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A Level Chemistry > Organic Chemistry - Topic 6 > Flashcards

Organic Chemistry - Topic 6 Flashcards

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1
Q

What is a hydrocarbon

A

a compound consisting of hydrogen and carbon only

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2
Q

What is a saturated compound

A

Contain single carbon-carbon bonds only

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3
Q

What is an unsaturated compound

A

A compound that Contains carbon to carbon double bonds

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4
Q

What is the molecular formula

A

The formula which shows the actual number of each type of atom

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5
Q

What is the empirical formula

A

The formula that shows the simplest whole number ratio of atoms of each element in the compound

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6
Q

What is the general formula

A

algebraic formula for a homologous series e.g. CnH2n

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7
Q

What does the structural formula show

A

the arrangement of atoms in a molecule e.g butane: CH3CH2CH2CH3 or CH3(CH2)2CH3,

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8
Q

What does the displayed formula show

A

All the covalent bonds present in a molecule

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9
Q

What is the bond angle and shape around the carbon atom in a saturated hydrocarbon

A

Shape: tetrahedral
Bond angle: 109.5

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10
Q

What is the homologous series

A

families of organic compounds with the same functional
group and same general formula

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11
Q

What is a functional group

A

An atom or group of atoms which when present in different molecules
causes them to have similar chemical properties

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12
Q

Functional groups of
alkanes,
alkenes,
alcohols,
halogenoalkanes,
aldehydes,
ketones,
carboxylic acids
esters

A

Alkanes: c-c
Alkenes: c=c
Alcohol:C-OH
Halogenoalkane: c - halogen
Aldehyde: O =C- H
Ketone: C = O
Carboxylic acid: O=C-OH
Ester: O = C - O

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13
Q

What are the prefix/suffix of ,
aldehydes,
ketones,
esters
Carboxylic acid
Alcohol

A

Alcohol: prefix: hydroxy suffix: ol
Aldehyde: suffix: al prefix: formyl
Ketone: suffix: one prefix: oxo
Esters: suffix: yl - oate e.g methylethanoate

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14
Q

What is the order of priority for the different homologous series except esters (highest first)

A

Carboxylic acids >aldehydes>ketones>alcohols>alkenes>halogenoalkanes

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15
Q

Rules for naming alcohols

A

1) alcohols have a high priority than halogenoalkanes and alkene so they usually start on the lowest carbon when with a halogenoalkane and alkene
2) if there is more than one alcohol then you add an e on the stem of the name e.g Ethane-1,2-diol NOT ethan - 1,2 - diol
3) if the compound has another functional group in addition to the OH that is higher in priority than the OH can be named with the prefix hydroxy and the higher priority keeps it’s suffix e.g 2-hydroxypropanoic acid
4) if there is more than one OH we use diol triol ect…

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16
Q

Rules of naming aldehydes

A

1) an aldehydes name ends in al
2) if there are two aldehydes then the di is put before the al and an e is added onto the stem e.g pentanEDIal

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17
Q

Rules of naming ketones

A

1) Ketones end in -one
2) When ketones have 5C’s or more in a chain then it needs a number to show the position of the
double bond. E.g. pentan-2-one
3) two ketone groups then di is put before – one and e is added onto the stem

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18
Q

Rules of naming carboxylic acids

A

1) always ends in oic acid
2) numbering starts at the carboxylic acid as it’s the highest priority
3) if there is a carboxylic acid at either end it’s called a dioic acid and the e is added into the stem

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19
Q

Rules of naming carboxylic acids

A

1) always ends in oic acid
2) numbering starts at the carboxylic acid as it’s the highest priority
3) if there is a carboxylic acid at either end it’s called a dioic acid and the e is added into the stem

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20
Q

What are structural isomers

A

same molecular formula different structures

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21
Q

What are chain isomers

A

Compounds with the same molecular formula but different structures of the carbon skeleton

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22
Q

What are position isomers

A

Compounds with the same molecular formula but different structures due to different positions of the same functional group on the same carbon skeleton

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23
Q

What are stereoisomers

A

Isomers that have the same structural formulae but have a different spatial arrangement of atoms

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24
Q

What causes E-Z isomerism to arise

A

1) When there is restricted rotation around the C=C double bond.
2) When there are two different groups/atoms attached both ends of the double bond

