4A,B,C,D organic chemistry Flashcards
(108 cards)
1
Q
how are alkanes named?
A
-They all end in the suffix –ane
- the prefix corresponds to the number of carbons
1-Meth
2-Eth
3-Prop
4-But
5-Pent
6 -Hex
7-Hept
8-Oct
9-Non
10-Dec
2
Q
Are Alkanes saturated?
A
Alkanes are an example of saturated compounds meaning that they are only single compounds (only single carbon carbon bonds)
3
Q
What is the boiling point and state at room temp of Methane?
A
-161C, Gas
4
Q
What is the boiling point and state at room temp of Ethane?
A
-89C, gas
5
Q
What is the boiling point and state at room temp of Propane?
A
-42C, gas
6
Q
What is the boiling point and state at room temp of Butane?
A
-1C, gas
7
Q
What is the boiling point and state at room temp of Pentane?
A
36C, Liquid
8
Q
Formula for an alkane
A
CnH(2n+2)
9
Q
Formula for an alkene
A
CnH2n
10
Q
Why are the C-C and C-H covalent bonds so strong but easy to separate?
A
Little energy is required to separate alkane molecules as they have weak intermolecular forces between molecules which require relatively little energy to overcome, although there are strong covalent bonds between molecules
11
Q
Why does boiling point increase as carbon chain increases
A
As the chain gets longer, there are more surface points of contact, increasing the net strength of intermolecular forces which require more energy to overcome
12
Q
Why are long chain alkenes more viscous and less volatile than short chain alkanes?
A
Longer chain alkanes are more viscous and less volatile as there are more surface points of contact and the intermolecular forces are stronger so it is harder for the chains to slide over and separate
13
Q
isomer
A
Compound with the same molecular formula but different structural formula
14
Q
Homologous series
A
A group of chemicals that have similar chemical structures
15
Q
Alkanes
A
A homologous series of hydrocarbons which contain only carbon and hydrogen atoms
16
Q
How many bonds can carbon make
A
4 bonds
17
Q
How many bonds does a hydrogen atom make
A
1 bond
18
Q
Functional group
A
Group of atoms that determine how a molecule reacts
19
Q
Alkenes
A
A homologous series of hydrocarbon with in double carbon functional group
20
Q
Test for Alkenes
A
Using an Alkene, put it into a boiling tube with bromine water. Shake and the alkene will decolourise the bromine water turning it from orange to colourless. This is because an addition reaction takes place where bromine is added across the alkene double bond
21
Q
Why don’t alkanes react with bromine water?
A
They don’t contain double bonds
22
Q
what is a hydrocarbon?
A
Hydrocarbons are chemical compounds that contain the elements carbon and hydrogen only. They are compounds that are obtained from the fossil fuel crude oil by a process called fractional distillation.
23
Q
what is unsaturated
A
containing double/triple bonds
24
Q
what is an empirical formula?
A
the simplest whole number ratio of the atoms in a compound
25
what is molecular formula?
the actual number of each type of atom present in a molecule
26
Define homologous series
Homologous series are families or groups of organic compounds that have similar features and chemical properties due to them having the same functional group
27
Define saturated (bonds)
A saturated solution is one in which no more solid can dissolve in the liquid at a given temperature.
Saturated compounds have molecules in which all carbon-carbon bonds are single bonds
28
Define unsaturated
Unsaturated compounds consist of molecules in which one or more carbon-carbon bonds are not single bonds
They contain carbon-carbon double bonds (C=C)
29
Define isomer
Isomers are compounds with the same molecular formulae but different structural formulae
30
Define functional group
A functional group is defined as a particular group of atoms which are responsible for how the molecule reacts
31
What is crude oil?
A mixture of hydrocarbons
32
How does the industrial process of fractional distillation separate crude oil into fractions
1. Crude oil is heated until it boils and the vapours pass into a fractioning column which is cooler at the top and hotter at the bottom
2. As the vapour travels up the column the hydrocarbon condenses and can be removed.
3. Smaller molecules have lower boiling points, so condense further up in the chain and vise versa
4. Some larger hydrocarbons can’t be separated because they have chain lengths that are too long so they are removed as residue at the bottom of the column
33
Recall the names and uses of the main fractions obtained from crude oil, describe their trend in colour, viscosity, boiling point
Refinery: gases-black/dark brown, BP 30 degrees-high viscosity, use: Domestic heating and cooking
gasoline: transparent yellowish, boiling point 100-150 degrees , the longer the chain length the more viscous, use: fuel for car engines
kerosene: pale, yellow or colourless, bp 200-300 degrees, use: fuel for aircraft and stoves
diesel: Clear, yellow, BP 200-300 degrees, use: fuel for road vehicles and trains
Fuel oil: dark brown, BP 350-450 degrees, use: fuel for ships, heating and power stations
bitumen: black, BP above 500, high viscosity, use: road surface and roofing
34
What can an issue with fractional distillation be?
