Topic 7 - Organic Chemistry Flashcards
1
Q
What is a hydrocarbon?
A
Any compound that is formed from carbon and hydrogen atoms only.
2
Q
What are alkanes?
A
The simplest type of hydrocarbon.
A homologous series.
Saturated compounds - each carbon forms four single covalent bonds.
3
Q
What is the general formula of alkanes?
A
CₙH₂ₙ₊₂.
4
Q
What are the first four alkanes?
A
Methane, ethane, propane and butane.
5
Q
What is the formula for methane?
A
CH₄.
6
Q
What is the formula for ethane?
A
C₂H₆.
7
Q
What is the formula for propane?
A
C₃H₈.
8
Q
What is the formula for butane?
A
C₄H₁₀.
9
Q
Describe the viscosity of hydrocarbons in relation to their chain lengths.
A
The shorter the carbon chain, the less viscious it is (more runny).
10
Q
Describe the volatility of hydrocarbons in relation to their chain lengths.
A
Shorter carbon chains are more volatile (lower boiling points).
11
Q
Describe the flammability of hydrocarbons in relation to their chain lengths.
A
Shorter carbon chains are more flammable (easier to ignite).
12
Q
What is the word equation for complete combustion?
A
hydrocarbon + oxygen = carbon dioxide + water (+energy)
13
Q
What happens during combustion?
A
Both carbon and hydrogen from the hydrocarbon are oxidised.
14
Q
Why are hydrocarbons used as fuels?
A
Due to the amount of energy released when they combust completely.
15
Q
How is crude oil formed?
A
From the remains of plants and animals, mainly plankton, that died millions of years ago and were buried in mud. Over millions of years, with high temperatures and pressure, the remains turn to crude oil, which can be drilled up from the rocks where it’s found.
16
Q
What is crude oil?
A
A mixture of lots of different hydrocarbons, most of which are alkanes.
17
Q
How are different compounds in crude oil seperated?
A
By fractional distillation.
18
Q
How does fractional distilation work?
A
- The oil is heated until most of it has turned into gas.
The gas enters a fractionating column. - In the column there’s a temperature gradient (hot at the bottom, cooler at the top).
- The longer hydrocarbons have higher boiling points. They condense back into liquids and drain out of the column early on, when they’re near the bottom.
The shorter hydrocarbons have lower boiling points. They condense and drain out much later on, near to the top of the column where it’s cooler. - You end up with the crude oil mixture seperated out into different fractions.
19
Q
What types of oils come from crude oil and what are they generally used for?
A
Diesel oil, kerosene, heavy fuel oil and liquid petroleum gas. Provide the fuel for most modern transport.
20
Q
What does the petrochemical industry use some hydrocarbons from crude oil for?
A
As feedstock to make new compounds for things like polymers, solvents, lubricants and detergents.
21
Q
What are organic compounds?
A
Compounds containing carbon atoms, products from crude oil are an example of this. :(
22
Q
Why do you get a large variety of products from crude oil?
A
Because carbon atoms can bond together to form different groups called homologous series.
23
Q
What are homologous series?
A
Groups contain similar compounds with many properties in common. Examples are alkanes, alkenes…
24
Q
Why do short-chain hydrocarbons make good fuels?
A
They are flammable and in high demand.
25
Why aren't long-chain hydrocarbons that useful?
They form thick, gloopy liquids like tar.
26
What is cracking?
The process where longer alkane molecules produced from fractional distillation are turned into smaller, more useful ones.
27
As well as alkanes, what other type of hydrocarbon can be produced by cracking?
Alkenes.
28
What are alkenes used as?
As a starting material when making lots of other compounds and can be used to make polymers.
29
What are some of the products of cracking useful as?
Fuels, eg. petrol for cars or paraffin for jet fuel.
30
What type of reaction is cracking?
A thermal decomposition reaction - breaking molecules down by heating them.
31
How does catalytic cracking work?
Long-chain hydrocarbons are heated to vaporise them. The vapour is then passed over a hot powdered aluminium oxide catalyst. The long-chain molecules split apart on the surface of the specks of catalyst.
32
What is steam cracking?