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25
Q

What functional group can posses E-Z isomerism

A

Alkenes

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26
Q

Why can’t alkanes posses E-Z isomerism

A

As there single carbon to carbon bonds can easily rotate

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27
Q

Rules for naming E-Z isomerism

A

1) if the priority group is on the same side then it is Z isomerism (Zame Zide)
2) if the priority group is in different side the it is E isomerism (Epposite side)

THE GROUPS DONT HAVE TO BE THE SAME ON EITHER SIDE IF THE DOUBLE BOND

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28
Q

What is the priority group in isomerism

A

The atom with the highest atomic number

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29
Q

Rules for naming cis trans isomers

A

1) Look at the group that is the SAME on both sides of the double bond
2) if the group is on the same side then it is a cis isomer
3) if the group is on different sides then it is a trans

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30
Q

Process of fractional distillation

A

1) the crude oil is vaporised in a furnace

2) the crude oils vapours move up the fractioning column, the column is hotter at the bottom and becomes cooler at the top

3) as each alkane moves up the column at some point it will reach a temp which is cooler than its bp causing it to condense back to liquid and pass out of the column,

4) Boiling point depends on size of molecules, The larger the molecule the larger the London forces

5) the alkanes with shorter carbon chains condense near the top of the column due to their low bp whilst the longer chain alkanes condense at the bottom due to their high bp and alkanes with very long chains form a thick liquid called bitumen which is collected from the very bottom

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31
Q

What is cracking

A

conversion of large hydrocarbons to smaller molecules by breakage of C-C bonds

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32
Q

Equation for cracking

A

Large alkanes —> smaller alkanes+ alkenes + (hydrogen)

Both sides have to equal number of carbons and hydrogens

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33
Q

What is petroleum

A

A mixture consisting mainly of alkane hydrocarbons

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34
Q

What are petroleum fractions

A

A mixture of hydrocarbons with a similar chain length and boiling point range

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35
Q

What bonds are broken in fractional distillation and cracking

A

Fractional distillation: Weak London Forces
Cracking: Strong covalent bonds

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36
Q

Economic reasons for catalytic cracking

A

1) The petroleum fractions with shorter C chains are in more demand than larger fractions.
2) To make use of excess larger hydrocarbons and to supply and demand for shorter ones, longer hydrocarbons are cracked.
3) The products of cracking are more useful and valuable than the starting products. The smaller alkanes are used for motor fuels which burn more efficiently

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37
Q

What is catalytic cracking

A

a chemical process involving the splitting of strong covalent bonds so requires high temperatures

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38
Q

What is reforming

A

Turning straight chain alkanes into branched and cyclic alkanes and Aromatic hydrocarbons

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39
Q

Problems of the pollutants

A
  • Carbon monoxide - is toxic to humans as CO can from a strong bond with haemoglobin in red blood cells. This is a stronger bond than that made with oxygen and so it prevents the oxygen attaching to the haemoglobin, causing death and starvation of oxygen.
  • Nitrogen oxides - NO is toxic and can form smog , NO2 is toxic and acidic and forms acid rain
  • Carbon dioxide - Contributes towards global warming
  • Unburnt hydrocarbons - Contributes towards formation of smog
  • Soot/particulates - Global dimming and respiratory problems
  • sulfur dioxide - acidic and will dissolve in atmospheric water and can produce acid rain
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40
Q

How does nitrogen oxides form

A

Nitrogen oxides form from the reaction between N2 and O2 inside the car engine.
The high temperature and spark in the engine provides sufficient energy to break strong N2 bond

N2 + O2 —> 2NO N2 + 2O2 —> 2NO2

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41
Q

How do catalytic converters help reduce the environmental problems of pollutants

A

They remove CO, NOx and unburned hydrocarbons from the exhaust gases, turning them into ‘harmless’ CO2, N2 and H2O.
2 CO + 2 NO —> 2 CO2 + N2
C8H18 + 25 NO —> 8 CO2 + 12½ N2

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42
Q

Describe and explain the structure of catalytic convertors

A

Converters have a ceramic honeycomb coated with a thin layer of catalyst metals platinum, palladium, rhodium – to give a large surface area.

