3.3 Organic chemistry Flashcards
(168 cards)
1
Q
Alkanes are saturated hydrocarbons, what does this mean?
A
The only have single C-C bonds.
2
Q
What is petroleum?
A
A mixture consisting mainly of alkane hydrocarbons that can be separated by fractional distillation.
3
Q
What is cracking in terms of bonds?
A
Breaking C-C bonds in alkanes.
4
Q
What are the conditions and products of thermal cracking?
A
Conditions: high pressure, high temperature
Products: high percentage of alkenes
5
Q
What are the conditions and products of catalytic cracking?
A
Conditions: slight pressure, high temperature, zeolite catalyst
Products: motor fuels, branched alkanes, cycloalkanes
6
Q
What are the benefits of catalytic cracking?
A
It saves time and money, as the catalyst speeds up the reaction and a lower temperature and pressure is needed.
7
Q
What are the economic reasons for cracking alkanes?
A
There is a larger demand for lighter fractions like, naphtha and petrol. However, heavier fractions like bitumen aren’t in high demand. So, lighter fractions are much more valuable. Alkenes may also be formed which are useful premediates.
8
Q
What are alkanes mainly used for?
A
Fuels
9
Q
What are the 2 types of combustion?
A
Complete
Incomplete, occurs when there is a lack of oxygen, creates CO instead.
10
Q
What pollutants are created in an internal combustion engine?
A
Oxides of nitrogen
Carbon monoxide
Carbon dioxide
Unburnt hydrocarbons
Sulfur dioxide
11
Q
How are the gaseous pollutants from internal combustion engines removed?
A
Catalytic converters
12
Q
What happens when you combust hydrocarbons that contain sulfur?
A
It creates sulfur dioxide which leads to air pollution.
13
Q
What are the effects of sulfur dioxide on the environment?
A
Erosion of buildings
Killing of plants and trees
Contamination of lakes
14
Q
How do we remove sulfur from fuel?
A
Flue gas desulfurisation
15
Q
Describe the process of flue gas desulfurisation.
A
Calcium oxide/ calcium carbonate is coated on a mesh to increase surface area to react forming CaSO3 ( and CO2 for calcium carbonate.) The calcium sulphite is further oxidised to SO4 to make plaster and plasterboard.
16
Q
What are the environmental effects of oxides of nitrogen?
A
Acid rain which causes:
Erosion of buildings
Killing of plants and trees
Contamination of lakes
17
Q
What does a catalytic converter do?
A
It reacts NO, CO and unburnt fuel to produce H2O, CO2 and N2.
It has a honeycomb structure for increased surface area.
It uses a platinum catalyst
18
Q
What is the process used to make chloroalkanes?
A
Free radical substitution
19
Q
What are the 3 stages of free radical substitution?
A
Initiation
Propagation
Termination
20
Q
What are the conditions for the free radical substitution of chlorine and methane?
A
UV light
Excess methane to reduce further substitution
21
Q
What is initiation?
A
UV light is used to make a free radical.
22
Q
What happens in propagation?
A
A free radical is used to make another free radical.
23
Q
What is termination?
A
2 free radicals react together and stop the reaction.
24
Q
What is a free radical?
A
A species with an unpaired electron.
25
Why is free radical substitution a bad method for making chloroalkanes?
Polysubstitution reactions occur
Unwanted termination reactions occur
Lots of unwanted products and a poor atom economy
26
Why can crude oil have a different composition?
If it comes from a different source.
27
Why can crude oil sometimes contain sulfur?
Compounds containing sulphur are present in the organic matter that forms crude oil.
28
What is fractional distillation (crude oil)?
Heating the crude oil and collecting the fractions that boil over a range of temperatures.
29
What is a fraction?
A section of the crude oil containing hydrocarbons with similar chain lengths and properties.
30
Describe the process of fractional distillation.
-Heat the crude oil in a furnace.
-Liquid and vapour pass into the column which is cooler at the top.
