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A level Chemistry > Unit 2.7 - Alcohols and carboxylic acids > Flashcards

Unit 2.7 - Alcohols and carboxylic acids Flashcards

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1
Q

Alcohols

A

Compounds with one or more hydroxy (OH) groups attached to the aliphatic (straight) chain

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2
Q

How do we name an alcohol?

A

Add -ol to the alkane stem

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3
Q

Why and where would we put numbers in the names of alcohols?

A

From ethanol onwards, we need to specify the position of the hydroxy group

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4
Q

Hydroxy group

A

OH

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5
Q

What are the three groups which alcohols can be classified into?

A

Primary (1°), Secondary (2°), Tertiary (3°)

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6
Q

What can be classified as primary, secondary and tertiary?

A

Halogenoalkanes
Alcohols

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7
Q

Primary alcohols

A

The carbon which carries the OH group is only attached to 1 alkyl group (1 other carbon atom)

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8
Q

Alkyl group

A

Carbon atom group

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9
Q

What type of alcohol is ethanol?

A

Primary

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10
Q

What type of alcohol is propan-1-ol?

A

Primary

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11
Q

What type of alcohol is 2-methylpropan-1-ol?

A

Primary

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12
Q

What type of alcohol is propan-2-ol?

A

Secondary

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13
Q

What type of alcohol is butan-2-ol?

A

Secondary

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14
Q

What type of alcohol is pentan-3-ol?

A

Secondary

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15
Q

What type of alcohol is 2-methylpropan-2-ol?

A

Tertiary

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16
Q

What type of alcohol is 2-methylbuan-2-ol?

A

Tertiary

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17
Q

Secondary alcohols

A

The carbon which carries the OH group is attached to 2 alkyl groups (which may be the same or different)

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18
Q

Tertiary alcohols

A

The carbon which carries the OH group is attached to 3 alkyl groups (which may be any combination of same or different)

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19
Q

Name some physical properties

A

Melting and boiling point
Solubility

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20
Q

Describe the solubility of alcohols

A

The lower alcohols (shorter chain) are completely soluble in water (are able to form hydrogen bonds with water)
As the alkyl (hydrocarbon) chain increases in length, the contribution of the hydrogen bond to the overall intermolecular forces decreases, so the higher alcohols from butanol onwards are not very soluble in water

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21
Q

Lower alcohols

A

Shorter chain

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22
Q

Which alcohols are completely soluble in water and why?

A

Lower alcohols (shorter chain)
Are able to form hydrogen bonds with water

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23
Q

Which alcohols are less soluble in water and why?

A

The higher alcohols (longer chain) from butanol onwards
As the alkyl (hydrocarbon) chain increases in length, the contribution of the hydrogen bond to the overall intermolecular forces decreases

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24
Q

Alkyl chain

A

Hydrocarbon chain

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25
Q

Draw hydrogen bonding between ethanol and water

A

(See notes)

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26
Q

Why do alcohols form hydrogen bonds with water?

A

Highly polarising 𝛿+ hydrogen atom attracts a lone pair of electrons from a small, highly electronegative atom in another molecule (N, O, F)
(O in this case)

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27
Q

Describe the boiling points of alcohols

A

Alcohols have higher boiling points than alkanes of similar molar mass due to hydrogen bonding

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28
Q

Why do alcohols have higher boiling points than alkanes of similar molar mass?

A

Alcohols contain hydrogen bonding

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29
Q

Which bonds break when a covalent compound is boiled?

A

Intermolecular forces (Van der Waal, hydrogen bonding)
NOT Intramolecular forces (covalent, ionic, coordinate)

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30
Q

Compare the boiling points of alcohols to those of alkanes of similar molar mass in terms of intermolecular forces

A

Alkanes intermolecular forces = only induced dipole-induced dipole
Alcohols intermolecular forces = additional hydrogen bonding that elevate the boiling temperature

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31
Q

Draw the hydrogen bonds between ethanol and other ethanol molecules

A

(See notes)

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32
Q

Why does ethanol have a high boiling point?

A

The hydrogen bonds require a significant amount of energy to break

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33
Q

What is ethanol soluble in?