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43
Q

Examples of renewable plant fuels (biofuels)

A
  • Alcohols
  • Biodiesel
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44
Q

How are biodiesel made

A

by reacting vegetable oils with a mixture of alkali and methanol

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45
Q

How are alcohols made

A

from the fermentation of sugars from plants

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46
Q

Advantages of biofuels

A
  • Reduction of use of fossil fuels which are finite resources biofuels are renewable
  • Use of biodiesel is more carbon-neutral
  • Allows fossil fuels to be used as a feedstock for organic compounds
  • No risk of large scale pollution from exploitation of fossil fuels
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47
Q

Disadvantages of biofuels

A
  • Less food crops may be grown
  • Land not used to grow food crops
  • Rain forests have to be cut down to provide land
  • Shortage of fertile soils
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48
Q

What is a free radical

A

A Free Radical is a reactive species
which possess an unpaired electron

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49
Q

What happens in heterolytic fission

A

One atom gets both electrons

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50
Q

Conditions of free radical substitution

A

UV light

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51
Q

Steps of free radical substitution

A

1) Initiation
2) Propagation
3) Termination

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52
Q

What happens in homolytic fission

A

Each atom gets one electron from the covalent bond

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53
Q

Free radical mechanism of the reaction of alkanes with chlorine

A

Initiation
Cl2 —> 2Cl.
Uv light supplies energy to break the Cl-Cl bond but UV light does not have enough energy to break C-H bond

Propagation
CH4 + Cl. —-> HCl + .CH3
.CH3 + Cl2 —-> CH3Cl + Cl.
Chlorine free radicals are very reactive so remove the H from methane leaving methyl free radicals
As the Cl free radical is regenerated it can react with more alkane molecules in a chain reaction

Termination
.CH3 + Cl. —> CH3Cl
.CH3 + .CH3 —> CH3CH3
Cl. + Cl. —> Cl2

WRITE USING STRUCTURAL FORMULA

54
Q

Overall reaction for reaction of alkanes with chlorine

A

CH4 + Cl2 —> CH3Cl + HCl

55
Q

What can promote further substitution

A

Excess halogens
E.g Excess Cl2 will trigger further substitution and could produce CH2Cl2, CHCl3 and CCCl4

Propagation
CH3CL + CL. —> HCl + .CH2Cl
.CH2Cl + Cl2 —> CH2Cl2 + Cl.

Initiation
CH3Cl + Cl2 —> CH2Cl2 + HCl
CH2Cl2 + Cl3 –> CHCl3 + HCl
CHCl3 + Cl2 —> CCl4 + HCl

56
Q

Practice write the overall equation for these following reactions
1) formation of CCl4 from CH4 + Cl
2) formation of CFCl3 from CH3F + Cl

A

1) CH4 + 4 Cl2 —> CCl4 + 4 HCl
2) CH3F + 3 Cl2 —>CFCl3 + 3 HC

57
Q

How are pi bonds formed

A

sideways overlap of two p orbitals on each carbon atom forming a π-bond above and
below the plane of molecule

58
Q

Characteristics of pi bond

A
  • they are exposed and have high electron density so therefore are vulnerable to be attacked by species which ‘like’ electrons: which are called electrophiles
  • they are weaker between sigma bonds
  • there is restricted rotation about a pi bond
59
Q

Characteristics of sigma bond

A
  • rotation can occur
  • high levels of attraction between nuclei and shared electrons so are very strong
60
Q

What are addition reactions

A

reaction where two molecules react
together to produce one

61
Q

What are addition reactions

A

reaction where two molecules react
together to produce one

62
Q

Reaction of alkenes with hydrogen
1) what is produced
2) what is the reagent
3) conditions
4) type of reaction

A

Produced: hydrogen
Conditions: Nuckel catalyst
Type of reaction: Addition

63
Q

Reaction of alkenes with halogen
1) what is produced
2) what is the reagent
3) what are the conditions
4) what is the mechanism

A

Produced: dihalogenalkane
Reagent: Hydrogen halogen
Conditions: room temperature
Mechanism: Electrophilic addition

64
Q

Reaction of alkenes with hydrogen halogen
1) what is produced
2) what is the reagent
3) what are the conditions
4) what is the mechanism

A

Produced: halogenoalkane
Reagent: Hydrogen halogen
Conditions: room temperature
Mechanism: Electrophilic addition

