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Chemistry > Ch4.2 Alcohols, Haloalkanes and Analysis > Flashcards

Ch4.2 Alcohols, Haloalkanes and Analysis Flashcards

1
Q

What is the general formula for aliphatic alcohols?

A

CnH2n+1OH

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2
Q

How are aliphatic alcohols named?

A
  • remove final e from alkane name
  • add ol instead
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3
Q

How are isomers of alcohols named?

A

The position of the OH is given a number eg. propan-1-ol

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4
Q

What are aromatic alcohols?

A
  • the OH must be directly attached to a benzene ring
  • the OH on a side chain of a benzene ring behaves as a typical aliphatic alcohol
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5
Q

Describe how the boiling point changes with alcohols

A
  • increases with molecular size due to higher induced dipole-dipole interactions
  • higher boiling point than similar mass alkanes due to hydrogen bonding with OH group
  • boiling point decreases as branching increases
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6
Q

Describe the solubility of alcohols

A
  • low molecular mass alcohols are miscible with water due to the hydrogen bonding between the 2 molecules
  • alcohols themselves are very good solvents and they can dissolve a large number of organic molecules
  • larger molecular mass alcohols are less miscible as the hydrophobic part of the molecule gets larger
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7
Q

How can an alcohol be prepared from haloalkanes?

A
  • reflux with aqueous sodium or potassium hydroxide
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8
Q

How can an alcohol be prepared from an aldehyde?

A
  • reduction with sodium tetrahydridoborate (III)
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9
Q

How can an alcohol be prepared from alkenes?

A
  • acid catalysed hydration using concentrated phosphoric acid
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10
Q

Describe the reagents needed for fermentation

A
  • glucose from hydrolysis of starch
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11
Q

Describe the conditions needed for fermentation

A
  • yeast
  • warm (no higher than 37 degrees C)
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12
Q

State the equation for fermentation

A

C6H12O6 -> 2C2H5OH + 2CO2

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13
Q

Describe the reagent needed for direct hydration

A
  • ethene from cracking of fractions from crude oil
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14
Q

Describe the conditions needed for direct hydration of ethene

A
  • catalyst (phosphoric acid)
  • high temp and pressure
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15
Q

State the equation for the direct hydration of ethene

A

C2H4 + H2O ⇌ C2H5OH

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16
Q

Describe the chemical properties of alcohols

A
  • the lone pairs on the O atom makes alcohols Lewis bases (lone pair donors)
  • can use the lone pair to pick up protons or behave as nucleophiles (electron pair donor)
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17
Q

Describe the reagent needed for elimination

A
  • conc sulphuric acid or conc phosphoric acid
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18
Q

Describe the conditions needed for elimination

A
  • reflux
  • 180 degrees C
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19
Q

State the product of elimination

A
  • alkene
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20
Q

State the equation for elimination

A

C2H5OH -> C2H4 + H2O

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21
Q

How can you differentiate between primary, secondary and tertiary alcohols?

A
  • oxidise them and analyse the product
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22
Q

What reagents are included within the oxidation of alcohols?

A
  • potassium dichromate: orange->green when oxidised
  • potassium manganate
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23
Q

Describe what happens when a primary alcohol is oxidised

A
  • form aldehyde and then carboxylic acids
  • aldehyde is formed when the oxidation practical is under distillation
  • carboxylic acid is formed when done under reflux
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24
Q

State the 2 equations of alcohol oxidised to aldehyde and then aldehyde to carboxylic acid

A
  • CH3CH2OH + [O] -> CH3CHO + H2O
    (lost H2)
  • CH3CHO + [O] -> CH3COOH
    (gained O)
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25
Q

What do secondary acids form when they’re oxidised?

A

Ketones

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26
Q

State the equation of alcohol oxidised to ketone only stating the functional groups

A

CH2OH + [O] -> CHO + H2O

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27
Q

What is a carbonyl functional group?

A

-C=O

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28
Q

What is the difference between an aldehyde and a ketone?

A

The C=O is on the end carbon in an aldehyde whereas it is in the middle somewhere in a ketone

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29
Q

Why do alcohols make useful fuels?

A
  • they have high enthalpies of combustion
  • don’t contain sulphur so there is less pollution
  • they can be obtained from renewable resources
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30
Q

What are the products of combustion of alcohols?

A
  • carbon dioxide
  • water
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31
Q

Describe the reagents for the bromination of alcohols

A
  • either conc hydrobromic acid HBr
  • or sodium (or potassium) bromide and conc sulphuric acid
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32
Q

Describe the conditions needed for the bromination of alcohols

A
  • reflux
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33
Q

What is the product of the bromination of alcohols?

A

Haloalkane

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34
Q

State the word equation for esterification

A

carboxylic acid + alcohol ⇌ ester and water

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35
Q

Describe the conditions needed for esterification

A
  • reflux
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36
Q

State the reagents needed for esterification of an alcohol

A
  • carboxylic acid
  • conc sulphuric acid (catalyst)
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37
Q

What would the name be of an ester formed by methanoic acid and propanol?