-Vapour passes up the tower via trays containing bubble caps until they arrive at a tray that is cool enough, and they condense.
-The mixture of liquids on each tray is piped off.
-Shorter chain hydrocarbons condense in the trays towards the top as they have lower boiling points.
The thick residue at the bottom (tar/ bitumen,) is used for road surfacing . There’s not very high demand. So, it’s cracked.
31
What are the different fractions?
(C1-C3) gases- fuel onsite
(C4-C12) gasoline/petrol- cars
(C12-C16) kerosene/ paraffin- jet fuelling, lighting
(C15-C18) diesel oil- lorries, taxis
(C19-C35) lubricating oil/ waxes- candles, engine oil
(C35-C70) fuel oil- ships, power stations
(C70 up) tar/bitumen- roads, roofing
32
Why does thermal cracking produce alkenes?
When C-C bonds break, one electron from the pair goes to each carbon atom, leaving unpaired electrons so, carbon free radicals. One chain must have a carbon double bond as there aren’t enough hydrogens. To avoid decomposition into hydrogen, alkanes are taken out quickly
33
What is an aldehyde?
Carbonyl group in terminal carbon atoms
Suffix -al
34
What is a ketone?
Carbonyl group (C—O) not attached to terminal carbon atoms.
Suffix -one
35
Why are CFCs harmful to the environment?
The CI-C bonds can be broken through absorbance of uv radiation. This leads to the formation of chlorine atoms (which are free radicals.) which catalyse the decomposition of ozone and contribute to holes in the ozone layer.
36
What are CFCs and what are they used for?
Chlorofluorocarbons, used to cool air inside refrigerators. But, long chain ones are used as dry-cleaning and degreasing solvents.
37
What is ozone?
O3, formed naturally in the upper atmosphere.
38
What is the ozone layer?
A layer of the stratosphere. 15-30km above earths surface. It absorbs UV radiation from the sun.
39
How was a solution for CFCs created?
The results of research of different groups in the scientific community lead to evidence for the legislation to ban the use of CFCs as solvents of refrigerants. Chemists have now developed alternative chlorine-free alternatives.
40
What type of bonds do halogenoalkanes have?
Polar bonds
41
Which nucleophiles undergo substitution with halogenoalknes?
OH-
CN-
NH3
42
What are the properties of halogenoalkanes?
Not soluble in water as the bond isn't polar enough.
Contain permanent dipole-dipole forces and Van der Waals forces.
They mix with hydrocarbons so they can be used as dry-cleaning fluids and to remove oily stains.
43
Why are halogenoalkanes attacked by nucleophiles?
Due to polarity, the carbon atom attached to the halogen is electron deficient, so, it can be attacked by electron rich things.
44
What are nucleophiles?
Electron pair donor- contain a lone pair of electrons which can be used to form a covalent bond.
45
What are the reaction conditions for nucleophilic substitution with OH-?
Warm
Aqueous solution
46
What are the conditions for nucleophilic substitution with CN-?
Warm with aqueous alcoholic solution of potassium cyanide.
47
What are the reaction conditions for nucleophilic substitution with NH3?
Excess concentrated solution of ammonia in ethanol
Pressure
48
What is the role of OH- in elimination?
Instead of acting like a nucleophile, it acts as a base. It removes a H+ ion from the haloalkane.
49
What are the products of elimination?
Alkene
Water
Salt
50
What is the functional group of an amine?
NH2
51
What are the reaction conditions for elimination?
Heat
No water
Dissolved in ethanol
52
What is a structural isomer?
It has the same molecular formula but a different structure.
53
What is the functional isomer of an alkene?
Cycloalkanes
54
What are the 3 types of structural isomer?
Chain
Positional
Functional
55
What is the difference between different isomers?
Have different melting and boiling points (molecules with no branching tend to have higher boiling points due to their higher surface area leading to stronger VanderWaals forces.)
56
What is stereoisomerism?
Molecules with the some structural formula but with atoms arranged differently in space.