65
Q

Why is the major product is formed via the more stable carbocation intermediate

A
66
Q

Why is the secondary carbocation more stable and more likely to form a major product than the primary carbocation

A

As there are more alkyl groups attached to the secondary carbocation so has a stronger inductive effect,this is because the greater number of alkyl groups means that more electrons are pushed towards the positive charge, this provides it better stability as the positive charge is more reduced and because of this extra stability the secondary cation is more likely to form, resulting in it to form a major product

67
Q

Order of stability for carbocation

A

1) Tertiary (most stable)
2) Secondary
3) primary (least stable)

68
Q

Reaction of potassium maganate with alkenes

1) observation
2) what is the reagent
3) what are the conditions
4) type of reaction

A

1) purple colour of MnO4- ion will decolorisation to colourless
2) KMnO4 in acidified solution
3) Room temperature
4) Oxidation

69
Q

Reaction of bromine water with alkenes

1) what is the observations
2) what is the reagent
3) what are the conditions
4) what is the mechanism

A

1) orange colour of bromine water will decolorisation to colourless
2) bromine dissolved in water (bromine water)
3) room temperature
4) Addition

70
Q

Hydration of alkenes
1) conditions
2) product

A

1) temp: 300 to 600 degrees Celsius pressure: 70atm catalyst: concentrated H3PO4
2) alcohol

71
Q

Formation of addition polymers (poly(alkenes))
1) reactant
2) type of reaction

A

1) alkenes
2) addition polymerisation

72
Q

Why are poly(alkenes) unreactive

A

Due to the strong C-C and C-H bonds

73
Q

What is poly(ethene) used for

A
  • to make plastic bags and bottles
    —
74
Q

What is poly(properne) used for

A
  • utensils
  • containers
  • fibres in rope and carpets
75
Q

Methods of disposing waste polymers

A
  • incineration
  • recycling
  • feedstock for cracking
76
Q

What occurs during incineration

A
  • rubbish is is burnt and energy is produced to generate electricity
  • Some toxins can be released e.g HCl and greenhouse gasses can be emitted
77
Q

Advantages of recycling polymers

A
  • Saves raw materials
  • Thermoplastic polymers can be melted down and reshaped.
78
Q

Disadvantages of recycling polymers

A
  • Polymers need collecting/ sorting- expensive process in terms of energy and manpower.
  • Polymers can only be recycled into the same type – so careful separation needs to be done.
79
Q

What is feedstock for cracking and what is the advantage

A
  • This is when Polymers can be cracked into small molecules which can be used to make other chemicals and new polymers
  • Saves raw materials
80
Q

How do chemistry remove waste producer that are emitted by incarceration

A

By reacting the acidic HCL gas with a base or carbonate, neutralising it

81
Q

What are primary secondary and tertiary halogenoalkane

A

Primary - One carbon attached to the
carbon atom adjoining the halogen
Secondary - Two carbons attached to the
carbon atom adjoining the halogen
Tertiary - Three carbons attached to the
carbon atom adjoining the halogen

82
Q

What do nucleophile always have

A

A lone pair of electrons and act as electron pair donors

83
Q

Define hydrolysis

A

the splitting of a molecule by a reaction with water

84
Q

What is a Nucleophile

A

electron pair donator

(They always have a lone pair of electrons to donate)

85
Q

What does the rate of substitution reactions depend on

A

The strength of the C-X bond as the weaker the bond the easier it is to break so the faster the reaction

86
Q

What role does water play as a nucleophile

A

Water is a poor nucleophile but can react slowly with halogenoalkanes in a substitution reaction

87
Q

How can you compare the rate of hydrolysis of halogenoalkanes

A

Add aqueous silver nitrate to the halogenoalkane, the quicker the silver halide precipitate forms the faster the reaction and more reactive the halogenoalkane

88
Q

Order of rate of reaction of silver iodide, chloride and bromide

A

Fastest: silver iodide (yellow ppt)
Silver bromide (creamy coloured ppt)
Slowest: silver chloride (white ppt)

89
Q

What does iodoalkane forms a ppt with the silver nitrate the quickest compared to other halogenoalkanes