A

propyl methanoate

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38
Q

What would the name be of an ester formed by methanol and ethanoic acid?

A

methyl ethanoate

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39
Q

What would the name be of an ester formed by butanol and ethanoic acid?

A

butyl ethanoate

40
Q

Describe an advantage of using conc sulphuric acid during esterification

A
  • it is also a dehydrating agent
  • removes water as it’s formed
  • causes the equilibrium to move to the right
  • increases yield of ester
41
Q

Describe the reagents needed for dehydration of alcohols

A
  • conc sulphuric acid or conc phosphoric acid
42
Q

Describe the conditions needed for the dehydration of alcohols

A

reflux at 170 degrees C

43
Q

State the equation of the dehyration of alcohols

A

CH3CH2OH -> C2H4 + H2O

44
Q

What is the reagent for any halide substitution?

A

HCl, HBr, HI

45
Q

How do you form the reagent for bromination of alcohol?

A
  • can use conc HBr or NaBr + sulphuric acid which forms HBr
46
Q

How do you form the reagent for iodination of alcohol?

A
  • NaI + conc phosphoric acid which forms HI
47
Q

How do you form the reagent for the chlorination of alcohol?

A
  • use conc HCl (no reaction required)
48
Q

Describe the boiling points of haloalkanes

A
  • boiling point increases with mass
  • for isomeric compounds the greater the branching, the lower the boiling point
49
Q

Describe the solubility of haloalkanes

A
  • soluble in organic solvents but insoluble in water
  • they are not polar enough to dissolve in water as they don’t have hydrogen bonding
50
Q

Why are haloalkanes open to attack by nucleophiles?

A
  • halogens have a greater electronegativity than carbon
  • a dipole is induced in the C-X bond and it becomes polar
  • the carbon is therefore open to attack by nucleophiles
51
Q

Give some examples of nucelophiles

A
  • OH-
  • CN-
  • NH3
  • H2O
52
Q

Describe nucleophiles

A
  • possess at least one lone pair of electrons
  • they are attracted to the slightly positive carbon
  • they are electron pair donors
53
Q

Describe the nucleophilic substitution mechanism

A
  • the nucleophile uses its lone pair to provide the electrons for a new bond
  • as carbon can only have 8 electrons in its outer shell a halide ion is displaced
  • the result is substitution following attack by a nucleophile
54
Q

How is the rate of reaction of a nucleophilic substitution mechanism different with different halides?

A
  • the weakest bond is the easiest to break and breaks fastest so it gives the fastest reaction
  • C-I is least polar so is easiest to break
  • C-F is most polar so is hardest to break and reaction occurs the slowest
55
Q

State the reagent for the nucleophilic substitution reaction of a haloalkane using NaOH

A

aqueous sodium hydroxide (or KOH)

56
Q

State the conditions for the nucleophilic substitution reaction of a haloalkane using NaOH

A

reflux in aqueous solution

57
Q

State the product of the nucleophilic substitution reaction of a haloalkane using NaOH

58
Q

State the equation for the nucleophilic substitution reaction of a haloalkane using NaOH

A

C2H5Br + NaOH -> C2H5OH + NaBr

59
Q

Describe the difference between the nucleophilic substitution reaction of alcohol using NaOH and water

A
  • using water is slower
  • water is slower because liquids are immiscible so less chance of molecules colliding
  • water is a poor nucleophile
60
Q

State the reagent for the nucleophilic substitution reaction of a haloalkane using KCN

A

aqueous alcoholic sodium (or potassium) cyanide

61
Q

State the conditions for the nucleophilic substitution reaction of a haloalkane using KCN

A

reflux in aqueous alcoholic solution

62
Q

State the product of the nucleophilic substitution reaction of a haloalkane using KCN

A

nitrile (cyanide)

63
Q

State the equation for the nucleophilic substitution reaction of a haloalkane using KCN

A

C2H5Br + KCN -> C2H5CN +KBr

64
Q

What is important about the nucleophilic substitution of alcohol using KCN?

A
  • the carbon chain is extended by one
  • the CN group can then be converted to carboxylic acids or amines
65
Q

State the reagent for the nucleophilic substitution reaction of a haloalkane using NH3

A

aqueous alcoholic ammonia in excess

66
Q

State the conditions for the nucleophilic substitution reaction of a haloalkane using NH3

A

reflux in aqueous alcoholic solution under pressure

67
Q

State the product of the nucleophilic substitution reaction of a haloalkane using NH3

A

amine (or its salt due to a reaction with the acid produced)

68
Q

Why is excess ammonia needed in the nucleophilic substitution of alcohol using ammonia?

A
  • the second ammonia molecule ensures the removal of HBr which would lead to the formation of a salt
69
Q

What is the problem with the nucleophilic substitution of alcohol using ammonia?

