Organic chemistry I Flashcards
(96 cards)
1
Q
What are the types of formulas for an organic molecule?
A
General
Empirical
Molecular
Structural
Skeletal
Displayed
2
Q
General formula definition
A
An algebraic formula that can describe any member of a family of compounds.
3
Q
Empirical formula definition
A
The simplest whole number ratio of atoms of each element in a compound.
4
Q
Molecular formula definition
A
The actual number of atoms of each element in a molecule.
5
Q
Structural formula definition
A
Shows the arrangement of atoms carbon by carbon, with the attached hydrogens and functional groups.
6
Q
Skeletal formula definition
A
Shows the bonds of the carbon skeleton only, with any functional groups. (Hydrogens and carbons aren’t shown).
7
Q
Displayed formula definition
A
Shows how all the atoms are arranged, and all the bonds between them.
8
Q
What is meant by a homologous series?
A
A group of organic compounds with the same functional group and general formula.
9
Q
Name some homologous series and there prefix/suffix?
A
Alkanes (-ane)
Alkenes (-ene)
Halogenoalkanes (chloro/bromo/iodo-)
Alcohols (-ol)
Aldehydes (-al)
Ketones (-one)
Cycloalkanes (cyclo-…-ane)
Carboxylic acid (-oic acid)
10
Q
Name some reactions organic compounds take part in
A
Addition
Polymerisation
Elimination
Substitution
Hydrolysis
Oxidation
Reduction
11
Q
Define these reactions:
Addition
Polymerisation
Elimination
Substitution
Hydrolysis
Oxidation
Reduction
A
Addition - joining 2 or more molecules together to form a larger molecule.
Polymerisation - Joining together lots of simple molecules to form a giant molecule.
Elimination - When a small group of atoms breaks away from a larger molecule.
Substitution - When 1 species is replaced by another.
Hydrolysis - Splitting a molecule into 2 new molecules by adding H+ and OH- derived from water.
Oxidation - Any reaction in which a species loses electrons.
Reduction - Any reaction in which a species gains electrons.
12
Q
What do curly arrows represent on mechanism diagrams?
A
The movement of a pair of electrons.
13
Q
What are the 3 types of mechanisms?
A
Radical substitution
Electrophilic addition
Nucleophilic substitution
14
Q
Explain the difference between:
- Radical substitution
- Electrophilic addition
- Nucleophilic substitution
A
Radical substitution: happens to halogens in alkenes, forming halogenoalkanes.
Electrophilic addition: of hydrogen/hydrogen halides to alkenes, making halogenoalkanes.
Nucleophilic substitution: of primary halogenoalkanes with aqueous KOH forming alcohols and ammonia to make amines.
15
Q
What are nucleophiles?
A
Electron pair donors.
(Often -ve ions/species with a lone pair)
(Like to react with +ve ions or molecules with polar bonds)
16
Q
What are electrophiles?
A
Electron pair acceptors.
(Often +ve ions/β+ areas)
(Like to react with -ve ions or atoms with lone pairs or the electron rich area around a C=C bond.)
17
Q
What are radicals and how are chlorine radicals produced?
A
They are a species with an unpaired electron, and chlorine radicals are produced when UV light splits a chlorine molecule.
18
Q
What are isomers?
A
Molecules with the same molecular formula but different structural formulas.
19
Q
What are the 2 types of isomer?
A
Structural and stereoisomers.
20
Q
Give 3 types of structural isomer
A
Chain isomer
Positional Isomer
Functional group isomer
21
Q
What are chain isomers?
A
The carbon skeleton can be arranged differently, e.g. as a straight/branched chain.
Similar chemical properties but different physical properties.
(butane and methylpropane)
22
Q
What are positional isomers?
A
Carbon skeleton and functional group are the same but functional group is attached to different carbon atom.
Different chemical and physical properties.
(butan-1-ol and butan-2-ol)
23
Q
What are functional group isomers?
A
Same atoms can be arranged into different functional groups.
Very different physical and chemical properties.
(butanoic acid and methyl propanoate)
24
Q
Alkane general formula
A
CnH2n+2
25
Saturated definition
All carbon-carbon bonds are single bonds.
26
What is bond fission
Breaking a covalent bond
27
What are the 2 types of bond fission?
Heterolytic fission
Homolytic fission
28
What is heterolytic fission?
- Bond breaks unevenly
-1 of the bonded atoms receives both electrons from bond
- 2 different substances formed
29
What is homolytic fission?
- Bond breaks evenly
- Each bonding atom receives 1 electron from bonded pair
- 2 radicals formed, very reactive
30
What are the 3 stages of a free radical substitution reaction?
Initiation - radicals are produced by photodissociation and homolytic fission.
Propagation - Radicals are used up and created in a chain reaction.
