Organic Chemistry Flashcards
(164 cards)
1
Q
What are organic molecules
A
Covalent molecules based on the element carbon
2
Q
How many covalent bonds can hydrogen, carbon and oxygen form
A
Hydrogen - 1 bond
Carbon - 4 bonds
Oxygen - 2 bonds
3
Q
What is a functional group
A
The part of a molecule which determines how it reacts
4
Q
What is a homologous series
A
A series of molecules that have the same functional group but each successive member has an additional -CH2
5
Q
What are hydrocarbons
A
Covalent compounds that consist of hydrogen and carbon exclusively
6
Q
What are saturated and unsaturated hydrocarbons
A
Saturated - only single bonds between the carbons
Unsaturated - have double bonds between carbons
7
Q
Name these compounds
How do you know whether to start from the left or the right
A
But-1-ene
But-2-ene
Start from the end that produces the lowest possible numbers
So it but-1-ene instead of but-3-ene
8
Q
What is a branched hydrocarbon
A
Hydrocarbons that have a side-chain or branch
9
Q
Name this compound
A
10
Q
What is the prefix for seven
A
Hept-
11
Q
Name this compound
A
12
Q
Name this compound
A
13
Q
How do you find the central chain if the hydrocarbon is branched
A
Find the longest chain of carbons
14
Q
Name this compound
A
15
Q
What is molecular formula
A
Tells us the actual number of atoms of the elements in that compound
16
Q
What is empirical formula
A
The simplest whole number ratio of the atoms of each element in a compound
17
Q
A
You need to work out the number of moles of carbon and hydrogen:
- Carbon: 0.48/12 = 0.04mol
- Hydrogen: 0.08/1 = 0.08mol
Divide by the smallest of the numbers to get the empirical formula:
- Carbon : 0.04/0.04 = 1
- Hydrogen: 0.08/0.04 = 2
So the empirical formula is CH2
18
Q
If the compound has an empirical formula of CH2 what is the molecular formula
A
Divide Mr by molecular mass and times the empirical formula by that number
19
Q
What is a displayed formula
A
It shows that relative position of each atom in the compound and all the covalent bonds
20
Q
What is a structural formula
A
It shows how the atoms in a compound are arranged but don’t display the covalent bonds
21
Q
How do you display a methyl group in structural formula
A
(CH3)
22
Q
What is the structural formula of these compounds
A
23
Q
What is the structural formula of this compound
A
24
Q
What is the structural formula of these compounds
A
25
What are skeletal formulas
Only shows functional groups and doesn't show carbons and hydrogens
26
What is a general formula
The simplest algebraic formula for a member of a homologous series
27
What is the general formula for alkanes
28
What is the general formula for alkenes
29
What is the general formula for alcohols
30
What is a structural isomer
Molecules with the same molecular formula but different structural formulae
31
Name and explain the three different types of structural isomers
Functional group - different functional groups
Chain isomer - differ in arrangement of the hydrocarbon chain
Positional isomers - have different positions of the functional group
32
What are stereoisomers
Molecules with the same structural formula but the atoms are arranged differently in space
33
What are the two types of stereoisomers
Geometric isomers
Optical isomers
34
What are geometric isomers
Same molecular formula but different spatial arrangements of atoms or groups due to restricted rotation around a double ring
35
Explain the CIP rules
Assign greater priority to the elements with the highest atomic number attached to each side of the carbon carbon double bond
Based on the position of these high prority atoms then the isomer will be considered either E or Z
If the atoms on the same side of the double bond have the same atomic number move on to the next atom that is bonded to those two atoms
36
What constitutes an E isomer
If the atoms with the highest priority are attached diagonally to the carbon carbon double bond
37
What constitutes a Z isomer
If the atoms with the highest priority are attached on the same level to the carbon carbon double bond
38
Decide whether these isomers are E or Z
39
40
What are alkanes
41
Describe and explain the properites of alkanes
Non-polar - Carbon and Hydrogen have similar electronegativity
Insoluble in water - No permanent dipoles for a hydrogen bond to form
