6:Organic Chemistry I Flashcards
(159 cards)
1
Q
What is a homologous series?
A
A group of compounds that have the same functional group and general formula
- each successive member is increased by CH2
2
Q
What is the suffix for an alkane?
A
-ane
3
Q
What is the prefix for a branched alkane?
A
Alkyl-
4
Q
What is the suffix for an alkene?
A
-ene
5
Q
What is the suffix for an alcohol?
A
-ol
6
Q
What is the suffix for an aldehyde?
A
-al
7
Q
What is the suffix for a ketone?
A
-one
8
Q
What is the suffix for a carboxylic acid?
A
- oic acid
9
Q
What is the prefix and suffix for a cycloalkane?
A
Cyclo- -ane
10
Q
What are the steps of nomenclature?
A
1) Find the length of the stem
2) Functional group will give the suffix
3) Number the carbon chain so that the functional group sits on the lowest possible carbon
4) Make a note of the carbon number the functional group is attached to. Place this number before the suffix
5) Any side chains/less important chains are written as prefixes in alphabetical order
11
Q
What is a chemical mechanism?
A
They are curly arrows that show the movement of electrons
- the curly arrow starts from an area of electrons to an electron deficient area
12
Q
What are the types of mechanisms?
A
- Radical substitution
- Electrophilic addition
- Nucleophilic substitution
13
Q
What is radical substitution used for?
A
Reacting halogens to alkanes to make halogenoalkanes
14
Q
What is electrophilic addition used for?
A
Adding halogen and hydrogen halides to alkenes to make halogenoalkanes
15
Q
What is Nucleophilic Substitution used for?
A
Primary halogenoalkanes and aqueous hydroxide to make alcohols.
Amines are made by reactions with ammonia
16
Q
What are structural isomers?
A
Substances with the same molecular formula but different structural formula
17
Q
What are the three different types of structural isomers?
A
- Chain
- Positional
- Functional group
18
Q
What are chain isomers?
A
Isomers with the same molecular formula but different arrangement of the carbon skeleton
19
Q
What are positional isomers?
A
Isomers with the same molecular formula but different position of the functional group on the carbon skeleton
20
Q
What is a functional group isomer?
A
An isomer with the same molecular formula but different functional group
21
Q
What are alkanes?
A
Saturated hydrocarbons
22
Q
What are cycloalkanes functional group isomers with?
A
Alkenes
23
Q
What is bond fission?
A
The breaking of a covalent bond
24
Q
What are the two types of bond fission than can occur?
A
- Heterolytic fission
- Homolytic fission
25
What happens during heterolytic fission?
The bond break but the electrons are distributed unevenly to form two different ions
26
What happens during homolytic fission?
The bond breaks with the pair of electrons in the bond being shared equally to form two uncharged radicals.
27
What are the three stages of free radical chain reactions?
1) Initiation
2) Propagation
3) Termination
28
What happens during initiation in free radical chain reactions?
Radicals are produced normally using either visible light or UV (this process is called a photochemical reaction).
The bond breaks producing two radicals .
29
What happens during propagation in free radical chain reactions?
1. The Cl radical reacts with a methane molecule to make a methyl radical
2. The methyl radical reacts with a Cl2 molecule forming chloromethane and a Cl radical
This Cl radical can react with more methane thus making this a chain reaction
30
What is the equation that occurs during initiation in free radical chain reactions of making chloromethane?
Cl - Cl —> 2Cl°
UV used to produce this
31
What is the equation that occurs during propagation in free radical chain reaction of making chloromethane?
1. Cl° + CH4 —> HCl + °CH3
2. °CH3 + Cl2 —> CH3Cl + Cl°
32
What happens during termination in free radical chain reactions?
Two radicals react to make a stable non-radical molecule
33
What is the equation that occurs during termination in free radical chain reactions of making chloromethane?
°CH3 + °Cl —> CH3Cl
34
How can we reduce the likelihood of the production of di,tri and tetrachloromethane being formed when making chloromethane?
