-di-

18. Amides Cyclic amide is called a lactam Penicillins are referred to as b-lactam antibiotics

19. Amides the cephalosporins are also b-lactam antibiotics

20. Preparation of Amides Theoretically can form of an amide by reacting a carboxylic acid with an amine Remove -OH from the acid and an -H from the amine In practice, acid and amine undergo acid-base reaction to form ammonium salt. Can then heat salt to high temperature to form amide (water is eliminated)

21. Making an ester Esterification Needs acid catalyst (i.e., conc H2SO4) Reversible reaction

22. Making an Amide Generally prepare amides by reacting an amine with an anhydride

23. Hydrolysis of Amides Amides require more vigorous conditions for hydrolysis in both acid and base than do esters Hydrolysis in hot aqueous acid gives a carboxylic acid and an ammonium ion Hydrolysis is driven to completion by the acid-base reaction between ammonia or the amine and the acid to form an ammonium ion Each mole of amide requires one mole of acid

24. Hydrolysis of Amides Hydrolysis of an amide in aqueous base gives a carboxylic acid salt and ammonia or an amine Hydrolysis is driven to completion by the acid-base reaction between the carboxylic acid and base to form a salt Each mole of amide requires one mole of base

25. Anhydrides An anhydride has two carbonyl groups bonded to the same oxygen Symmetrical: two identical acids OR Mixed: two different acids Naming: Drop the word "acid" from the name of the carboxylic acid and add the word "anhydride"

26. Formation of Anhydride

27. Hydrolysis of Anhydrides Hydrolysis: break bond by adding water Carboxylic anhydrides react readily with water to give two carboxylic acids Low-molecular-weight anhydrides react very easily

28. Phosphoric Anhydrides A phosphoric anhydride has two phosphoryl (P=O) groups bonded to the same oxygen atom

29. Phosphoric Anhydrides Energy storage (ATP)

30. Polymers Addition polymers Have C=C double bonds Add each monomer to end of growing chain Step-Growth polymers Also called condensation polymers Small molecule removed when bond between monomers forms: H2O, HCl, etc. Formed by reaction of two different functional groups on monomers

32. Types of Step-Growth Polymers Found in Nature Polysaccharides: Individual sugars joined by glycosidic bonds Proteins: Amino acids joined by amide bonds Nucleic Acids: Nucleotides joined by phosphodiester bonds

33. Step-Growth Polymers Step-growth polymers are formed by reaction between molecules containing two functional groups, with each new bond created in a separate step Different types of step-growth polymers Polyamides Polyesters Polycarbonates

34. Polyamides Nylon-66 was the first purely synthetic fiber Synthesized from two six-carbon monomers

35. Polyamides Kevlar is made from an aromatic dicarboxylic acid and an aromatic diamine

36. Polyesters First polyester involved polymerization of this diacid and ethylene glycol

37. Polycarbonates Lexan, the most familiar polycarbonate, is formed by reaction between the disodium salt of bisphenol A and phosgene