Chemistry 4 - Core Organic Chemistry Flashcards
(151 cards)
1
Q
What does nomenclature mean?
A
The system used for naming organic compounds.
2
Q
What does the term empirical formula mean?
A
The simplest whole number ratio of atoms in a molecule.
3
Q
What does the term molecular formula mean?
A
It provides the actual number of atoms of different elements in a molecule.
4
Q
What does the term displayed formula mean?
A
It shows every atom and every bond in molecule.
5
Q
What does the term structural formula mean?
A
It shows the arrangement of atoms in a molecule without showing every bond.
6
Q
Define skeletal formula.
A
A type of formula which is drawn as each lines with each vertex being a carbon atom.
The carbon atom is not drawn, it is assumed each C atom has all unspecified bonds as C-H
7
Q
Define homologous series.
A
A series of organic compounds having the same functional group, but with each successive member differing by a CH₂.
8
Q
What is a functional group?
A
A group of atoms responsible for characteristic reactions of a compound.
9
Q
What is an aliphatic hydrcarbon?
A
A hydrocarbon with carbon atoms joined together in a straight line or a branched chain.
10
Q
What is an alicyclic hydrocarbon?
A
A hydrocarbon arranged in non aromatic rings with or without side chains.
11
Q
What is an aromatic hydrcarbon?
A
A hydrocarbon containing at least one benzene ring.
12
Q
Give the suffixes for a hydrocarbon with: No double bonds At least one double bond An alcohol group An aldehyde group A ketone group A carboxylic acid group
A
No double bonds; -ane At least one double bond; -ene An alcohol group; -ol An aldehyde group; -al A ketone group; -one A carboxylic acid group; -oic acid
13
Q
Give the prefixes for: A CH₃ group A C₂H₅ group A C₃H₇ group A C₄H₉ group A Cl group A Br group An I group
A
A CH₃ group; methyl- A C₂H₅ group; ethyl- A C₃H₇ group; propyl- A C₄H₉ group; butyl- A Cl group; chloro- A Br group; bromo- An I group; iodo-
14
Q
What is the general formula of alkanes?
A
CₙH₂ₙ₊₂
15
Q
What is the general formula of alkenes?
A
CₙH₂ₙ
16
Q
What is the general formula of alcohols?
A
CₙH₂ₙ₊₁OH
17
Q
What does saturated mean?
A
Organic compounds which only contain single bonds.
18
Q
What are unsaturated compounds?
A
Organic compounds that contain at least one carbon=carbon double covalent bond.
19
Q
Define structural isomerism.
A
When molecules have the same molecular formula but different structural formula.
20
Q
What are the 3 ways in which structural isomers can be formed?
A
Alkyl groups can be in different places
Functional groups can be bonded to different parts
There can be different functional groups.
21
Q
What are stereoisomers?
A
Organic compounds with the same molecular formula but have different arrangement of atoms in space.
22
Q
What is E-Z isomerism and how are the E and Z isomers decided?
A
E-Z isomerism is caused by the limited rotation about C=C double bonds.
If the two substituents with the highest molecular mass are on the same side of the double bond, it is the Z (zusammen) isomer.
If they are on different sides, it is the E (entgegen) isomer.
23
Q
What is cis-trans isomerism?
A
Special type of E/Z isomerism, where the substituents on each carbon atom are the same.
24
Q
What is homolytic fission?
A
It happens when each bonding atom receives one electron from the bonded pair forming two radicals.
25
What is heterolytic fission?
When one bonding atom receives both electrons from the bonded pair.
26
What are radicals?
Highly reactive, neutral species.
27
How is a covalent bond formed from two radicals?
The radicals collide and the free electrons are involved in the bond formation.
28
What is an alkane?
A saturated hydrocarbons containing C-H bonds only.
29
Are alkane bonds polar? Why/why not?
Nonpolar because carbon and hydrogen have similar electronegativities.
30
What is the shape and angle of an alkane?
Tetrahedral
| 109.5°
31
Describe the σ (sigma) bond in alkanes.
The sigma bond is a covalent bond which has a direct overlap of the electron clouds of bonding atoms.
32
What type of intermolecular forces do alkanes have? Why?