A

The iodoalkane forms a precipitate with
the silver nitrate first as the C-I bond is
weakest and so it hydrolyses the quickest

90
Q

What are the conditions, reagents, mechanism and reaction for nucleophilic substitution with aqueous hydroxide ions

A

Reaction: halogenoalkane—-> alcohol
Reagent : potassium (or sodium) hydroxide (OH-)
Mechanism: Nucleophilic substitution (SN2)
Conditions: in aqueous solutions, heat under reflux

91
Q

Draw the SN2 reaction between hydroxide ions and halogenoalkanes

A

Pg 20 in Chemrevise

92
Q

What happens if the solvent is changed from water to ethanol in the reactions of halogenoalkanes with aqueous hydroxide ions

A

An elimination reaction occurs instead of substitution

93
Q

Why is OH- a stronger nucleophile than water

A

OH- has a full negative charge making it more strongly attracted to the carbocation

94
Q

How do tertiary halogenoalkanes react with hydroxide ions

A

Through an SN1 reaction

95
Q

Why do tertiary halogenoalkanes undergo an SN1 mechanisms with aqueous hydroxide ions rather than SN2

A
  • As the tertiary carbocation is stabilised by the methyl groups surrounding the carbocation as the methyl groups shift their electrons towards the carbocation, stabilising it
  • the bulky methyl (the number and the position of methyl groups) prevent the hydroxide ions from attacking the halogenoalkane in the same way as SN2
96
Q

Why do primary halogenoalkane do not undergo SN1 reactions

A

As they would only form a unstable primary carbocation

97
Q

Reagent, conditions, mechanism and reaction of nucleophilic nucleophilic substitution with ammonia

A

Reagent: ammonia in dissolved ethanol
Conditions: heating under pressure in a sealed tube
Mechanism: nucleophilic substitution
Reaction: halogenalkane —-> amine

98
Q

Draw the reaction of bromopropane with ammonia

A

Pg 21

99
Q

Conditions, reagent, reaction and mechanism in the elimination with alcoholic (ethanol) hydroxide ions

A

Reaction: halogenoalkane —> alkene
Reagent: potassium (or sodium) hydroxide
Conditions: in ethanol, heat
Mechanism: elimination

100
Q

Uses of halogenoalkanes

A
  • refrigerenants
  • fire retardants
  • pesticides
  • chloroalkanes and chlorofluoralkanes can be used as solvents
101
Q

Bond angles in alcohols

A
  • all H-C-H and C-C-O are 109.5 - because there are 4 bond pairs of electrons repelling to a position of minimum repulsion
  • H-O-C bond is 104.5 - because there are 2 bond pairs of electrons and 2 lone pairs repelling to a position of minimum repulsion (lone pairs repelling more than bind pairs so the bond angle is reduced)
102
Q

What are the three types of alcohols

A
  • Primary alcohol- are alcohols where 1 carbon is attached to the carbon adjoining the oxygen
  • Secondary alcohols - alcohols where 2 carbon are attached to the carbon adjoining the oxygen
  • Tertiary alcohols - alcohols where 3 carbons are attached to the carbon adjoining the oxygen
103
Q

Test for alcohols

A
  • React the alcohol with sodium
  • reaction with PCl5
104
Q

Observations with the reaction with spodumene and alcohols

A

Observations:
- effervescence
- mixture gets hot
- sodium dissolves
- white solid is produced

105
Q

Observations with reaction with PCl5

A

Misty fumes of HCl

106
Q

What is the reagent to form halogenoalkanes form an alcohol

A

Hydrogen halide

107
Q

What is needed to make hydrogen bromide

A

Potassium bromide and 50% concentrated
H2SO4

108
Q

Equation for the reaction of phosphorus (III) with ethanol

A

PI3 + 3 CH3CH2OH —> 3CH3CH2I + H3PO

109
Q

Equation for the reaction of phosphorus (V) chloride with ethanol

A

CH3CH2OH + PCl5 —-> CH3CH2Cl + POCl3 + HCl

110
Q

Oxidation reaction with primary alcohols to aldehydes conditions, reagent, observation

A

Conditions: warm gently and distil out aldehydes as it forms
Reagent : potassium dichromate
Observations: orange dichromate ion (Cr2O72-) reduces to the green Cr 3+ ion