57
What is E-Z isomerism?
A form of stereoisomerism and occurs as a result of restricted rotation about the planar carbon-carbon double bond.
58
What is an electrophile?
An electron pair acceptor.
59
What are some examples of electrophiles?
Hydrogen halides
Halogens
Concentrated sulfuric acid
60
What is the test for alkene?
It turns bromine water colourless.
61
Why is there a major and minor product produces in electrophilic addition?
Positive inductive effect. The carbon on the double bond with the most R groups attached is more likely to have the positive charge of the carbocation.Because, surrounding carbons push electrons towards it as alkyl groups have larger electron density than H. So, tertiary carbocation intermediates are more stable.
62
What are addition polymers formed from?
Alkenes
Substituted alkenes
63
What are the properties of polymers?
Unreactive- contain strong bonds, that are non-polar and saturated. (Can lead to disposability problems.)
Produce toxic gases when burnt.
High mpts and bpts- strong VderW forces between chains.
64
What are the benefits of recycling polymers?
It reduces the consumption of finite oil resources.
Gets rid of plastics in landfill. (Reducing carbon footprint, energy consumption and water consumption.)
65
What are the energy costs of recycling plastics?
Transport of materials
Sorting, melting and shredding
Transport of new products
66
What is a plasticiser?
It makes a polymers more flexible. ( gets in between chains and pushes them apart reducing the strength of IMFs. So, they can slide around more and are easier to bend.)
67
What is PVC?
It contains long closely packed polymer chains.
Hard and Brittle at room temperature.
68
What is rigid PVC used for?
Drainpipes
Window frames
69
What is plasticised PVC used for?
It flexible so, it's used for:
Electric cable insulation
Flooring tiles
Clothing
70
What is an alkene?
An unsaturated hydrocarbon.
71
Describe the bonding in an alkene.
They contain a double covalent bond, which is a centre of high electron density.
72
How are alcohols produces industrially?
Hydration of alkenes in the presence of an acid catalyst.
73
What are the reaction conditions for the hydration of an alkene?
Steam
300 degrees
60atm
Solid phosphoric acid catalyst.
74
How is ethanol produced industrially?
Fermentation of glucose
75
What are the reaction conditions for fermentation of glucose?
Anaerobic
30-40 degrees
Aqueous
Yeast
76
What happens to ethanol made from fermentation?
It's separated from the mixture using fractional distillation and then used as a biofuel.
77
What is a biofuel?
A fuel that is made from biological material that's recently died.
78
Why do we use a temperature of 30-40 degrees for fermentation?
A high temperature would cause the enzyme to denature. A low temperature would slow down rate of reaction and yield.
79
Why is the statement that ‘ethanol from fermentation is a carbon neutral fuel’ invalid?
Fossil fuels need to be burnt to power machinery to:
Fertilise the crops
Harvest
Refine
Transport
Burning fuel to power machinery produces carbon dioxide.
80
What are the ethical and environmental issues with using biofuels?
Car engines may have to be modified to deal with high ethanol concentration.
The land can't be used to grow food so, you may not be able to feed everyone in the country.
It's not entirely carbon neutral.
VOCs are given off during the drying process.
81
What are the different classifications of alcohols?
Primary
Secondary
Tertiary
82
What can primary alcohols be oxidised to?
Aldehydes and then carboxylic acids
83
What are secondary alcohols oxidised to?
Ketones
84
What are tertiary alcohols oxidised to?
They are not easily oxidised.
85
What is a suitable mildly oxidising agent for the oxidation of alcohols?
Acidified potassium dichromate
86
What are the reaction conditions for the oxidation of an alcohol?
Reflux
Dilute H2SO4
(Acidified potassium dichromate)
87
What are the advantages of biofuels?
Alcohols burn cleaner than petrol, reducing pollution.
By-products are used as animal feed.
88
What are the advantages of fermentation?
Low tech
Cheap equipment
Renewable recourses
Low energy
89
What are the disadvantages of fermentation?