A

Water
Non-polar solvents

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34
Q

Why is ethanol soluble in non-polar solvents?

A

Due to the presence of the hydrocarbon chain

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35
Q

Why is ethanol an extremely important solvent?

A

Soluble in both water and non-polar solvents

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36
Q

What are the 2 methods for the preparation of alcohols?

A

From alkenes
By fermentation

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37
Q

How is ethanol reduced by an alkene?

A

Steam hydrolysis of ethene

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38
Q

What does the steam hydrolysis of ethene produce?

A

Ethanol

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39
Q

Conditions for the production of ethanol from ethene via steam hydrolysis?

A

Phosphoric acid catalyst/concentrated sulphuric acid
300 degrees Celsius
60 atm pressure

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40
Q

Write the equation for the formation of ethanol via the steam hydrolysis of ethene

A

CH2=CH2 + H2O (g) —> CH3CH2OH

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41
Q

What type of reaction is the steam hydrolysis of ethene to form ethanol?

A

Electrophilic addition

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42
Q

If ethanol is made by fermentation, what are the 2 processes required?

A

Fermentation
Distillation

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43
Q

What happens during fermentation?

A

Sugars (glucose) from plants are converted into ethanol by the action of enzymes in the yeast (zymase)

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44
Q

Enzymes in yeast

A

zymase

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45
Q

Equation for the fermentation of glucose to form ethanol

A

C6H12O6 (aq) —> 2C2H5OH (aq) + 2CO2 (g)

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46
Q

What’s the temperature used during fermentation to form ethanol and why?

A

The rate of this reaction is affected by temperature
At low temperatures, it’s slow
At high temperatures, it can denature the enzymes
The compromise is 35 degrees Celsius

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47
Q

Describe the conditions of the reaction vessels for fermentation to occur to create ethanol and explain why this is necessary

A

Air must be kept out of the reaction vessel
If not m ethanol will react (oxidise) and form ethanoic acid (vinegar)

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48
Q

What is done following fermentation to produce ethanol?

A

Distillation

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49
Q

When and how is ethanol distilled off the mixture following fermentation?

A

Once the solution contains 15% ethanol, fermentation stops and the ethanol is distilled off the mixture using fractional distillation

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50
Q

What’s the boiling point of ethanol?

A

78 degrees Celsius

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51
Q

Batch process

A

When the process has to be stopped and restarted

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52
Q

What’s the name of a process that has to be stopped and restarted?

A

Batch process

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53
Q

What type of process is fermentation to produce ethanol and why?

A

Batch process
The process has to be stopped and restarted

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54
Q

Draw the label the apparatus required for distillation

A

(See notes)

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55
Q

Why do we need a fractioning column when producing ethanol?

A

We need to separate hydrocarbons of similar boiling temperatures

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56
Q

Biofuels

A

Fuels that are produced from living organisms (plants, microorganisms)

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57
Q

2 main types of biofuels currently used

A

Bio ethanol
Bio diesel

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58
Q

What’s bioethanol obtained from?

A

Sugars in plants by fermentation

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59
Q

What’s biodiesel obtained from?

A

Oils and fats present from the seeds of some plans

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60
Q

How do both bioethanol and biodiesel burn and why is this significant?

A

Exothermically
Are good heat sources
Can be used as fuels

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61
Q

Advantages of biofuels

A

Renewable
Carbon neutrality
Economic and political security

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62
Q

Why are biofuels better than fossil fuels in terms of how renewable they are?

A

Fossil fuels will eventually run out
However…
Plants can be grown each year
Can produce biofuels using waste material from animals

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63
Q

Why is using biofuels as a fuel carbon neural?

A

Although CO2 is produced in exactly the same way by biofuels and fossil fuels when combusted, CO2 is taken in by plants when they grow via photosynthesis to produce sugars

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64
Q

Equation for plants photosynthesising to achieve carbon neutrality with biofuels

A

6CO2 + 6H2O —> C6H12O6 + 6O2

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65
Q

How do biofuels provide economic and political security?

A

Countries that do not have fossil fuels as a natural resource are less dependant on changes in price and availability tat having to import fossil fuels imposes

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66
Q

Disadvantages of biofuels

A

Land use
Use of resources
Carbon neutrality ???