111
Q

How to represent the oxidising agent in an equation

A

[O]

112
Q

What is a dehydration reaction

A

removal of a water molecule from a molecule

113
Q

Dehydration reaction of alcohol reaction, reagent, conditions, mechanism, role of reagent

A

Reaction: Alcohol —> Alkene
Reagents: Concentrated phosphoric acid
Conditions: warm (under reflux)
Role of reagent: dehydrating agent/catalyst
Type of reaction: acid catalysed elimination

114
Q

Why can’t tertiary alcohols be oxidised by potassium dichromate

A

because there is no hydrogen
atom bonded to the carbon with the OH group

115
Q

Distillation reaction: of primary alcohol to aldehydes
Reaction, reagent, conditions and observations

A

Reaction: primary alcohol  aldehyde
Reagent: potassium dichromate (VI) solution and
dilute sulfuric acid.
Conditions: use a limited amount of dichromate
and warm gently and distil out the aldehyde as it
forms [This prevents further oxidation to the
carboxylic acid]
CH3CH2CH2OH + [O] —-> CH3CH2CHO + H2O
Observation
Orange dichromate solution changes to green
colour of Cr3+ ions

116
Q

Draw distillation equipment

A

Pg 26 Chemrevise

117
Q

Draw distillation equipment

A

Pg 26 Chemrevise

118
Q

Draw reflux equipment

A

Pg 26 Chemrevise

119
Q

What does the condenser do in reflux

A

prevents organic vapours from escaping
by condensing them back to liquids

120
Q

What is reflux

A

heating organic reaction mixtures for long
periods

121
Q

What is distillation

A

Separating an organic product from its reacting mixture

122
Q

Why should you never seal the end of a condenser

A

As the build up of gas pressure could cause the apparatus to explode. This is true of any
apparatus where volatile liquids are heated

123
Q

Reflux reaction: primary alcohols to carboxylic acid
Conditions
Reaction
Reagent
Observations

A

Reaction: primary alcohol —-> carboxylic acid
Reagent: potassium dichromate(VI) solution and dilute
sulfuric acid
Conditions: use an excess of dichromate, and heat
under reflux: (distil off product after the reaction
has finished using distillation set up)
CH3CH2CH2OH + 2[O] —-> CH3CH2CO2H + H2O
Observation
Orange dichromate solution changes to green colour of
Cr3+

124
Q

Why are anti bumping granules added in the flask of both distillation and reflux reactions

A

prevent vigorous,
uneven boiling by making small bubbles form instead of large bubbles

125
Q

How to purify an organic liquid

A

1) put the distillate of impure product into a separating funnel
2) wash product by adding either - sodium hydrogencarbonate solution , shaking and
releasing the pressure from CO2 produced or Saturated sodium chloride solution
3) Allow the layers to separate in the funnel, and then run and discard the aqueous layer.
4) Run the organic layer into a clean, dry conical flask and add three spatula loads of drying agent (anhydrous sodium sulfate) to dry the organic liquid.
5) Carefully decant the liquid into the distillation flask
6) Distil to collect pure product

126
Q

What does sodium hydrocarbonate and sodium chloride do during the purification of an organic liquid

A

Sodium hydrocarbonate - will neutralise any remaining reactant acid
Sodium chloride - will help separate the
organic layer from the aqueous layer

127
Q

What conditions do the drying agents need to have during the purification of an organic liquid

A

•be insoluble in the organic liquid
• not react with the organic liquid

128
Q

How to conduct a solvent extraction

A

1) Mix organic solvent and oil-water mixture in a separating funnel then separate the oil layer.
2) Distil to separate oil from organic solvent
3) Add anhydrous CaCl2 to clove oil to dry oil
4) Decant to remove CaCl2

129
Q

Draw a separating funnel

A

Pg 28 Chemrevise

130
Q

How can you measure the purity of a substance

A

By measuring the boiling point

This can be done in a distillation set up or by simply boiling a tube of the sample in an
heating oil bath

131
Q

Why isn’t measuring the boiling point the most accurate method of identifying a substance

A

several substances may have the same boiling

132
Q

Does primary and secondary halogenoalkane undergo an elimination or substitution reaction

A

Primary - substitution
Tertiary - elimination

A Level Chemistry (15 decks)

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