London forces/ induced dipole-dipole forces because the bonds are nonpolar.
33
What happens to the boiling point as alkane chain length increases? Why?
The boiling point increases because there is more surface area and so more numbers of induced dipole-dipole interactions. Therefore more energy is required to overcome the attraction.
34
Does a branched molecule have lower or higher boiling point compared to an equivalent straight chain? Why?
The branched molecule has a lower boiling point because they have a smaller surface area and hence less induced dipole-dipole interactions.
35
Are alkanes soluble in water? Why?
Insoluble because hydrogen bonds in water are stronger than alkanes' London forces of attraction.
36
How reactive are alkanes?
Very unreactive.
37
What reactions will alkanes undergo?
Combustion and reaction with halogens.
38
What type of reaction is combustion?
An oxidation reaction
39
What is complete combustion?
Combustion that occurs with a plentiful supply of air.
40
What are the products of complete combustion when alkanes are used?
Carbon dioxide and water.
41
What is the colour of the Bunsen burner flame during complete combustion?
Blue flame.
42
What is incomplete combustion and what products are formed in the case of alkanes?
Combustion in a limited supply of oxygen
| Products: water, carbon dioxide and carbon monoxide.
43
Write an equation for the complete combustion of propane.
C₃H₈+5O₂→3CO₂+4H₂O
44
What type of hydrocarbon are most likely to undergo incomplete combustion?
Longer chain hydrocarbons.
45
What is the environmental impact of carbon monoxide?
It is toxic/poisonous.
46
What is the environmental impact of soot (carbon)?
Asthma, cancer, global dimming.
47
How are halogenoalkanes formed from alkanes?
Radical substitution.
48
In the presence of what do alk?
UV light.
49
What are the three stages of free radical substitution?
Initiation: breaking the halogen bond to form free radicals
Propagation: chain part of the reaction where products are formed but free radicals remain
Termination: free radicals are removed, so stable products are formed.
50
Write equations for the reaction of CH₄ with Cl₂ to form CH₃Cl.
```
Initiation: Cl₂(+UV light)→2Cl•
Propagation: Cl•+CH₄→Hcl+•CH₃
•CH₃+Cl₂→CH₃Cl+Cl•
Termination: •CH₃+Cl•→CH₃Cl
2Cl•→Cl₂
•CH₃+•CH₃→CH₃CH₃
```
51
What are alkenes?
Unsaturated hydrocarbons that contain at least one C=C bond made up of a σ-bond and a π-bond.
52
How is a π-bond formed?
Electrons in the adjacent p orbitals overlap above and bellow the carbon atoms, they can only be made after a σ-bond is formed.
53
What bond restricts the rotation of carbon atoms?
The π-bond.
54
What is the angle and shape of a double bond?
Trigonal planar, with an angle of 120°.
55
Are alkenes more or less reactive than alkanes? why?
They are more reactive due to the high electron density of the double bond and the fact that the π-bond is slightly easier to break than the σ-bond.
56
What intermolecular forces of attraction do alkenes have?
Only London forces due to the non-polarity of their bonds
57
Are alkenes soluble in water? Why/why not?
No, they only have non-polar bonds so they cannot integrate into the system of hydrogen bonds in water.
58
Write an equation for the complete combustion of pent-2-ene.
CH₃CH=CHCH₂CH₃+7½O₂→5CO₂+5H₂O
59
What are the types of isomers that can be formed using alkenes?
E/Z isomers, due to restricted rotation about a π-bond
60
What is an electrophile?
Species that are electron pair acceptors.
61
What is the most stable type of carbocation? Why?
Alkyl groups have a positive inductive effect, so the most stable carbocation is the one bonded to the other most other carbon atoms, i.e. a tertiary carbocation.
62
Major products will be formed from which kinds of carbocations?
Tertiary (or the most stable available).
63
What conditions are needed for the electrophilic addition of H₂O to an alkene?
What is this type of reaction called?
Steam in the presence of an acid catalyst, usually phosphoric acid.
It is a hydration reaction.
64
What are the products of a hydration reaction of an alkene?
An alcohol
65
What conditions are needed for the electrophilic addition of a hydrogen halide to an alkene?