Hydrocarbons are vaporised, mixed with steam and then heated at very high temperatures.
33
What is a general equation for cracking?
Long-chain hydrocarbon molecule = shorter alkane molecule + alkene.
34
What are alkenes?
Hydrocarbons which have a double bond between two of the carbon atoms on their chain. They are unsaturated.
35
Why are alkenes unsaturated?
The C=C double bond means that the alkenes have two fewer hydrogens compared with alkanes containing the same number of carbon atoms.
36
Why are alkenes far more reactive than alkanes?
The C=C double bond can open up to make a single bond, allowing the two carbon atoms to bond with other atoms.
37
What are the first four alkenes?
Ethene, propene, butene and pentene.
38
What is the general formula for alkenes?
CₙH₂ₙ.
39
Why do alkenes tend to undergo incomplete combustion?
Alkenes only combust completely in a large amount of oxygen but there isn't enough oxygen in the air for this
40
What is the equation for incomplete combustion of alkenes?
alkene + oxygen = carbon + carbon monoxide + carbon dioxide + water (+energy).
41
What does incomplete combustion result in?
A smoky yellow flame and less energy being released compared to complete combustion of the same compound.
42
What is a functional group?
A group of atoms in a molecule that determine how that molecule typically reacts.
43
What is the functional group of alkenes?
C=C.
44
Why do all alkenes react in similar ways?
They have the same functional group.
45
How do most alkenes react?
Via addition reactions. The carbon-carbon double bond will open up to leave a single bond and a new atom is added to each carbon.
46
What is hydrogenation?
The addition of hydrogen. When hydrogen reacts with the double bonded carbons to open the double bond and form the equivalent, saturated, alkane.
47
What condition is needed for an alkene to react with hydrogen?
The presence of a catalyst.
48
What happens when alkenes react with steam?
Water is added across the double bond and an alcohol is formed.
49
How is ethanol made industrially?
After the reaction has taken place, the reaction mixture is passed from the reactor into a condenser. Ethanol and water have a higher boiling point than ethene, so both condense whilst any unreactive ethenegas is recycled back into the reactor. The alcohol can then be purified from the mixture by fractional distillation.
50
What is a third addition reaction with alkenes?
They will react in addition reactions with halogems such as bromine, chlorine and iodine.
51
What is formed when halogens react with alkenes?
The molecules formed are saturated, with the C=C bond each becoming bonded ot a halogen atom.
52
What is formed when bromine and ethene react?
Dibromoethane.
53
What can the addition of bromine to a double bond test for? How does this work?
Alkenes.
1. When orange bromine water is added to a saturated compound, like an alkane, no reaction will happen and it will stay bright orange.
2. If it's added to an alkene the bromine willl add across the double bond, making it a colourless dibromo-compound - so the bromine water is decolourised.
54
Bromine water + alkene =....
Colourless solution.
55
What are polymers?
Long molecules formed when lots of small molecules called monomers join together.
56
What is polymerisation?
The reaction when lots of monomers form a polymer. Usually needs high pressure and a catalyst.
57
What monomers do plastics normally have?
Alkenes.
58
What is addition polymerisation?
Lots of unsaturated monomer molecules (alkenes) can open up their double bonds and join together to form polymer chains.
59
Why does an addition polymer contain exactly the same type and number of atoms as the monomer that formed it?
The only product is the polymer.
60
What is the general formula for an alcohol?
CₙH₂ₙ₊₁OH.
61
What is the functional group of alcohols?
-OH.
62
How do you name alcohols?
Same as alkanes but replace the -e with an -ol.
63
What are properties of the first four alcohols?
- Flammable - undergo compete combustion in air to produce carbon dioxide and water.
- Methanol, ethanol, propanol and butanol are all soluble in water.
- They react with sodium with one of the products being hydrogen.
- They can be oxidised to produce a carboxylic acid.
- Can be used as fuels
- Solvents
64
Why are alcohols such as methonol and ethanol used in the solvent industry?
They can dissolve most things, including substances water is unable to dissolve.
65
What is an example of ethanol being used as a fuel?
Used as a fuel in spirit burners - burns fairly cleanly and it's non-smelly.
66
What alcohol is found in alcoholic drinks and how is it made?
