5.6 Physical properties

1. 5.6 Physical properties • Sharp odors (up to C9)Sour taste (citric acid)

2. 5.6 Physical properties (cont.) • High b.p • These are the most polar compounds encountered so far.All dioic acids are solids. acetic acid

3. 5.6 Physical Properties of Carboxylic Acids • Fig. 5.7 The boiling points of mono-carboxylic acids are compared to those of other types of compounds.

4. Carboxylic Acids, Esters, and Other Acid Derivativescont’d • Fig. 5.9 A given carboxylic acid molecule can form two hydrogen bonds to another carboxylic acid molecule, producing a “dimer.”

5. Carboxylic Acids, Esters, and Other Acid Derivativescont’d • Fig. 5.8 Unbranched mono and dicarboxylic acids at room temperature and pressure.

6. 5.6 Physical properties (cont.) • Water soluble (completely up to C4) acetic acidH2O

7. Carboxylic Acids, Esters, and Other Acid Derivativescont’d • Fig. 5.10 The solubility in water of saturated unbranched-chain carboxylic acids.

8. 5.7 Preparation • Primary alcohol oxidation • Oxidation of aldehydes

9. 5.8 Acidity of Carboxylic Acids

10. Ionization • Ionization movie • Acid, base, conjugate acid, conjugate base • Ka and pKa • pH and pKa • Carboxylic acids are weak acids (Table 5.3)

11. Models of carboxylic acids • acetic acid • acetate ion • propanoic acid • Propionate • oxalic acid • pyruvic acid • Salicylic acid

12. 5.8 Acidity of Carboxylic Acids Table 5.3

13. If pH=pKa then [HA]=[A-] If pH<pKa then [HA]>[A-] If pH>pKa then [HA]<[A-]

14. 5.9 Carboxylic acid salts • Reactions with bases • “ate” ions (weak bases) • Solubility properties of acids and “ate” ions • Reactions of “ate” ions with acids • demo

15. 5.9 Carboxylic acid salts Fig. 5.11 Propionates, salts of propanoic acid, extend the shelf life of bread.