Termination - Radicals react together to form stable molecules.
31
What is the problem with radical substitution reactions?
- You get a mixture of products
- E.g. if you're trying to make chloromethane, add an excess of methane, so there's a greater chance of chlorine radical colliding with a methane rather than chloromethane molecule.
- Another problem is that it can take place at any point along the carbon chain, so a mixture of structural isomers can be formed. E.g. 1-chloropropane and 2-chloropropane.
32
What is crude oil and give another name for it
It's a mixture of hydrocarbons, but mostly alkanes. Another name for it is petroleum.
33
Describe the process of fractional distillation on crude oil.
1. The crude oil is vaporised at about 350°C.
2. The vaporised crude oil goes into a fractionating column and rises up through the trays.
3. The largest hydrocarbons don't vaporise at all, their bpt is too high, so they just run to the bottom and form a gooey residue.
4. As, the crude oil vapour rises, it cools.
5. Due to having different chain lengths, the alkanes have different bpt's, so they condense at different temperatures. Fractions are drawn off at different levels in the column.
6. Hydrocarbons with the lowest bpt's don't condense, they're drawn off as gases at the top of the column.
34
What are the uses of these crude oil fractions:
Gases
Naphtha
Kerosene (paraffin)
Gas oil (diesel)
Mineral oil (lubricating)
Residue (fuel oil and bitumen)
Gases - LPG (camping gas)
Naptha - Petrol
Kerosene (paraffin) - jet fuel/central heating fuel/petrochemicals
Gas oil (diesel) - diesel fuel/central heating fuel
Mineral oil (lubricating) - lubricating oil
Residue (fuel oil and bitumen) - ships/power stations/road surfacing
35
What are the 7 main fractions of crude oil?
Gases
Naptha
Kerosene (paraffin)
Gas oil (diesel)
Mineral oil (lubricating)
Residue (fuel oil and bitumen)
36
What is cracking and why are alkanes cracked?
It's the process of breaking long chain alkanes into smaller hydrocarbons, involves breaking C-C bonds.
This is done because shorter chain hydrocarbons are more in demand and more valuable than longer chains.
37
What are the 2 types of cracking?
Thermal - Takes place at a high temp. (1000°C) and high pressure (70atm) and produces a lot of alkenes, which are used to make polymers.
Catalytic - Uses a zeolite catalyst, at a slight temp. (450°C) and pressure, and produces aromatic hydrocarbons and motor fuels. A catalyst cuts costs and saves time.
38
What is reforming and why is it used?
It's the process of converting straight chain alkanes into branched chain alkanes and cyclic hydrocarbons, with the use of a catalyst (platinum stuck on aluminium oxide).
This is done to reduce knocking (where alkanes explode when the fuel mixture in the engine is compressed) so combustion is more efficient.
39
What does the reforming of hexane form?
Forms cyclohexane and hydrogen gas, which can be reformed into benzene (C6H6) and hydrogen gas.
40
What is formed when you burn alkane with oxygen?
- Carbon dioxide and water are formed when there's a lot of oxygen.
- Carbon, carbon monoxide and water are formed when there's not enough oxygen.
41
Which state does an alkane need to be in to be combusted?
Gas
42
What is meant by alkanes being volatile and are shorter or longer chain alkanes more volatile?
Being volatile means burning easily. Smaller alkanes turn into gases more easily, so are more volatile.
43
Are combustion reaction exothermic or endothermic?
Exothermic
44
What harmful emissions are produced by combustion of alkanes?
- Carbon monoxide
- Sulfur dioxide and Nitrogen oxides
45
How is carbon monoxide toxic?
1. The oxygen in your bloodstream is carried around by haemoglobin.
2. Carbon monoxide is better at binding to haemoglobin than oxygen, so binds to it instead of oxygen.
3. So less oxygen can be carried around the body, leading to oxygen deprivation.
46
How does Sulfur dioxide and Nitrogen oxides lead to acid rain?
1. Burning fossil fuels containing sulfur releases sulfur dioxide gas, which enters atmosphere, dissolves in the moisture, and converted to sulfuric acid.
2. Oxides of nitrogen are produced when high pressure/temp in a car engine cause the nitrogen an oxygen in air to react. When oxides of nitrogen escape into the atmosphere and dissolve in the moisture, they're converted into nitric acid, which falls as acid rain.
3. Acid rain destroys trees and vegetation, and corrodes buildings and kills fish in lakes.
47
What are catalytic converters?
- They are found in car exhausts and stop cars releasing CO, nitrogen oxides and unburnt hydrocarbons.
- They use a platinum catalyst to change them into water vapour/nitrogen/CO2.
48
What are biofuels and give 3 examples.
They're fuels made from living matter over a short period of time.