Ethanol. Using fermentation.
67
What is fermentation?
When an enzyme in yeast is used to convert sugars into ethanol. Carbon dioxide is produced.
68
Why is the ethanol produced in fermentation aqueous?
The reaction occurs in a solution.
69
What is the equation for fermentation?
sugar=(yeast over arrow) ethanol + carbon dioxide.
70
What conditions does fermentation happen fastest at?
Around 37*C, in sightly acidic solution, anaerobic conditions (no oxygen).
71
What could happen if the conditions for fermentation were different?
The enzyme could be denatured or could work at a slower rate.
72
What are carboxylic acids?
A homologous series of compounds that all have -COOH as a functional group. Their names end in -anoic acid.
73
How do carboxylic acids react?
Like any other acid with carbonates to produce salt, water and carbon dioxide.
74
What does the salt formed at the end of a carboxylic acid reaction end in?
-anoate.
75
What is the reaction between ethanoic acid and sodium carbonate?
= sodium ethanoate + water + carbon dioxide.
76
Do carboxylic acids dissolve in water?
Yes.
77
Why do carboxylic acids form weak solutions?
When they dissolve, they ionise and release H+ ions resulting in an acidic solution. But they don't ionise completely - not all the molecules release H+ ions.
78
Why do carboxylic acids have a higher pH than aqueous solutions of strong acids with the same concentration?
They don't ionise completely so form weak solutions.
79
What is the functional group of esters?
-COO
80
How are esters formed?
From an alcohol and carboxylic acid, an acid catalyst like concentrated sulfuric acid is usually used.
81
What is the general equation for an alcohol and carboxylic acid?
alcohol + carboxylic acid = ester + water (acid catalyst over the arrow).
82
What ester can be made from ethanoic acid and ethanol with an acid catalyst?
ethyl ethanoate.
83
What are condensation polymers?
Involve monomers with contain different functional groups. The monomers react together and bonds form between them, making polymer chains. For each new bond formed, a small molecule eg. water is lost.
84
What do the simplest type of monomer contain?
Two different types of monomer, with two of the same functional groups.
85
How is the number of types of monomers different between addition polmerisation and condension polymerisation?
Addition- Only one monomer type containing C=C bond.
Condensation- Two monomer types each containing two of the same functional groups. or one monomer type with two different functional groups.
86
How is the number of products different between addition and condensation polymers?
Addition- Only one product is formed.
| Condensation- Two types of product - the polmer and a small molecule (eg.water).
87
How is the functional groups involved in polymerisation different between addition and condensation polymers?
Addition- Carbon-carbon double ond in monomer.
| Condensation- Two reactive groups on each monomer.
88
What functional group do amino acids contain?
Basic amino group (NH₂) and an acidic carboxyl group (COOH).
89
What is the smallest and simplest amino acid possible?
Glycine.
90
What polymers do amino acids form?
Polypeptides - via condensation polymers. The amino group of an amino acid can react with the acid group of another, to form a polymer chain. For every new bond formed a molecule of water is lost.
91
What are one or more long chains of polypeptides know as?
Proteins.
92
What are important uses of proteins in the body?
Enzymes work as catalysts, haemoglobin transports oxygen, antibodies form part of the immune system and the majority of body tissue is made fro proteins.
93
What gives proteins their different properties and shapes?
The order of the amino acids in the polymer chains.
94
What is DNA?
Found in every living thing and many viruses. Contains genetic instructions that allows the organism to develop and operate. Large molecule that takes a double helix structure.
95
What is DNA made of?
Two polymer chains of monomers called 'nucleotides'. The nucleotides each contain a small molecule knowna as a 'base'.
96
What are the four different bases?
A, C, G, T/
97
What do the bases on each polymer chain do?
Pair up with each other and form cross links keeping the two stands of nucleotides together and giving the double helix stucture.
98
What do the order of the bases act as?
A cod for an organisms genes.
99
What are sugars?
Small molecules that contain carbon, oxygen and hydrogen.
100
How do sugars form larger carbohydrate polymers?
They react together through polymerisation reactions. Can form starch (living things use to store energy), and cellulose (found in plant cell walls).