By adding excess methane
35
How does fractional distillation work?
- The vaporised oil enters the column and rises through the trays (the longest hydrocarbons don’t vaporise and run down to the bottom)
- The column has a temperature gradient (cooler at the top)
- As the vapour rises parts of the mixture condenses out at different temperatures.
36
What are the use of gas?
Used in LPG and stove gas
37
What are the uses of petrol?
Used in petrol cars
38
What are the uses of diesel oil?
Used as diesel fuel
39
What are the uses of kerosene?
Used as jet fuel and heating
40
What are the uses of fuel oil?
Used in ships and power stations
41
What are the uses of bitumen?
Used in roofing and tarmac
42
What are alkenes?
Unsaturated hydrocarbons with at least one double bond
43
What are sigma bonds?
2 ‘s’ orbitals, they align horizontally to give a single covalent bond
44
What are pi bonds?
The parallel overlap of 2 ‘p’ orbitals
-> ‘p’ orbitals are dumbbell shaped and when they merge they form two oblong shapes. One
on the top and one on the bottom
45
Why are pi bonds weaker than sigma bonds?
Sigma binds have direct overlapping of orbitals where as pi bonds have parallel overlapping which is less effective
46
Why are alkenes more reactive?
The double bond in alkenes have a high electron density
-> alkenes have both sigma and pi bonds between the bond
The pi bond sticks out so it’s open to attack from electrophiles. The pi bond also has low bond enthalpy.
47
Why are alkanes less reactive compared to alkenes?
- Alkanes only have a sigma bond
- They are non-polar
48
What are stereoisomers?
Isomers with the same structural formula but different arrangement of atoms in a space
49
What shape are atoms bonded to C=C bond?
Planar
50
Can atoms rotate around the C=C bond?
No, they are rigid
51
What is an Entgagen (E) isomer/trans-isomer?
Isomers that have the same group on the **opposite** side of the double bond (diagonal)
52
What is an Zusammen (Z) isomer/cis-isomer?
Isomers that have the same group on the **same** side of the double bond (horizontal)
53
How can we determine if an isomer is an E/Trans or Z/Cis isomer if there are four different groups around the double bond?
We use the Cahn-Ingold-Prelog rules
54
What are the Cahn-Ingold-Prelog rules for stereoisomers?
Rule 1: Label carbons on the double bond as ‘carbon1’ and ‘carbon2’
Rule 2: Calculate the atomic number of the first element directly bonded to the C=C. The atom with the highest atomic number is given higher priority
-> If atomic number is the same, check further down the chain to workout the priority
55
Why are alkenes attacked by electrophiles?
The double bond has high electron density. The electrophile adds to the molecule.
56
What are electrophiles?
Substances which are electro pair acceptors.
*- they are deficient in electrons*
57
What are examples of electrophiles?
- positively charged ions
- polar molecules (due to the δ+ part)
58
Where does the curly arrow start from electrophilic addition?
From the double bond
59
What conditions are required to form ethane from ethene (electrophilic addition)?
React with hydrogen gas.
150°C
Nickel catalyst
60
What is the chemical test for alkenes?
Decoloration of bromine water (addition reaction)
61
What is the colour change in the addition of bromine for the test for alkenes?
Brown-orange Bromine water turns colourless
62
What are the steps for the addition of bromine?
1) Br2 is polarised as electrons in the double bond (of alkene) repels electrons in Br2
2) An electron pair in the double bond is attracted to the δ+ Bromine and forms a bond (this breaks the Br-Br bond)
3) A carbocation intermediate (C+) is formed and the δ- Bromine is attracted to it
4) Colourless dibromoalkane is formed
63
What are the products of the hydration of alkene?
Alcohols
64
What conditions are used in the hydration of alkenes?
Steam and an acid catalyst (H+)
65
How can we make ethanol by the hydration of alkenes?
By reacting steam and ethene with a phosphoric acid catalyst.
A temperature of 300°C and pressure of 60atm is needed
- *this is a reversible reaction*
66
How are alcohols formed from alkenes?