Fractional distillation can mean that more long chain hydrocarbons are produced than needed, and not enough short-chain carbons
35
What is cracking? What is it for? What is needed for cracking?
Cracking is the process in which long chain alkanes are converted into alkenes and shorter chain lengths
A catalyst, either silica or alumina, is needed for cracking at around 600-700 degrees.
During the cracking process, the single C-C bonds are broken and new C-C double bonds are formed.
Cracking is used to make more useful shorter-chain length hydrocarbons so more petrol can be produces, and to produce more alkenes for polymers (plastic)
36
Explain complete combustion of a hydrocarbon
- happens when there is a good supply of air
- products are water (l) and carbon dioxide (g)
37
Explain incomplete combustion of a hydrocarbon
- happens when there is a lack of supply of oxygen
- products are either: water (l) and carbon monoxide (g) or water and carbon (s)
38
What happens in UV light with halogens and alkanes?
Alkanes react with halogens in the presence of ultraviolet radiation (e.g., sun)
A hydrogen atom in the alkane is replaced by a halogen atom. This is a substitution reaction, because one atom has been replaced by a different one.
E.g., CH4 (g) + Br2 (g) -> CH3Br (g) + HBr (g)
Mono substitution occurs –hen only ONE hydrogen atom is replaced
The products of these reactions are called halogenoalkanes. They are named using the format x-haloalkane (x=position of halogen atom) – e.g., 1-bromopropane
39
What are addition reactions (with bromine)?
Part of the double bond breaks to become a single C-C bond and the electrons are used to join other atoms onto the two carbon atoms.
Bromine add to alkenes without any need for heat, light, a catalyst. This is often carried out using bromine water. It goes from orange (bromine water) to colourless. They produce dibromoalkanes. To name the product you name wher ethe bromine is in the dibromoalkane, and then name the alkane
40
How can you use bromine to test for a alkanes and alkenes?
Any compound with a carbon carbon bond will react with bromine. If you shake bromine water with the unknown organic compound, and the colour goes from ORANGE to COLOURLESS, so the water is DECOLOURISED, the compound contains a C=C double bond (alkene).
If your compound is a gas you can bubble it through bromine water instead.
41
What is an addition polymer
The joining up of monomers to make a polymer.
E.g., lots of ethene molecules join together to make poly(ethene)
42
What are the problems with disposing of addition polymers?
- addition polymers have strong covalent bonds, essentially making them inert at ordinary temperatures, and can’t break down
- They are non –biodegradable
one solution is to bury them in landfills (cheap), but they remain unchanged for thousands of years. It also requires a lot of land, and will be ugly and smelly
- you can also incinerate (burn) plastics, which releases a lot of energy which can be used to generate electricity and requires little space, but also produces toxic gases such as CO2, carbon monoxide, hydrogen chloride, which contributes to climate change. Ash is produced which also need to be disposed of.
43
What does non-biodegradable mean?
-cannot be broken down by bacteria or the environment
44
Why is incomplete combustion bad?
- carbon monoxide might be produced which is toxic
- This is bad because carbon monoxide preferentially binds to haemoglobin, which reduces the capacity of the blood to carry oxygen (meaning the rate of respiration is lower)
45
What happens in car engines when complete combustion takes place at a high enough temperature? Why is it bad? (+ sulfur dioxide)
- nitrogen and oxygen can react to produce oxides of nitrogen. (when temp is high enough)
- this can be converted to nitric acid which can contribute to acid rain. This is a major problem it can have devastating effects on trees, and on life in lakes . It kills trees and fish. In some lakes the conc. Is so high it can’t support life at all.
46
what is a homologous series?
a series of compounds with similar chemical properties because they share the same functional group
47
how can organic molecules be presented using empirical formula, molecular formula, general formula, structural formula and displayed formula?