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67
Q

How is land use a disadvantage to biofuels?

A

Land that is used to produce plants for biofuels cannot be used to produce food
Destroying environmentally significant areas (e.g - forests) to create land for biofuel production

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68
Q

Which resources are large quantities of needed for biofuels?

A

Large quantities of water and fertilisers

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69
Q

Why is the large use of water for biofuels bad?

A

Strains local resources

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70
Q

How can water become polluted using biofuels?

A

The use of large quantities of fertilisers to grow the same crop year after year

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71
Q

What effect can using fertilisers year after year for biofuels have?

A

Polluted water

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72
Q

Why is using biofuels not certainly carbon neutral?

A

When the fuel needed to build and run the factories needed in biofuel production (e.g - to transport new materials and finished products) are considered, it can be argues that the use of such fuels is not carbon neutral

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73
Q

What are the 2 chemical reactions of alcohols?

A

Oxidation
Dehydration

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74
Q

Oxidise agent for the oxidation of alcohols

A

Potassium dichromate (VI) acidified with concentrated sulphuric acid

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75
Q

Equation for acidified dichromate

A

H+/CrO7^-2

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76
Q

Equation for acidified potassium dichromate

A

H+/K2Cr2O7

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77
Q

What has to occur to the mixture for the oxidation of alcohols?

A

Has to be heated

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78
Q

The oxidation of what occurs in 2 stages?

A

Primary alcohols

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79
Q

Stages of oxidising a primary alcohol

A

1 - mild oxidation to produce an aldehyde
2 - further oxidise the aldehyde under reflux to produce a carboxylic acid

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80
Q

How does the first stage of the oxidation of a primary alcohol occur?

A

With heat
Distilled

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81
Q

Equation for the first stage of the oxidation of ethanol, a primary alcohol

A

(See notes)

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82
Q

What occurs during the second stage of the oxidation of a primary alcohol?

A

The aldehyde is oxidised further under reflux

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83
Q

What is produced at the first and second steps of the oxidation of primary alcohols?

A

1 - aldehyde
2 - carboxylic acid

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84
Q

Write the equation for the second stage of the oxidation of ethanol, a primary alcohol

A

(See notes)

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85
Q

Draw a diagram to summarise the oxidation of ethanol, a primary alcohol

A

(See notes)

86
Q

What happens to the dichromate ion (VI) during the oxidation of the primary alcohol, ethanol?

A

It’s reduced to the chromium (III) ion
We see this as a colour change from orange to green

87
Q

Why do we see a colour change during the oxidation of a primary alcohol and what is this colour change?

A

During the reaction, the dichromate (VI) ion, CrO7^2- is reduced to the chromium (III) ion, Cr^3+
Colour change form orange to green

88
Q

What are the stages that occur during the oxidation of secondary alcohols?

A

Only one stage - oxidation

89
Q

Write the equation for the oxidation of propan-2-ol, a secondary alcohol

A

(See notes)

90
Q

What’s the product of the oxidation of a secondary alcohol?

A

A ketone

91
Q

Ketone functional group

A

C=O

92
Q

Aldehyde functional group

A

C =O
- H

93
Q

What are the steps in the oxidation of tertiary alcohols?

A

Since there is no hydrogen on the adjacent carbon atom that can be lost, no reaction takes place

94
Q

Why does no reaction occur during the oxidation of tertiary alcohols compares to primary and secondary alcohols?

A

Since there is no hydrogen on the adjacent carbon atom that can be lost, no reaction takes place.
Only primary and secondary alcohols (and aldehydes) have an oxidisable hydrogen

95
Q

What have an oxidisable hydrogen?

A

Primary alcohols
Secondary alcohols
Aldehydes

96
Q

What happens during the dehydration of primary alcohols?

A

Primary alcohol is reacted with concentrated sulfuric acid in excess

97
Q

What is a primary alcohol reacted with for its dehydration?

A

Concentrated sulfuric acid in excess

98
Q

Temperature for the dehydration of primary alcohols

A

170 degrees Celsius

99
Q

Main product of the dehydration of primary alcohols

A

Alkene

100
Q

What does the sulfuric acid do during the dehydration of primary alcohols?

