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CAPE Chemistry (Online) > Unit 2.7 - Alcohols and carboxylic acids > Flashcards

Unit 2.7 - Alcohols and carboxylic acids Flashcards

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
Draw hydrogen bonding between ethanol and water
(See notes)
26
Why do alcohols form hydrogen bonds with water?
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)
27
Describe the boiling points of alcohols
Alcohols have higher boiling points than alkanes of similar molar mass due to hydrogen bonding
28
Why do alcohols have higher boiling points than alkanes of similar molar mass?
Alcohols contain hydrogen bonding
29
Which bonds break when a covalent compound is boiled?
Intermolecular forces (Van der Waal, hydrogen bonding) NOT Intramolecular forces (covalent, ionic, coordinate)
30
Compare the boiling points of alcohols to those of alkanes of similar molar mass in terms of intermolecular forces
Alkanes intermolecular forces = only induced dipole-induced dipole Alcohols intermolecular forces = additional hydrogen bonding that elevate the boiling temperature
31
Draw the hydrogen bonds between ethanol and other ethanol molecules
(See notes)
32
Why does ethanol have a high boiling point?
The hydrogen bonds require a significant amount of energy to break
33
What is ethanol soluble in?
Water Non-polar solvents
34
Why is ethanol soluble in non-polar solvents?
Due to the presence of the hydrocarbon chain
35
Why is ethanol an extremely important solvent?
Soluble in both water and non-polar solvents
36
What are the 2 methods for the preparation of alcohols?
From alkenes By fermentation
37
How is ethanol reduced by an alkene?
Steam hydrolysis of ethene
38
What does the steam hydrolysis of ethene produce?
Ethanol
39
Conditions for the production of ethanol from ethene via steam hydrolysis?
Phosphoric acid catalyst/concentrated sulphuric acid 300 degrees Celsius 60 atm pressure
40
Write the equation for the formation of ethanol via the steam hydrolysis of ethene
CH2=CH2 + H2O (g) —> CH3CH2OH
41
What type of reaction is the steam hydrolysis of ethene to form ethanol?
Electrophilic addition
42
If ethanol is made by fermentation, what are the 2 processes required?
Fermentation Distillation
43
What happens during fermentation?
Sugars (glucose) from plants are converted into ethanol by the action of enzymes in the yeast (zymase)
44
Enzymes in yeast
zymase
45
Equation for the fermentation of glucose to form ethanol
C6H12O6 (aq) —> 2C2H5OH (aq) + 2CO2 (g)
46
What’s the temperature used during fermentation to form ethanol and why?
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
47
Describe the conditions of the reaction vessels for fermentation to occur to create ethanol and explain why this is necessary
Air must be kept out of the reaction vessel If not m ethanol will react (oxidise) and form ethanoic acid (vinegar)
48
What is done following fermentation to produce ethanol?
Distillation
49
When and how is ethanol distilled off the mixture following fermentation?
Once the solution contains 15% ethanol, fermentation stops and the ethanol is distilled off the mixture using fractional distillation
50
What’s the boiling point of ethanol?
78 degrees Celsius
51
Batch process
When the process has to be stopped and restarted
52
What’s the name of a process that has to be stopped and restarted?
Batch process
53
What type of process is fermentation to produce ethanol and why?
Batch process The process has to be stopped and restarted
54
Draw the label the apparatus required for distillation
(See notes)
55
Why do we need a fractioning column when producing ethanol?
We need to separate hydrocarbons of similar boiling temperatures
56
Biofuels
Fuels that are produced from living organisms (plants, microorganisms)
57
2 main types of biofuels currently used
Bio ethanol Bio diesel
58
What’s bioethanol obtained from?
Sugars in plants by fermentation
59
What’s biodiesel obtained from?
Oils and fats present from the seeds of some plans
60
How do both bioethanol and biodiesel burn and why is this significant?
Exothermically Are good heat sources Can be used as fuels
61
Advantages of biofuels
Renewable Carbon neutrality Economic and political security
62
Why are biofuels better than fossil fuels in terms of how renewable they are?
Fossil fuels will eventually run out However… Plants can be grown each year Can produce biofuels using waste material from animals
63
Why is using biofuels as a fuel carbon neural?
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
64
Equation for plants photosynthesising to achieve carbon neutrality with biofuels
6CO2 + 6H2O —> C6H12O6 + 6O2
65
How do biofuels provide economic and political security?
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
66
Disadvantages of biofuels
Land use Use of resources Carbon neutrality ???
