Organic Chemistry (basics) Flashcards
(103 cards)
1
Q
What is a homologous series?
A
Series of organic compounds having the same functional group but with each successive member differing by CH2
2
Q
What is a functional group?
A
Group of atoms responsible for characteristic reactions of a compound
3
Q
What is a hydrocarbon?
A
Any compound containing only hydrogen and carbon
4
Q
What is an aliphatic hydrocarbon?
A
A straight chained hydrocarbon which can be branched or unbranched
5
Q
What is an alicyclic hydrocarbon?
A
Hydrocarbon with a non aromatic ring structure which can also be branched or unbranched
6
Q
What is an aromatic hydrocarbon?
A
A hydrocarbon that contains at least one benzene ring
7
Q
General formula example (decane)
A
CnH2n+2
8
Q
Molecular formula example (decane)
A
C10H22
9
Q
Empirical formula example (decane)
A
C5H11
10
Q
Structural formula example (decane)
A
CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3
11
Q
Skeletal formula example (decane)
A
/\/\/\/\/
12
Q
What is an alkane?
A
A saturated hydrocarbon containing only C-H bonds
13
Q
What is the general formula of an alkane?
A
CnH2n+2
14
Q
What types of bonds do alkanes have?
A
Four sigma bonds, either C-H or C-C
15
Q
What shape and bond angle do alkanes have?
A
Tetrahedral shape and 109.5* because every carbon atom is surrounded by 4 electron pairs and the shape is caused by the repulsion of these electrons
16
Q
Why don’t alkanes have a fixed shape?
A
Because the sigma bonds act as axis for the atoms to rotate around freely
17
Q
Why is fractional distillation possible in alkanes?
A
Because the boiling points of the alkanes differ
18
Q
What are the rules for the boiling points of alkanes?
A
- Increases as chain length increases as the molecule has a larger surface area so there are more points of contact and so the London forces are stronger and b.p increases
- Decreases as branching increases as the molecules cannot pack together as closely so there are less points of contact which makes the London forces weaker and b.p decreases
19
Q
Why are alkanes so unreactive?
A
- C-C and C-H sigma bonds are strong
- C-C bonds are non-polar
- Electronegativity of C and H is so similar
20
Q
Why are alkanes used as fuel?
A
Because they are readily available and easy to transport
21
Q
Can alkanes undergo combustion? If so, what do they produce?
A
In a plentiful supply of oxygen they can undergo complete combustion to produce CO2 and H20
22
Q
Equation for butane undergoing combustion
A
2C4H10(g) + 1302(g) —–> 8CO2(g) + 10H20(g)
23
Q
General equation for alkane complete combustion
A
CxHy + (x+y/4)02 —-> XCO2 + y/2H20
24
Q
When does incomplete combustion occur?
A
When there is a limited of supply of oxygen
25
What products can be formed in incomplete combustion?
CO2 + H20 + CO (carbon dioxide) and/or C(soot)
26
Why is carbon monoxide so dangerous?
It is a colourless, odourless and highly toxic gas, which binds to haemoglobin more readily (higher affinity) than oxygen to form carboxyhaemoglobin. This prevents oxygen from being transported around the body so the victim suffocates to death.
27
What are structural isomers?
Compounds with the same molecular formula but a different structural formula
28
What type of reation is combustion?
Oxidation
29
What are the environmental impacts of soot being formed during incomplete combustion?
- Asthma
- Cancer
- Global dimming
30
What are the three ways structural isomers can be formed?
1. Alkyl groups in different places
2. Functional groups bonded to different parts
3. Different functional groups
31
What are the two reactions alkanes can undergo?
- Radical substitution
| - Combustion
32
Describe the sigma bond in an alkane
Sigma bond is a covalent bond which has a direct overlap of the electron clouds of bonding atoms
33
Why are alkanes insoluble?
Because the hydrogen bonds in water are stronger than London forces and alkanes contain no hydrogen bonds.
34
What is an addition reaction?
Where 2 reactants join to make 1 product
35
What is a subsitution reaction?
Where an atom or group of atoms is replaced by a different group of atoms
36
What is an elimination reaction?
