Introduction to Organic Chemistry and Alkanes Flashcards
1
Q
What is the empirical formula?
A
The simplest whole number ratio of atoms in a compound or molecule
2
Q
What is the molecular formula?
A
The actual number of atoms in a molecule or element
3
Q
What is the general formula?
A
i.e alkanes = CnH2n+2
alkenes= CnH2n
alcohols= CnH2n + 1 OH
4
Q
What is the structural formula?
A
The arrangement of atoms in a molecule without showing all the bonds (CH3 CH2 CH2 CH2 OH)
5
Q
What does the skeletal formula show?
A
The bonds of the carbon skeleton only. Hydrogen and carbon atoms aren’t shown, but functional groups are.
6
Q
What does the displayed formula show?
A
The arrangement of atoms and shows all the bonds and atoms in a molecule
7
Q
What is a homologous series?
A
A group of compounds that has the same functional group and the same general formula.
8
Q
What is a functional group?
A
an atom or group of atoms within a molecule that has similar chemical properties
9
Q
What are structural isomers?
A
Molecules that have the same molecular formula, but a different arrangement of atoms in space.
10
Q
What are the 3 types of structural isomer?
A
Chain, positional, functional group
11
Q
What is a chain isomer?
A
A molecule that has the same molecular formula, but a different arrangement of carbon atoms i.e is branched.
12
Q
What is a positional isomer?
A
A molecule that has the same molecular formula, but a different position of the functional group
13
Q
What is a functional group isomer?
A
A molecule that has the same molecular formula, but a different functional group
14
Q
What is the functional group isomer of an aldehyde?
A
A ketone
15
Q
What is the functional group isomer of a ketone?
A
An aldehyde
16
Q
Where is the carbonyl group located in an aldehyde?
A
At the end of the molecule
17
Q
Where is the carbonyl group located in a ketone?
A
In the middle of the molecule
18
Q
What is the functional group isomer of an alcohol?
A
An ether
19
Q
What is the functional group isomer of a carboxylic acid?
A
An ester
20
Q
Give 3 examples of an ester?
A
Ethyl ethanoate , methyl propanoate, propyl methanoate
21
Q
Give an example of an ether
A
1-ethoxy ethane
22
Q
Stereoisomerism
A
chem vid
23
Q
What is the general formula of an alkene?
A
CnH2n
24
Q
Are alkanes and cycloalkanes saturated hydrocarbons?
A
Yes
25
What 3 ways are alkane fuels formed?
Through the fractional distillation, cracking and reforming of crude oil
26
What is the functional group isomer of an alkene?
A cycloalkane
27
What is reforming?
the processing of straight-chain hydrocarbons into branched-chain alkanes and cyclic hydrocarbons for efficient combustion.
28
Describe the process of fractional distillation?
1) The crude oil is vaporised in a blast furnace at about 350 degrees celcius.
2) The vaporised crude oil enters the fractioning column and rises. The longer chained hydrocarbons don't vaporise and just run to the bottom.
3) The fractioning column has a temperature gradient, it's cooler at the top and hotter at the bottom. As each hydrocarbon has a different boiling point, they will each cool and condense at different temperatures.
4) The hydrocarbons with the lowest boiling points don't condense. They're drawn off as gases at the top of the column.
29
What is an addition reaction?
Where 2 or more molecules are joined together to form a larger molecule
30
What is a polymerisation reaction?
Where lots of simple molecules are joined together to form a giant molecule
31
What is an elimination reaction?
Where a small group of atoms breaks away from a larger molecule
32
What is a substitution reaction?
Where one species is replaced by another species
33
What is a hydrolysis reaction?
Where a molecule is split into 2 new molecules by adding water
34
What is an oxidation reaction?
Where a species loses electrons in a reaction
35
What is a reduction reaction?
Where a species gains electrons in a reaction
36
Nucleophiles ......
contain a lone pair of electrons and are attracted to areas of positive charge
37
Electrophiles....
are electron deficient and so are attracted to areas of high electron density
38
Radicals....
have an unpaired electron ad are very reactive and so basically react with anything
39
What is gas used for?
Liquified petroleum gas (LPG) and camping gas
40
What is petrol used for?
41
What is Naptha used for?
42
What is Kerosene(parrafin) used for?
43
What is gas oil (diesel) used for?