67
How is land use a disadvantage to biofuels?
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
68
Which resources are large quantities of needed for biofuels?
Large quantities of water and fertilisers
69
Why is the large use of water for biofuels bad?
Strains local resources
70
How can water become polluted using biofuels?
The use of large quantities of fertilisers to grow the same crop year after year
71
What effect can using fertilisers year after year for biofuels have?
Polluted water
72
Why is using biofuels not certainly carbon neutral?
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
73
What are the 2 chemical reactions of alcohols?
Oxidation Dehydration
74
Oxidise agent for the oxidation of alcohols
Potassium dichromate (VI) acidified with concentrated sulphuric acid
75
Equation for acidified dichromate
H+/CrO7^-2
76
Equation for acidified potassium dichromate
H+/K2Cr2O7
77
What has to occur to the mixture for the oxidation of alcohols?
Has to be heated
78
The oxidation of what occurs in 2 stages?
Primary alcohols
79
Stages of oxidising a primary alcohol
1 - mild oxidation to produce an aldehyde 2 - further oxidise the aldehyde under reflux to produce a carboxylic acid
80
How does the first stage of the oxidation of a primary alcohol occur?
With heat Distilled
81
Equation for the first stage of the oxidation of ethanol, a primary alcohol
(See notes)
82
What occurs during the second stage of the oxidation of a primary alcohol?
The aldehyde is oxidised further under reflux
83
What is produced at the first and second steps of the oxidation of primary alcohols?
1 - aldehyde 2 - carboxylic acid
84
Write the equation for the second stage of the oxidation of ethanol, a primary alcohol
(See notes)
85
Draw a diagram to summarise the oxidation of ethanol, a primary alcohol
(See notes)
86
What happens to the dichromate ion (VI) during the oxidation of the primary alcohol, ethanol?
It’s reduced to the chromium (III) ion We see this as a colour change from orange to green
87
Why do we see a colour change during the oxidation of a primary alcohol and what is this colour change?
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
What are the stages that occur during the oxidation of secondary alcohols?
Only one stage - oxidation
89
Write the equation for the oxidation of propan-2-ol, a secondary alcohol
(See notes)
90
What’s the product of the oxidation of a secondary alcohol?
A ketone
91
Ketone functional group
C=O
92
Aldehyde functional group
C =O - H
93
What are the steps in the oxidation of tertiary alcohols?
Since there is no hydrogen on the adjacent carbon atom that can be lost, no reaction takes place
94
Why does no reaction occur during the oxidation of tertiary alcohols compares to primary and secondary alcohols?
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
What have an oxidisable hydrogen?
Primary alcohols Secondary alcohols Aldehydes
96
What happens during the dehydration of primary alcohols?
Primary alcohol is reacted with concentrated sulfuric acid in excess
97
What is a primary alcohol reacted with for its dehydration?
Concentrated sulfuric acid in excess
98
Temperature for the dehydration of primary alcohols
170 degrees Celsius
99
Main product of the dehydration of primary alcohols
Alkene
100
What does the sulfuric acid do during the dehydration of primary alcohols?
Removes the elements of water form the alcohol
101
Write the equation for the dehydration of ethanol, a primary alcohol
CH3CH2OH ⇌ CH2 = CH2 + H2O
102
What type of reaction is the dehydration of primary alcohols?
Elimination reaction
103
What can we notice from the e hydration reaction of ethanol?
It’s the reverse of producing industrial strength alcohol
104
What can we use to test for primary and secondary alcohols?
Acidified dichromate solution
105
What happens when we use acidified dichromate solution to identify primary and secondary alcohols?
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
Why is there a colour change fro orange to green when testing for primary and secondary alcohols?
The dichromate (V) ion is reduced to the chromium (III) ion
107
Why can’t we use acidified dichromate solution to test for tertiary alcohols?
They will not react with potassium dichromate
108
What does acidified dichromate solution help us identify and what’s the observation?
Primary and secondary alcohols (not tertiary) Colour change form orange to green
109
What’s an alternative catalyst to concentrated sulfuric acid for the dehydration of an alcohol from an alkene?
Aluminium oxide
110
What type of sulfuric acid is used in the preparation of alcohols from alkenes?
Concentrated
111
Advantage of producing ethene from alkenes
100% atom economy
112
What is another way that bumping can be avoided apart from using anti-bumping granules?
Carrying the reaction out in a larger container
113
Carboxylic acids functional group
COOH
114
Draw the functional group of carboxylic acids
(See notes)
115
How do we name carboxylic acids?
