3.3.5 Alcohols Knowledge Flashcards
(106 cards)
1
Q
what is an alcohol?
A
molecule with a hydroxyl functional group attached to a hydrocarbon chain
2
Q
what is the general formula of alcohols?
A
CnH2n+1OH
3
Q
what is the functional group isomer of butan-1-ol?
A
ethoxyethane - H3CCHOCHCH3
4
Q
what is the carbonyl group?
A
C=O
5
Q
what is the carbonyl group bonded to in aldehydes?
A
Carbonyl bonded to at least one H atom
6
Q
what is the structural formula for the carbonyl group in an aldehyde?
A
CHO
7
Q
what is the suffix for an aldehyde?
A
-al
8
Q
what number is the carbonyl group in an aldehyde?
A
The carbonyl group in an aldehyde is always C number 1
9
Q
what is the carbonyl group bonded to in ketones?
A
Carbonyl bonded to two C atoms
10
Q
what is the structural formula for the carbonyl group in a ketone?
A
CO
11
Q
what is the suffix for a ketone?
A
-one
12
Q
what number is the carbonyl group in a ketone?
A
Because the C= can be at different positions in a chain, they often require a number that is not 1
13
Q
what is the carbonyl group bonded to in carboxylic acids?
A
Carbonyl bonded to an OH group
14
Q
what is the structural formula for the carbonyl group in a carboxylic acid?
A
COOH
15
Q
what is the suffix for a carboxylic acid?
A
-oic acid
16
Q
what number is the carbonyl group in a carboxylic acid?
A
The carbonyl in carboxylic acids is always C number 1
17
Q
How many [o]s are used in the oxidation of a primary alcohol through distillation?
A
1
18
Q
How many [o]s are used in the oxidation of an aldehyde through reflux?
A
1
19
Q
How many [o]s are used in the oxidation of a primary alcohol through reflux?
A
2
20
Q
How many [o]s are used in the oxidation of a secondary alcohol?
A
1
21
Q
How many waters are produced in the oxidation of a primary alcohol under distillation?
A
1
22
Q
How many waters are produced in the oxidation of an aldehyde under reflux
A
0
23
Q
How many waters are produced in the oxidation of a primary alcohol under reflux.
A
1
24
Q
How many waters are produced in the oxidation of a secondary alcohol?
A
1
25
What is the oxidising agent for the the oxidation of alcohols?
Acidified potassium dichromate
26
What is the observation for alcohol oxidation?
Orange (Cr2O7^2-) to green (Cr3+)
27
How do you test for types of alcohols?
1. Test that you have an alcohol by testing for the -OH group; show that it is a neutral liquid, free of water and that it reacted with solid phosphorus(V) chloride to produce a burst of acidic steamy hydrogen chloride fumes.
2. Add a few drops of the alcohol to a test tube containing potassium dichromate(VI) solution acidified with dilute sulphuric acid.
3. Warm tube would be in a hot water bath.
4. In the case of a primary or secondary alcohol, the orange solution turns green. With a tertiary alcohol there is no colour change.
5. Produce enough of the aldehyde (from oxidation of a primary alcohol) or ketone (from a secondary alcohol) to be able to test them. There are various things which aldehydes do which ketones don't. These include the reactions with Tollens' reagent, Fehling's solution and Benedict's solution
28
Why don’t tertiary alcohols oxidise?
- With primary and secondary alcohols, the oxidising agent removes the hydrogen from the -OH group, and a hydrogen from the carbon atom attached to the -OH. Tertiary alcohols don't have a hydrogen atom attached to that carbon.
- You need to be able to remove those two particular hydrogen atoms in order to set up the carbon-oxygen double bond.
29
what is the reagent for turning a primary alcohol into an aldehyde?
acidified potassium dichromate
30
what conditions are required for turning a primary alcohol into an aldehye?
Heat under distillation
31
what does a primary alcohol become when it is heated under distillation with acidified potassium dichromate?
aldehyde
32
what is the reagent for turning an aldehyde into a carboxylic acid?
acidified potassium dichromate
33
what conditions are required to turn an aldehyde into a carboxylic acid?
heat under reflux
34
what does an aldehyde become when it is heated under reflux with acidified potassium dichromate?
carboxylic acid
35
what is the reagent for turning a primary alcohol into a carboxylic acid?
acidified potassium dichromate
36
what conditions are required to turn a primary alcohol into a carboxylic acid?
heat under reflux, excess oxidising agent
37
what does a primary alcohol become when it is heated under reflux with excess acidified potassium discorhomae?
carboxylic acid
38
what is the reagent for turning a secondary alcohol into a ketone?
acidified potassium dichromate
39
what conditions are required to turn a secondary alcohol into a ketone?
heat under reflux or distillation
40
what does a secondary alcohol become when it is heated with acidified potassium dichromate?
ketone
41
why does the choice of heat under reflux or distillation affect what is produced from the oxidation of a primary alcohol?
because of the different boiling points of alcohols, aldehydes, and carboxylic acids
42
what is the strongest IMF in alcohols?
hydrogen bonding
43
what is the strongest IMF in carboxylic acids?
hydrogen bonding
44
what is the strongest IMF in aldehydes?
p.d.d
45
which out of alcohols, aldehydes, and carboxylic acids have the lowest boiling point and why?
