4.3 carboxylic acid and its derivatives

Question 1

the derivatives of carboxylic acid

Answer 1

acyl chlorides

esters

amides

Question 2

physical properties of carboxylic acids

1. solubility
   acids are very soluble in organic solvents
   the lower members of carboxylic acids are soluble in water why?

Answer 2

carboxylic acid form hydrogen bond with water molecules. the lower members have shorter hydrocarbon chain. hence are less hydrophobic

Question 3

hydrogen bonding between ethanoic acid and water

Answer 3

pg 2

Question 4

physical properties of carboxylic acids

2. boiling temperature

alkane
aldehyde
alcohol
carboxylic acid ( highest )

why carboxylic acids have higher boiling temp than similar alcohols why?

Answer 4

alkane
aldehyde
alcohol
carboxylic acid ( highest )

one molecule of carboxylic acid can form 2 hydrogen bonding with another carboxylic acid

one molecule of alcohol can form 1 hydrogen bonding with another alcohol

the intermolecular force of carboxylic acid is stronger than alcohols. more energy is required to break

Question 5

hydrogen bonding btwn 2 carboxylic acid

Answer 5

pg 2

Question 6

physical properties of carboxylic acids

3. smell

ethanoic acid

malic acid

citric acid

Answer 6

ethanoic acid: vinegar

malic acid: apples

citric acid: lemon and oranges

Question 7

preparation of carboxylic acid

2 ways

Answer 7

1. oxidation of primary alcohols and aldehydes by K2Cr2O7 / H2SO4 + heat
   eq pg 3
2. acidic hydrolysis of nitriles by strong acids ( HCl ) + heat
   eq pg 3

Question 8

ethanal to 2-hydroxypropanoic acid

give eq

Answer 8

pg 3

Question 9

reactions of carboxylic acid

name 3

Answer 9

reduction

neutralisation

nucleophilic substitution / elimination

Question 10

reactions of carboxylic acid
1. reduction

LiAlH4 in dry ether is a powerful reducing agent

write eq carboxylic acids to primary alcohols

Answer 10

pg 4

Question 11

alkenes are reduced using?

Answer 11

hydrogen gas in the presence of a catalyst of nickel / platinum

Question 12

why LiAlH4 cannot be used to reduce alkenes to alkanes

Answer 12

LiAlH4 is a powerful reducing agent that provides H- which is a strong nucleophile

H- only attacks slightly+ C from polar bonds C=O

alkene had C=C which is non polar and will repel nucleophiles due to its high electron density cloud

Question 13

reactions of carboxylic acid
2. neutralisation / Acid - base reaction

carboxylic acid shows characteristic of acids by reacting with

name 3

Answer 13

metals
eq

bases
eq

carbonates /
eq

pg 5

Question 14

comfirmatory test for carboxylic acid

Answer 14

carboxylic acid react with carbonates/hydrogencarbonates

the rest no because no observable change

Question 15

methanoic acid + potassium hydroxide

Answer 15

potassium methanoate

Question 16

propanoic acid + sodium carbonate

Answer 16

sodium propanoate

Question 17

butanoic acid + ammonia

Answer 17

ammonium butanoate

Question 18

why sodium ethanoate can exist as solid in room tmp while ethanoic acid is liquid

Answer 18

sodium ethanoate is an ionic compound, bonds need more heat to be broken down

ethanoic acid is a simple molecule with hydrogen bond and has covalent bond

Question 19

sodium ethanoate can be converted into ethanoic acid

type of reaction
reagent
condition
eq

Answer 19

type of reaction: hydrolysis

reagent: aq sulphuric acid
condition: heat is needed for condition

Question 20

experiment

neutralisation
citric acid + NaOH

write an eq

Answer 20

pg 6

Question 21

experiment

neutralisation
citric acid + NaOH

method

Answer 21

pg 6

Question 22

reactions of carboxylic acid
3. nucleophilic substitution / elimination reaction

formation of acyl chloride

Answer 22

carboxylic acids react vigorously with PCl5 at room temp

eq pg 7

Question 23

reactions of carboxylic acid
3. nucleophilic substitution / elimination reaction

formation of esters

Answer 23

esterification reactions are acid-catalysed ( concentrated sulphuric acid ) and reversible

eq pg 7

Question 24

synthesis of propyl ethanoate

Answer 24

pg 7

Question 25

synthesis of ethyl propanoate

Answer 25

pg 7

Question 26

reactions of carboxylic acid 3. nucleophilic substitution / elimination reaction formation of esters method

Answer 26

pg 8

Question 27

reactions of carboxylic acid 3. nucleophilic substitution / elimination reaction formation of esters esterification reactions are acid-catalysed ( concentrated sulphuric acid ) and reversible use of conc sulphuric acid

Answer 27

act as catalyst

Question 28

reactions of carboxylic acid 3. nucleophilic substitution / elimination reaction formation of esters esterification reactions are acid-catalysed ( concentrated sulphuric acid ) and reversible why conc sulphuric acid is added slowly with cooling?