Generally unreactive - Strong covalent bonds
42
Why do van der Waals forces increase when the chain of an alkane increases
More electrons
Greater surface area - many points along the molecule where van der Waals forces can form
43
Do branched alkanes have lower or higher boiling points than straight chain alkanes
Explain why
Lower boiling points
Branches prevent alkane molecules from getting close together
44
Where does crude oil come from
Formed underground from the remains of plants and animals
Over millions of years, heat and pressure convert the chemicals in these remains into crude oil
45
Describe the stages of the distillation of crude oil
Crude oil is heated in a furnace and is converted to a gas
The crude iol vaours and liquid pass into the fractionating column
The column progressively gets cooler going upwards
Vapours make their way up the column - there are collecting trays at different levels of the column
These trays have bubble caps which allow vapours to pass upwards
At some point each vapour will reach a level that is cooler than their boiling point and it will condense into a liquid
Alkanes with very long chains form a thick liquid called bitumen and it is collected at the bottom of the column
Very short chains (methane and ethane) are collected at the top of the column as gases
46
Name the 6 different fractions when distilling crude oil
Bitumen
Fuel oil
Lubricating oil
Diesel
Kerosene
Petrol/Naptha
47
What is Petrol/Naptha used for
For petrol and as a raw material for the chemical industry
48
What are the two benefits of cracking
Converts long chain hydrocarbons into shorter chain hydrocarbons which there is a higher demand for
Produces alkanes wihch are highly reactive molecules
49
Why are alkenes important for chemical industry
A major feedstock (raw material) for chemical industry and they are used to make a range of products including polymers
50
What are the two ways to carry out cracking
Thermal
Catalytic
51
Describe thermal cracking (products, conditions etc.) and what are the benefits
Long chain alkanes -> shorter chain alkanes and alkenes (hydrogen could also be one of products)
The benefits is that shorter chain alkanes are produced
52
Illustrate what happens to a long chain alkane in thermal cracking
Covalent bond splits to form intermediate molecules
Both molecules have one unpaired electron - these are called free radicals
53
Describe catalytic cracking (products, conditions etc.) and what are the benefits
Uses zeolite catalyst
The products are normally branched chain alkanes, cyclic alkanes and aromatic hydrocarbons (such as benzenes)
The benefit to the production of branched alkanes is that they combust very efficiently
54
What is a zeolite catalyst and why is it effective
Contains a mixture of AlO2 and SiO2
Has a large surface are which helps to make it effective
55
What is a free radical
Any species with an unpaired electron
56
How do you portray free radicals
57
Describe the reactivity of free radicals
They are very reactive
58
What are the three stages of free radical substitution
Initiation
Propagation
Termination
59
Describe and explain initiation (including conditions)
UV light is shined on the reaction mix - the energy causes the covalent bond between the two halogens to break forming two halogen free radicals
60
Describe and explain the first step of propagation
Halogen free radical reacts with methane
To make an electron pair, the halogen free radical takes a hydrogen atom and one electron from the methane molecule
This produces a methyl free radical and a hydrogen halogen
61
Describe and explain the second step of propagation
The methyl free radical now reacts with a halogen molecule
This produces molecule with a halogen and methyl group together and another halogen free radical
The halogen free radical produced can take place in step 1 again and this will continue until termination takes place
62
Describe and explain termination
Two free radicals react together to form a molecule with no unpaired electrons
63
What are the three possible reactions in termination
Two halogen free radicals can form a halogen molecule
Two methyl free radicals can form a molecule of ethane
A methyl free radical and a halogen free radical can form a molecule (bromoethane e.g.)