- Bioethanol: ethanol made by fermentation of sugar from maize.
- Biodiesel: Made by refining renewable fats/oils such a vegetable oil.
- Biogas: Produced by the breakdown of organic waste matter.
49
What is the general formula of alkenes?
CnH2n
50
How are sigma bonds created in organic compounds?
- 2 orbitals overlap, in a straight line, in the space between 2 atoms.
- Giving the highest possible electron density between the 2 +ve nuclei. So there's a strong electrostatic attraction between the nuclei and shared pair of electrons.
- So the sigma bonds have a high bond enthalpy - strongest type of covalent bond.
51
What are double bonds in organic compounds made of?
Made of a sigma and pi bond
52
How are pi bonds created in organic compounds?
- Formed when 2 lobes of 2 orbitals overlap sideways, 1 part above and 1 part below the molecular axis.
- E.g. p-orbitals can form pi bonds.
- The electron density is spread out above and below the nuclei, causing the electrostatic attraction between the nuclei and the shared pair of electrons to be weaker in the sigma bonds, so they have a relatively low bond enthalpy.
53
What causes alkenes to be stereoisomers?
The atoms can't rotate about a double bond.
54
What's the difference between E/Z isomerism?
- The same groups/larger atomic number are both above or below the double bond results in a Z-isomer.
- The same groups/larger atomic number are diagonal (1 above and 1 below the double bond) results in an E-isomer.
55
What happens in electrophilic addition with alkenes?
- The double bond is electron rich and attacked by electrophiles (electron pair acceptors).
- The double bond opens up and atoms are added to the carbon atoms.
56
What is the reagent and conditions for producing alkanes from alkenes?
Add hydrogen gas, a nickel catalyst and a temp of 150°C.
57
What is made from an alkene to produce an alkane in real life?
- Margarine is made by 'hydrogenating' unsaturated vegetable oils.
- By removing some double bonds, you raise the mpt so that it becomes solid at room temp.
58
Halogens react with alkenes to form ... by ...
Dihalogenoalkanes
Electrophilic substitution
59
What is the test for alkenes?
- Add bromine water
- Solution decolourises
60
What is the reagent and conditions for producing an alcohol from an alkene?
React with steam at 300°C and a pressure of 60-70atm, with a solid phosphoric (V) catalyst.
61
What is a diol and how is it produced by an alkene?
It's an alcohol with 2 -OH groups.
You need to shake an alkene with acidified potassium manganate (VII), the purple solution is decolourised. So the alkene is oxidised.
62
What type of reaction do alkenes undergo when reacting with hydrogen halides to form halogenoalkanes?
Addition reactions
63
What happens when a hydrogen halide is added to an unsymmetrical alkene?
- There are 2 possible products
- Carbocation with more alkyl groups are more stable because the alkyl groups feed electrons towards the +ve charge.
- More stable carbocation is more likely to form.
64
Give 3 ways of disposing of polymers
Buried - not enough space in landfill
Reused - either by melting/remoulding them or cracking into monomers.
Burned - heat produced can be used for electricity. If it contains chlorine, it will produce HCl when burnt, which must be removed.
65
How to test for halides?
1. Add silver nitrate solution. A silver halide precipitate will form.
2. Cl= white Br= cream, I= yellow
3. Cl= soluble in any conc. ammonia solution, Br= soluble only in conc. ammonia solution, I= isn't soluble in any conc. ammonia solution
66
What is the rate of hydrolysis for the 3 halides?
- Tertairy have the fastest rate, primary the slowest
- Iodoalkanes have the fastest hydrolysis rate, chloroalkanes the slowest.
67
How do halogenoalkanes react by nucleophilic substitution?
- Halogens are generally more electronegative than carbon, so the carbon-halogen bond is polar.
- The δ+ carbon doesn't have enough electrons, so it can be attacked by a nucleophile (EP donor).
- The C-X bond breaks heterolytically, both electrons taken by the halogen.
- Nucleophile bonds to the carbon and halogen falls off.
68
What are some examples of nucleophiles that readily react with halogenoalkanes?
OH-
CN-
NH3
H2O (weak nucleophile)
69
What is the reagent and conditions required for forming an alcohol from a halogenoalkane?
Use warm aqueous KOH and do the reaction under reflux.
70
What is the reagent and conditions required for forming a nitrile from a halogenoalkane?
Reflux a halogenoalkane with potassium cyanide (KCN) in ethanol.
71
What is the reagent and conditions required for forming an amine from a halogenoalkane?
Warm a halogenoalkane with excess ethanolic ammonia.
72
Describe the nucleophilic reaction when a halogenoalkane forms an amine.
- The δ+ carbon doesn't have enough electrons, so it can be attacked by a NH3 nucleophile (EP donor).
