Chapter 17

Question 1

Carboxylic acid structure

Answer 1

• functional group is carboxyl group
• general formula: RCO2H
• formula for aromatic: ArCO2H

Question 2

nomenclature for carboxylic acids

Answer 2

• drop -e add -oic acid
• carboxyl group take precedence over most other functional groups
• dicarboxylic acid: add -dioic acid
• if bonded to a ring, -carboxylic acid
• when common names are used, greek letters used

Question 3

physical properties of carboxylic acids

Answer 3

• significantly higher BP
• polar, strong IMF
• more soluble in water than alcohols, ethers, aldehydes, and ketones of comparable molecular weight.
• They form hydrogen bonds with water molecules through both their C=O and OH groups.

Question 4

acidity

Answer 4

-weak acids
-electron withdrawing substituents near the carboxyl group increase acidity through their inductive effect.
–The form of a carboxylic acid present in aqueous solution depends on the pH of the solution.

Question 5

5 ways to prepare a carboxylic acid

Answer 5

1. oxidation of 1 alcohols and aldehydes
2. organometallic with CO2
3. lab version of liver metabolism
4. haloform reaction
5. PhCN + H30-> Ph COOH

Question 6

reactions of carboxylic acids

Answer 6

1. decarboxylation
2. acid-base
3. esterification
4. conversion to acyl halides
5. reduction (use ester instead)

Question 7

reactions with bases

Answer 7

• Carboxylic acids, whether soluble or insoluble in water, react with NaOH, KOH, and other strong bases to give water-soluble salts.
• They also form water-soluble salts with ammonia and amines.
• react with sodium bicarbonate and sodium carbonate to form water-soluble salts and carbonic acid.

Question 8

reduction

Answer 8

• The carboxyl group is very resistant to reduction.
• Lithium aluminum hydride reduces a carboxyl group to a 1° alcohol. But, even here, the yield isn’t usually high.
• Nor are carboxyl groups reduced by NaBH4.

Question 9

Fischer esterification

Answer 9

Esters can be prepared by treating a carboxylic acid with an alcohol in the presence of an acid catalyst, commonly H2SO4, ArSO3H, or gaseous HCl.
-an equilibrium reaction
-A key intermediate in Fischer esterification is the tetrahedral carbonyl addition intermediate (TCAI) formed by addition of ROH to the C=O group.
•Activation of carbonyl group by protonation of carbonyl oxygen
•Nucleophilic addition of alcohol to carbonyl groupforms tetrahedral intermediate
•Elimination of water from tetrahedral intermediate restores carbonyl group

Question 10

diazomethane

Answer 10

-Diazomethane, CH2N2
–A potentially explosive, toxic, yellow gas; it is best represented as a hybrid of two contributing structures
-Esterification occurs in two steps
.Step 1: Proton transfer to diazomethane.
Step 2: Nucleophilic displacement of N2.

Question 11

decarboxylation

Answer 11

The loss of CO2 from a carboxyl group.

• Most carboxylic acids, if heated to a very high temperature, undergo thermal decarboxylation.
• carboxylic acids that have a carbonyl group beta to the carboxyl group–This type of carboxylic acid undergoes decarboxylation on mild heating.
• Malonic acid and substituted malonic acids, for example, also undergo thermal decarboxylation.