Involved the removal of a smaller molecule from a larger one. 1 reactant molecule forms two products
37
What is heterolytic fission?
Where one bonding atom receives both electrons from the bonded pair
38
What is homolytic fission?
Where each bonding atom receives one electron from the bonded pair, forming two radicals
39
Why do we use radical subsitution?
Because alkanes are very unreactive but if we make radicals then we can get alkanes to react
40
What are the conditions for radical substitution?
UV light
41
What are the three main stages of radical substitution?
- Initiation
- Propogation
- Termination
42
What are the limitations of radical substitution?
- Further substitution (polysubstitution)
| - Substitution at different carbons
43
What is an alkene?
An unsaturated hydrocarbon containing at least one C to C double bond, made up of one pi and one sigma bond
44
What is the angle around a C to C double bond?
120* because there are three regions of electron density around each carbon and these electrons repel each other
45
Why can't alkenes rotate?
Because the p orbitals need to be able to interact and so the two carbon atoms are locked in place, either side of the double bond. This causes stereoisomerism to occur
46
What is stereoisomerism?
Compounds with the same structural formula but a different arrangement of atoms in space
47
Why are alkenes more reactive?
- High electron density of C to C double bond
| - Pi bond is slightly easier to break
48
What is a radical?
Any species with an unpaired electron
49
Where is E/Z isomerism found?
Found in alkenes where both carbon atoms have 2 different groups attached
50
What is E isomerism?
When the highest priority groups are on opposite sides of the C to C double bond
51
What is Z isomerism?
When the highest priority groups are on the same side of the C to C double bond
52
What is cis/trans isomerism?
Should only be used when there are two hydrogen atoms and two non-hydrogen groups attached to to each carbon
53
Which letter does cis/trans correspond to?
Z - CIS (same)
| E- TRANS (opposite)
54
What is an example of a molecule with cis/trans isomerism?
but-2-ene
55
Why doesn't but-1ene have E/Z isomerism?
Because it doesn't have two different groups attached to each carbon
56
How to work out the priority of a group?
Priority increases as atomic number increases
57
Why do some alkenes show E/Z isomerism?
Because of the restricted rotation about at least one bond due to too high an energy requirement
58
How to assign the priority of chains?
Move down each chain until there is a point of difference
59
What type of fission occurs in radical substitution?
Homolytic fission as radicals need to be formed
60
What reactions can alkenes undergo?
- Combustion
- Electrophilic addition
- Polymerisation
61
What is hydrogenation and what are the conditions?
- Alkene turns into an alkane
| - Conditions are H2, Nickel Catalyst and 423K
62
What is halogenation and what are the conditions?
- Gaseous halogen
- This reaction can be used to test for unsaturation
- When bromine water is added to an alkene, if the colour disappears then a carbon double bond is present
63
What is hydration and what are the conditions?
- Alkenes turn into alcohols
| - Conditions are steam and phosphoric acid catalyst
64
Alkene reaction with hydrogen halide and conditions
Reacts with gaseous hydrogen halides
65
How does a molecule with a non-polar bond act as if it is an electrophile?
- C to C double bond with high electron density induces temporary dipole in halogen molecule
- Partially positive atom is attracted to double bond
66
Why are there major and minor products formed in reactions?
Because each carbon in a chain has a different stability, depending upon which type of carbocation it is
67
What are the different types of carbocation?
- Tertiary, carbon is bonded to 3 alkyl groups
- Secondary, carbon is bonded to 2 alkyl groups
- Primary, carbon is bonded to 1 alkyl group
68
How does stability change dependent on the type of carbocation?
Primary , Secondary, Tertiary
--------------------------------------->
stability
69
When are major and minor products formed?
Major products are products that are more likely to be formed by bonding to the more stable carbocation
Minor products are formed when they bond to a less stable carbocation
70
What is a nucleophile?
Electron pair donors
71
What is an electrophile?
Electron pair acceptors
72
What do curly arrows show in a mechanism?
Shows the movement of an electron pair
73
Why is recycling important?
-Reduces environmental impact by conserving fossil fuels and decreasing waste going to landfill
74
What is the basic process of recycling?