Hydrogen halide gases must be at room temperature.
66
What is the reaction called when a halogen is added to an alkene?
Halogenation.
67
How does a molecule with a non-polar bond react as if it were an electrophile?
C=C double bonds with a high electron density can induce a temporary dipole in the halogen molecule which produces a δ+ atom which is attracted to the double bond.
68
How can an alkene be converted into an alkene? What is this type of reaction called and what conditions are required?
Alkene+hydrogen=alkane
Hydrogenation
Conditions; 150°C with a nickel catalyst
69
What is an addition polymer?
Many monomers bonded together via rearrangement of bonds without the loss of any atom or molecule.
70
What are monomers? What form do they usually take?
Molecules which combine to form a polymer.
| They usually contain a C=C bind which breaks to leave a repeating pattern.
71
How would you represent the polymerisation of ethene?
H H ⌈ H H ⌉
\ / | | | |
n C = C → + C - C +
/ \ | | | |
H H ⌊ H H ⌋ₙ
72
What are the ways in which plastics can be disposed?
```
Landfill
Combustion
Electricity generation
Reuse
Recycling
Organic feedstock
```
73
What are the disadvantages of recycling?
Plastics must be sorted into different types
The process is expensive
Labour intensive
Requires a high level of technology
74
How do photodegradable polymers break?
They break down chemically using energy with wavelengths similar to light.
Once the breakdown process begins it is not possible to stop.
75
Explain what happens in organic feedstock.
Plastics are separated and broken down into small organic molecules through a series of reaction. The molecules can then be used produce plastics and in other industries.
76
Give a disadvantage of photodegradable polymers.
They cannot be exposed to too much light, so they can't be used in sunlit places.
77
What is the functional group of an alcohol?
Hydroxyl group, -OH.
78
How do you name alcohols?
With the prefix Hydroxyl-
| Or the suffix -ol.
79
What kind of intermolecular forces do alcohols have? Why?
Hydrogen bonding, due to the electronegativity difference in the O-H bond,
80
How do alcohols' melting point and boiling point compare to other hydrocarbons' of similar C chain lengths? Why?
They are higher, because they have hydrogen bonding, which is the strongest type of intermolecular forces, holding them together, which is stronger than the London forces holding other types of hydrocarbons together.
81
Are alcohols soluble in water? Describe the effects of increasing chain length on solubility.
They are soluble when the chain length is short, this is due to the -OH groups forming hydrogen bonds with the water.
They are insoluble when the chain length is long, since the non-polarity of the C-H bond takes precedence.
82
What is a primary alcohol?
An alcohol where the C atom that the OH is bonded to is only bonded to one other C atom.
83
What is a secondary alcohol?
An alcohol where the C atom that the OH is bonded to is bonded to two other C atoms.
84
What is a tertiary alcohol?
An alcohol where the C atom that the OH is bonded to is bonded to three other C atoms.
85
Write an equation for the combustion of ethanol.
C₂H₅OH(l)+3O₂(g)→2CO₂(g)+3H₂O(l)
86
What forms if you partially oxidise a primary alcohol?
An aldehyde.
87
What conditions are necessary to partially oxidise a primary alcohol?
Dilute sulphuric acid, potassium dichromate(VI), gently heated in distillation to prevent full oxidation.
88
Write an equation for the partial oxidation of ethanol.
CH₃CH₂OH(l)+[O]→CH₃CHO(g)+H₂O(l)
89
What forms if you fully oxidise a primary alcohol?
A carboxylic acid.
90
What conditions are necessary to fully oxidise a primary alcohol?
Concentrated sulphuric acid, potassium dichromate(VI), strong heating all under reflux.
91
Write an equation for the full oxidation of ethanol.
CH₃CH₂OH(l)+2[O]→CH₃COOH(g)+H₂O(l)
92
What forms if you oxidise a secondary alcohol?
A ketone.
93
What conditions are necessary to oxidise a secondary alcohol?
Concentrated sulphuric acid, potassium dichromate(VI) and strong heating.
94
Write an equation for the oxidation of propan-2-ol.
