17c - carboxylic acids

Question 1

what is the relative strength of carboxylic acids?

Answer 1

weak acids that dissociate partially

Question 2

what is the name of the ion RCOO-?

Answer 2

carboxylate ion

Question 3

describe the solubility of carboxylic acids in water.

Answer 3

• hydrogen bonding up to C4

Question 4

describe the hydrogen bonding between carboxylic acids.

Answer 4

pure liquid carboxylic acids form dimer with each other

Question 5

in which 2 ways could carboxylic acids be made?

Answer 5

1- oxidation from primary alcohols
2- hydrolysis of nitriles

Question 6

what are the reagents & conditions of hydrolysis of nitriles?

Answer 6

reagents - HCl (aq)
conditions - heat under reflux

Question 7

what are the reagents & conditions of reduction of carboxylic acids? what is the product?

Answer 7

reagent - LiAlH4 in dry ether
condition - room temperature & Pa
carboxylic acid -> primary alcohol

Question 8

what are the 2 tests for carboxylic acids?

Answer 8

• test with carbonate - effervescence
• test with PCl5 - HCl tested with NH3 produce white steamy fumes

Question 9

what is an example of salt formed from reacting a carboxylic acid with a base?

Answer 9

CH3COO-Na+

Question 10

how many [H] are needed in reduction of carboxylic acids?

Answer 10

4

Question 11

what are the products of reacting PCl5 with carboxylic acids?

Answer 11

acyl chloride + POCl3 + HCl

Question 12

how are esters formed? list the reagents & conditions.

Answer 12

reagents - carboxylic acid, alcohol, under H2SO4 catalyst
conditions - heat under reflux

Question 13

how are esters seperated from the equilibrium mixture?

Answer 13

distillation is done in situ as reaction is reversible

Question 14

why do esters not form hydrogen bonds?

Answer 14

hydrogen not bonded to highly electrogenative atom

Question 15

what is the relative boiling point of an ester compared to its relative carboxylic acid?

Answer 15

lower

Question 16

what are the products of acid hydrolysis?

Answer 16

carboxylic acids & alcohols

Question 17

what are the reagents & conditions of acid hydrolysis?

Answer 17

reagents - dilute acid catalyst
conditions - heat under reflux

Question 18

what are the problems of acid hydrolysis?

Answer 18

doesn’t produce a good yield since reaction is reversible

Question 19

what are the products of base hydrolysis?

Answer 19

carboxylate ion & alcohol

Question 20

what are the reagents and conditions of base hydrolysis?

Answer 20

reagents - NaOH
conditions - heat under reflux

Question 21

what is the difference between base & acid hydrolysis?

Answer 21

base hydrolysis is irreversible since anion is resistant to attack by nucleophiles

Question 22

what is the functional group of an acyl chloride?

Answer 22

-COCl

Question 23

what is the relative reactivity of an acyl chloride compared to its carboxylic acid? why?

Answer 23

much more reactive
- Cl is a good leaving group

Question 24

in which 4 ways could an acyl chloride react?

Answer 24

• H2O
• alcohols
• NH3
• primary amines

Question 25

what are the reagents, conditions and products of reacting acyl chlorides with H2O?

Answer 25

reagents - H2O conditions - room temp products - carboxylic acid + HCl gas

Question 26

what are the reagents, conditions and products of reacting acyl chlorides with alcohols?

Answer 26

reagents - alcohols conditions - room temp products - ester + HCl gas

Question 27

what are the reagents, conditions and products of reacting acyl chlorides with NH3?

Answer 27

reagents - NH3 conditions - room temp products - primary amide + NH4Cl

Question 28

what are the reagents, conditions and products of reacting acyl chlorides with primary amines?

Answer 28

reagents - primary amine conditions - room temp products - n-linked amide + HCl gas

Question 29

why is reacting acyl chlorides with alcohols a better way of making esters?

Answer 29

reaction is not reversible & quicker

Question 30

what is the functional group of a primary amide?

Answer 30

-CONH2

Question 31

what is the difference between an amide & an amine?

Answer 31

amide has an oxygen bonded to the same carbon

Question 32

how are polyesters formed by condensation polymerisation?

Answer 32

1- dicarboxylic acid + diol -> polyester + H2O 2- diacyl chloride + diol -> polyester + HCl 3- carboxylic acid + alcohol -> ester + H2O (in equilibrium mixture)