- The strongest IMF in alcohols is hydrogen bonding
- The strongest IMF in carboxylic acids is hydrogen bonding
- The strongest IMF in aldehydes is p.d.d; this is the weakest IMF so has the lowest boiling point
46
describe the structure and function of a condenser
- Are open at both ends
- Cold water flows around the outside
- Cools hot vapour and condenses it to a liquid
47
what is the purpose of anti-bumping granules?
- Heating of a reaction mixture can cause the formation of large bubbles and 'bumping' of the equipment, which is unsafe
- Anti-Bumping Granules added to the reaction mixture prevent the formation of large bubbles
48
why is Reflux is used to oxidise a primary alcohol to a carboxylic acid?
as it doesn't allow any reactant vapour to escape
49
describe the production of ethanoic acid from ethanol useing reflux apparatus
1. Ethanol and acidified K2Cr2O7 are heated to boiling point for a prolonged time.
2. Ethanal vapour is formed which escapes from the liquid mixture
3. Ethanal vapour is then condensed back into liquid and returns to the reaction mixture.
4. Any ethanal and ethanol that initially evaporates can then be oxidised.
50
describe the process of creating a carboxylic acid from a primary alcohol using reflux apparatus?
1. Aldehyde vapour rises and enters condenser
2. Aldehyde vapour cools and condenses, then drops back into reaction mixture
51
why do condensers have an open top/end?
to prevent pressure build up, which could cause an explosion
52
where should the thermometer be in distillation apparatus?
The thermometer must be level with the side arm
53
why is distillation used to produce aldehydes from primary alcohols?
As the aldehyde is produced in distillation, it forms a vapour and escapes from the reaction mixture into the condenser. Distillation allows the aldehyde to escape the reaction mixture and prevents further oxidation.
54
describe how aldehydes are produced from primary alcohols under distillation
- Aldehyde vapour rises and enters condenser
- Aldehyde vapour cools and condenses
- Aldehyde product is collected
55
what shape are the H-C-H and C-C-O bonds in alcohols?
tetrahedral, 109.5 - there are 4 BP of electrons repelling to a position of minimum repulsion
56
what shape is the H-O-C bond in alcohols?
104.5, bent - there are 2 BP and 2LP
57
do alcohols have relatievly high or low volatitlity?
low
58
do alcohols have relatively high or low BP?
high
59
why do alcohols have relateivly low volatility and high BP?
due to their ability to form hydrogen bonds between alcohol molecules
60
why can smaller alcohols dissolve in water?
they can form hydrogen bonds to water molecules
61
why are electric heaters often used to heat organic chemicals?
they are normally highly flammable and could set on fire with a naked flame
62
how can you improve the yield of distillate in distillation?
the collection flask can be cooled in ice
63
why can't tertiary alcohols be oxidised by potassium dichomate?
there are no hydrogen atoms bonded to the carbon with the -OH group
64
give the equation for the reaction of CH3CHO with tollen's reagent
CH3CHO + 2Ag+ + H2O -> CH3COOH + 2Ag + 2H+
65
give the equation for the reaction of CH3CHO with Fehling's solution
CH3CHO + 2Cu2+ + 2H2O -> CH3COOH + Cu2O + 4H+
66
what are 2 methods for ethanol production?
- Direct Hydration
- Fermentation
67
give the equation for the production of ethanol through direct hydration
H2C=CH2(g) + H2O(g) ⇒ CH3CH2OH(l)
68
what is the reagent required for the production of ethanol through direct hydration?
H2O(g)
69
what are the conditions required for the production of ethanol through direct hydration?
concentrated H3PO4 catalyst, high temperature (200-450 degrees), high pressure (50-100 atm)
70
what are the advantages of the production of ethanol through direct hydration?
- high-purity ethanol produced
- continuous production
- fast rate of reaction
71
what are the disadvantages of the production of ethanol through direct hydration?
- Crude oil is not renewable
- high temperature and pressure requires a lot of energy (expensive)
- hi-tech equipment required (expensive)
72
give the equation for the production of ethanol through fermentation
C6H12O6 ⇒ 2CH3CH2OH + 2CO2
73
what are the conditions required for the production of ethanol through fermentation?
yeast catalyst/enzyme, no air (anaerobic conditions), temperature 30-40 degrees
74
what happens if the temperature is too low in the production of ethanol through fermentation?
the reaction will be too slow
75
what happens if the temperature is too high in the production of ethanol through fermentation?
the yeast enzyme will be destroyed/denatured
76
what are the advantages of the production of ethanol through fermentation?