44
What is mineral oil (Lubricating) used for?
45
What's in greater demand- heavier fractions or lighter fractions?
Lighter fractios
46
What is cracking?
Breaking long chained hydrocarbons (alkanes) into shorter chained hydrocarbons (alkenes and alkanes) . It involves breaking a C-C bond
47
What are the 2 type of cracking?
Thermal cracking and catalytic cracking
48
What temperature and pressure does thermal cracking take place at?
- At high temperatures of up to 1000 degrees Celsius
- At a high pressure of up to 70 atm
49
What are the main products of thermal cracking?
Alkenes and hydrogen (which can be used in the haber process)
50
What can the alkenes produced by thermal cracking be used to make?
Polymers (plastics)
51
What conditions are needed for catalytic cracking?
- a zeolite catalyst
- a slight pressure
- a high temperature of around 450 degrees celcius
52
What compounds does catalytic cracking mostly produce?
Aromatic hydrocarbons, cyclic alkanes, branched alkanes, motor fuels
53
What are aromatic hydrocarbons?
compounds containing benzene rings. benzene rings contain a ring of 6 carbon atoms with a delocalised ring of electrons
54
How can you convert straight chained hydrocarbons into branched alkanes and cyclic hydrocarbons?
By reforming via the use of a catalyst. Hydrogen is produced as the by product of the reactions
55
What conditions are needed for reforming?
high pressure and high temperature in the presence of a platinum catalyst
56
Why does reforming hydrocarbons allow for more efficient combustion?
-Because reformed hydrocarbons have lower boiling points and so combust easier and quicker
-Reforming hydrocarbons also reduces the knocking effect, which is where alkanes explode when the fuel or air mixture in the engine is compressed.
57
Which pollutants are formed during the combustion of alkane fuels?
- Carbon Monoxide
- Oxides of Nitrogen
- Oxides of Sulfur
- Carbon particulates
- Unburned hydrocarbons
58
What happens when you burn alkanes with oxygen?
you get carbon dioxide and water
59
What is the possible combination of products when incomplete combustion occurs?
- Carbon monoxide, water, carbon, carbon dioxide
60
Why is carbon monoxide toxic?
Because the carbon monoxide binds to the haemoglobin in our blood and makes it difficult for oxygen to be transported around the body
61
How can carbon monoxide be removed?
By using a catalytic converter
62
Why are oxides of nitrogen formed?
Due to the high temperatures and pressures in the car engine
63
What happens when nitrogen oxides react with water?
nitric acid can be produced, which can then fall as acid rain
64
How is sulfur dioxide produced?
By burning fuels with sulfur impurities
65
What happens when sulfur dioxide is produced?
It reacts with water to form sulfuric acid and this then falls as acid rain
66
What problems does acid rain cause?
- Destroys plants
- Corrodes buildings and statues
- Kills fish and aquatic life living in bodies of water
67
How are particulates formed?
From the incomplete combustion of fuels
68
What problems do particulates cause?
- they can damage the lungs and cause respiratory problems
- They can cover buildings and statues, making them look unclean and accelerating corrosion
- They can reflect sunlight back into space reducing the amount of light reaching the earth, this is called global dimming
69
What do Catalytic converters do?
They use a platinum catalyst to convert pollutants into harmless gases, hence limiting the amount of pollutants that enter the atmosphere
70
What are the main fossil fuels?
Coal, oil, and natural gas
71
Is there a finite or infinite amount of fossil fuels?
There's a finite amount of fossil fuels
72
Which fossil fuel will be the first to run out?
Oil
73
Are fossil fuels renewable or non-renewable?
They're non-renewable
74
75
What are some alternatives to fossil fuels?
Biofuels and alcohol
76
What are the 3 main biofuels?
Bioethanol. biodiesel, biogas
77
What is bioethanol?
A biofuel made from the fermentation of sugar from crops such as maize
78
What is biodisel?
a biofuel made by refining renewable fats and oils, such as vegetable oil
79
What is biogas?
a biofuel produced by the breakdown of organic waste matter
80
Why are biofuels describes as being carbon neutral?
- This is because as the plants grow they absorb carbon dioxide which is equivalent to the amount of carbon dioxide that will be released when they are burnt.