64
What is one problem with free radical substitution of alkanes
You get a whole range of side-products
65
In what process do alkenes react
Electrophilic addition
66
Describe the first part in how hydrogen halides react with symmetrical alkenes
Electrophilia addition
Halides are more electronegative than hydrogen so the molecule is polar
When the hydrogen halide is close to the alkene the positive hydrogen on the hydrogen halide is attracted to the high electron density of the double bond
A covalent bonds are formed towards the hydrogen atom in the hydrogen halide from the alkene
The hydrogen atom can only form one covalent bond so the pair of electrons in the bond between the hydrogen and the halogen move to the halogen and the bond is broken
67
What is an electrophile
Any positive ion or molecule which is attracted to a region of high electron density
68
Describe the second part in how hydrogen halides react with symmetrical alkenes
The lone pair on the halogen is attracted to the positive carbon atom and a covalent bond is formed
69
What is a carbocation intermediate
An intermediate that has a carbon atom bearing a postiive charge and three bonds instead of four
70
What does major and minor product mean
When there are two different isomers of a compound that are produced as a result of an alkene reacting with a halogen there will be one isomer that is produced more than the other one
That isomer is the major product
71
What does the stability of the carbocation depend on
The amount of alkyl groups bonded to it
72
What is a primary and secondary carbocation
Primary - When the carbocation is bonded to only one alkyl group
Secondary - When the carbocation is bonded to two alkyl groups
73
If there are carbocations produced in a reaction which one will be produced the most: the primary carbocation or the secondary carbocation
The secondary carbocation will because it is more stable and will exist for a longer period of time and it is more likely to form the product
74
Which product is the major product
The one on the right has a secondary carbocation which is more stable so it will exist for a longer period of time
This means that it is more likely to form the product so that is the major product
75
Why are secondary carbocations more stable than primary carbocations
Because of the positive inductive effect
76
What is the positive inductive effect
The electrons in the alkyl groups can shift towards the positive charge and the effect of this is to stabilise the positive charge
77
Describe the first stage of the mechanism that takes place in the reaction between halogen molecules and alkenes
Halogen approaches alkene
The region of high electron density repels the electrons in the halogen molecule which forms an induced dipole
78
Describe the second stage of the mechanism that takes place in the reaction between halogen molecules and alkenes
The electrons in the double bond are attracted to the delta positive halogen in the halogen molecule
A covalent bond is now formed between the carbon and the delta positive bromine and the covalent bond between the two halogens now break and the electrons move to the halogen that doesn't bond to the carbon
79
Describe the third stage of the mechanism that takes place in the reaction between halogen molecules and alkenes
The electron pair on the halide ion are attracted to the positive carbon atom in the carbocation intermediate
A covalent bond is formed and the final product is formed
80
How do you test for alkene
Add drops of bromine water (orange) and gently shake
If solution turns colourless then alkene is present
81
What are the conditions and the catalyst for the hydration of alkenes
The water is in the form of steam
82
What is the displayed formula of phosphoric acid
Is it polar or non-polar and why
Oxygen is extremely electronegative and hydrogen isn't so it is polar
83
Describe the first stage in the hydration of alkenes
The phosphoric acid approaches the alkene and the delta positive hydrogen is attracted to the high electron density in the double bond and the covalent bond between the hydrogen and the oxygen breaks
This produces a carbocation intermediate and a dihydrogen phosphate ion
84
Describe the second stage in the hydration of alkenes
The carbocation intermediate reacts with steam
One of the lone pairs on the oxygen in the water molecule forms a covalent bond with the positive carbocation
The oxygen is positive because its lone pair of electrons have formed a covalent bond
85
Describe the third stage in the hydration of alkenes
The dihydrogen phosphate ion forms a covaletn bond to a hydrogen in the intermediate molecule and the hydrogen breaks the covalent bond with oxygen and leaves the intermediate
This produces an alcohol and regenerates phosphoric acid
86
What is Markownikoff's rule
When a hydrogen halide reacts with an asymmetric alkene, the hydrogen atom of the hydrogen halide is more likely to bond to the carbon atom which is attached to the greater number of hydrogen atoms
87
If the alkene that is getting hydrated is asymmetric how do you decide on the carbon that the hydrogen forms a bond with in the first stage
Use Markownikoff's rule
Choose the carbon that is bonded to the highest number of hydrogens
88
Describe the first stage of the reaction between alkenes and sulfuric acid