CH₃CH₂(OH)CH₃(l)+[O]→CH₃COCH₃(g)+H₂O(l)
95
What forms if you oxidise a secondary alcohol?
A ketone.
96
What conditions are necessary to oxidise a secondary alcohol?
Concentrated sulphuric acid, potassium dichromate(VI) and strong heating.
97
Write an equation for the oxidation of propan-2-ol.
CH₃CH₂(OH)CH₃(l)+[O]→CH₃COCH₃(g)+H₂O(l)
98
Is it possible to oxidise tertiary alcohol?
No.
99
What is a dehydration reaction?
A reaction where water is lost to form an organic compound.
100
What are the products of a dehydration reaction of alcohol?
An alkene and water.
101
What are the conditions required for the dehydration of alcohol?
Concentrated sulfuric acid or concentrated phosphoric acid at 170°C.
102
What are haloalkanes?
Haloalkanes, also known as halogenoalkanes and alkyl halides, are saturated organic compounds that contain carbon atoms and at least one halogen atom.
103
Are halogenoalkanes soluble in water?
Insoluble, since C-H bonds are non-polar and the bond polarity of the carbon-halogen bond isn't enough to compensate sufficiently.
104
How is hydrogen halide made in situ? Give examples.
A salt is reacted with acid to form the hydrogen halide.
E.g. Sodium bromide reacts with sulfuric acid to form HBr, when iodine is reacted phosphoric acid is used since sulfuric acid oxidises iodide ions into iodine.
105
What are haloalkanes?
Saturated organic compounds that contain carbon atoms and at least one halogen atom.
106
Do halogenoalkanes have a polar bond? Why?
Yes, they have a polar bond because the halogen has a higher electronegativity than the carbon atom (Halogen is δ-, carbon is δ+).
107
What type of intermolecular forces do haloalkanes have? Why?
Permanent dipole-dipole and London forces of attraction.
| C-X bond polarity creates permanent dipoles.
108
What would haloalkanes to have a higher boiling point.
An increase in carbon chain length (due to the increased number of intermolecular forces)
Halogens further down group 7 (due to the increased strength of the dipole moment).
109
How would the mass of a haloalkane compare to the mass of an alkane of the same chain lengh?
It would be greater, since the mass of the halogen atoms is greater than the mass of the hydrogen atoms they take the place.
110
What would bond enthalpies suggest the order of halogenoalkane reactivity be?
C-I would be the most reactive, since it has the lowest bond enthalpy.
111
What would bond polarity suggest the order of halogenoalkane reactivity be?
C-F would be the most reactive, since it is the most polar bond, with decreasing reactivity down group 7.
112
What is a primary halogenoalkane?
The halogen atom is present at the end of the carbon chain.
113
Define nucleophile.
An electron pair donor.
114
Give 3 examples of nucleophiles.
:OH⁻
:CN⁻
:NH₃
115
What is nucleophilic substitution?
A reaction where a nucleophile donates a lone pair of electrons to δ+C atom and the δ- atom leaves the molecule to be replaced by the nucleophile(s).
116
What is hydrolysis?
A reaction where water is a reactant.
117
What reactant often produces hydroxide ions for hydrolysis?
Water.
118
What type of fission does water undergo to produce OH⁻ ions?
Heterolytic fission.
119
What is the problem with CFCs?
Although unreactive under normal conditions, they catalyse the breakdown of ozone in the atmosphere through free radical substitution.
120
What is the problem with CFCs?
Although unreactive under normal conditions, they catalyse the breakdown of ozone in the atmosphere through free radical substitution.
121
What is the main function of the ozone layer?
It provides protection from harmful UV radiation.
122
Does ozone play a protective role in all layers of the atmosphere?
No, in the troposphere it contributes towards photochemical smog.
123
How do CFCs break the ozone layer down?
Free radical substitution.
124
Write free radical substitution equations to show how Cl• catalyse the breakdown of O₃.
Cl₂→2Cl• (in the presence of UV light)
Cl•+O₃→ClO•+O₂
ClO•+O₃→2O₂+Cl•
Overall: 2O₃→3O₂
125
Write free radical substitution equations to show how nitrogen monoxide can decompose ozone.