Answer 28

reaction is exothermic alcohol is volatile dont want to dehydrate the alcohol

Question 29

reactions of carboxylic acid 3. nucleophilic substitution / elimination reaction formation of esters draw the distillation diagram

Answer 29

pg 8

Question 30

reactions of carboxylic acid 3. nucleophilic substitution / elimination reaction formation of esters the distillate is an impure product 3 steps required for purfication

Answer 30

wash with dilute sodium carbonate and release the pressure at intervals - to remove acid add a little anyhydrous calcium chloride solution and swirl until clear - to remove water redistilled to narrow temp 75-78

Question 31

acyl chloride contain group

Answer 31

pg 9

Question 32

acyl chloride undergos 2 reactions

Answer 32

nucleophilic addition and followed by elimination

Question 33

why acyl chlorides are very reactive than carboxylic acid

Answer 33

the C atom of C-Cl bond has a stronger slightly + charge and much more susceptible to nucleophilic attack than C of COOH in carboxylic acid

Question 34

acyl chloride | 1. reaction with water

Answer 34

acyl chloride is hydrolysed by water to form parent carboxylic acids and HCl eq pg 9 reaction is very vigorous liquid will fume in air and is responsible for its choking smell

Question 35

why ethanoyl chloride must be protected from the atmospheric moisture during storage

Answer 35

the atmosphere contain water | will react rapidly with water to form carboxylic acid

Question 36

acyl chloride formation of propanoyl chloride from propanoic acid eq

Answer 36

pg 9

Question 37

acyl chloride 1. reaction with water why acyl chloride react with water gives solution of pH1

Answer 37

Carboxylic acid dissociate in water acyl chloride reacts with water * notice the difference room temp, HCl fumes cold water, HCl dissolves release H+ ions

Question 38

acyl chloride 1. reaction with water 2. reaction with alcohol to give ?

Answer 38

esters and HCl eq refer to pg 10

Question 39

acyl chloride 1. reaction with water 2. reaction with alcohol more effective way to make ester why

Answer 39

non reversible, faster higher yield no catalyst no heat required

Question 40

acyl chloride 1. reaction with water 2. reaction with alcohol disadvantage of this reaction

Answer 40

toxic fumes of HCl is produced acyl chloride cannot be stored is an expensive chemical reaction is highly exothermic ( process does not need heat C--Cl bond broken releases a lot of energy ) , requires cooling

Question 41

acyl chloride 1. reaction with water 2. reaction with alcohol 3. reaction with conc ammonia form?

Answer 41

amides | eq pg 10

Question 42

acyl chloride 1. reaction with water 2. reaction with alcohol 3. reaction with conc ammonia 4. reaction with amine to form?

Answer 42

produce a substituted amide eq pg 10

Question 43

esters contain group

Answer 43

pg 12

Question 44

esters 2 reactions

Answer 44

hydrolysis transesterification

Question 45

esters 1. hydrolysis heated under reflux with either aq acid or aq alkali acid hydrolysis reagent condition reaction type

Answer 45

acid hydrolysis eq pg 12 reagent - dilute H2SO4 / dilute HCl condition - heat reaction type acidic hydrolysis

Question 46

esters 1. hydrolysis heated under reflux with either aq acid or aq alkali base hydrolysis reagent condition reaction type

Answer 46

base hydrolysis eq pg 13 reagent - dilute KOH / NaOH condition - heat reaction type - hydrolysis

Question 47

soap is made from

Answer 47

alkaline hydrolysis of fats or oils to produce sodium carboxylates saponification

Question 48

esters 1. hydrolysis 2. transesterification one ester is converted into another catalysed by acid or base ``` reaction with another carboxylic acid eq reagent condition product reaction type importance ```

Answer 48

eq pg 15 reagent -methanoic acid condition - acid +heat for hydrolysis product - ethyl methanoate + ethanoic acid reaction type -transesterification importance - low fat margarine

Question 49

esters 1. hydrolysis 2. transesterification one ester is converted into another catalysed by acid or base ``` reaction with another alcohol eq reagent condition product reaction type importance ```

Answer 49

eq pg 15 reagent - methanol condition - acid + heat hydrolysis product - methyl ethanoate + ethanol reaction type transesterification importance - biodiesel

Question 50

vegetable oils can be hardened to make margarine in 2 ways

Answer 50

partial hydrogenation transesterification

Question 51

partial hydrogenation how

Answer 51

a contorlled amount of H2 is added to oil in catalyst nickel double bond are saturated harder fat is produced trans fat

Question 52

transesterification how

Answer 52

a saturated chain fatty acid and vegetable oil is catalysed by an enzyme the satyrated fatty acid replaces one of the unsaturated acids in oil spreadable margarine

Question 53

biodiesel eq

Answer 53

pg 16

Question 54

polyesters condensation polymers

Answer 54

joining of monomers with elimination of small molecule as H2O and HCl

Question 55

polyesters condensation polymers monomers must have?

Answer 55

2 functional group

Question 56

polyesters condensation polymers can be broken down by

Answer 56

acidic or alkaline hydrolysis