E - simplest whole number ratio of atoms in a compound
M- actual number of each atom present in a compound
G- tells you composition of any member of a whole homologous series of an organic compound
D-is full structural formula, showing all the bonds in a molecule with individual lines (which represents a pair of electrons shared in a covalent bond) but it can also be condensed (by omitting all c-c bonds and c-h bonds e.g., CH3CH2CH3)
S- shows how the atoms in a molecule are joined together
48
how are alkanes joined?
joined together with single covalent bonds
49
what is the difference between but-1-ene and but-2-ene
in but-1-ene the double bond it ins the first chain whereas in but-2-ene its in the second chain
(only in alkenes because of the double bond)
50
what is crude oil?
a mixture of hydrocarbons
51
what does each fraction of crude oil consist of?
Each fraction consists of groups of hydrocarbons of similar chain lengths
The molecules in each fraction have similar properties and boiling points, which depend on the number of carbon atoms in the chain
The fractions in petroleum are separated from each other in a process called fractional distillation
52
How does fractional distillation work?
How does fractional distillation work?
Fractional distillation is carried out in a fractionating column which has a temperature gradient
It is very hot at the bottom of the column and cooler at the top
During the process of fractional distillation:
The crude oil is heated and vapourises
The vapours of hydrocarbons enter the column which has a temperature gradient
The vapours of hydrocarbons with high boiling points condense at the bottom of the column
The vapours of hydrocarbons with lower boiling points rise up the column and condense at the top
53
how does viscosity change in the fractions
If the number of carbon atoms increases, the attraction between the hydrocarbon molecules also increases which results in the liquid becoming more viscous with the increasing length of the hydrocarbon chain
(The liquid flows less easily with increasing molecular mass)
54
how does colour change in the fractions
Colour
As carbon chain length increases the colour of the liquid gets darker as it gets thicker and more viscous
55
how does melting/boiling point change in the fractions
Melting point/boiling point
As the molecules get larger, the intermolecular attraction becomes greater
So more heat is needed to separate the molecules
With increasing molecular size there is an increase in boiling point
56
how does volatility change in the fractions
Volatility refers to the tendency of a substance to vaporise
With increasing molecular size hydrocarbon liquids become less volatile
This is because the attraction between the molecules increases with increasing molecular size
57
what happens when a fuel is burned?
it releases heat energy
58
what is a structural isomer?
molecules with the same molecular formula but different structural formula
THIS IS NOT TO BE CONFUSED WITH ISOTOPES
what does this mean?
this means that you could have the formula C5H12 but end up with pentane, 2-methylbutane, 2,2-dimethylpropane because of the position of the C and H (you have broken the bonds and reconnected them to other atoms)
59
how do you code for a side chain?
you are likely to come across only small side chain (methyl-CH3- and CH3CH2- which is ethyl)
1. count the number of chains there are e.g., but - 4
2. figure out what type of side chain it is
3. locate what chain the side chain is on
4. e.g., if it is on the 2nd one and it is methyl, you put it all together, and you get 2-methylbutane
So: (chain the side chain is on) - (what type of side chain it is) + (how many chains there are)
5. what do I do if there is more than one side chain?
- instead of just one number at the beginning, name where both side chains are e.g., 2,2 or 2,3 instead of just 2
- then you must also add a di- tot he beginning to signify there are 2 side chains e.g., 2,2, dimethyl....
6. what do I do if it is an alkene?
- e.g., butene not butane
you must note where the double chain is, so if it was butene and the C=C chain started on the second C, then it would be but-2-ene. this would be substitute din instead of butane in the formula
60
which alkenes don't have any isomers?
ethene and propene
61
what are the structural isomers of C4H8 (making sure it stays an alkene- c=c bond)? How many are there? draw them out
check pg 263 for reference
1. But-1-ene
2. but-2-ene
3. 2-methylpropene
62
how can you identify alcohols? what are they?
Alcohols are a homologous series of compounds which all contain an -OH functional group attached to the hydrocarbon. This is coded for in the name by the ending -ol.
e.g., propanol, ethanol, methanol
there are also structural isomers of alcohols e.g., propane-1-ol and propane-2-ol which describe the placement of the -OH side chain
63
what is a substitution reaction? when does it occur?
it occurs when an atom or group of atoms is replaced by a different atom or group of atoms. e.g., hydrogen atoms in an alkane can be replaced by halogen atoms
so- ethane + bromine -> bromoethane + hydrogen bromide
64
what is an addition reaction?
when something is added to a molecule without taking anything away e.g., ethene+bromine-> 1,2,dibromoethane
65
what type of energy source Is crude oil?
finite, non renewable
66
what are the possible products of complete combustion s hydrocarbon with oxygen in air?