- The C-X bond breaks heterolytically, both electrons taken by the halogen.
- NH3 bonds to the carbon and halogen falls off.
- An ammonia molecule removes a hydrogen from the NH3 group to leave an amine.
73
What is the reagent and conditions required for forming an alkene from a halogenoalkane? What is the reaction?
- React a halogenoalkane with a warm alkali (KOH/NaOH) dissolved in ethanol under reflux. (so volatile gas isn't lost)
- Elimination
74
What else is formed when forming an alkene from a halogenoalkane?
Water and K-X
75
What's the difference between primary, secondary and tertiary alcohols?
primary - the C atom that the OH is connected to is attached to 1 other C atom.
secondary - the C atom that the OH is connected to is attached to 2 other C atoms.
tertiary - the C atom that the OH is connected to is attached to 3 other C atoms.
76
What reactions are used to convert alcohols to halogenoalkanes?
Substitution reactions
77
What's the reagent and conditions for forming chloroalkanes from an alcohol?
Include general equation
React an alcohol with PCl5 (phosphorus pentachloride) or HCl.
ROH + PCl5 → RCl + HCl + POCl3
ROH + HCl → RCl +H2O
78
What's the reagent and conditions for forming bromoalkanes from an alcohol?
Include general equation
React the alcohol with KBr and an acid catalyst (e.g. 50% conc. H2SO4)
2KBr + H2SO4 → HBr + K2SO4
ROH + HBr → RBr + H2O
79
What's the reagent and conditions for forming iodoalkanes from an alcohol?
Include general equation
Reflux the alcohol with red phosphorus and iodine (PI3 is made in situ).
3ROH + PI3 → 3RI + H3PO4
80
What type of reaction forms from forming an alkene from an alcohol?
Elimination reaction
80
Which colour flame does ethanol burn with?
Pale blue
80
What's the reagent and conditions for forming an alkene from an alcohol? Other than the alkene, what else is released?
Heat the alcohol with an acid catalyst (e.g. conc. phosphoric acid H3PO4).
Water is also formed.
81
What is formed when you burn an alcohol with plenty of oxygen?
Carbon dioxide
water
82
What reagent do you need to use to mildly oxidise alcohols, and what do different alcohols form?
Oxidising agent acidified dichromate (VI) e.g. K2Cr2O7/H2SO4
Primary alcohols - Aldehydes, then carboxylic acids.
Secondary alcohols - Ketones only.
Tertiary alcohols - Won't be oxidised.
83
What is the functional group and general formula of aldehydes and ketones?
C=O and CnH2nO
84
What's the difference between aldehydes and ketones?
Aldehydes: 1 hydrogen and 1 alkyl group attached to the carbonyl carbon atom. (=O is in the end)
Ketones: 2 alkyl groups attached to the carbonyl carbon atom. (=O is in the middle)
85
What test can you use to tell the difference between ketones and aldehydes?
Use Benedict's solution (copper (II) ions dissolved in sodium carbonate).
If heated with an aldehyde, the blue copper ions are reduced to brick red precipitate of copper (I) oxide.
86
What is the method for oxidising alcohols to form aldehydes and carboxylic acid?
1. Gently heat excess alcohol with a controlled amount of oxidising agent in a distillation apparatus, so the aldehyde (which boils at a lower temperature than the alcohol) is distilled off immediately.
2. To produce the carboxylic acid, the alcohol must be vigorously oxidised and heated under reflux and mixed with excess oxidising agent.
87
Why must we use distillation apparatus when oxidising a primary alcohol into an aldehyde?
1. When we gently heat ethanol with potassium dichromate (VI) solution and sulfuric acid in a test tube, an 'apple' smelling ehanal will be produced.
2. It's really tricky to control the amount of heat, so the aldehyde is usually oxidised to form 'vinegar' smelling ethanoic acid.
88
Describe the method used to oxidise secondary alcohols to ketones
Reflux a secondary alcohol with acidified dichromate (VI).
89
What is refluxing used for?
- To make sure you don't lose any volatile organic substances
- So that the reactants aren't evaporated before they have had time to react.
90
What is distillation used for?
- Separating substances with different boiling points.
91
What is separation used for?
- The organic layer and aqueous layer (containing any water soluble impurities) separate into 2 distinct layers.
- Open the tap to run off the aqueous layer containing water soluble impurities.
92
What is an example of an anhydrous salt and what is it used for?
- Magnesium sulfate (MgSO4) or calcium chloride (CaCl2).
- They are used as drying agents which bind to any water, becoming hydrated.
- Mix with the organic layer and then filter off the solid drying agent.
93
What is measuring boiling point used for?
To determine purity
94
Stereoisomers definition
- compounds with the same structural formula
- where the atoms have a different arrangement in space