Slow
Impure ethanol
Batch process
90
How are alkenes formed from alcohols?
Acid-catalysed elimination reactions
91
What are alkenes produced from elimination of alcohols used for?
To produce addition polymers without using monomers from crude oil.
92
What are the disadvantages of producing alkenes from elimination?
The product isn't pure. It's in a solution of water.
93
Why are reflux conditions used?
It allows the reaction to occur at a high temperature without losing volatile reactants or products to evaporation. Leading to a higher percentage yield and a more complete reaction.
94
Why do you get a mixture of products when dehydrating alcohols?
The carbon-carbon double bond can form on either side of the C with the OH group attached.
95
What are the 3 ways of identifying organic molecules?
Melting and boiling point- but many have similar ones.
Spectroscopy analysis- mass spectra, MIR, IR
Identification tests
96
Which test is Tollen's reagent used for?
Aldehydes
Warm tollen's reagent
Result: silver mirror
97
Which test is Fehlings solution used for?
Aldehydes
Warm the solution
Result: blue solution - brick red precipitate
98
What test is used for primary and secondary alcohols and aldehydes?
Warm with potassium dichromate and dilute sulfuric acid
Result: orange solution - green solution
99
What test is used for carboxylic acids?
Add sodium carbonate or sodium hydrogen carbonate.
Result: effervescence
100
What happens when sulfuric acid reacts with an alkene?
Alkenes will react with cold concentrated sulfuric acid to form alkyl hydrogen sulfates. You can then convert the alkyl hydrogen sulfates formed into alcohols by adding water and warming the reaction mixture. If you then add cold water and warm the product, it hydrolyses to form an alcohol. The sulfuric acid isn't used up — it acts as a catalyst.
101
Anti-bumping granules are placed in the flask when refluxing.
Suggest why these granules prevent bumping.
form smaller bubbles or prevent large bubbles
102
Describe the method, including apparatus and practical details, that the student should use to prepare a standard solution.
Weigh the weighing boat containing the solid on a balance
Transfer to beaker and reweigh the weighing boat
Record the difference in mass
Add distilled/ deionised water
Stir (with a glass rod) or swirl
Until all solid has dissolved
Transfer to volumetric flask
With washings
Make up to 250cm mark with water
Invert multiple times
103
What are the 2 methods of removing impurities?
Distillation- Separates based on boiling point
Separating funnel- Separates based on solubility
104
What are some examples of impurities?
By-products
Unreacted reactants
105
Describe the process of using a separating funnel.
Add a solvent that dissolves the impurities but not the desired product.
Shake a few times and remove the stopper to release pressure.
Remove the lower waste layer.
Repeat the process a few times.
Pour the desired product into a beaker.
Add anhydrous calcium chloride to dry the product.
The product may now be filtered or distilled again to further purify and confirm purity by testing the boiling point.
106
Describe the nature of the bonding in a benzene ring.
Each Carbon forms 3 covalent bonds.
All 6 C-C bonds have the same length intermediate between a single and double bond.
The delocalisation of electrons stabilises the molecule.
107
Describe the nature of the structure of a benzene ring.
All 6 C-C bonds have the same length, between that of a single and double bond. So, the molecule is a regular planar hexagon.
There are 6 carbons in the ring with a bond angle of 120 degrees.
108
Why is benzene more stable than cyclohexa-1,3,5-triene?
The delocalisation of the p electrons
109
What is the evidence behind the benzene structure?
ΔH of hydrogenation of cyclohexene is -120 kJmol-1
So, the expected ΔH of hydrogenation of cyclohexatriene is 3 x -120 = -360 kJmol-1
But, ΔH of hydrogenation of benzene is -208 kJmol-1
The difference is -208 - (-360) = 152 kJmol-1
Benzene is lower in energy than cyclohexatriene and therefore more stable due to delocalisation of electrons.
110
Why does benzene undergo substitution reactions rather than addition reactions?
Benzene revisits addition reactions as it involves breaking delocalisation and losing stability.
