Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Chemistry A-level > Topic 6 - Organic Chemistry > Flashcards

Topic 6 - Organic Chemistry Flashcards

(63 cards)

Start Studying
1
Q

what are the proporties of halogenoalkanes

A

halogenoalkanes are polar, because halogens are more electronegative than carbon. So, the carbon atoms carry a partial positive charge, and the halogens carry a partial negative charge.
Halogenoalkanes undergo substitution reactions with ammonia, hydroxide ions and cyanide ions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are nucleophiles and electrophiles

A

a nucleophile is a molecule that is attracted to a nucleus. They tend to be negatively charged. Molecules with a lone pair of electrons are nucleophiles

an electrophile is a molecule that is attracted to a pair of electrons. They tend to be positively charged.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

show the nucleophilic substitution reaction between ammonia and chloromethyl.

A

see notes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

show the nucleophilic substitution reaction between cyanide ions and chloromethyl.

A

see note

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

when a halogenoalkane reacts with a hydroxide, what is the product produced

A

alcohol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

when a halogenoalkane reacts with ammonia, what is the product produced

A

amine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

when a halogenoalkane reacts with cyanide ions, what is the product produced

A

nitrile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what controls halogenoalkanes’ reactivity

A

polar carbon-halogen bonds

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

show the mechanisms of the elimination reaction between a hydroxide ion chloroethane

A

see notes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

hydroxide reacting with a halogenoalkane can either eliminate to produce an alkene, or substitute to produce an alcohol. Both are very possible.
How can we promore the elimination reaction

A
  • use ethanol as the solvent instead of water
  • heat the reaction under reflux conditions (using a reflux condenser to condense gases back into the reaction flask)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is CFCs and ozone

A

CFC is a chlorofluorocarbon molecule.
Ozone has the formula O3, and is less stable than O2. It is formed from O2 under UV light. O3 is present in low concentrations, but its highest concentrations are in the ozone layer of the Earth’s atmosphere

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is ozone depletion

A

when CFC undergo photolysis (broken down by light), producing chlorine radicals. These radicals react with the ozone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

show the free radical mechanisms for ozone depletion

A

see notes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

how were CFCs band

A

CFCs were used in aerosols, as coolants in fridges and as solvents in industry. Scientists in the 1970s discovered that CFCs were damaging the ozone layer. The led to bans and the development of safer alternative such as HFCs and hydrocarbons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

why are alkenes more reactive than alkanes

A

because alkenes have a double bond, so has higher electron density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the proporties of the carbon to carbon double bond

A
  • the bond is made up of one sigma bond and one pi bond
  • the pi bond involves electrons in the p-orbitals existing above and below the plane of the bond, meaning there is no overlapping.
  • the pi bond causes the double bond to be unable to rotate, giving alkenes a fixed shape around the double carbon bond
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Describe the reactions of alkenes

A

alkenes are nucleophiles because of their high electron density between the carbon atoms, so react with hydrogenalkanes in an electrophilic addition reaction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

show the mechanisms for the electrophilic addition reaction between ethane and hydrogen bromide

A

see notes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

show the mechanisms for the electrophilic addition reaction between ethane and sulfuric acid

A

see notes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

show the mechanisms for the electrophilic addition reaction between ethane and bromine

A

see notes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

why is the electrophilic addition reaction between an alkene and bromine important

A

the reaction with bromine is used as a test for alkenes. In the presence of an alkene, bromine will go from light orange to colourless.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

why is the electrophilic addition reaction between an alkene and sulfuric acid important

A

produces an alcohol, as a sulfate ion is removed by nucleophilic substitution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

how do asymmetric alkenes produce multiple products

A
  • the selectivity is driven by carbocation intermediate stability. Tertiary carbocations are most stable, whilst primary carbocations are least stable.
  • The more alkyl groups there are next to the positive charge, the more stable the intermediate is. Because the alkyl groups push the electrons, and help to stabilise the positive charge
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