they burn in air to form carbon dioxide and water and release a lot of heat in the process so can be used as fuel
e.g., CH4 (g) + 2O2 (g) -> CO2 (g) + 2H2O(l)
e.g.,2 2C8H18(l) + 5O2 (g) -> 16CO2 (g) + 18H2O(l)
67
what are the possible products of incomplete combustion s hydrocarbon with oxygen in air?
this happens when there isn't enough air which leads to the formation of carbon monoxide instead of carbon dioxide. this is very dangerous as it is colourless, odourless and very poisonous
68
why is carbon monoxide dangerous?
this is very dangerous as it is colourless, odourless and very poisonous. It also reduces the ability ofd the blood to carry oxygen around the body (because haemoglobin preferentially bonds to carbon monoxide, meaning less oxygen gets to the body). this can make you very ill/even die
69
what colour, BP, Viscosity, use does refinery gases have?
Refinery: gases-black/dark brown, BP 30 degrees-high viscosity, use: Domestic heating and cooking
70
what colour, BP, Viscosity, use does gasoline have?
gasoline: transparent yellowish, boiling point 100-150 degrees , the longer the chain length the more viscous, use: fuel for car engines
71
what colour, BP, Viscosity, use does kerosine have?
kerosene: pale, yellow or colourless, bp 200-300 degrees, use: fuel for aircraft and stoves
72
what colour, BP, Viscosity, use does diesel have?
diesel: Clear, yellow, BP 200-300 degrees, use: fuel for road vehicles and trains
73
what colour, BP, Viscosity, use does fuel oil have?
Fuel oil: dark brown, BP 350-450 degrees, use: fuel for ships, heating and power stations
74
what colour, BP, Viscosity, use does bitumen have?
bitumen: black, BP above 500, high viscosity, use: road surface and roofing
75
what are the problems associated with crude oil?
it is bad for the environment
when hydrocarbons are produced- co2 is produced, which is a greenhouse gas. they trap heat radiated from the earth's surface which contribute to climate change
it also causes acid rain. this is because water and oxygen react with sulphur dioxide int he atmosphere to form sulphuric acid (H2SO4) or with various oxides of nitrogen to form nitric acid (HNO3).
A small amount of sulphur is contained in fossil fuels so when is it burned it produces sulfur dioxide: S(s)+o2(g)-> SO2(g). reactions with oxygen and water int he atmosphere produce sulphuric acid (2SO2(g)+2H2O+O2->2H2SO4(aq)) or sulphurous acid (H2SO3) when it reacts with only water. When is rains, it kills trees, and fish in lakes (because the acidity can't support life). Some metals like iron, marble statues and limestone (calcium carbonate) are also attacked by acid rain
76
what is the formula for sufluric acid
H2SO4
77
what is the formula for nitric acid
HNO3
78
why is sulfur dioxide bad?
A small amount of sulphur is contained in fossil fuels so when is it burned (combustion) it produces sulfur dioxide: S(s)+o2(g)-> SO2(g). reactions with oxygen and water int he atmosphere produce sulphuric acid (2SO2(g)+2H2O+O2->2H2SO4(aq)) or sulphurous acid (H2SO3) when it reacts with only water. When is rains, it kills trees, and fish in lakes (because the acidity can't support life). Some metals like iron, marble statues and limestone (calcium carbonate) are also attacked by acid rain
(the reaction with limestone and sulfuric acid:
CaCO3(s) +H2SO4(aq) -> CaSO4(s) + H2O(l) + CO2(g)
79
why is nitrogen oxide bad?
in petrol engines, sparks are used to ignite the petrol-air mixture to power the car. the temperature in the engine get shigh enough to allow nitrogen and oxygen in the air to combine to produce oxides of oxygen e.g., N2(g) +O2(g) -> 2NO(g). these nitrogen oxides can be converted to nitric acid (HNO3) in the atmosphere and therefore contribute to acid rain
this is bad because when is rains, it kills trees, and fish in lakes (because the acidity can't support life). Some metals like iron, marble statues and limestone (calcium carbonate) are also attacked by acid rain
80
what is the solution to acid rain?
it is removing sulfur form fuels (which is usually done for petrol used in cars), 'scrubbing' these gases from power stations and factories to remove SO2 and Nix, and using catalytic converters in cars
81
what is cracking?