A

Removes the elements of water form the alcohol

101
Q

Write the equation for the dehydration of ethanol, a primary alcohol

A

CH3CH2OH ⇌ CH2 = CH2 + H2O

102
Q

What type of reaction is the dehydration of primary alcohols?

A

Elimination reaction

103
Q

What can we notice from the e hydration reaction of ethanol?

A

It’s the reverse of producing industrial strength alcohol

104
Q

What can we use to test for primary and secondary alcohols?

A

Acidified dichromate solution

105
Q

What happens when we use acidified dichromate solution to identify primary and secondary alcohols?

A

The primary alcohol gets converted to a carboxylic acid
The secondary alcohol gets converted into a ketone
The colour of the potassium dichromate (VI) cages from orange to green as the dichromate (VI) ion is reduced to the chromium (III) ion

106
Q

Why is there a colour change fro orange to green when testing for primary and secondary alcohols?

A

The dichromate (V) ion is reduced to the chromium (III) ion

107
Q

Why can’t we use acidified dichromate solution to test for tertiary alcohols?

A

They will not react with potassium dichromate

108
Q

What does acidified dichromate solution help us identify and what’s the observation?

A

Primary and secondary alcohols (not tertiary)
Colour change form orange to green

109
Q

What’s an alternative catalyst to concentrated sulfuric acid for the dehydration of an alcohol from an alkene?

A

Aluminium oxide

110
Q

What type of sulfuric acid is used in the preparation of alcohols from alkenes?

A

Concentrated

111
Q

Advantage of producing ethene from alkenes

A

100% atom economy

112
Q

What is another way that bumping can be avoided apart from using anti-bumping granules?

A

Carrying the reaction out in a larger container

113
Q

Carboxylic acids functional group

A

COOH

114
Q

Draw the functional group of carboxylic acids

A

(See notes)

115
Q

How do we name carboxylic acids?

A

Add -oic acid to the alkane stem

116
Q

Methanoic acid common name

A

Formic acid

117
Q

Formic acid

A

Methanoic acid

118
Q

Ethanoic acid common name

A

Acetic acid

119
Q

Acetic acid

A

Ethanoic acid

120
Q

Glucose formula

A

C6H12O6

121
Q

Give the graphical formula of Methanoic acid

A

(See noteS)

122
Q

Give the skeletal formula of Methanoic acid

A

(See notes)

123
Q

Give the graphical formula of ethanoic acid

A

(See notes)

124
Q

Give the skeletal formula of ethanoic acid

A

(See notes)

125
Q

Shortened structural formula of Methanoic acid

A

HCOOH

126
Q

Shortened structural formula of ethanoic acid

A

CH3COOH

127
Q

Where do we get Methanoic/Formic acid?

A

Released by stinging ants

128
Q

What do ants release when stinging?

A

Methanoic/Formic acid

129
Q

Where do we get ethanoic/acetic acid?

A

Vinegar

130
Q

What type of acid is in vinegar?

A

Ethanoic/acetic

131
Q

Why are carboxylic acids acidic?

A

They release H+ ions when added to water

132
Q

Are carboxylic acids weak or strong acids?

A

Weak acids

133
Q

Why are carboxylic acids weak acids?

A

They do not fully dissociate into their ions in aqueous solution - there’s often less than 1% dissociation

134
Q

What happens as a result of carboxylic acids being weak acids?

A

The ionisation that is needed to produce the H+ is in equilibrium

135
Q

Write an equation for the dissociation of a carboxylic acid into its ions

A

RCOOH ⇌ RCOO- + H+

136
Q

How do carboxylic acids react with all in a similar way?

A

Bases, carbonates and hydrogen carbonates

137
Q

How do carboxylic acids react with bases, carbonates and hydrogen carbonates?

A

In a similar way to strong inorganic acids such as hydrochloric acid

138
Q

What type of acid is hydrochloric acid?

A

Strong inorganic acid

139
Q

Salt

A

A chemical compound formed by ionic bonds between cations and anions

140
Q

What makes up the salt in the neutralisation reaction between an acid and a base?

