Organic Chemistry Flashcards
1
Q
What is a hydrocarbon?
A
A compound that is formed from carbon and hydrogen atoms only
2
Q
Do the properties of hydrocarbons change as the chain changes length?
A
Yes
3
Q
Name 3 properties of shorter carbon chain
A
- More runny hydrocarbon is - less viscous (gloopy)
- More volatile (turns into a gas at a lower temperature)
- More flammable
4
Q
Name 2 hydrocarbons
A
- Alkanes
- Alkenes
5
Q
What type of series are alkanes?
A
Homologous series
6
Q
Define a homologous series
A
A group of organic compounds that react in a similar way
7
Q
What type of bonds to alkanes have?
A
C-C single bonds
8
Q
What is the general formula for alkanes?
A
Cn H2n+2
9
Q
What type of compounds are alkanes and what does this mean?
A
Saturated Compounds
Each carbon atom forms four single covalent bonds
10
Q
Name the 1st four alkanes
A
- Methane
- Ethane
- Propane
- Butane
11
Q
Name the formula for methane and draw it
A
12
Q
Name the formula for ethane and draw it
A
13
Q
Name the formula for propane and draw it
A
14
Q
Name the formula for butane and draw it
A
15
Q
When does complete combustion occur?
A
When there’s plenty of oxygen
16
Q
Does complete combustion release a lot of energy?
A
Yes
17
Q
Name the waste products of complete combustion
A
Carbon dioxide and water vapour
18
Q
What happens during complete combustion to both the carbon and hydrogen from hydrocarbon?
A
They are oxidised
19
Q
Why are hydrocarbons used as fuels?
A
Due to (large) amount of energy released when they combust completely
20
Q
State the word equation for complete combustion
A
hydrocarbon + oxygen → carbon dioxide + water (+energy)
21
Q
What happens when you burn alkenes in large amounts of oxygen?
A
Alkenes combust completely to produce only water and carbon dioxide
22
Q
When you burn alkenes in the air, what do they tend to do?
A
They tend to undergo incomplete combustion
23
Q
State the word equation incomplete combustion of when using alkenes
A
alkene + oxygen → carbon + carbon monoxide + carbon dioxide + water (+energy)
24
Q
What type of flame does incomplete combustion result in?
A
Smoky yellow flame
25
Does incomplete combustion release a lot of energy?
Not really - less energy is released compared to complete combustion (of same compound)
26
What is crude oil?
Mixture of lots of different hydrocarbons (most are alkanes)
27
How is crude oil formed?
- Formed from remains of plants and animals, (mainly plankton) that died millions of years ago and were buried in mud
- Over millions of years, with high temperature and pressure, the remains turn into crude oil
28
Is crude oil useful?
The mixture as a whole is useless but compounds are useful
29
How can the different compounds in crude oil be separated?
By fractional distillation
30
What is 1st step in fractional distillation?
Oil is heated until most of it has turned into gas. Gases enter a fractionating column (liquid bit is drained off).
31
Step 2: In the fractionating column what is temperature gradient?
It's hot at the bottom and gets cooler at the top
32
Step 3: What happens to the longer hydrocarbons and why?
They condense back into liquids and drain out of column early on - when they're near bottom bc longer hydrocarbons ← high boiling points
33
Step 4: What happens to the shorter hydrocarbons and why?
They condense and drain out much later on - near top of column where it's cooler ← lower boiling points
34
Step 5: What overall happens to the crude oil?
Crude oil mixture is separated into different fractions
35
What does each fraction contain?
Mixture of hydrocarbons that contain a similar number of carbon atoms = have similar boiling points
36
Name 2 uses of crude oil
- Fuel for most modern transport e.g. diesel oil
- Used as feedstock to make new compounds e.g. polymers
37
What are all products from crude oil examples of?
Organic compounds
38
What are organic compounds
Compounds containing carbon atoms
39
Why do you get such a large variety of products from crude oil?
Carbon atoms can bond together to form different groups
40
Why do short-chain hydrocarbons make good fuels?
They are flammable
41
What do long-chain hydrocarbons form?
Form thick gloopy liquids like tar (isn't that useful)
42
What is cracking?
The process of splitting up longer alkane molecules (long-chain hydrocarbons) into smaller more useful ones
43
What does cracking produce?
Alkanes and alkenes
44
What are alkenes used for?
Used as a starting material when making lots of other compounds (can be used to make polymers)
45
What type of reaction is cracking?
