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a level chemistry > Chapter 26 - Carboxylic Acids > Flashcards

Chapter 26 - Carboxylic Acids Flashcards

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1
Q

what are CA made from?

A

primary alcohols

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2
Q

what if there are 2 CA groups?

A
  • dioic acid

e. g. propanedioic acid

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3
Q

what can the carboxyl group be attached to?

A

a benzene ring e.g. benzenecarboxylic acid

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4
Q

what is the name if an OH is attached to the CA?

A

add hydro- to first part of name e.g. hydrohexanoic acid

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5
Q

which C IS C1 in a CA?

A

The COOH C

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6
Q

Dissociation of Benzoic acid equation?

A

Benzoic acid (reversible ➡) Benzoate ion + H+

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7
Q

benzoate ion not ?

A

BENZONOATE

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8
Q

Why is a CA a weak acid?

A

only partially dissociates/ ionises into weak H+ ions in water

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9
Q

How do CAs react ?

A

like normal acids

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10
Q

Acid + metal ➡

A

H2 + metal salt

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11
Q

Acid + metal Hydroxide ➡

A

H20 + salt

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12
Q

Acid + carbonate ➡

A

CO2 + H2O + SALT

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13
Q

Acid + metal Oxide ➡

A

H2O + salt

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14
Q

ethanoic acid dissociation equation?

A

CH3COOH ➡(Reversible) CH3COO- + H+

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15
Q

⭐ Remember?

A

reversible arrow as CAs are weak acids

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16
Q

be careful w ?

A

charge on the metal ion

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17
Q

how can esters be made?

A

by reacting a CA w an alcohol. This rac

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18
Q

what is the ester FG?

A

-COO and it’s in the middle of the molecule

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19
Q

which part of the ester comes from the alcohol?

A

-O-

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20
Q

which part of the ester comes from the CA?

A

-C=O-

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21
Q

what is an ester and what does this mean?

A

A derivative of a CA - this means that an ester can be hydrolysed (broken down by the addition of H2O) to form a CA

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22
Q

How is an ester named?

A
  • after CA
    -oic acid is replaced with -oate
    first part of name is from alcohol
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23
Q

Reagents and Conditions needed to make an Ester?

A

R: An alcohol
C: Reflux w H2SO4

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24
Q

ester prep: why is a water bath used?

A

for safety as ethanol and the ester are flammable

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25
Q

ester prep: why are anti-bumping granules added into the reflux flask?

A

to promote smooth boiling

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26
Q

ester prep: what is the role of conc H2S04?

A
  • catalyst + dehydrating agent

as it removes the water, the equilibrium shifts forwards forming more ester

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27
Q

ester prep: the esterification reaction is?

A

reversible so after reflux there is a mixture pf r+ p in the flask

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28
Q

ester prep: How is the sulfuric acid removed from the products?

A
  • add 10cm3 of aq Na2CO3 at a time until no further fizzing, this neutralises acid forming a salt that is Na2CO3
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29
Q

ester prep: How is the sulfuric acid removed from the products?

A
  • add 10cm3 of aq Na2CO3 at a time until no further fizzing, this neutralises acid forming a salt that is Na2SO4
  • Na2CO3 + H2SO4 ➡ Na2SO + H2O + CO2
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30
Q

ester prep: why are there 2 layers in the separating funnel?

A

organic esters are insoluble in the water and H2SO4 is aq. The ester is less dense so floats on the surface of the aq layer.

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31
Q

ester prep: when the ester is removed from the separating funnel, why is some anhydrous sodium sulphate added?

A

a small amount of H2O is always left mixed w the ester, to dry ester

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32
Q

ester prep: what is the last stage?

A

redistill the ester to remove any remaining impurities

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33
Q

Uses of esters: Ethyl 2-methylbutanoate?

A

apple

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34
Q

Uses of esters: butyl butanoate?

A

pineapple

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35
Q

Uses of esters: 1-methylbutyl ethanoate?

A

banana

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36
Q

(general uses of esters)?

A
  • solvents for chemical industry
  • solvent for adhesives
  • flower & plant fragrances used to make perfumes
  • for flavouring food
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37
Q

what is hydrolyiss?

A

the chemical break down of a substance by reaction of water

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38
Q

conidtions for acid hydrolyiss of an ester?

A

reflux the ester w dilute HCl (aq) or dilute H2SO4

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39
Q

equation for acid hydrolysis of ester?