A

A metal ion from the base replaces the H+ ion in the acid to form a salt

141
Q

What does the hydrogen ion in acid replace to form a salt?

A

Metal or ammonium ion

142
Q

Worded equation for the reaction between an acid and a base

A

ACID + BASE ——> SALT + WATER

143
Q

What is sodium hydroxide an example of?

A

A strong alkali

144
Q

Alkali

A

Base that dissociates in water

145
Q

What does ethanoic acid and sodium hydroxide form?

A

Sodium ethanoate

146
Q

Equation for the reaction between ethanoic acid and sodium hydroxide

A

CH3COOH + NaOH —> CH3COONa + H2O

147
Q

Ethanoate ion

A

CH3COO-

148
Q

Which ion is CH3COO-?

A

Ethanoate ion

149
Q

What does ethanoic acid react with copper (II) oxide to form?

A

Copper (II) ethanoate

150
Q

Equation for the reaction between ethanoic acid and copper (II) oxide

A

2CH3COOH + CuO —> (CH3COO)2Cu + H2O

151
Q

Worded equation for the reaction between acids and metals

A

ACID + METAL —> SALT + H2

152
Q

What does the H2 formed when an acid reacts with a metal do?

A

Causes effervescence

153
Q

What does magnesium react with propanone acid to form?

A

Magnesium propanoate

154
Q

Write the equation for the reaction between propanoic acid and magnesium

A

2CH3CH2COOH (aq) + Mg (s) —> (CH3CH2COO)2Mg (aq) + H2 (s)

155
Q

Propanoate ion

A

CH3CH2COO-

156
Q

Charges on anions from carboxylic acids

A

-1

157
Q

Write a worded equation for the reaction between carboxylic acids and carbonates/hydrogencarbonates

A

ACID + CARBONATE —> SALT + CARBON DIOXIDE + WATER

158
Q

Write the equation between propanoic acid and copper cabonate

A

2CH3CH2COOH + CuCO3 —> (CH3CH2COOH)2Cu + CO2 + H2O

159
Q

Write the equation for the reaction between Methanoic acid and sodium hydrogencarbonate

A

HCOOH + NAHCO3 —> HCOONa + CO2 + H2O

160
Q

How can we test for the presence of carboxylic acids?

A

Using carbonate or hydrogencarbonate

161
Q

What are the steps for testing the presence of a carboxylic acid?

A
  1. Addition of sodium carbonate/sodium hydrogencarbonate
  2. Effervescence can be observed - test for CO2 by checking if it turns limewater milky
162
Q

Write the reaction between ethanoic acid and sodium hydrogencarbonate

A

CH3COOH + NAHCO3 —> CH3COONa + CO2 + H2O

163
Q

Write the equation for the reaction between ethanoic acid and sodium carbonate

A

2CH3COOH + Na2CO3 —> 2CH3COONa + CO2 + H2O

164
Q

What are the 2 types of reactions of carboxylic acids?

A

As an acid
Esterification

165
Q

Esterification

A

Carboxylic acids react with alcohols to form an ester

166
Q

What’s noticeable about an ester?

A

Sweet smelling

167
Q

How do esters smell and what are they used for therefore?

A

Sweet smelling, used in fragrances

168
Q

Functional group of esters

A

COO

169
Q

What is COO the functional group of?

A

Esters

170
Q

What are ester bonds important in?

A

Lipids

171
Q

Draw the functional group of an ester

A

(See notes)

172
Q

What’s the chemical formula of an ester?

A

RCOOR1
Where R is the alkane stem

173
Q

Write the worded equation for the reaction between a carboxylic acid and alcohol

A

carboxylic acid + alcohol ⇌ ester + water

174
Q

How is the carboxylic acid and alcohol added during esterification?

A

In equimolar amounts

175
Q

what is required for the reaction between carboxylic acid and alcohol to occur?

A

concentrated sulfuric acid

176
Q

why is it necessary to have concentrated sulfuric acid for the reaction between a carboxylic acid and an alcohol?

A

acts as a catalyst - the reaction would otherwise be very slow
powerful dehydrating agent = removes water from the equilibrium mixture

177
Q

under which conditions is carboxylic acid added to alcohol during esterification?

