Ch 10: Chapter Outline

1. Ch 10: Chapter Outline 10.1Carboxylic Acids 10.2Phenols 10.3Carboxylic Acids and Phenols as Weak Organic Acids 10.4Other Reactions of Carboxylic Acids 10.5 Oxidation of Phenols 10.6 Amines 10.7Amines as Weak Organic Bases 10.8Amides 10.9Stereoisomers

2. 10.1: Carboxylic Acids Some carboxylic acids have common names. ethanoic acid = acetic acid (found in vinegar) methanoic acid = formic acid

4. Naming Carboxylic Acids • When naming a carboxylic acid according to the IUPAC rules, the parent is the longest continuous carbon chain that includes the carboxyl group. • Numbering begins at the carboxyl carbon, and alkyl groups are identified by name, position, and number of appearances. • IUPAC names for carboxylic acid main chains are formed by dropping the final “e” on the name of the corresponding alkanes and adding “oic acid”.

5. Exercise: Give the IUPAC name of each carboxylic acid.

6. Exercise: Draw each molecule. Hint: When named as a substituent, -OH is hydroxyl; -OH is taken to be a branch. The –COOH takes priority over the –OH group. 4-hydroxybutanoic acid 2-bromopropanoic acid 4-chlorohexanoic acid

7. Physical Properties of CA’s: • Compared to other organic compounds with a similar molecular weight, carboxylic acids have relatively high boiling points due to their ability to form more more hydrogen bonds with one another. • The ability to form hydrogen bonds in these groups C=O, C-O, and O-H, gives small carboxylic acids a significant water solubility. • As we have seen before, an increasing number of carbon atoms leads to a reduction in water solubility.

8. In the simplest phenol, named phenol, the -OH group is the only group attached to a benzene ring.When substituents are added to this molecule, the carbon atom carrying the -OH is designated as carbon 1. 10.2: Phenols

10. 10.3: Carboxylic Acids and Phenols are Weak Organic Acids Having a Ka of 1.8 x 10-5 (pKa = 4.74), acetic acid is a weak acid. Phenols are weaker acids than CA’s; pKa is about 10.

11. A biochemical significance of the form of the carboxylic acid (as a carboxylate anion at physiological pHs) relates to fatty acids.At physiological pHs, fatty acids exist as amphipathic ions that can mix with water, to some extent.In general, carboxylate anions with 12 or more carbon atoms, like palmitate ion, are amphipathic compounds, while those with fewer than 12 carbon atoms are water soluble.

12. Naming Carboxylate Ions • To name a carboxylate ion, the ending on the name (IUPAC or common) of the related carboxylic acid is changed from ic acid to ate. • Palmiticacid becomes palmitate ion, and aceticacid becomes acetate ion.

13. Rxn of phenol with NaOH: Carboxylate ions are more soluble in water than carboxylic acids. Phenoxide ions are more soluble in water than phenols.

15. 10.4: - Reactions of CA’s to make Esters - Hydrolysis of Esters

16. Naming Esters

17. Exercise: Draw the product of the reaction. Name the ester that forms. Strategy: Ester formation is a double replacement reaction, and the product ester contains a carboxylic acid residue and an alcohol residue. Each of these residues is considered when assigning a name to the ester.

18. Ester formation is a reversible process. • In hydrolysis reactions, esters are broken apart by water to form a carboxylic acid plus an alcohol. • Esters can also be hydrolyzed under basic conditions.

19. Decarboxylation • Decarboxylation is a decomposition reaction that results in the loss of carbon dioxide (CO2) from a beta-keto and alpha-keto carboxylic acid.

20. Examples of Decarboxylation rxn:

21. Exercise: Draw the products of each decarboxylation reaction. Strategy: In a decarboxylation reaction, CO2 is released from a carboxylic acid reactant.

22. 10.5: Oxidation of Phenols

23. Exercise: Draw the product of the reaction between KOH and butanoic acid p-bromophenol

24. 10.6: Amines Amines are classified based on the number of carbon atoms directly attached to the nitrogen atom. • primary (1) - only one carbon atom attached to the amine nitrogen atom • secondary (2) - two attached carbon atoms • tertiary (3) - three attached carbon atoms • quaternary (4) ammonium ions - four carbon atoms are directly attached to the nitrogen atom and the nitrogen carries a +1 charge.

25. Naming Amines • To name a 1, 2, or 3 amine using IUPAC rules, the parent, the longest chain of carbon atoms attached to the amine nitrogen atom, is numbered from the end nearer the point of attachment of the nitrogen. • The parent chains of amines are named by dropping “e” from the name of the corresponding hydrocarbon and adding “amine.”

26. Naming Amines • If an amine is 2 or 3, the carbon-containing groups attached to the nitrogen atom that are not part of the parent chain are substituents and N is used to indicate their location (N-methyl, N,N-diethyl, etc.). • Simple amines, those with a relatively few number of carbon atoms, are often identified by common names by placing “amine” after the names of the groups attached to the nitrogen. • methylamine = CH3NH2

29. Exercise: Match each IUPAC and common name to the correct structural formula:

30. Heterocyclic amines

31. 1 and 2 amines form hydrogen bonds with like amines. • 3 amines do not form hydrogen bonds among themselves; why?

32. 10.7: Amines as Weak Organic Bases (Which is the H+ acceptor?)

33. Rxn of amine with acids: A strong acid converts an amine into its conjugate acid.

34. 10.8: Amides and Rxn of Amides

35. Formation of Amide: Hydrolysis of Amide:

36. What functional groups are present on these molecules?

37. 10.9: Stereoisomers • Members of one class of stereoisomers are called enantiomers. • Enantiomers are nonsuperimposable mirror image forms of a molecule.

39. The Chirality of an object: • The term chiral is used to describe objects that cannot be superimposed on their mirror image. • Example: Your hands are chiral because your left hand is not superimposable on your right hand, its mirror image. (Try it!)

40. Exercise: Use an asterisk to label the chiral carbon atom in each molecule.