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Chemistry > 4.3 carboxylic acid and its derivatives > Flashcards

4.3 carboxylic acid and its derivatives Flashcards

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1
Q

the derivatives of carboxylic acid

A

acyl chlorides

esters

amides

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2
Q

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?
A

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

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3
Q

hydrogen bonding between ethanoic acid and water

A

pg 2

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4
Q

physical properties of carboxylic acids

  1. boiling temperature

alkane
aldehyde
alcohol
carboxylic acid ( highest )

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

A

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

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5
Q

hydrogen bonding btwn 2 carboxylic acid

A

pg 2

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6
Q

physical properties of carboxylic acids

  1. smell

ethanoic acid

malic acid

citric acid

A

ethanoic acid: vinegar

malic acid: apples

citric acid: lemon and oranges

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7
Q

preparation of carboxylic acid

2 ways

A
  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
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8
Q

ethanal to 2-hydroxypropanoic acid

give eq

A

pg 3

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9
Q

reactions of carboxylic acid

name 3

A

reduction

neutralisation

nucleophilic substitution / elimination

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10
Q

reactions of carboxylic acid
1. reduction

LiAlH4 in dry ether is a powerful reducing agent

write eq carboxylic acids to primary alcohols

A

pg 4

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11
Q

alkenes are reduced using?

A

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

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12
Q

why LiAlH4 cannot be used to reduce alkenes to alkanes

A

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

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13
Q

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

carboxylic acid shows characteristic of acids by reacting with

name 3

A

metals
eq

bases
eq

carbonates /
eq

pg 5

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14
Q

comfirmatory test for carboxylic acid

A

carboxylic acid react with carbonates/hydrogencarbonates

the rest no because no observable change

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15
Q

methanoic acid + potassium hydroxide

A

potassium methanoate

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16
Q

propanoic acid + sodium carbonate

A

sodium propanoate

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17
Q

butanoic acid + ammonia

A

ammonium butanoate

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18
Q

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

A

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

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19
Q

sodium ethanoate can be converted into ethanoic acid

type of reaction
reagent
condition
eq

A

type of reaction: hydrolysis

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

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20
Q

experiment

neutralisation
citric acid + NaOH

write an eq

A

pg 6

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21
Q

experiment

neutralisation
citric acid + NaOH

method

A

pg 6

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22
Q

reactions of carboxylic acid
3. nucleophilic substitution / elimination reaction

formation of acyl chloride

A

carboxylic acids react vigorously with PCl5 at room temp

eq pg 7

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23
Q

reactions of carboxylic acid
3. nucleophilic substitution / elimination reaction

formation of esters

A

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

eq pg 7

24
Q

synthesis of propyl ethanoate

A

pg 7

25
Q

synthesis of ethyl propanoate

A

pg 7

26
Q

reactions of carboxylic acid
3. nucleophilic substitution / elimination reaction

formation of esters

method

A

pg 8

27
Q

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

A

act as catalyst

28
Q

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?

A

reaction is exothermic
alcohol is volatile

dont want to dehydrate the alcohol

29
Q

reactions of carboxylic acid
3. nucleophilic substitution / elimination reaction

formation of esters

draw the distillation diagram

A

pg 8

30
Q

reactions of carboxylic acid
3. nucleophilic substitution / elimination reaction

formation of esters

the distillate is an impure product
3 steps required for purfication

A

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

31
Q

acyl chloride contain group

A

pg 9

32
Q

acyl chloride undergos

2 reactions

A

nucleophilic addition and followed by elimination

33
Q

why acyl chlorides are very reactive than carboxylic acid

A

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

34
Q

acyl chloride

1. reaction with water

A

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

35
Q

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

A

the atmosphere contain water

will react rapidly with water to form carboxylic acid

36
Q

acyl chloride

formation of propanoyl chloride from propanoic acid

eq

A

pg 9

37
Q

acyl chloride
1. reaction with water

why acyl chloride react with water gives solution of pH1

A

Carboxylic acid dissociate in water
acyl chloride reacts with water

  • notice the difference

room temp, HCl fumes
cold water, HCl dissolves release H+ ions

38
Q

acyl chloride

  1. reaction with water
  2. reaction with alcohol

to give ?

A

esters and HCl

eq refer to pg 10

39
Q

acyl chloride

  1. reaction with water
  2. reaction with alcohol

more effective way to make ester
why

A

non reversible, faster higher yield

no catalyst

no heat required

40
Q

acyl chloride

  1. reaction with water
  2. reaction with alcohol

disadvantage of this reaction

A

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

41
Q

acyl chloride

  1. reaction with water
  2. reaction with alcohol
  3. reaction with conc ammonia

form?

A

amides

eq pg 10

42
Q

acyl chloride

  1. reaction with water
  2. reaction with alcohol
  3. reaction with conc ammonia
  4. reaction with amine

to form?

A

produce a substituted amide

eq pg 10

43
Q

esters

contain group

A

pg 12

44
Q

esters

2 reactions

A

hydrolysis

transesterification

45
Q

esters
1. hydrolysis

heated under reflux with either aq acid or aq alkali

acid hydrolysis
reagent
condition
reaction type

A

acid hydrolysis
eq pg 12

reagent
- dilute H2SO4 / dilute HCl

condition
- heat

reaction type
acidic hydrolysis

46
Q

esters
1. hydrolysis

heated under reflux with either aq acid or aq alkali

base hydrolysis
reagent
condition
reaction type

A

base hydrolysis
eq pg 13

reagent
- dilute KOH / NaOH

condition
- heat

reaction type
- hydrolysis

47
Q

soap is made from

A

alkaline hydrolysis of fats or oils to produce sodium carboxylates

saponification

48
Q

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
A

eq pg 15

reagent
-methanoic acid

condition
- acid +heat for hydrolysis

product
- ethyl methanoate + ethanoic acid

reaction type
-transesterification

importance
- low fat margarine

49
Q

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
A

eq pg 15

reagent
- methanol

condition
- acid + heat hydrolysis

product
- methyl ethanoate + ethanol

reaction type
transesterification

importance
- biodiesel

50
Q

vegetable oils can be hardened to make margarine in 2 ways

A

partial hydrogenation

transesterification

51
Q

partial hydrogenation

how

A

a contorlled amount of H2 is added to oil in catalyst nickel

double bond are saturated harder fat is produced

trans fat

52
Q

transesterification

how

A

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

53
Q

biodiesel

eq

A

pg 16

54
Q

polyesters

condensation polymers

A

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

55
Q

polyesters

condensation polymers

monomers must have?

A

2 functional group

56
Q

polyesters

condensation polymers

can be broken down by

A

acidic or alkaline hydrolysis

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