A

Ester + water ➡ CA+ alcohol (this is the reverse of esterification)

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40
Q

conditions for acid hydrolysis of an ester?

A

reflux the ester w dilute HCl (aq) or dilute H2SO4

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41
Q

equation for acid hydrolysis of ester?

A

Ester + water (acid not written in equation) ➡ CA+ alcohol (this is the reverse of esterification)

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42
Q

acid vs alkali hydrolysis of esters?

A
  • acid produces CA+ alc but alkali produces carboxylate salt + alc
  • acid involves reaction of ester w acid, but alkali w alkali
43
Q

equation for alkali hydrolysis of ester?

A

ester + aq alkali ➡ alcohol + carboxylate salt

44
Q

solubility of CAs?

A
  • C=O and O-H bonds in CAs are polar, allowing them to form H bonds w H2O
  • CAs with up to 4 C atoms are soluble in H2O
  • As the number of C atoms ⬆, the solubility ⬇ as the non polar C chain has a greater effect on the overall polarity of the molecule
45
Q

Dicarboxylic acids?

A

have 2 polar carboxyl grs to form H bonds. they are solids at room temp and dissolve readily in water

46
Q

CAs take place in ? reactions

A
  • redox (w metals) and neutralisations reactions (w bases - alkalis, metal oxides, carbonates)
47
Q

how are carboxylate ions named?

A

by changing the -ic ending of the CA to -ate

48
Q

CA derivatives have a ?

A

common sequence of atoms in their structure known as an acyl group - R-C=O. Esters, Acyl chlorides, acid anhydrides are all derivatives of CAs.

49
Q

TO carry out acid hydrolysis?

A
  • the ester is heated under reflux with dilute aq acid

- the ester is broken down by water, w the acid acting as a catalyst

50
Q

alkaline hydrolysis?

A
  • known as saponification + is irreversible

- ester heated under reflux w aq hydroxide ions

51
Q

test for the carboxyl group?

A
  • the neutralisation reaction of CAs w carbonates
  • CAs are the only common organic compounds sufficiently acidic to react w carbonates.
  • this is espec useful for distinguishing CAs from phenols - which aren’t acidic enough to react w carbonates.
52
Q

how to name CA?

A
  • anoic ending
  • no of Cs is the first part of the name - LONGEST CHAIN
  • C in COOH is C1
53
Q

Solubility of CAs?

A

decreases as chain length increases - as the chain length increases so does the number of induced dipole forces -> harder to break in order to dissolve -> molecule stays bonded together instead of dissolving

54
Q

carboxylic acid salts have the ending?

A

-oate

55
Q

reaction of a carboxylic acid + metal?

A

e.g.(ethan)oate + H2

56
Q

reaction of a carboxylic acid + oxide?

A

-oate salt and water

57
Q

reaction of a carboxylic acid + carbonate?

A

-oate and water

58
Q

reaction of CA with alkali?

A

metal (ethan)oate

59
Q

When writing the equation for an alcohol and CA?

A

Write the alcohol first and CA back to front as alcohol forms the first part of the name.

60
Q

how to know which side of ester is from CA?

A

the side that contains the carbonyl bond is from the CA

61
Q

uses of esters?

A
  • solvents
  • fragrances
  • flavourings
62
Q

⭐

A

look out for branches esters - if there’s a branch on C1 of the alcohol then it’s made from a secondary or tertiary alcohol

63
Q

propan-2-ol becomes ? in an ester?

A

1-ethylmethyl

64
Q

Alcohol name may be different ?

A

in the esters name!

65
Q

Carboxylic acid loses?

A

the OH

66
Q

Alcohol loses?

A

H

67
Q

cyclocarboxylic acid?

A

a separate C with the OOH needs to be attached to the cyclo compound

68
Q

when figuring out the name of the CA and Alc from the ester?

A
  • break the O and the CO (ester bond)

the O side is the alc side and the C=O side is the CA side

69
Q

acid anhydrides FG?

A

c=o - o - c=o

70
Q

how are anhydrides made?

A

from 2 CAs by removing a mol of water - one CA used loses OH and other loses H

71
Q

how to name an anhydride?

A

look at one side of the O and count the number of carbons on that side (e.g. propanoic anydride has 6 Cs in total :)

72
Q

anhydrides vs CAs?

A

anhydrides are CA derivatives but are MORE REACTIVE than CAs. They can also form esters.

73
Q

making an ester using alc + CA vs making an ester from alc and acid anhydride?