Thermal decomposition reaction - breaking down molecules by heating them
46
Name the 2 methods of cracking
Catalytic cracking & steam cracking
47
Describe catalytic cracking
1. Heat long-chain hydrocarbons to vaporise them (turn them into a gas)
2. Vapour can be passed over a hot powdered aluminium oxide catalyst
3. Long-chain molecules split apart on surface of specks of catalyst
48
Describe steam cracking
1. Vaporise long-chain hydrocarbons
2. Mix them with steam
3. Then heat them to a very high temperature
49
What types of bonds do alkenes have?
C=C Double Bond
50
What are alkenes?
Hydrocarbons which have double bond between two carbon atoms in their chain
51
What does having C=C double bond mean for alkenes?
Means that alkenes have two fewer hydrogens compared with alkanes containing the same number of carbon atoms
52
What makes alkenes unsaturated?
C=C double bond means that alkenes have two fewer hydrogens compared with alkanes containing the same number of carbon atoms
53
What makes alkenes more reactive than alkanes?
C=C double bond can open up to make a single bond = allowing two carbon atoms to bond with other atoms
54
What is the general formula for alkenes?
Cn H2n
55
Name the 1st 4 alkenes and how carbon atoms each has
1. Ethene - 2 carbon atoms
2. Propene - 3 carbon atoms
3. Butene - 4 carbon atoms
4. Pentene - 5 carbon atoms
56
Draw ethene and name the formula
57
Draw propene and name the formula
See mind map
58
Draw butene and name the formula
59
Draw pentene and name the formula
60
What happens when bromine water is added to a saturated compound like an alkane?
No reaction will happen & it'll stay bright orange
61
What happens bromine water is added to an alkene?
The bromine will add across the double bond, making a colourless solution (dibromo-compound - so bromine water is decolourised)
62
When alkenes react with steam, what happens?
Water is added across the double bond and an alcohol is formed
63
How can ethanol be made?
By mixing ethene with steam and then passing it over a catalyst (ethene + water → ethanol)
64
Describe how ethanol can be made industrially from reacting steam with alkenes
1. Ethene and steam is reacted together
2. After reaction mixture is passed from reactor into a condenser
3. Ethanol and water have a higher boiling point than ethene = both condense whilst any unreacted ethene gas is recycled back into reactor
4. Alcohol can then be purified from mixture by fractional distillation
65
What is the functional group for alcohols?
'-OH'
66
What is general formula for alcohols?
Cn H2n+1 OH
67
Name the first 4 alcohols in homologous series
1. Methanol
2. Ethanol
3. Propanol
4. Butanol
68
Name 4 properties of 1st four alcohols
1. Soluble in water - their solutions have a neutral pH
2. Flammable - undergo complete combustion in air
3. React with sodium (one of products is hydrogen)
4. Can be oxidised by reacting with oxygen (e.g. from air) to produce carboxylic acid
69
Name the 2 ways alcohols can be made
Fermentation & Hydration (reacting alkenes with steam)
70
Describe how ethanol can be produced using fermentation
1. Fermentation uses an enzyme yeast to convert sugars into ethanol (sugar → ethanol + carbon dioxide)
71
Why is the ethanol produced aqueous?
Reaction occurs in solution
72
What is produced bedsides ethanol when using fermentation?
Carbon dioxide
73
Name the 3 conditions that fermentation happens fastest in
- At a temperature of around 37°C
- In a slightly acidic solution
- Under anaerobic conditions (no oxygen)
74
Why does fermentations occur fastest in certain conditions?
Under the right conditions, the enzyme in yeast works best to covert sugar to alcohol
75
What happens if the conditions for fermentation are different (e.g. lower pH/higher temperature or higher pH/lower temperature)?
Enzyme could be denatured or could work at much slower rate
76
How can ethanol can be oxidised to ethanoic acid?
Either by chemical oxidising agents or by microbial action
77
What is ethanoic acid the main ingredient in?
vinegar
78
Name 2 advantages of using fermentation to make ethanol
- Renewable resource (glucose from plants)
- Warm (30°C), normal pressure (1 atm) - less energy need = cheaper costs
79
Name 3 disadvantages of using fermentation to make ethanol
- Process is in batches (stop-start) = slow
- Rate of reaction is slow
- A lot of workers needed
- Product is impure (needs treatment)
80
Name 4 advantages of using hydration to make ethanol
- Continuous process (runs all the time)
- Few workers needed
- Fast rate of reaction
- Pure ethanol produced (no by-products made)
81
Name 2 disadvantages of using hydration to make ethanol
- Non-renewable resoruce (ethene from crude oil)
- High temperature (300°C) and high pressure (60-70 atm) = lot of energy needed = higher costs
82
What are polymers?