- glucose is a renewable resource
- lower temperatures require less energy
- simpler equipment required is cheaper
77
what are the disadvantages of the production of ethanol through fermentation?
- land used to grow crops is not available for food crops
- ethanol is impure and must be distilled to purify
- low yield
- slow rate of reaction
- batch production method is difficult to automate
78
give equations supporting the statement that bio-ethanol is a carbon-neutral feul
- overall there is no CO2 released into the atmosphere when using bio-ethanol as a fuel; 6CO2 taken in during photosynthesis. A total of 6CO2 are released during fermentation and combustion of ethanol.
- Photosynthesis: 6CO2 + 6H2O ⇒ C6H12O6 + 6O2
- Fermentation: C6H12O6 ⇒ 2CH3CH2OH + 2CO2
- Combustion: 2CH3CH2OH + O2 ⇒ 4CO2 + 3H2O
79
why is Bio-ethanol not really a carbon-neutral fuel?
multiple processes involved in producing and distributing bioethanol use fossil fuels that releases CO2. e.g. - planting
- harvesting
- transport
- extracting sugar
- distilling ethanol solution
- fertiliser production
80
what do alcohols combust to form?
Combust to form CO2 and H2O
81
what do alcohols undergo incomplete combustion to form?
Incomplete combustion leads to the formation of CO or C particles
82
why does petrol now contain 10% ethanol?
to reduce the environmental impact of burning fossil fuels to power cars, as ethanol can be made renewably
83
how does ethanol content in petrol reduce the environmental impact of burning fossil fuels to power cars?
as ethanol can be made renewably
84
how can cyclohexene be made?
from the dehydration of cyclohexanol using concentrated phosphoric acid as a catalyst
85
what is the functional group in cyclohexanol?
OH alcohol group
86
what is the functional group in cyclohexene?
C=C alkene group
87
What is the strongest IMF present between molecules of cyclohexanol?
hydrogen bonds
88
What is the strongest IMF present between molecules of phosphoric acid?
hydrogen bonds
89
What is the strongest IMF present between molecules of cyclohexen?
induced dipole-dipole
90
What is the strongest IMF present between molecules of water?
hydrogen bonds
91
does cyclohexanol, phosphoric acid, cyclohexene, or water have the lowest boiling point? explain your answer
- cyclohexene has the lowest boiling point as it has the weakest IMF
- cyclohexene has induced dipole-dipole attractions between molecules
- all others have hydrogen bonds between molecules
- hydrogen bonding is stronger than i.d.d
92
what temperature should the thermometer be maintained at when distilling the product from the dehydration of cyclohexanol, and why?
85-90 degrees - above the boiling point of cyclohexene, below the boiling point of water
93
are the molecules in cyclohexanol polar or non-polar?
polar
94
are the molecules in phosphoric acid polar or non-polar?
polar
95
are the molecules in cyclohexene polar or non-polar?
non-polar
96
are the molecules in water polar or non-polar?
polar
97
draw a diagram of the separating funnel used for solvent extraction
98
state why cyclohexene can be separated from an aqueous solution using a separating funnel
different layers are immiscible
99
comment on the density of cyclohexene compared to the aqueous layer
cyclohexene is less dense than the aqueous layer
100
state why the two liquid layers in a separating funnel are mixed by shaking before the aqueous layer was drained from the separating funnel
to ensure all water soluble impurities are in the aqueous layer
101
explain why it is important to open the tap of the separating funnel periodically after shaking the liquid layers together
to allow built-up gas to escape
102
why is a spatula of anhydrous calcium chloride added to the cyclohexene after separation
drying agent absorbs any remaining water
103
name the apparatus used to separate two immiscible liquids
separating funnel
104
why is sodium hydrogen carbonate solution added to the impure product of the reaction between cyclohexanol and water
the sodium hydrogen carbonate solution will react with the acid catalyst not used up in the reaction, thus neutralising it. 2H^+ + CO3^2- -> H2O + CO2
105
describe how re-distillation removes unreacted cyclohexanol from the product when creating cyclohexene
- cyclohexanol and cyclohexene have different boiling points
- cyclohexene has weak i.d.d. attractions between molecules
- cyclohexanol has stronger hydrogen bonds between molecules
- cyclohexene has a lower boiling point and will boil first in the mixture, and thus will be collected as a distillate when separated from cyclohexanol
106
why could there be a build up of pressure in the separating funnel when creating cyclohexene from cyclohexanol
The build-up of pressure comes from acid catalyst impurites reacting with sodium hydrogen carbonate, creating CO2 gas
