C6.2 - Organic chemistry Flashcards
(93 cards)
1
Q
what is crude oil?
A
- fossil fuel from remains of marine organisms that lived millions of years
2
Q
how is crude oil formed?
A
chemical reactions + action of heat and pressure turned remains of dead marine organisms into crude oil
3
Q
Methane formula
A
CH4
4
Q
Ethane formula
A
C2H6
5
Q
Propane formula
A
C3H8
6
Q
Butane formula
A
C4H10
7
Q
what does crude oil contain?
A
mixture of hydrocarbons - mostly alkanes
8
Q
what are hydrocrabons?
A
substances made of only hydrogen and carbon atoms
9
Q
what happens when alkanes get bigger?
A
bpt increases - TMT you can separate different molecules using fractional distillation
10
Q
what is an alkane?
A
a hydrocarbon
11
Q
what is the general formula for an alkane?
A
CnH2n+2
12
Q
What is the Ethane displayed formula
A
H H
| |
H - C - C - H
| |
H H
13
Q
what is the ethane structural formula?
A
CH3CH3
14
Q
What is the ethane skeletal formula?
A
/
15
Q
What is the Propane displayed formula
A
H H H
| | |
H - C - C - C - H
| | |
H H H
16
Q
What is the structural formula of Propane?
A
CH3CH2CH3
17
Q
What is the skeletal formula for propane?
A
/\
18
Q
What is the Butane displayed formula?
A
H H H H
| | | |
H - C - C - C - C - H
| | | |
H H H H
19
Q
What is the structural formula for Butane?
A
CH3CH2CH2CH3
20
Q
What is the skeletal formula for butane?
A
/\/
21
Q
properties of alkanes
A
- saturated molecules (as only contain single covalent bonds)
- unreactive (as only contain strong single covalent bonds)
- Bpt and viscosity increases as you increase the chain length
- flammability + volatility decrease as you increase chain length
- form homologous series - as have similar chem properties + trend in physical properties as you change the chain by -CH2
22
Q
when do alkanes undergo combustion reactions?
A
when they react with oxygen in the air and burn
23
Q
complete combustion equation
A
Alkane + oxygen –> carbon dioxide + water
CH4 + 2O2 –> CO2 + 2H2O
24
Q
what is complete combustion?
A
when lots O2 available, reaction is complete & produces CO2 and water
- E.g. Bunsen burner with an open air-hole
25
incomplete combustion reaction
Alkane + oxygen --> Carbon dioxide + water + carbon monoxide + soot
4CH4 + 6O2 --> CO2 + 8H2O + 2CO + C
26
What is incomplete combustion?
when not enough O2 available - e.g. Bunsen burner with closed air-hole (safety flame)
27
how do you separate alkanes from crude oil?
fractional distillation - bpt increases as chain length increases - TIB the longer the chain the stronger the intermolecular forces
28
How does fractional distillation work?
- crude oil piped into fractionating column
- bottom of column has highest temp
- smaller molecules have lowest bpt so evaporate 1st rising to top of column - continue to rise until it becomes cool enough to condense back into liquid (when they are collected)
29
what are alkanes used as?
fuels - basic form of a hydrocarbon found in crude oil
30
what is cracking?
turning longer alkane chains into shorter ones (shorter chains are more useful)
31
example formula of cracking
decane --> octane + ethene
| C10H22-->C8H18 + C2H4
32
Industrial conditions for cracking
high temps required (often means heating samples to 600-700°C in presence of hot catalyst of alumina/silica)
- under these conditions, strong covalent bonds between atoms can break
33
what does cracking produce?
shorter alkane chains and alkenes
34
why are alkenes useful?
helpful in production of polymers - e.g. plastics
35
what are alkenes produced from?
by-product of cracking
36
alkene general formula
CnH2n
37
Alkene characteristics
- form homologous series - TIB of common features
| - unsaturated molecules as contain double bond between 2 carbon atoms
38
Ethene structural formula
```
H H
| |
C = C
| |
H H
```
39
Ethene structural formula
C2H4
40
Propene displayed formula
C3H6
41
Propene displayed formula
```
H H H
| | |
H - C - C = C
| |
H H
```
42
Butene structural formula
C4H8
43
Butene displayed formula
```
H H H H
| | | |
H - C - C - C = C
| | |
H H H
```
44
Pentene structural formula
C5H10
45
Pentene displayed formula
```
H H H H H
| | | | |
H - C - C - C - C = C
| | | |
H H H H
```
46
How do you check cracking has taken place effectively?
test for alkene - bromine water
- Alkane + bromine water --> no reaction (bromine water remains orange)
- Alkene + bromine water --> reaction (bromine water turns from orange to colourless)
47
what happens in an addition reaction?
atom / group of atoms combine with a molecule to forma larger molecule - - no other products are made
48
what is hydrogenation?
where hydrogen adds across the double bond to turn an alkene into an alkane
49
what does alkene and water make?
alcohol
50
alkenes + oxygen =
carbon dioxide + water
51
is it more likely for a complete or incomplete combustion reaction to take place?
