17c - Carboxylic Acids

Question 1

What are the intermolecular forces present in carboxylic acids? (high boiling point)

Answer 1

• Hydrogen Bonding (allows for solubilty)
• London forces
• Interact with themselves forming dimers (doubling the size of the molecule in pure carboxylic acid)

Question 2

Why does solubility decrease as chain length increases in carboxylic acids?

Answer 2

• The hydrocarbon part of the molecule increases and makes it harder to hydrogen bond with water

Question 3

How can you turn a nitrile into a carboxylic acid?

Answer 3

• Hydrolysis of the CN with dilute acid or aqueous alkali

dilute acid: CH3CN + H+ + 2H2O –> CH3COOH + NH4+

aqueous alkali : CH3CN + OH- + H2O –> CH3COO- + NH3, Then add acid to protonate the COO- group

Question 4

Carboxylic acid + LiAlH4 (dry ether) (REDUCTION)

Answer 4

• reduced to primary alcohol

Question 5

Carboxylic acid + aqueous alkali (NaOH) (NEUTRALISATION)

Answer 5

• Carboxylate salt i.e RCOONa

Question 6

Carboxylic acid + PCL5 (halogenation)

Answer 6

• Forms an acyl chloride, POCl3 + HCl

Question 7

How do you make an ester from carboxylic acids? (ESTERIFICATION)

Answer 7

• Alcohol and an Acid catalyst

Question 8

Acyl Chloride + H2O

Answer 8

• Produces a Carboxylic acid + HCL

Question 9

Acyl Chloride + Alcohol

Answer 9

• ESTER is formed and HCl

Question 10

Acyl Chloride + concentrated Ammonia

Answer 10

• Forms an Amide + HCl

Question 11

Acyl Chloride + Amine

Answer 11

• Substituted Amide + HCl

- examples : N-methylamide, N,N-methyl propyl methanamide

Question 12

Hydrolysis of esters in both acidic and alkaline solutions

Answer 12

Acidic: CH3COOCH3 + H2O -> CH3OH + HCOOH

Alkaline: Carboylate salt which needs to react with acid

CH3COOCH3 + OH- –> CH3OH + HCOO-

HCOO- + H+ –> HCOOH

Question 13

How can you make polyesters?

Answer 13

• Diol + Carboxylic acid

- Condensation reaction