5.6 Physical properties

5.6 Physical properties

1. Sharp odors (up to C9)Sour taste (citric acid)

5.6 Physical properties (cont.)

acetic acid

3. High b.p

• These are the most polar compounds encountered so far.All dioic acids are solids.

→Fig. 5.7 The boiling points of mono-carboxylic acids are compared to those of other types of compounds.

5.6 Physical Properties of Carboxylic Acids

→Fig. 5.9 A given carboxylic acid molecule can form two hydrogen bonds to another carboxylic acid molecule, producing a “dimer.”

Carboxylic Acids, Esters, and Other Acid Derivatives cont’d

←Fig. 5.8 Unbranched mono and dicarboxylic acids at room temperature and pressure.

Carboxylic Acids, Esters, and Other Acid Derivatives cont’d

5.6 Physical properties (cont.)

acetic acid H2O

4. Water soluble (completely up to C4)

←Fig. 5.10 The solubility in water of saturated unbranched-chain carboxylic acids.

Carboxylic Acids, Esters, and Other Acid Derivatives cont’d

5.7 Preparation• Primary alcohol oxidation

• Oxidation of aldehydes OHCO2H[O]

5.8 Acidity of Carboxylic Acids

Ionization

• Ionization movie

• Acid, base, conjugate acid, conjugate base

• Ka and pKa

• pH and pKa

• Carboxylic acids are weak acids (Table 5.3)

Models of carboxylic acids

• acetic acid

• acetate ion

• propanoic acid

• Propionate

• oxalic acid

• pyruvic acid

• Salicylic acid

Table 5.3

5.8 Acidity of Carboxylic Acids

If pH=pKa then [HA]=[A-]

If pH<pKa then [HA]>[A-]

If pH>pKa then [HA]<[A-]

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

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

5.9 Carboxylic acid salts