- However, this is not completely true, as carbon dioxide will also be produced in the refining and transport of the plants
81
Can biodiesel and biogas also be made from waste that would otherwise go to landfill?
Yes
82
What is one problem with free radical substitution?
You often get a mixture of products, not just the desired product
82
What's the problem with trying to use biofuels in car engines?
car engines would have to be modified and this could cost a lot of money
83
In alkane what does the first example of structural isomerism begin at?
Butane (C4H10)
83
Why do branched molecules have a lower boiling point than straight chains?
Because branched molecules are more compact and so have less London forces. This means a lesser amount if energy is required for them to boil
84
Are alkanes very reactive?
No, they're fairly unreactive
85
What's a trick for balancing complete combustion Equations?
- In complete combustion, every carbon in the original hydrocarbon gives a carbon dioxide.
- Every 2 hydrogens give a water molecules.
- Then all you need to do is balance the oxygen
86
What can SO2 be reacted with to limit its polluting effects?
So2 can be reacted with effluent gases with a suitable base compound e.g CaO
87
What is Carbon monoxide converted into in catalytic convertors?
To carbon dioxide
88
What is NOx converted into in catalytic convertors?
N2
89
What are unburnt hydrocarbons converted to in catalytic convertors?
C02 and H20
90
Which metals are usually used in catalytic convertors?
Platinum, palladium, and rhodium
91
Why is the catalyst in catalytic convertors used in a finely divided form?
To increase the surface area that the reaction can take place over. This increases the rate of reaction
92
Are alkanes aliphatic?
Yes
93
The greater the branching....
The lower the boiling point
94
Why can't leaded petrol pass through the catalyst?
Because the lead deposit on the catalysts surface and "poisons" it. Hence blocking sites for the reaction to take place
95
What does heterolytic fission produce?
Ions (one gets both of the 2 electrons from the bond)
96
What does homylitic fission produce?
Radicals (each getting an electron each)
97
Can free radicals be formed during thermal cracking ?
Yes
98
Give the overall reaction, the initiation steps, the propagation steps, and the termination steps for the reaction of CH4 with CL2
99
Show the mechanism and overall equation of CH3CL reacting with Cl2
100
Show the mechanism and overall equation of CH2CL2 reacting with Cl2
101
Show the mechanism and overall equation of CHCL3 reacting with Cl2
102
Alkene + Halogen ->
Dihalogenoalkane
103
Alkene + Hydrogen ->
Alkane
104
Alkene + Hydrogen Halide ->
Halogenoalkane
105
Alkene + Potassium Mangate ->
Diol
106
Alkene + Steam ->
Alcohol
107
Why is a tertiary carbocation more likely to form?
Because it is more stable than both a primary and secondary carbocation
108
How many R groups is a primary carbocation bonded to ?
1
109
How many R groups is a secondary carbocation bonded to?
2
110
How many R groups is a tertiary carbocation bonded to?
3
111
Do symmetrical or unsymmetrical alkenes form carbocations?
Unsymmetrical
112
What is Markownikoff's rule?
The major product from the addition of a hydrogen halide to an unsymmetrical alkene is the one where hydrogen adds to the carbon with the most hydrognes already attached
113
Thre can be a major product and a what product?
A minor product
114
What happens when you add an alkene to acidified potassium manganate (VII)?
The purple solution decolourises as the alkene has been oxidised and a diol has been produced.
115
What is an electrophile?
something attracted to areas of high electron density
116
What is an nucleophile?
something attracted to areas of positive charge
117
What conditions are needed for the hydrogenation of an alkene?
A nickel catalyst and a temperature of 150 degrees celcius
118
What conditions are needed for the reaction of an alkene with steam to form an alcohol?
a temperature of 300 degrees celsius; a pressure of 60-70 atm, and a solid phosphoric(V) acid catalyst
119
What is H3P04?
Phosphoric acid
120
What is KMn04?
Potassium Manganate
121
Why are all the reactions with alkenes examples of electrophilic addition reactions?
Because alkenes have double bonds with high electron densities that attract positively charged molecules
122
What type of reactions usually take place with halogenoalkanes?
Nucleophilic substitution reactions
123
Halogenoalkane + Aqueous Potassium Hydroxide ->
Alcohol
124
What conditions are needed for the reaction between a halogenoalkane and aqueous potassium hydroxide to form an alcohol?