Cracking is the process in which long chain alkanes are converted into alkenes and shorted chain alkanes. e.g., big hydrocarbon molecules in fuel oil can be broken down into small ones used in petrol
e.g., C14H30 -> C10H22 +C4H8
82
why is cracking necessary in terms of the balance between supply and demand between the different fractions?
some fractions are more profitable to sell than others. long chain hydrocarbons, which there are far too many of, are not in such high demand + profitable to sell and there are not enough shorter chain hydrocarbons that can be used as fuel for cars. SO, these longer chain alkanes are converted into alkenes/shorter-chain alkanes.
IN addition, cracking is used to produce more petrol, produce more alkenes to produce polymers (plastics)
83
what is catalytic cracking?
when fuel oil is heated to give a gas and then passed over to a catalyst of silicon dioxide (AKA silica) and aluminium oxide (AKA alumina) at around 600-700 degrees C. (it can also happen at higher temperatures without a catalyst and it is called thermal cracking). Cracking is an example of thermal decomposition
84
what can be used as a catalyst and at what temperate in catalytic cracking?
silicon dioxide (AKA silica) and aluminium oxide (AKA alumina) at around 600-700 degrees C.
85
what is cracking an example of?
thermal decomposition-meaning a big molecule is split into smaller ones on heating
86
what happens after catalytic cracking?
the mixture is complex so it has to go through further processing including further fractional distillation to separate everything out into pure compounds
87
what must a homologous series all have in common?
-same functional group
- show a trend (graduation in physical properties)
- can be described by general formula
88
what is the state fo the first 4 alkanes?
gases, any higher and they are liquids until C18H38, then they are solid
89
why does boiling point increase with molecules increasing?
the intermolecular forces of attraction between them increases so more energy has to be put in in order to break the attractions between one molecule and its neighbour.
90
what are alkanes (chemical properties)?
inert due to strong bonds (in terms of being a organic compounds)
91
give me an example fo structural formula in an alkane (e.g., ethane, pentane)
ethane CH3CH3
pentane CH3CH2CH2CH2CH3
92
draw the displayed formula for the first five members of the alkanes series
93
what is an example fo a substitution reaction with alkanes
alkanes react with halogens in the presence of UV light (ultraviolet radiation), e.g., sunlight.
94
what happens in a substitution reaction with an alkane and halogen in the presence of UV
a hydrogen atom is replaced by a halogen atom (substitution)
95
what is a mono substitution reaction?
when only one hydrogen atom in the alkanes is replaced by a halogen atom
96
what is an example fo a substitution reaction with alkanes?
CH4(G)+Br2(g)-> CH3Br(g)+HBr(g)
97
what is the name for products of substitutions reactions of halogens with alkanes?
halogenoalkanes
they are named according to the format
x-haloalkane (x indicating the position of the halogen atom)
e.g., 2-bromopropane
98
what is the functional group of alkenes
the C=C bond
99
what is a functional group?
a functional group is a group of atoms in a molecule that is responsible for the molecule's chemical reactions. Functional groups have the same or similar chemical reactions regardless of the rest of the molecule's composition.
100
write out the structural formula + displayed formula for the first three alkenes
ethene- CH2=CH2
propene CH2=CHCH3
but-1-ene CH2=CHCH2CH3
use pg 282 for reference
101
why are alkenes unsaturated compounds?
because they contain a C=C bond. A saturated compound contains only C-C bonds, whereas C=C bonds and triple bonds are unsaturated
102
what happens in a combustion reaction with alkenes
they burn in air to give CO2 and water
(not common because they are too useful to be burnt)
103
what happens in an addition reaction with alkenes
Alkenes undergo addition reactions where the C=C double bond breaks to become a single C-C bond and the other electrons are used to join the atoms onto two carbon atoms (because they are more reactive than alkanes)
104
what happens in an addition reaction with ethene and bromine? + alkenes in general
bromine adds to alkenes without any need for heat, light, or a catalyst. you can tell the reaction has taken place because the bromine water is orange but 1,2-dibromoethane is a colourless liquid
CH2=CH2 (g)+Br2(aq)->CH2BrCH2Br(l)
105
what is produced when alkenes and bromine react?
dibromoalkanes
106
what is the test for unsaturated compounds>
The test for alkanes is to mix an orange-brown solution of bromine in water, called bromine water, with the substance being tested:
Alkanes: When bromine water is mixed with an alkane, there is no change.
Alkenes: When bromine water is mixed with an alkene, the bromine water turns colorless.
107
what is hydration?
a reaction which involves the addition of water. An alkene reacts with water to form an acahol
e.g., ethene and steam + 300 degrees temp + pressure of 60-70 atmospheres + catalyst of phosphoric acid ethanol
CH2=CH2+H2O->CH3CH2OH
108