A
  • the amine produced is a nucleophile (lone pair on the N)
  • this amine can attack another molecule of haloalkane to produce a secondary amine
  • this can attack another to produce a tertiary amine
  • this can react further to produce an ionic quaternary ammonium salt
70
Q

What does the large excess of ammonia ensure during the nucelophilic substitution of alcohol using ammonia?

A

Ensures further substitution doesn’t take place

71
Q

Describe Friedel Crafts alkylation

A
  • substitutes an alkyl group onto a benzene ring
72
Q

Describe the reagents of Friedel Crafts alkylation

A
  • a haloalkane
  • anydrous aluminium chloride (AlCl3)
73
Q

Describe the conditions needed for Friedel Crafts alkylation

A
  • room temp
  • dry inert solvent (ether)
74
Q

Describe the mechanism of Friedel Crafts alkylation

A
  • electrophilic substitution
75
Q

State the equation of Friedel Crafts alkylation

A

C2H5Br + C6H6 -> C6H5C2H5 + HBr

76
Q

Describe how haloalkanes play an important role in synthetic organic chemistry and give an example

A
  • the reactivity of the C-X bond means they are important
  • the haalogen can be replaced by a variety of groups via a nucleophilic substitution mechanism
  • during the manufacture of ibuprofen, substitution of a bromine atom takes place
77
Q

Describe the polymer of the monomer chloroethene and give its use

A
  • poly(chloroethene)
  • PVC
  • used for packaging
78
Q

Describe the polymer of the monomer tetrafluoroethene and give its use

A
  • poly(tetrafluoroethene)
  • PTFE
  • used to create non-stick surfaces
79
Q

Name 3 CFCs and give some features of these

A
  • dichlorofluoromethane
  • trichlorofluoromethane
  • bromochlorodifluoromethane
  • low reactivity
  • volatility
  • non-toxicity
80
Q

Give the use of dichlorofluoromethane

A

Refrigerant

81
Q

Give the use of trichlorofluoromethane

A

Aerosol propellant
Blowing agent

82
Q

Give the use of bromochlorodifluoromethane

A

Fire extinguishers

83
Q

Describe CFCs generally

A

A class of organic compounds containing chlorine and fluorine atoms

84
Q

Generally describe some uses of CFCs and why they are used for this

A
  • used a lot because they are inert
  • used lots in fire-fighting equipment
  • domestic uses such as refrigerants as they are non-toxic
  • first made in 1900s for use as refrigerant gases
  • later used as blowing agents (to form bubbles in materials eg. polystyrene)
85
Q

Describe how CFCs can affect the environment

A
  • gases at room temp and disperse after use
  • diffuse through layers of atmosphere and eventually become exposed to UV in the stratosphere
  • the C-Cl bond goes under homolytic fission due to UV
  • the chlorine radicals from CFCs can catalyse the decomposition of ozone to make diatomic oxygen
86
Q

Describe the ozone layer

A
  • about 20km from the earth’s surface
  • layer of O3 molecules
  • toxic to humans in the troposphere and key contributor to photochemical smog
87
Q

How does the ozone layer protect humans?

A
  • protects us from harmful radiation from the sun
  • stabilises temperature
  • absorbs all UV-C radiation and most UV-B radiation which protects organisms from genetic damage
88
Q

What are the potential effects of prolonged exposure to UV-B?

A
  • cell mutations
  • skin cancer
  • cateracts
89
Q

Is UV-A absorbed by ozone?

A

No, but it has lower energy and doesn’t pose health concerns

90
Q

Does ozone decompose naturally?

A

Yes, it decomposes naturally by UV light but more ozone is made in a natural process

91
Q

State the mechanism equations for the decomposition of ozone via CFCs

A

C2F2Cl2 -> C2F2Cl’ + Cl’
Cl’ + O3 -> ‘ClO + O2
‘ClO + O3 -> Cl’ + 2O2

overall: 2O3 -> 3O2

92
Q

Describe the history and future of the ozone

A
  • the ozone layer is shrinking and in some areas there is no ozone in the upper stratosphere and lower troposphere
  • scientists have measured an average of a 4% reduction in ozone per decade since 1970s using satellites
  • polar regions show a larger and seasonal decline
  • CFCs remain in the atmosphere for 50+ years
  • 1 CFC molecule can destroy 100 000 ozone molecules
93
Q

What other molecule other than CFCs can destroy ozone?

A
  • nitrogen monoxide
94
Q

State the mechanism equations for how nitrogen monoxide can destroy ozone

A

‘NO + O3 -> ‘NO2 + O2
‘NO2 + O -> ‘NO + O2

overall: O3 + O -> 2O2

95
Q

What have CFCs been blamed for?

A

Environmental damage by thinning the ozone layer

96
Q

What is the solution to using CFCs and causing environmental damage?

A
  • chemists now synthesise alternatives to CFCs to protect the environment such as hydrocarbons and HCFCs
  • CO2 can be used as an alternative blowing agent
  • this will allow the reversal of the ozone layer problem

Chemistry (17 decks)

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