Add -oic acid to the alkane stem
116
Methanoic acid common name
Formic acid
117
Formic acid
Methanoic acid
118
Ethanoic acid common name
Acetic acid
119
Acetic acid
Ethanoic acid
120
Glucose formula
C6H12O6
121
Give the graphical formula of Methanoic acid
(See noteS)
122
Give the skeletal formula of Methanoic acid
(See notes)
123
Give the graphical formula of ethanoic acid
(See notes)
124
Give the skeletal formula of ethanoic acid
(See notes)
125
Shortened structural formula of Methanoic acid
HCOOH
126
Shortened structural formula of ethanoic acid
CH3COOH
127
Where do we get Methanoic/Formic acid?
Released by stinging ants
128
What do ants release when stinging?
Methanoic/Formic acid
129
Where do we get ethanoic/acetic acid?
Vinegar
130
What type of acid is in vinegar?
Ethanoic/acetic
131
Why are carboxylic acids acidic?
They release H+ ions when added to water
132
Are carboxylic acids weak or strong acids?
Weak acids
133
Why are carboxylic acids weak acids?
They do not fully dissociate into their ions in aqueous solution - there’s often less than 1% dissociation
134
What happens as a result of carboxylic acids being weak acids?
The ionisation that is needed to produce the H+ is in equilibrium
135
Write an equation for the dissociation of a carboxylic acid into its ions
RCOOH ⇌ RCOO- + H+
136
How do carboxylic acids react with all in a similar way?
Bases, carbonates and hydrogen carbonates
137
How do carboxylic acids react with bases, carbonates and hydrogen carbonates?
In a similar way to strong inorganic acids such as hydrochloric acid
138
What type of acid is hydrochloric acid?
Strong inorganic acid
139
Salt
A chemical compound formed by ionic bonds between cations and anions
140
What makes up the salt in the neutralisation reaction between an acid and a base?
A metal ion from the base replaces the H+ ion in the acid to form a salt
141
What does the hydrogen ion in acid replace to form a salt?
Metal or ammonium ion
142
Worded equation for the reaction between an acid and a base
ACID + BASE ——> SALT + WATER
143
What is sodium hydroxide an example of?
A strong alkali
144
Alkali
Base that dissociates in water
145
What does ethanoic acid and sodium hydroxide form?
Sodium ethanoate
146
Equation for the reaction between ethanoic acid and sodium hydroxide
CH3COOH + NaOH —> CH3COONa + H2O
147
Ethanoate ion
CH3COO-
148
Which ion is CH3COO-?
Ethanoate ion
149
What does ethanoic acid react with copper (II) oxide to form?
Copper (II) ethanoate
150
Equation for the reaction between ethanoic acid and copper (II) oxide
2CH3COOH + CuO —> (CH3COO)2Cu + H2O
151
Worded equation for the reaction between acids and metals
ACID + METAL —> SALT + H2
152
What does the H2 formed when an acid reacts with a metal do?
Causes effervescence
153
What does magnesium react with propanone acid to form?
Magnesium propanoate
154
Write the equation for the reaction between propanoic acid and magnesium
2CH3CH2COOH (aq) + Mg (s) —> (CH3CH2COO)2Mg (aq) + H2 (s)
155
Propanoate ion
CH3CH2COO-
156
Charges on anions from carboxylic acids
-1
157
Write a worded equation for the reaction between carboxylic acids and carbonates/hydrogencarbonates
ACID + CARBONATE —> SALT + CARBON DIOXIDE + WATER
158
Write the equation between propanoic acid and copper cabonate
2CH3CH2COOH + CuCO3 —> (CH3CH2COOH)2Cu + CO2 + H2O
159
Write the equation for the reaction between Methanoic acid and sodium hydrogencarbonate
HCOOH + NAHCO3 —> HCOONa + CO2 + H2O
160
How can we test for the presence of carboxylic acids?
Using carbonate or hydrogencarbonate
161
What are the steps for testing the presence of a carboxylic acid?
1. Addition of sodium carbonate/sodium hydrogencarbonate 2. Effervescence can be observed - test for CO2 by checking if it turns limewater milky
162
Write the reaction between ethanoic acid and sodium hydrogencarbonate
CH3COOH + NAHCO3 —> CH3COONa + CO2 + H2O
163
Write the equation for the reaction between ethanoic acid and sodium carbonate
2CH3COOH + Na2CO3 —> 2CH3COONa + CO2 + H2O
164
What are the 2 types of reactions of carboxylic acids?