- hydration
- acidified potassium manganate (VII)
67
How does adding acidified potassium manganate (VII) to alkenes turn them into alcohol?
Potassium manganate (VII) is an oxidising agent and oxidises the alkene to make a diol
68
What is the observation when acidified potassium manganate (VII) reacts with ethene?
Purple to colourless
69
What forms when alkenes react with hydrogen halides?
Halogenoalkanes
70
Describe the mechanism for the addition of hydrogen halide using HBr as an example.
1) HBr is polarised
2) An electron pair in the double bond is attracted to δ+ hydrogen and forms a bond. This breaks the H-Br bond
3) A carbocation intermediate is formed and Br- is attracted to C+
4) Bromoethane is formed
71
What is cracking?
The breaking of long hydrocarbon chain alkanes to shorter (more useful) hydrocarbons
72
What are the two types of cracking?
- thermal
- catalytic
73
What are the conditions required for thermal cracking?
1000°C and 70atm of pressure
74
What tends to be the main products of thermal cracking?
Alkenes , use to make polymers such as plastics
75
What are the conditions needed for catalytic cracking?
450°C with slight pressure and zeolite catalyst *(to lower the temperature)*
76
What tend to be the main products of catalytic cracking?
Aromatic hydrocarbons, useful in fuels for vehicles
77
What is an aromatic compound?
A compound that contains a benzene ring
78
What is a benzene ring?
Six carbons in a ring with a delocalised electron system
79
What is reforming?
Converting straight-chain alkanes into either branched-chain alkanes and/or cyclic hydrocarbons by heating them with a catalyst (platinum) to make them burn more efficiently
80
What compounds contribute to acid rain?
SO2 and oxides of nitrogen
81
Why is carbon monoxide bad?
It’s poisonous as it binds with haemoglobin better than oxygen
82
How can carbon monoxide be removed?
By using a catalytic converter
83
Why is soot bad?
It causes breathing problems
Makes buildings dirty
Clogs up engines
84
What happens when fossil fuels with sulphur based impurities burn?
Sulphur reacts with oxygen to form sulphur dioxide
-> sulphur dioxide is an acidic gas. It reacts with water to form sulphuric acid which causes acid rain (same can be said for oxides of nitrogen)
85
What metals do catalytic converters contain?
Platinum, rhodium and iridium metals
86
What are catalytic converters?
A device found in a vehicle to help reduce the amount of unburnt hydrocarbons and oxides of nitrogen from going into the atmosphere
87
What is biodiesel?
Diesel made from refining oils and fats
88
What is biogas?
Gas made from the breakdown of organic matter
89
What are the advantages of biofuels?
- they are renewable -> more sustainable than fossil fuels
- they are carbon neutral
90
What are the disadvantages of biofuels?
- expensive to convert to biofuel
- it may lead to a shortage of food growing land
91
What determines the amount of each product formed from reacting hydrogen halide with unsymmetrical alkenes?
There are two products.
It is determined by the stability of the carbocation intermediate
92
In the reaction between hydrogen halides and unsymmetrical alkenes, what makes the carbocation more stable?
The more alkyl groups bonded to the carbocation the more stable it will be
93
Why is a carbocation more stable when there are more alkyl groups attached to it?
The alkyl groups push electrons towards the positive carbocation, stabilising it.
94
Which carbocations are the most stable?
Tertiary (most stable) -> Secondary -> Primary (least stable)
95
What is Markownikoff’s Rule?
The major product when we add a hydrogen halide to an unsymmetrical alkene is where the hydrogen adds to the carbon with the most number of hydrogen attached to it already.
96
What are the monomers for addition polymers?
Alkenes
97
What are the two types of polymers?
- Natural (*e.g. proteins and natural rubber*)
- Synthetic (*e.g poly(ethene) and poly(propane)*)
98
Why do most polymers need to be disposed carefully?
They are not biodegradable
99
What points are considered when making sustainable polymers?
- Reactants
- Solvents
- Raw materials
- Energy
- Waste
- Longevity
100
What are the advantages of biodegradable polymers?