•NO+O₃→•NO₂+O₂
•NO₂+O→•NO+O₂
Overall: O₃+O→2O₂
126
What happens when a molecule absorbs infrared radiation?
It makes the covalent bond vibrate more in a stretching or bending motion.
127
What factors affect the amount of vibration of a bond?
Bond strength
Bond length
The mass of each atom in the bond
128
How does infrared spectroscopy work?
Every bond has a unique vibration frequency in the infrared region of the EM spectrum.
Bonds absorb radiation that has the same frequency as their frequency of vibration.
Infrared radiation emerged from a sample is missing the frequencies that have been absorbed, this information can be used to identify the compound's functional group.
129
What do the peaks on an infrared spectrum represent?
The absorbance of energy from the infrared radiation.
130
What are the 2 peaks that must be present to identify a substance as a carboxylic acid?
Very broad peak at 2500-3300cm⁻¹ for the O-H group.
| Sharp peak at 1680-1750cm⁻¹ for the C=O group.
131
What happens inside a mass spectrometer?
The organic compound is vaporised and passed through the spectrometer.
Some molecules lose an electron and form molecular ions.
Excess energy from the ionisation makes the bonds vibrate more, whuich causes bonds to weaken.
This causes molecular ions to split by fragmentation.
132
What is the symbol of molecular ion?
M⁺
133
Is fragmentation predictable? Why?
No, because it can happen anywhere in the molecule.
134
In mass spectrometry how is a molecular ion represented?
It is the peak with the highest mass/charge ratio.
135
The molecular mass of the molecular ion is equal to what?
The relative molecular mass of the compound.
136
Will the molecular ion peaks of two isomers of the same compound be the same or different?
The same.
137
What are the advantages of using mass spectrometry?
It is cheap
| It only requires small quantities of samples
138
What is the main disadvantage of using mass spectrometry?
The sample is completely destroyed
139
Describe how a Quickfit apparatus is connected.
Greases the joints using some petroleum jelly on the inside of the joints before connecting the pieces together.
140
In a distillation setup, why is it necessary to have a continuous water flow around the condenser?
So that the water remains cool in order for the mixture to be distilled.
141
Describe a method that can be used to separate immiscible liquids.
Pour the mixture into a separating funnel and add some distilled water.
Add the stopper and invert the flask to mix the mixture.
Equalise the pressure by opening the stopper as required.
Continue shaking until there is no 'whistle' sound.
To collect the water in the lower layer, open the stopper and place a beaker under the spout.
Use another beaker to collect the desired organic layer.
Shake the liquid with some drying agent.
142
Name two drying agents.
Magnesium sulphate
| Calcium chloride
143
Describe how to use drying agents.
Add a selected drying agent to the organic product.
If the drying agent forms clumps, add more until they are moving freely.
Use gravity filtration to collect the dry product.
The filtrate is the product.
144
What does re-distillation mean?
When a liquid is purified by using multiple distillations.
145
How can unsaturated hydrocarbons be tested for? What are the observations?
Use bromine water.
Add a few drops of bromine water to the sample and mix well.
The positive result is that the bromine water turns colourless.
146
What are the reagents used to test for haloalkanes and what are the observations?
The reagents are silver nitrate, ethanol and water.
The observations are a white precipitate for chloroalkanes, a cream precipitate for bromoalkanes and a yellow precipitate for iodoalkanes.
147
What are the 3 reagents that can be used to test carbonyls?
Acidified potassium dichromate
Fehling's solution
Tollens' reagent
148
What are the observations when acidified potassium dichromate reacts with ketones and aldehydes?
For ketones, no change is observed.
| For aldehydes the colour changes from orange to green.
149
What are the observations when Fehling's solution is reacted with ketones and aldehydes?
For ketones, no change is observed.
| For aldehydes, a dark red precipitate forms.
150
What are the observations when Tollens' reagent is reacted with ketones and aldehydes?
For ketones, no silver mirror forms.
| For aldehydes, a silver mirror forms.
151
What are the reagents that can be used to test carboxylic acid? What are the corresponding observations?
Universal indicator- displays the pH of weak acid
A reactive metal- causes hydrogen effervescence
A metal carbonate- causes carbon dioxide effervescence