Are long molecules
83
What is polymerisation?
When lots of small molecules (monomers) join together to form long molecules (polymers)
84
What are used to make polymers?
Alkenes e.g. poly(ethene)
85
What are 2 things polymerisation usually needs?
Usually needs high pressure and a catalyst
86
What are plastics made up of
Polymers that are usually carbon based and their monomers are often alkenes
87
What are 2 things that affect the properties of polymers?
- Monomers used (what they're made out of)
- Reaction conditions
88
What conditions are needed to produce low-density (LD) poly(ethene)?
Very high pressures & trace of oxygen
89
What are polymer chains like in LDPE and how does this affect its density?
Polymer chains randomly branched ∴ they cannot pack closely together = lower density
90
What conditions are needed to produce high-density (HD) poly(ethene)?
Uses catalyst at 50°C & slightly raised pressure
91
What are polymer chains like in HDPE and how does this affect its density?
Made up of straighter poly(ethene) chains ∴ they can pack more closely together = higher density
92
How does HDPE's properties differ from LDPE's properties?
HDPE has higher softening temperature & is stronger than LDPE
93
How are atoms in polymer chains bonded together?
Bonded together with very strong covalent bonds
94
What is the size of the forces between polymer molecules in plastics?
Size of forces varies in different plastics
95
Describe what happens if thermosetting polymers are heated and why?
Will not soften because of their 'cross linking' but will eventually char if heated very strongly
96
What is meant by 'cross linking'?
Monomers in (thermosetting polymers) make strong covalent bonds between polymer chains = covalent 'cross links' don't let them separate
97
Describe what happens if thermosoftening polymers are heated and why?
Will soften or melt easily because when heated their intermolecular forces (between polymer chains) are relatively weak
98
What is the general formula for carboxylic acids?
Cn H2n+1 COOH (starts at ethanoic acid (n=1) & DOESN'T apply to methanoic acid)
99
Why can unsaturated monomer molecules (alkenes) join together to form polymer chains?
Because they can open their double bonds & join together to form polymer chains
100
Draw ethene → poly(ethene)
101
What are carboxylic acids?
A homologous series of compounds that all have '-COOH' as a functional group
102
What do the names of carboxylic acids end in?
'anoic acid'
103
Name the 1st four carboxylic acids
1. Methanoic Acid
2. Ethanoic Acid
3. Propanoic Acid
4. Butanoic Acid
104
Name the formula and draw the methanoic acid
105
How do carboxylic acids react with carbonates?
They react like any other acid with carbonates to produce a salt, water & carbon dioxide
106
What do salts formed from carboxylic acids and carbonates end with?
'-anoate'
107
Will carboxylic acids dissolve in water?
Yes
108
What happens when carboxylic acids dissolve in water?
They ionise and release H+ ions = resulting in acidic solution
109
Why do carboxylic acids form weak acidic solutions when they dissolve in water and does this mean?
* They don't ionise completely (not all acid molecules release their H+ ions)
* Means they have higher pH than aqueous solutions of strong acids with same concentration
110
What are esters formed from?
An alcohol and a carboxylic acid
111
What is functional group for esters?
'-COO-'
112
What is usually used during the production of an ester?
An acid catalyst is usually used (e.g. concentrated sulfuric acid)
113
Name an ester
Ethyl ethanoate
114
What is ethyl ethanoate made from?
Ethanotic acid and ethanol with an acid catalyst
115
Write the word equation for producing ethyl ethanoate
ethanotic acid + ethanol → ethyl ethanoate + water
116
Write the balanced symbol equation for producing ethyl ethanoate
CH3COOH + C2H5OH → CH3COOC2H5 + H2O
117
Draw the equation for producing ethyl ethanoate
118
What are esters?
Volatile compounds with distinctive smells
119
What are esters used as?
Used as favourings and perfumes
120
What is general word equation for producing esters?
alcohol + carboxylic acid → ester + water
\* above → is acid catalyst
121
Name the formula and draw the ethanoic acid
122
Name the formula and draw the propanoic acid
123
Name the formula and draw the butanoic acid
124
Name the formula and draw the methanol
125
Name the formula and draw the ethanol
126
Name the formula and draw the propanol
127
Name the formula and draw the butanol