- Crude oil doesn’t need to be used *(which is non-renewable)*
- Plant based polymers degrade and release CO2. This CO2 is absorbed by plants used to make the polymer
- Over the product’s lifetime plant based polymers use less energy to make than oil based ones
101
What are primary halogenoalkanes?
When the halogen is attached to the carbon which is attached to **one** alkyl group.
102
What are secondary halogenoalkanes?
When the halogen is attached to the carbon which is attached to **two** alkyl group.
103
What are tertiary halogenoalkanes?
When the halogen is attached to the carbon which is attached to **three** alkyl group.
104
What do halogenoalkanes form when they react with water?
They form alcohols via nucleophilic substition
105
Why is the reaction of halogenoalkanes slower with water than a hydroxide?
Hydroxides are stronger nucleophiles than water, so the reaction in quicker
106
What determines the reactivity of halogenoalkanes?
The bond strength
-> the halide ion gets larger down the group and this leads to a weaker bond
107
Which halogenoalkanes react the quickest?
Tertiary (quickest) —> Secondary —> Primary (Slowest)
108
In the halogen-carbon bond in a halogenoalkane, which atom is delta negative?
The halogen
(It’s more electronegative so it’ll pull the electrons towards itself)
109
What is a nucleophile?
A substance that is an electron donor
110
What are some example of nucleophile? (need to know for spec)
Ammonia - NH3
Hydroxide ion - OH-
Cyanide ion - CN-
111
What are the conditions required for the reaction of halogenoalkanes and hydroxide ions in nucleophilic substitution?
1) Warm aqueous sodium hydroxide (source of OH ions) -> water could be used but it’s a much slower reaction
2) Must be carried out in reflux
112
What happens when a halogenoalkane reacts with hydroxide ions via nucleophilic substitution?
The C-X bond breaks, both electrons move from the bond to the halogen. A new bond is formed between OH- and carbon
113
What is the product when halogenoalkane reacts with hydroxide ions via nucleophilic substitution?
Alcohol + halide ion
114
What are the conditions required for the reaction of halogenoalkanes and cyanide ions in nucleophilic substitution?
1) Warm ethanolic potassium cyanide (source of CN ions)
2) Carried out under reflux
115
What happens when a halogenoalkane reacts with cyanide ions via nucleophilic substitution?
The C-X bond breaks, both electrons move from the bond to the halogen. A new bond is formed between the CN- and carbon.
*- as CN- has an extra carbon the carbon stem changes, therefore changing the name*
116
What is the product when halogenoalkane reacts with cyanide ions via nucleophilic substitution?
Nitrile + halide ion
117
What are the conditions required for the reaction of halogenoalkanes and ammonia in nucleophilic substitution?
1) Heat with ethanolic ammonia
2) Must have excess ammonia
118
What happens when a halogenoalkane reacts with ammonia via nucleophilic substitution?
1) Ammonia will attach the δ+ carbon and will replace the halogen forming an intermediate
2) Another molecule of NH3 acts as a base by reacting with hydrogen *(this is why we need the excess NH3)*
119
What is the product when halogenoalkane reacts with ammonia via nucleophilic substitution?
Amine + ammonium ion (which reacts with the halide ion)
120
What are the conditions required for the reaction of halogenoalkanes and hydroxide ions in an elimination reaction?
1) Warm ethanolic sodium hydroxide (source of OH- ions)
2) Carried out under reflux
121
What happens when a halogenoalkane reacts with hydroxide ions via an elimination reaction?
1) The OH- ions will attach the hydrogen on a carbon adjacent to the carbon attached to the halogen. OH- acts as a base (proton acceptor) forming water.
2) The electrons in the bond move to form a double bond between two carbons
3) The C-X bond breaks, both electron move from the bond to the halogen
122
What is the product when halogenoalkane reacts with hydroxide ions via an elimination?
Alkene + water + halide ion
123
When reacting a halogenoalkane with sodium hydroxide, how do we know if the reaction will be elimination (forming alkene) or substitution (forming alcohol)?