A
  • alc+ CA: reversible reaction, conc H2SO4 catalyst, reflux

- alc + anhydride: non reversible, no catalyst needed, can be refluxed

74
Q

2 reasons why chemists prefer to use anhydrides to prepare esters?

A
  • anhydrides: irreverible reaction thfr ⬆ yield as reaction goes to completion
  • anhydrides: CA is produced which can be sold so increased atom economy, water produced when CA is used
75
Q

what happens when a dioic acid reacts w a base?

A

2 mol of base needed as 2 mol of H are lost from the dioic acid

76
Q

what happens when a dioic acid reacts w a G2 metal?

A

the metal has a 2+ charge and the acid loses 2 H so no need to double the acid ion
- H is also produced

77
Q

which C is C1?

A

first C of COOH

78
Q

Solubility of CAs?

A

⬇as chain length ⬆

more induced dipole forces, harder to overcome in order to dissolve

79
Q

reaction of CA w metal?

A

2 CH3COOH + Mg ➡ (CH3COO-)2Mg2+ + H2

magnesium ethanoate

80
Q

reaction of CA w carbonate?

A

2CH3COOH + CaCO3 ➡ (CH3COO-)2Ca+ + H2O

calcium ethanoate

81
Q

reaction of CA w oxide?

A

2CH3COOH + CuO ➡ (CH3COO-)2Cu+ + H2O

copper ethanoate

82
Q

reaction of CA w alkali?

A

CH3COOH + NaOH ➡ CH3COONa + H2O

sodium ethanoate

83
Q

esterification REMEBER?

A
  • water formed
  • reversible arrow
  • CA loses OH, Alc loses H
84
Q

ester uses?

A

solvents
fragrances
flavourings

85
Q

⭐ look out for?

A

Branched esters - if there’s a branch on C1 of the alcohol, then its made from a 2/3’ alc

86
Q

acid hydrolysis is?

A

reversible

alkali catalysed hydrolysis is not

87
Q

alkali hydrolysis is the higher ? reaction

A

yield

88
Q

NaOH splits into (alkali hydrolysis)

A

NaO and H

H bonds to O and NaO to O of O=C

89
Q

Propan-2-ol is what in an ester?

A

1-methylethyl

90
Q

⭐

A

alcohol name may be diff in the ester name

91
Q

how to work out the alc + CA from an ester?

A
  • Break ester bond
  • c=o is CA side
  • o is alc side
92
Q

anyhydrides?

A
  • made from 2 CA molecules
  • by removing a molecule of water (OH from 1, H from another)
  • anhydrides have 2x as many Cs as the CA making em
93
Q

why is it necessary to use an anhydride when forming an ester from phenol?

A
  • they’re both acids
  • phenol is the weaker acid so it acts as a base (accepts protons)
  • the anhydride is more acidic so it donates protons
  • 2 ions formed
    (reversible reaction)
94
Q

CA derivatives?

A

have a common sequence of atoms in their structure known as acyl groups (RC=O)
All acyl groups are attached to a electronegative atom/ group of atoms

95
Q

reactions of anhydrides?

A
  • react w phenol to produce phenyl ???-oate and CA

- react w water to form 2 CA molecules9

96
Q

ACYL CHLORIDES?

A
  • more reactive than anhydrides which are more reactive than CA
  • used in OS
  • high yield reactions
97
Q

how are acyl chlorides prepared?

A
  • reacting CA w thionyl chloride SOCl2
  • reaction produces 3 products: HCl (g), SO2(g) both are acidic and corrosive
    and the acyl chloride
98
Q

acyl chlorides and acid anhydrides react INSTEAD OF?

A

CA

99
Q

Reactions of acyl chlorides: w alc to form ester?

A

HCl ALWAYS FORMED, rest of mols just join up lol

100
Q

when acyl chlorides form esters?

A

arrow is NOT reversible

101
Q

when acyl chlorides react w phenol?

A
  • ester formed - phenyl ???-oate, HCl formed

- join whats left together

102
Q

for it to be safer when making an ester?

A

use acid anhydride not acyl chlorides as HCl formed when acyl chlorides used

103
Q

other reactions of acyl chlorides?

A
  • react w water
  • it’s a very vigorous reaction
    HCl formed + CA
104
Q

what is the advantage of using CA derivatives?

A

using anhydrides and acyl chlorides in reactions like esterification means no catalyst required

a level chemistry (39 decks)

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