- Discarded polymers have to be sorted by type to prevent polymers being mixed
- Polymers are chopped into flasks, washed and dried then melted
- Recycled polymers are cut into pellets and used by manufacturers to make new products
75
Why is PVC recycling dangerous?
- Hazardous due to the high chlorine content (and range of other additives)
- Dumping them into landfill isn't sustainable
- Burning them causes PVC to release hydrogen chloride (corrosive), CO2 (polluter) and CO (toxic)
76
What is the new method to recycle PVC safely?
- Uses solvents to dissolve to dissolve the polymer
| - High grade PVC is then recovered by precipitation from the solvent and the solvent is reused again
77
How are waste polymers used for fuel?
- Waste polymers that have a high energy value from being derived from petroleum or natural gas
- These waste polymers can be incinerated to produce heat, generating steam to drive a turbine for electricity
78
What is feedstock recycling?
- Refers to a variety of chemical and thermal processes that can reclaim monomers, gases , or oil from waste polymers
- Materials can be used as raw materials for production of new polymers
- An advantage of this method is that it can handle unsorted and unwashed polymers
79
Why should we use biodegradable polymers?
- They can be broken down by microorganisms into water, CO2 and biological compounds
- They degrade and leave no visible or toxic residues
80
Where are biodegradable polymers being used?
- Supermarket bags made from plant starch can be used as bin liners for food waste so they can be composted together
- Compostable plates, cups and food trays from sugar cane fibres are replacing polystyrene
81
What are biodegradable plastics made out of?
Usually made from starch or cellulose
82
What are photodegradable polymers?
- Polymers that contain bonds that are weakened by absorbing light to start the degradation
- Alternatively, light-absorbing additives are used.
83
What are the requirements for hydrogen bonding?
- First molecule has hydrogen attached to a N, O or F
| - Second molecule has a lone pair of electrons on a small, highly electronegative N, O or F atom
84
Does ethanal have hydrogen bonding?
Not on its own, but it does in water
85
What products can the oxidation of a primary alcohol form?
- Alcohol to Aldehyde
- Aldehyde to Carboxylic acid
- Water
86
What are the conditions of oxidation of a p alcohol to just an aldehyde?
- Distillation
- Potassium Dichromate/H2SO4
- 1 mole of oxidising agent [O]
87
What are the conditions of oxidation of a p alcohol to a carboxylic acid?
- Heating under reflux
- K2Cr2O7/H2SO4
- 2 moles of oxidising agent 2[O]
88
What products is formed from the oxidation of a secondary alcohol?
Ketone
| Water
89
What are the conditions of oxidations of a s alcohol to a ketone?
- Heat under reflux
- K2Cr2O7/H2SO4
- 1 mole of oxidising agent [O]
90
Can tertiary alcohols be oxidised?
No because
91
What is the colour change?
-Orange to green
92
Why does distillation prevent further oxidation?
- Aldehydes have lower bp than alcohols
| - Aldehydes will be evaporated and condensed down another tube to be collected
93
How does reflux allow further oxidation?
- Aldehyde formed vaporises and immediately condenses
| - In Liebig condenser liquid returns to reaction so no substance is lost and is converted into a carboxylic acid
94
What does dehydration of an alcohol form?
Alcohol to Alkene
95
What does dehydration do?
Remove water
96
What are the conditions for dehydration?
- Phosphoric acid catalyst
- 160* C
- Need -OH and -H on adjacent carbon
97
What does the substitution of a metal halide of an alcohol form?
A haloalkane
98
What are the conditions for substitution of a metal halide?
Metal halide and sulfuric acid
99
What is the equation for substitution of a metal halide?
Alcohol +NaBr + H2SO4 ----> Haloalkane
100
What species are haloalkanes?
Electrophiles
101
How does substitution of a metal halide work?
- NaBr and H2SO4 react to form NaHSO4 and HBr
| - HBr goes on to react with the alkane to form the haloalkane
102
What are some examples of nucelophiles?
- OH-
- H2O:
- NH3:
103
What type of reaction is the hydrolysis of haloalkanes?
Nucleophilic substitution