**The solvent decides whether the reaction is elimination or substitution**
- When using ethanol as a solvent (OH acts as a base) - alkene is formed
- When using water as a solvent (OH acts as a nucleophile) - alcohol is formed
- When using a mixture of both solvents, both products are formed
124
How are chloroalkanes made?
By reacting alcohols with either PCl5 or HCl
- PCl5 used for Primary and Secondary
- HCl used of Tertiary
125
What are the products from the chlorination of alcohols with PCl5?
Chloroalkane + Hydrogen Chloride + Phosphorous Oxychloride
126
What are the conditions for the chlorination of alcohols with PCl5?
Room temperature (*reaction is very vigorous so no heating is needed*)
127
What are the products formed from the chlorination of alcohols with HCl?
Chloroalkane + Water
128
What conditions are needed for the chlorination of alcohols with HCl?
Room temperature
129
Which alcohols react the fastest in chlorination?
Tertiary alcohols
130
How are bromoalkanes made?
When an alcohol is reacted with a bromide ion source (KBr) and an acid catalyst (50% concentrated H2SO4) is used.
1) KBr reacts with H2SO4 to form HBr
2) Alcohol reacts with HBr
131
What are the products from the reaction of alcohol and bromide ions?
Bromoalkanes + Water
132
How are iodoalkanes made?
By reacting alcohols with PI3
133
What are the products when reacting alcohols with PI3?
Iodoalkane + phosphorous acid
134
What conditions are required for the forming of iodoalkanes?
Heated under reflux
135
What is dehydration?
A chemical change in which hydrogen and oxygen are eliminated in a ratio of 2:1 and a C=C bond is formed
136
What do alcohols form when they are dehydrated?
Alkene + Water
137
What is required for alcohols to be dehydrated?
A dehydrating agent (an acid catalyst). Either H2SO4 or H3PO4.
138
What happens during the dehydration of an alcohol?
An OH group and a hydrogen from an adjacent carbon is removed and a C=C bond is formed
139
What can the dehydration of non-primary alcohols lead to?
3 different alkenes forming (positional isomers and E/Z isomers)
140
What is the oxidising agent for the oxidation of alcohols?
Potassium dichromate
141
What happens to drichomate during the oxidation of alcohols?
It gets reduced.
Dichromate ions (orange) become chromium(III) ions (green)
142
What are primary alcohols oxidised to?
Aldehydes, them carboxylic acids
143
What must you do to stop the formation of carboxylic acid when oxidising a primary alcohol?
Once aldehyde is formed, distill the product. (Aldehyde has a lower boiling point than alcohols)
144
What are secondary alcohols oxidised to?
Ketones
145
What are tertiary alcohols oxidised to?
They can’t be oxidised using dichromate
146
Why do sigma bonds have high enthalpy?
There is a strong electrostatic attraction between the nuclei and shared pair of electrons due to the high electrons density between the nuclei.
147
Why is ethanol used in the hydrolysis of halogenoalkanes?
Halogenoalkanes are insoluble in water, ethanol ensures the halogenoalkane dissolves so it can react with the water molecules.
148
What is the equation between carbon monoxide and nitrogen oxide in a catalytic converter?
2CO + 2NO —Pt(s)—> 2CO2 + N2
149
What is the equation between oxygen and carbon monoxide in a catalytic converter?
2CO + O2 —> 2CO2
150
Why do branched or cycloalkanes have a lower boiling point than straight chained alkanes?
They have a lower surface area/ not so closely packed together. This means the intermolecular forces are weaker.
151
How many lone pairs does a hydroxide ion have?
Three
152
How many lone pairs does a cyanide ion have?
One
153
How many lone pairs does a ammonia molecule have?
One
154
How many lone pairs does a halide ion have?
Four
155
156
What is the test for chemical aldehydes?
Blue Fehling solution will turn brick red
157
What is the chemical test for carboxylic acid?
React with sodium carbonate to form bubbling
158
159