The sulfuric acid approaches the alkene and the electron density in the double bond attracts the delta positive hydrogen atom on the sulfuric acid
A covalent bond is formed with the hydrogen atom and the covalent bond between that hydrogen atom and the oxygen atom is broken and the pair of electrons move onto the oxygen atom
The products are a carbocation intermediate and a hydrogensulfate ion with a negatively charged oxygen atom
89
What is the displayed formula for sulfuric acid
90
Describe the second stage of the reaction between alkenes and sulfuric acid and what is the mechanism called that takes place in this stage
The lone pair of electrons on the hydrogensulfate ion is attracted to the positive carbocation intermediate
The lone pair on the oxygen forms a covalent bond with the carbon which forms ethylhydrogensulfate
Electrophilic addition
91
What are the products of this reaction
92
What are the two types of polymers
Addition
Condensation
93
In terms of size what type of molecule are large polymers
What are they made up of
Large molecules
Made of thousands of small identical monomers
94
What does polymerisation require
High temperature and pressure as well as a catalyst
95
When ethene is made into a polymer what is it called
Poly(ethene)
96
What type of hydrocarbon are polymers
Alkanes
97
Describe and explain the reactivity of addition polymers
Since these molecule consists of hydrogen and carbon the bonds are non-polar and covalent so they are hard to break
Because of this they are unreactive
98
What is the repeating unit for this polymer
99
What is the monomer that makes up this polymer
100
What is the name of this polymer
Poly(chloroethene)
101
What is poly(phenylethene) commonly known as
What is commonly used as
Polysterine
Used to make foam food containers and drinks cups
102
What is poly(chloroethene) commonly known as
PVC (Polyvinyl Chloride)
103
Describe the two types of PVC
Rigid - It is a rigid polymer that's used to make plastic pipes among other products
Flexible - Relatively soft and is used to make flooring and the insulation on electrical cables
104
How do you produce flexible PVC
Add plasticisers to rigid PVC
Causes the chains to move further apart and weakens the intermolecular forces between the chains
105
What IMF are present in PVC
Permanent dipoles
Van deer Waals forces
106
What is a plasticiser
A small molecule that fits between the polymer chains so that the chain
107
Why does the fact that addition polymers aren't reactive make them useful
Because they can be used to make containers without the molecules reacting with the food
108
Describe and explain the 4 environmental problems caused by addition polymers
Since they are unreactive they are also non-biodegradeable
This means that they can pollute the environment for decades or longer - harmful for wildlife
Involve the use of crude oil
Occupy space in landfills
109
What is meant by non-biodegradeable
Not broken down by microorganisms in the environment
110
What are the two ways to mitigate the effects to the environment caused by addition polymers
Instead of being sent to landfills they can be combusted, generating energy
Polymer waste can be sorted into the different polymers and recycled into new products
111
Why is combusting poly(chloroethene) harmful
What is done to mitigate this problem
When combusted HCl is produced - which is corrosive
Must be removed from any waste gases before they are released
112
What is feedstock recycling
Waste polymers are converted back to simpler hydrocarbons
Then they are cracked and converted to different polymers
113
What are two advantages of feedstock recycling
The waste polymers do not need sorting
Allows us to convert one polymer into a different polymer
114
What are the benefits of biodegradeable polymers
They are biodegradeable
Made from plants so they are a renewable resource
115
What are photodegradeable polymers
Oil-based polymers which slowly break down in sunlight
116
What is the name for alcohols that contain two OH functional groups
-diol
117
What is this compound called
118
Which three functional groups have naming priority over alcohols
Aldehydes
Ketones
Carboxylic acids
119
What is the name of these compounds
120
How do you name alcohols that contain functional groups that have naming priority over them
Hydroxy- at the beginning
121
Explain the three types of alcohol
Primary - the C bonded to the OH is bonded to one other C atom
Secondary - the C bonded to the OH is bonded to two other C atoms
Tertiary - the C bonded to the OH is bonded to three other C atoms
122
What type of alcohol is methanol
Primary
123
Which homologous series has the higher boiling points: alkanes or alcohols
Alkanes are non-polar so they only have van der Waals forces
Alcohols are polar because of the hydroxyl functional group and they can form both van der Waals forces and London forces because they contain oxygen
124
What does volatility mean
How readily a molecule turns into a gas
125
Compare the volatility of alcohols and alkanes
Alcohols are less volatile because they have higher boiling points
126
Describe and explain the trend in boiling point as you add more carbons to alkanes and alcohols
It increases as you add more carbons
This is because the strength of the van der Waals forces increase