As an acid Esterification
165
Esterification
Carboxylic acids react with alcohols to form an ester
166
What’s noticeable about an ester?
Sweet smelling
167
How do esters smell and what are they used for therefore?
Sweet smelling, used in fragrances
168
Functional group of esters
COO
169
What is COO the functional group of?
Esters
170
What are ester bonds important in?
Lipids
171
Draw the functional group of an ester
(See notes)
172
What’s the chemical formula of an ester?
RCOOR1 Where R is the alkane stem
173
Write the worded equation for the reaction between a carboxylic acid and alcohol
carboxylic acid + alcohol ⇌ ester + water
174
How is the carboxylic acid and alcohol added during esterification?
In equimolar amounts
175
what is required for the reaction between carboxylic acid and alcohol to occur?
concentrated sulfuric acid
176
why is it necessary to have concentrated sulfuric acid for the reaction between a carboxylic acid and an alcohol?
acts as a catalyst - the reaction would otherwise be very slow powerful dehydrating agent = removes water from the equilibrium mixture
177
under which conditions is carboxylic acid added to alcohol during esterification?
reflux
178
what happens to the position of equilibrium during esterification?
as concentrated sulfuric acid removes water, the position of equilibrium moves to the right and the reaction goes to completion
179
when does the position of equilibrium move during esterification and in which direction?
as concentrated sulfuric acid removes water moves to the right and the reaction goes to completion
180
write the chemical reaction between ethanoic acid and ethanol
CH3COOH + CH3CH2OH ⇌ CH3COOCH2CH3 + H2O
181
what is the esterification reaction also known as and why?
a condensation reaction as there's a small molecule (water) lost
182
how is the ester separated from the mixture during esterification?
through distillation
183
which two processes are used during esterification?
reflux distillation
184
why is distillation used during esterification?
to separate the ester
185
draw a diagram for reflux equipment
(See notes)_
186
draw and label a diagram for the distillation part of the esterification reaction
(see notes)
187
write the structural formula of the esterification reaction between ethanoic acid and ethanol
(See notes)
188
what is the name of an ester derived from?
from the names of the 2 reactants from which it formed
189
how do we name esters?
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
explain why the ester methyl ethanoate is called this
methyl - comes from methanol, CH3OH ethanoate - comes from ethanoic acid, CH3COOH
191
draw the structural formula for the esterification reaction between methanol and ethanoic acid
(See notes)
192
explain why the ester ethyl methanoate is called this
ethyl comes from ethanol, CH3CH2OH methanoate comes from methanoic acid, HCOOH
193
what makes it easier to write the structural equations for the formation of an ester?
put the functional groups that are reacting facing each other
194
write the structural formula for the esterification reaction that forms 2-methylethylpropanoate
(see notes)
195
methanoic acid formula
HCOOH
196
What are the conditions required for the production of as ketone from a secondary alcohol?
Reflux Cr2O7^2-/H+
197
Why is reflux used?
To avoid loss of reagents/ products
198
Does an aldehyde react with sodium carbonate? Why?
No It’s not acidic
199
Does a ketone react with sodium carbonate? Why?
No It’s to acidic
200
What is the catalyst when producing ethanol from the hydrolysis of ethane?
Phosphoric acid
201
What’s higher- the boiling point of a carboxylic acid or it’s corresponding alcohol? Why?
The boiling point of the carboxylic acid is higher It forms stronger hydrogen bonds
202
Under which condition do we use acidified potassium dichromate to test for the presence of a primary or secondary alcohol?
Under reflux
203
In what condition is the water in the production of ethanol from ethane?
Steam
204
Describe the method for preparing a sample of ethanal by oxidising ethanol
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
Describe the boiling points of esters and explain
Low as they don’t form hydrogen bonds
206
Which carbons are counted and for naming what when naming an ester?
Carbons after COO group —> alcohol (-yl) Carbons up to and including COO group —> carboxylic acid (-oate)
207
What causes the colour change to green in oxidation of alcohols reactions?
The chromium ion
208
What do you do about the side groups present when naming esters?
Name them as you would normally (first)
209
What else can acidified dichromate be used to test for except primary and secondary alcohols?
Aldehydes
210
What type of property is the fact that esters have a sweet smell?
Physical property
211
Why are enzymes good in terms of green chemistry in reactions?
Bring down the energy required
212
Which mass do we use in percentage yield questions as the theoretical mass?
The least mass

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