111
What are the conditions for nitration?
Conc.HNO3
Conc.H2SO4
Warm
112
What is the reagent used for reduction of a nitrobenzene?
H2 / Pt
113
What are nitrobenzenes used for?
Explosives
Manufacture of amines
114
What are the 2 methods of making a primary aliphatic amine?
Nucleophilic substitution of haloalkanes with ammonia
Reduction of nitriles
115
What are the disadvantages of using nucleophilic substitution to make aliphatic amines?
Polysubstitution takes place as the product is also a nucleophile. So, when there is excess haloalkane, you can get a quaternary ammonium salt.
116
How are aromatic amines produced?
By the reduction of nitrogen compounds.
117
What are the uses of aromatic amines?
The manufacture of dyes
118
What are ammonium salts used for?
Cationic surfactants used in detergent, fabric conditioner and conditioner.
119
What the uses of ammonium salts?
Cationic surfactants used in detergent, fabric conditioner and conditioner.
120
What factor affects the base strength of an amine?
The availability of the lone pair on the nitrogen atom.
121
What factors affect the availability of the lone pair on a nitrogen atom?
Alkyl groups push the electrons towards the nitrogen and have a positive inductive effect. The more alkyl groups, the larger the positive inductive effect.
122
Why are aromatic amines weak bases?
The lone pair on the nitrogen is partially delocalised in the pi bond of the benzene ring. So, the availability of the lone pair decreases and base strength decreases.
123
Is an amino acid an acid or a base and why?
It acts as both as it has an amino group and a carboxyl (COOH) group as well.
124
What is a zwitterion?
When an amino acid has 2 charges on it. The amino group is protonated and the carboxyl group is deprotonated.
125
When does an amino acid exist in its zwitterion form?
Solid form
Isoelectric point
126
Why do amino acids have relatively high boiling points?
They ionically bond to each other in their solid zwitterion form.
127
What is a protein?
A sequence of amino acids joined by peptide links.
128
What type of reaction takes place when 2 amino acids react with each other?
A condensation reaction takes place where the acids react with the loss of water to form a peptide bond.
129
What are the reagents and conditions for the acid hydrolysis of a peptide bond?
Reflux
HCl
(Water molecule adds across the bond)
130
What are the reagents and conditions for the base hydrolysis of a peptide bond?
NaOH
Followed up with H+
131
What method is used to separate amino acids and analyse them?
Thin-layer chromatography
132
Describe the method used for the thin-layer chromatography of proteins.
Break down the proteins into amino acids
Heat with concentrated HCl
Use chromatography to separate the mixture
Spray on ninhydrin which makes the amino acids appear pink, but ninhydrin itself is colourless.
Or, you can use UV
Then, identify the amino acids by using their Rf values
133
What is the primary structure of a protein?
The sequence of amino acids
134
What is the secondary structure of a protein?
At different points, the chain can curl or fold. The chains are held together by the hydrogen bonds between the N-H and the C=O.
135
Give 2 examples of secondary structures of proteins.
Alpha helix
Beta-pleated sheet
136
What is the tertiary structure of a protein?
It is held together by the interaction of the R-groups. Covalent and ionic bonds can be formed, giving the protein a 3D shape.
137
What are the 2 different bonds that hold a tertiary structure together?
Hydrogen bond- acts between polar groups
Disulfide bridge- The amino acid cysteine has a S-H group which can bond to another S-H group after losing the H.
138
What are the properties of an enzyme?
It’s a protein.
It acts as catalyst.
It’s soluble in water.
They have a stereospecific active site that binds to a substrate molecule.
139
How does a drug act as an enzyme inhibitor?
It blocks the active site
140
How are enzyme inhibitor drugs made?
Computers are used to help design drugs.
141
Wha is the definition of an enzyme?
They speed up chemical reactions by acting as biological catalysts.
142
Why does the active site only bond to 1 enantiomeric form of a substrate?