The potassium hydroxide has to be warm and the reaction usually takes place under reflux
125
What happens when you react a halogeonalkane with aqueous silver nitrate in ethanol?
You get an alcohol, a hydrogen ion, and a halide ion
126
What can the halide ion formed from the reaction between a halogenoalkane and aqueous silver nitrate consequently react with?
The silver ions in silver nitrate to form silver precipitates. Thr colour of the precipitate allows you to identify the halide ion present.
127
Cl- + Ag+ ->
AgCl
128
Br- + Ag+ ->
AgBr
129
I- + Ag+ ->
AgI
130
What colour precipitate is AgCl?
White precipitate
131
What colour precipitate is AgBr?
Cream precipitate
132
What colour precipitate is AgI?
A yellow precipitate
133
Halogenoalkane + Potassium Cynaide(in ethanol) ->
Nitrile
134
What condition is needed for the reaction between a halogenoalkane and potassium cyanide to form a nitrile ?
Reflux
135
What is reflux?
Heating with a condenser placed vertically in the flask to prevent the loss of volatile substances from the mixture
136
What's the benefit of the reaction between a halogeinalkane and potassium cyanide to form a nitrile?
This reaction helps lengthen the carbon chain
137
Halogenoalkane + Ammonia(in ethanol) ->
Amine
138
Halogenoalkane + Ethanolic Potassium Hydroxide ->
Alkene
139
What conditions are needed for the reaction of a halogenoalkane and ethanolic potassium hydroxide to form an alkene?
- The alkali potassium hydroxide must be warmed
- The mixture must be heated under reflux
- The Potassium Hydroxide must be dissolved in ethanol
140
What sort of reaction is the reaction between a halogenoalkane and ethanol potassium hydroxide to form an alkene ?
Elimination
141
Alcohol + Concentrated Phosphoric acid ->
Alkene
142
What type of reaction is the reaction between alcohol and concentrated phosphoric acid to form an alkene ?
An elimination reaction
143
What reaction conditions are needed for the reaction between an alcohol and concentrated phosphoric acid to form an alkene?
- Alcohol must be heated under reflux
- Phosphoric acid catalyst
- Alkene can be purified by distillation
144
What type of reaction is a dehydration reaction ?
An elimination reaction
145
What do alcohols combust with oxygen to give ?
Carbon dioxide and water
146
C2H5OH + 3O2 ->
2CO2 + 3H20
147
What is PCL5?
Phosphorous Pentachloride
148
Alcohol + PCL5 ->
Chloroalkane
149
Alcohol + HCl ->
Chloroalkane
150
Ethanol + Phosphorous Chloride ->
Chloroethane + Phosphoryl trichloride + Hydrogen Chloride
151
ROH + PCl5 ->
RCl + POCl3 + HCl
152
Alcohol + Potassium Bromide + Sulfurinc acid ->
Bromoethane + water + Potassium Hydrogen Sulfate
153
C2H5OH + KBr + H2SO4 ->
C2H5Br + H2O + KHSO4
154
What conditions are needed for the reaction of Alcohol and Potassium Bromide and Sulfuric acid ?
- Reflux
- 50% concentrated sulfuric acid
155
Alcohol + Red Phosphorous + Iodine ->
Iodoalkane
156
Oxidation of Primary alcohols....
Primary alcohols are oxidised by potassium dichromate(VI) in dilute sulfuric acid to form aldehyde and carboxylic acids
157
Oxidation of Secondary Alcohols...
Secondary alcohols are oxidised by Potassium Dichromate(VI) in dilute sulfuric acid to form ketones
158
Oxidation of tertiary alcohols....
Tertiary alcohols aren't oxidised
159
Cr2O72-/H+ come from K2Cr2O7/ H2SO4
160
How can you get only the aldehyde product from the oxidation of primary alcohols?
Via fractional distillation
161
How can you test for aldehydes/ketones using Benedicts solution ?
- If benedicts is heated with an aldehyde, a red precipitate will form.
- If Benedicts is heated with a ketone, no precipitate will form
162
How can you test for an aldehyde/ketone using Fehlings solution?
- Red precipitate will form in the presence of an aldehyde.
- No precipitate will form in the presence of a ketone
163
What colour change is observed when an alcohol is oxidised with Potassium Dichromate(VI)?
A colour change from orange to green