incomplete - smaller carbon: hydrogen ratio - fewer H2 atoms for every C atom
52
which is more likely to undergo an incomplete combustion reaction - hexane or hexene?
hexene
53
how can alcohols be identified?
by their O-H functional group
54
why can alcohols take part in different reactions?
as they have a different functional group
55
methanol structural formula
CH3OH
56
Ethanol structural formula
CH3CH2OH
57
Propanol structural formula
CH3CH2CH2OH
58
Methanol displayed formula
```
H
|
H - C - O - H
|
H
```
59
Ethanol displayed formula
```
H H
| |
H - C - C - O - H
| |
H H
```
60
Propanol displayed formula
```
H H H
| | |
H - C - C - C - O - H
| | |
H H H
```
61
how many bonds do hydrogen, oxygen and carbon form
hydrogen - 1
oxygen - 2
carbon - 4
62
general formula for alcohols
CnH2n+1OH
63
Ethanol from steam and ethene reaction
- phosphoric acid - catalyst - speeds up reaction rate
| - high pressures used to improve yield + reaction rate
64
Ethanol from fermentation
- relies on action of yeast - yeast = single celled fungi containing enzymes which act as a catalyst
- plant sugars can produce ethanol in fermentation
- C6H12O6 (glucose) --> 2CO2 +2C2H5OH (ethanol)
- must be carried out below 50°C so yeast doesn't denature - typically done in 35°C (anaerobic conditions)
65
uses of alcohols
- drink
- fuel - flammable, release lots energy, burn with clean flame (complete combustion
- solvents - substances dissolve easily in alcohol
- disinfectants - kill bacteria effectively
66
oxidation of alcohols
- alcohols can be oxidised from carboxylic acids
67
carboxylic acid general formula
CnH2n+1COOH
68
Ethanol --> Ethanoic acid
H H H O
| | | //
H - C - C - O - H ---> H - C - C
| | | \
H H H OH
69
Methanoic acid displayed formula
```
O
//
H - C
\
O - H
```
70
Methanoic acid structural formula
HCOOH
71
Ethanoic acid displayed formula
```
H O
| //
H - C - C
| \
H O - H
```
72
Ethanoic acid structural formula
CH3COOH
73
propanoic acid displayed formula
```
H H O
| | //
H - C - C - C
| | \
H H O - H
```
74
Propanoic acid structural formula
CH3CH2COOH
75
making carboxylic acids - method 1 - both use oxidising agent
alcohol + potassium manganate (VII) solution
- mix together + warm in a water bath
- add little bit of dilute sulfuric acid
colour change - purple to v.pale pink or colourless
76
making carboxylic acids - method 2 - both use oxidising agent
alcohol + potassium dichromate solution
- mix together + warm in a water bath
- add a little bit of dilute sulfuric acid
colour change - orange to green
77
reactions of carboxylic acids
- weak acids
| - react with metal to produce hydrogen + salts
78
what react together to make esters?
alcohols and carboxylic acids - called condensation reaction as 2 molecules react to form 1 large & 1 smaller molecule - smaller one is often water
79
making esters
- put drop concentrated sulfuric acid into test tube
- add approx 10 drops carboxylic acid to tt
- add approx 10 drops alcohol to tt
- add some hot water to beaker - put tt in hot water bath
- after few min remove tt and leave to cool on a tt rack
- half fill a 2nd tt with sodium carbonate solution - once cooled pour ester solution into sodium carbonate solution
- pour contents back into OG tt + leave to settle - smell ( gentle waft)
80
what do alkenes join to form?
large chains - polymers
81
are alkenes monomers or polymers?
monomers
82
What is polymerisation?
a chemical reaction where monomer molecules join to form polymer chains
83
what does the type of polymer formed depend on?
depends on the monomer initially used
- e.g. ethene --> poly(ethene)
- e.g. propene --> poly(propene)
84
What are the three types of polymers?
- addition polymers - formed from alkenes
- biological polymers - formed in nature
- condensation polymers - often formed from carboxylic acids
85
what are some examples of natural forming polymers?
DNA, proteins and carbohydrates such as starch
86
what are proteins?
polymers made from monomers (amino acids)
87
what are carbohydrates?
compounds of carbon, hydrogen and oxygen
| - include simple sugars (sucrose) and complex carbs (starch)
88
what is sucrose made from?
glucose + fructose combining
89
what are DNA molecules made from?
DNA molecules are polymers made from monomers called nucleotides (which contain base pairings)
90
what are condensation polymers?
polymers that form from condensation reactions
91
monomers need to have two...
...functional groups present - one at each end of the structure
- when monomers join - a small molecule is eliminated (often water)
92
what are polyesters and how do they form?
- form when di-carboxylic acids react with di-alcohols
- called polyesters as contain many ester groups
- used for clothing and in production of drink bottles
93
what are polymides and how do they form?
- form when di-carboxylic acids react with di-amines
- called polymides as contain amide groups
- E.g. Nylon used to make clothing + carpets