Enzymes contain chiral centres. So, their active sites are stereospecific and will only work on one enantiomer of a substrate. The other enantiomer wont fit properly so the enzyme won’t work.
143
What is a nucleotide made of?
A 2-deoxyribose bonded to a phosphate ion and a base.
144
What is a single strand of DNA made up of?
A polymer of nucleotides linked by covalent bonds between the phosphate group of one nucleotide linked to the 2-deoxyribose of another nucleotide. This creates a sugar-phosphate-sugar-phosphate chain.
145
What is the structure of DNA?
It exists as 2 complementary strands arranged in the form of a double helix.
146
What type of polymer is a strand of DNA?
Condensation polymer
147
What are the 2 complementary base pairs?
Adenine + Thymine
Guanine + Cytosine
148
Why are there specific base pairs?
A and T form 2 hydrogen bonds whereas G and C can form 3. This is why the 2 strands of DNA must be complementary.
149
Which complex is used as an anticancer drug?
Cisplatin
150
How does cisplatin work as an anticancer drug?
It prevents DNA replication on cancer cells by a ligand replacement reaction with DNA where a bond is formed between the platinum and a nitrogen atom of the guanine. A second nitrogen from a nearby guanine can bond to the platinum and replace the second chlorine ligand.
151
Why does transplatin not work as an anticancer drug?
The second guanine can’t donate a lone pair of electrons as the ammonia ligand is in the way.
152
How does cisplatin prevent DNA replication?
When it bond to the guanine, it causes a kink in the DNA stopping DNA replication, leading to the death of the cell.
153
What are the disadvantages of using cisplatin as an anticancer drug?
They bind to DNA in healthy cells too, preventing them from replicating. Leading to:
Hair loss
Suppresses the immune system
Tiredness
Fatigue
154
How are the side effects of cisplatin reduced?
Lowering the dose
Taking breaks between doses to allow healthy tissue to recover.
Target the tumour by delivering it directly to the cancerous cells.
155
Why is cisplatin used despite all the disadvantages?
The long-term positive effects outweigh the negative short-term side effects.
156
Which organic molecules react to form condensation polymers?
Dicarboxylic acids + Diols
Dicarboxylic acids + Amines
Amino acids
157
Why are polyalkenes unreactive?
The C-C bond sin the backbone of the structure are non-polar and difficult to break. So, they’re not open to nucleophilic attack.
158
Are polyesters biodegradable?
Yes as there’s a polar carbonyl group, creating a delta positive carbon which can be attacked by nucleophiles.
The ester links are also subject to hydrolysis, so the polymer breaks down.
159
What is an alternative way in which a polyester is made?
A hydroxy carboxylic acid reacts with itself.
160
What are the uses of nylon 6,6?
Clothing
Carpets
161
What is the use of Kevlar?
Bulletproof vests
162
Are polyamides biodegradable?
They are biodegradable.
They are readily attacked by strong acids but resistant to base hydrolysis. React better at higher temperatures.
Doesn’t undergo hydrolysis with water.
163
What is the order of melting points for polyalkenes, polyesters and polyamides? Why?
Polyamides > Polyesters > Polyalkenes
Polyamides have hydrogen bonding between chains
Polyesters have pd-d attractions
Polyalkenes have VanderWaals
164
What are the different options for disposing of waste plastics?
Burying in landfill
Burning as fuel
Reusing
Recycling
165
What are the disadvantages of sending waste plastics to landfill?
You need a lot of land
As the waste decomposes, it releases methane
Leaks from landfill sites can contaminate water supplies
166
What are the disadvantages of burning waste plastics?
Need to control the release of toxic gases like HCl.
Greenhouse gases like CO2 are released.
167
What are the advantages of reusing/ recycling plastics?
It saves raw materials
It’s cheaper than making new plastics from scratch
Doesn’t produce greenhouse gases
Reduces waste going to landfill
168
What are the disadvantages of reusing/ recycling plastics?
It is technically difficult
The collecting and sourcing process can be difficult