A

reflux

178
Q

what happens to the position of equilibrium during esterification?

A

as concentrated sulfuric acid removes water, the position of equilibrium moves to the right and the reaction goes to completion

179
Q

when does the position of equilibrium move during esterification and in which direction?

A

as concentrated sulfuric acid removes water
moves to the right and the reaction goes to completion

180
Q

write the chemical reaction between ethanoic acid and ethanol

A

CH3COOH + CH3CH2OH ⇌ CH3COOCH2CH3 + H2O

181
Q

what is the esterification reaction also known as and why?

A

a condensation reaction as there’s a small molecule (water) lost

182
Q

how is the ester separated from the mixture during esterification?

A

through distillation

183
Q

which two processes are used during esterification?

A

reflux
distillation

184
Q

why is distillation used during esterification?

A

to separate the ester

185
Q

draw a diagram for reflux equipment

A

(See notes)_

186
Q

draw and label a diagram for the distillation part of the esterification reaction

A

(see notes)

187
Q

write the structural formula of the esterification reaction between ethanoic acid and ethanol

A

(See notes)

188
Q

what is the name of an ester derived from?

A

from the names of the 2 reactants from which it formed

189
Q

how do we name esters?

A

1st part - alcohol, with name changes to end with -yl
2nd part - carboxylic acid or acid anhydride, with name changed to end in -oate

190
Q

explain why the ester methyl ethanoate is called this

A

methyl - comes from methanol, CH3OH
ethanoate - comes from ethanoic acid, CH3COOH

191
Q

draw the structural formula for the esterification reaction between methanol and ethanoic acid

A

(See notes)

192
Q

explain why the ester ethyl methanoate is called this

A

ethyl comes from ethanol, CH3CH2OH
methanoate comes from methanoic acid, HCOOH

193
Q

what makes it easier to write the structural equations for the formation of an ester?

A

put the functional groups that are reacting facing each other

194
Q

write the structural formula for the esterification reaction that forms 2-methylethylpropanoate

A

(see notes)

195
Q

methanoic acid formula

A

HCOOH

196
Q

What are the conditions required for the production of as ketone from a secondary alcohol?

A

Reflux
Cr2O7^2-/H+

197
Q

Why is reflux used?

A

To avoid loss of reagents/ products

198
Q

Does an aldehyde react with sodium carbonate? Why?

A

No
It’s not acidic

199
Q

Does a ketone react with sodium carbonate? Why?

A

No
It’s to acidic

200
Q

What is the catalyst when producing ethanol from the hydrolysis of ethane?

A

Phosphoric acid

201
Q

What’s higher- the boiling point of a carboxylic acid or it’s corresponding alcohol? Why?

A

The boiling point of the carboxylic acid is higher
It forms stronger hydrogen bonds

202
Q

Under which condition do we use acidified potassium dichromate to test for the presence of a primary or secondary alcohol?

A

Under reflux

203
Q

In what condition is the water in the production of ethanol from ethane?

A

Steam

204
Q

Describe the method for preparing a sample of ethanal by oxidising ethanol

A

Acid and dichromate until it dissolves
Cool mixture and add ethanol dropwise (shaking between additions)
Set up distillation apparatus
Heat gently until liquid bois over

205
Q

Describe the boiling points of esters and explain

A

Low as they don’t form hydrogen bonds

206
Q

Which carbons are counted and for naming what when naming an ester?

A

Carbons after COO group —> alcohol (-yl)
Carbons up to and including COO group —> carboxylic acid (-oate)

207
Q

What causes the colour change to green in oxidation of alcohols reactions?

A

The chromium ion

208
Q

What do you do about the side groups present when naming esters?

A

Name them as you would normally (first)

209
Q

What else can acidified dichromate be used to test for except primary and secondary alcohols?

A

Aldehydes

210
Q

What type of property is the fact that esters have a sweet smell?

A

Physical property

211
Q

Why are enzymes good in terms of green chemistry in reactions?

A

Bring down the energy required

212
Q

Which mass do we use in percentage yield questions as the theoretical mass?

A

The least mass

A level Chemistry (39 decks)

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