127
Explain why as you add more carbons to alkanes and alcohols the boiling points get closer together
Because the molecule gets larger and hydrogen bonds become less significant and van der Waals forces play a bigger role so the difference changes
128
Describe and explain the solubility of alcohols in water
Very soluble in water
Because the functional group can form hydrogen bonds with water molecules
129
What is the the trend in solubility as you add more carbons to the carbon chain of an alcohol
The solubility decreases because their are more C-H bonds that can't form hydrogen bonds and can't dissolve in water
130
Describe and explain the solubility of alkanes in water
Insoluble in water
Because they are non-polar molecules they can't form hydrogen bonds with water
131
What happens when you oxidise a primary alcohol
You get an aldehyde
132
When ethanol is oxidised what will the products be
Ethanal
Water
133
What is the common oxidising agent for the oxidation of primary alcohols
Potassium dichromate with dilute sulfuric acid
134
What does acidified potassium dichromate contain
Potassium dichromate
Sulfuric acid
135
What is the colour acidified potassium dichromate
Orange
136
What is the formula for acidified potassium dichromate
137
What does this mean
It shows that one molecule of oxidising agent is taking part in the reaction
138
What happens to the oxidising agent in this reaction
Reduced from the dichromate (VI) ion which is orange to the chromium (III) ion which is green
139
What is the problem with this reaction and how can it be mitigated
It is very easy to oxidise aldehydes further
So you have to remove it from the reaction as soon as it forms
140
Describe and explain the relative boiling points of aldehydes
Why is this useful
They are low
Because they can't form hydrogen bonds
It can be removed from the reaction via distillation
141
What is the apparatus for removing aldehydes from the reaction of alcohol with acidified potassium dichromate
Happens via distillation
142
What happens when aldehydes are oxidised
Produce carboxylic acids
143
How many molecules of oxidising agent is required to convert a primary alcohol into a carboxylic acid
2
144
What are three things you can do to make sure that all of the aldehyde is converted into a carboxylic acid
Use an excess of oxidising agent (potassium dichromate)
Use concentrated H2SO4 instead of dilute in the oxidising agent
Heat the reaction under reflux
145
What does heating the reaction under reflux mean and why is it effective in terms of the production of a carboxylic acid
Any volatile products are condensed and return to the reaction mix
Can heat chemicals until the reaction completes
146
What is the apparatus for heating a reaction under reflux
147
Describe and explain the difference between aldehydes and carboxylic acids with regard to boiling points
Carboxylic acids can form hydrogen bonds so they have higher boiling points
148
When heating under reflux what should you do when the reaction completes
Distil the reaction mix until carboxylic acid is separated
149
What happens when you use acidified potassium dichromate to oxidise a secondary alcohol
Ketone
Water
150
Can a ketone be oxidised further and why
No
Because the carbon bonded to the oxygen isn't bonded to any other hydrogens
151
Describe the process of oxidising a secondary alcohol
Heat the reaction under reflux
Distil products to separate the ketone from the reaction mix
152
Describe and explain the properties of ketones
Volatile and have relatively low boiling points
Can't form hydrogen bonds
153
What happens when you heat a tertiary alcohol in the presence of acidified potassium dichromate
Nothing will happen because the carbon isn't bonded to any hydrogen atoms
154
How do you convert an alcohol into an alkene
Heat the alcohol under reflux in the presence of concentrated sulfuric/phosphoric acid
155
What are the products for the dehydration of alcohols
Alkene
Water
156
What is an elimination reaction
A small molecule is removed from a larger parent molecule
157
What type of reaction is the dehydration of alcohols
Elimination
158
Explain the first stage of the dehydration of alcohols
Lone pair of electrons on the oxygen atom are attracted to the positive hydrogen ion from the acid catalyst
A covalent bond is formed and an intermediate is produced
159
Explain the second stage of the dehydration of alcohols
The electrons in the covalent bond between the carbon and the oxygen move onto the oxygen atom
This causes a molecule of water to be released
The electrons between the hydrogen and the carbon move between the two carbons and a hydrogen ion is released
160
How would you produce ethanol from bromoethane
Heat ethanol under reflux with a mixture of sodium bromide and sulfuric acid (with a concentration of 50%)
This produces bromoethane, water and sodium hydrogen sulfate
161
What is the first stage of the production of bromoethane from ethanol
162
What is the second stage of the production of bromoethane from ethanol
That alcohol group on the ethanol is switched with the bromine - this is called a substitution reaction
163
Describe the volatility of haloalkanes
They are volatile molecules
164
Is the combustion of alcohols a endothermic or exothermic reaction
Exothermic
