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

Ch4.2 Alcohols, Haloalkanes and Analysis Flashcards

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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
What do secondary acids form when they're oxidised?
Ketones
26
State the equation of alcohol oxidised to ketone only stating the functional groups
CH2OH + [O] -> CHO + H2O
27
What is a carbonyl functional group?
-C=O
28
What is the difference between an aldehyde and a ketone?
The C=O is on the end carbon in an aldehyde whereas it is in the middle somewhere in a ketone
29
Why do alcohols make useful fuels?
- they have high enthalpies of combustion - don't contain sulphur so there is less pollution - they can be obtained from renewable resources
30
What are the products of combustion of alcohols?
- carbon dioxide - water
31
Describe the reagents for the bromination of alcohols
- either conc hydrobromic acid HBr - or sodium (or potassium) bromide and conc sulphuric acid
32
Describe the conditions needed for the bromination of alcohols
- reflux
33
What is the product of the bromination of alcohols?
Haloalkane
34
State the word equation for esterification
carboxylic acid + alcohol ⇌ ester and water
35
Describe the conditions needed for esterification
- reflux
36
State the reagents needed for esterification of an alcohol
- carboxylic acid - conc sulphuric acid (catalyst)
37
What would the name be of an ester formed by methanoic acid and propanol?
propyl methanoate
38
What would the name be of an ester formed by methanol and ethanoic acid?
methyl ethanoate
39
What would the name be of an ester formed by butanol and ethanoic acid?
butyl ethanoate
40
Describe an advantage of using conc sulphuric acid during esterification
- 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
Describe the reagents needed for dehydration of alcohols
- conc sulphuric acid or conc phosphoric acid
42
Describe the conditions needed for the dehydration of alcohols
reflux at 170 degrees C
43
State the equation of the dehyration of alcohols
CH3CH2OH -> C2H4 + H2O
44
What is the reagent for any halide substitution?
HCl, HBr, HI
45
How do you form the reagent for bromination of alcohol?
- can use conc HBr or NaBr + sulphuric acid which forms HBr
46
How do you form the reagent for iodination of alcohol?
- NaI + conc phosphoric acid which forms HI
47
How do you form the reagent for the chlorination of alcohol?
- use conc HCl (no reaction required)
48
Describe the boiling points of haloalkanes
- boiling point increases with mass - for isomeric compounds the greater the branching, the lower the boiling point
49
Describe the solubility of haloalkanes
- 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
Why are haloalkanes open to attack by nucleophiles?
- 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
Give some examples of nucelophiles
- OH- - CN- - NH3 - H2O
52
Describe nucleophiles
- possess at least one lone pair of electrons - they are attracted to the slightly positive carbon - they are electron pair donors
53
Describe the nucleophilic substitution mechanism
- 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
How is the rate of reaction of a nucleophilic substitution mechanism different with different halides?
- 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
State the reagent for the nucleophilic substitution reaction of a haloalkane using NaOH
aqueous sodium hydroxide (or KOH)
56
State the conditions for the nucleophilic substitution reaction of a haloalkane using NaOH
reflux in aqueous solution
57
State the product of the nucleophilic substitution reaction of a haloalkane using NaOH
alcohol
58
State the equation for the nucleophilic substitution reaction of a haloalkane using NaOH
C2H5Br + NaOH -> C2H5OH + NaBr
59
Describe the difference between the nucleophilic substitution reaction of alcohol using NaOH and water
- using water is slower - water is slower because liquids are immiscible so less chance of molecules colliding - water is a poor nucleophile
60
State the reagent for the nucleophilic substitution reaction of a haloalkane using KCN
aqueous alcoholic sodium (or potassium) cyanide
61
State the conditions for the nucleophilic substitution reaction of a haloalkane using KCN
reflux in aqueous alcoholic solution
62
State the product of the nucleophilic substitution reaction of a haloalkane using KCN
nitrile (cyanide)
63
State the equation for the nucleophilic substitution reaction of a haloalkane using KCN
C2H5Br + KCN -> C2H5CN +KBr
64
What is important about the nucleophilic substitution of alcohol using KCN?
- the carbon chain is extended by one - the CN group can then be converted to carboxylic acids or amines
65
State the reagent for the nucleophilic substitution reaction of a haloalkane using NH3
aqueous alcoholic ammonia in excess
66
State the conditions for the nucleophilic substitution reaction of a haloalkane using NH3
reflux in aqueous alcoholic solution under pressure
67
State the product of the nucleophilic substitution reaction of a haloalkane using NH3
amine (or its salt due to a reaction with the acid produced)
68
Why is excess ammonia needed in the nucleophilic substitution of alcohol using ammonia?
- the second ammonia molecule ensures the removal of HBr which would lead to the formation of a salt
69
What is the problem with the nucleophilic substitution of alcohol using ammonia?
- 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
What does the large excess of ammonia ensure during the nucelophilic substitution of alcohol using ammonia?
Ensures further substitution doesn't take place
71
Describe Friedel Crafts alkylation
- substitutes an alkyl group onto a benzene ring
72
Describe the reagents of Friedel Crafts alkylation
- a haloalkane - anydrous aluminium chloride (AlCl3)
73
Describe the conditions needed for Friedel Crafts alkylation
- room temp - dry inert solvent (ether)
74
Describe the mechanism of Friedel Crafts alkylation
- electrophilic substitution
75
State the equation of Friedel Crafts alkylation
C2H5Br + C6H6 -> C6H5C2H5 + HBr
76
Describe how haloalkanes play an important role in synthetic organic chemistry and give an example
- 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
Describe the polymer of the monomer chloroethene and give its use
- poly(chloroethene) - PVC - used for packaging
78
Describe the polymer of the monomer tetrafluoroethene and give its use
- poly(tetrafluoroethene) - PTFE - used to create non-stick surfaces
79
Name 3 CFCs and give some features of these
- dichlorofluoromethane - trichlorofluoromethane - bromochlorodifluoromethane - low reactivity - volatility - non-toxicity
80
Give the use of dichlorofluoromethane
Refrigerant
81
Give the use of trichlorofluoromethane
Aerosol propellant Blowing agent
82
Give the use of bromochlorodifluoromethane
Fire extinguishers
83
Describe CFCs generally
A class of organic compounds containing chlorine and fluorine atoms
84
Generally describe some uses of CFCs and why they are used for this
- 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
Describe how CFCs can affect the environment
- 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
Describe the ozone layer
- about 20km from the earth's surface - layer of O3 molecules - toxic to humans in the troposphere and key contributor to photochemical smog
87
How does the ozone layer protect humans?
- 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
What are the potential effects of prolonged exposure to UV-B?
- cell mutations - skin cancer - cateracts
89
Is UV-A absorbed by ozone?
No, but it has lower energy and doesn't pose health concerns
90
Does ozone decompose naturally?
Yes, it decomposes naturally by UV light but more ozone is made in a natural process
91
State the mechanism equations for the decomposition of ozone via CFCs
C2F2Cl2 -> C2F2Cl' + Cl' Cl' + O3 -> 'ClO + O2 'ClO + O3 -> Cl' + 2O2 overall: 2O3 -> 3O2
92
Describe the history and future of the ozone
- 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
What other molecule other than CFCs can destroy ozone?
- nitrogen monoxide
94
State the mechanism equations for how nitrogen monoxide can destroy ozone
'NO + O3 -> 'NO2 + O2 'NO2 + O -> 'NO + O2 overall: O3 + O -> 2O2
95
What have CFCs been blamed for?
Environmental damage by thinning the ozone layer
96
What is the solution to using CFCs and causing environmental damage?
- 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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