which product is most likely to be produced from an asymmetric alkene

A

the major product will be the most stable carbocation, whilst the minor products will be the least stable.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
which forces hold the molecules of polymers together
London Dispersion forces
26
what are the 2 types of addition polymers
- straight-chain polymers: pack closely together and are strong and rigid - branched-chain polymers: pack less densely and are more flexible
27
describe the reactivity of addition polymers
addition polymers are mostly unreactive. This is because if the monomers were reactive, they'd get lots of side reactions during polymerisation. Addition polymers are also not reactive because the carbon chain is saturated and the side chains are non-polar
28
what is the role of plasticisers in polymers
plasticisers make straight-chain addition polymers more flexible, as they stick between the chains and keep the polymers further apart from each other. This weakens the London Dispersion forces and lets the chains slide more easily.
29
what is PVC / poly(chloroethene)
PVC is used for rigid plastics like drainpipes. This is because it has strong Dipole-Dipole forces due to the chlorine atom
30
how do you dispose of waste polymers
- the disposal of polymers is difficult, as they are very unreactive. - Landfill sites are used to dispose of plastics, but it is not sustainable as conventional polymers will not break down in hundreds of years, meaning there is limited space in landfill sites - Waste polymers are combusted in incinerators, which is beneficial as it could lower our reliance on fossil fuels, and produces energy that can be used - Waste polymers can be used as organic feedstock to produce plastics and other organic compounds. -
31
how are toxins removed from waste polymers before they are incinerated
via neutralisation, but this process can be expensive
32
how are biodegradable polymers advantageous
in the right conditions, biodegradable polymers can be broken down by microorganisms to produce carbon dioxide and water. However, burying the biodegradable plastics in landfill sites can create anaerobic conditions, which reduces the capacity of microorganisms to decompose the polymers
33
how are photodegradable polymers advantageous
photodegradable polymers can be broken down into smaller biodegradable pieces in sunlight. However, the smaller pieces may just accumulate into the environment without getting broken down any further. This causes problems in the ocean, as sea animals will digest the plastics. Also, photodegradable plastics that are buried in landfill sites are unlikely to get exposed by sufficient sunlight to break up into smaller pieces
34
what is fractional distillation
the process of separating crude oil into groups of hydrocarbons with similar numbers of carbon atoms, called fractions.
35
explain the process of fractional distillation
1. Evaporation: Crude oil is heated into a vapour, and put into the fractionating column at the bottom and rises upwards. 2. Condensation: The temperature is highest at the bottom of the column, so long-chain hydrocarbons condense at the bottom and are collected as liquids. Short-chain hydrocarbons have lower boiling points, as they pass up the column and condense at lower temperatures nearer to the top 3. Collection: The fractions are collected and processed to create end products
36
what is cracking
the process of converting alkanes into alkenes and shorter alkanes, because shorter chain alkanes are more valuable
37
what is thermal cracking
thermal conditions uses harsher conditions such as 1,000°C and 70 atm pressure, to break down the alkanes into a high percentage of alkenes
38
what is catalytic cracking
uses lower temperatures and pressures, such as 450°C and 1 atm pressure, with the catalyst zeolite, to break down alkanes into molecules containing benzene rings and short chain hydrocarbons. This reduces the cost and makes the reaction faster
39
the ionic compound zeolite contains which elements
aluminium, silicon and oxygen
40
meaning complete combustion
when a molecule combusts in an excess of oxygen, giving a blue flame, and producing only carbon dioxide and water
41
meaning incomplete combustion
when a molecule combusts in a shortage of oxygen, giving an orange smokey flame, and producing carbon dioxide, water, soot, hydrocarbons, and carbon monoxide. Incomplete combustion is more likely to occur with long-chain alkanes, as they need more oxygen to combust completely
42
what are some common impurities from the internal combustion engine
- nitrous oxide - unburned hydrocarbons - carbon monoxide - sulfur dioxide
43
how are impurities from the internal combustion engine removed
- sulfur dioxide removed by reacting it with calcium oxide or calcium carbonate, in a neutralisation reaction - unburned hydrocarbons and nitrous oxides are removed by catalytic converters
44
show the mechanisms of free radical substitution of chlorine with methane
see notes
45
What is the product of a primary alcohol being partially oxidised and when it's fully oxidised What is the oxidising agent used in this reaction
- partially oxidised: aldehyde - fully oxidised: carboxylic acid - acidified sodium dichromate, which turns from orange to green
46
what is the product of a secondary alcohol being oxidised
- ketone
47
how can an aldehyde be formed into a carboxylic acid
when aldehydes are further oxidised, they produce a carboxylic acid. This involves breaking the C-H bond that is attached to the oxygen
48
why can ketones no be oxidised further, and a tertiary alcohol
they don't have a C-H bond attached to the oxygen, so to oxidise either of these, the carbon skeleton of the compounds would have to be disrupted, which is not possible
49
What is the colour change when Benedict's solution oxidises an aldehyde
colour change from blue to brick-red
50
describe the reaction when an alcohol is converted into an alkene.
a dehydration reaction occurs, where a water molecule is lost and a double carbon bond is formed. A strong acid catalyst is needed
51
show the mechanisms of an elimination reaction between phosphoric acid and hydrogen ions
see notes
52
what is the general formula of alcohols
C n H 2N+1 O H
53
how are alcohols produced
by the hydrogenation of alkenes
54
what are the products when an alcohol performs complete combustion
carbon dioxide and water
55
what are the products when an alcohol performs incomplete combustion
carbon monoxide, carbon (not shown) and water
56
what are the conditions for the partial oxidation of a primary alcohol to an aldehyde
- use dilute sulphuric acid (not concentrated) and use distillation with addition - have an excess of alcohol - heat relatively gently - distil off the product aldehyde as soon as it is formed
57
what are the conditions for the complete oxidation of a primary alcohol to an aldehyde
- concentrated sulphuric acid - use a considerable excess of oxidising agent (potassium dichromate) - reflux the mixture
58
write the chemical equation for the partial oxidation of a primary alcohol
RCH2OH + [O] → RCHO + H2O
59
write the chemical equation for the complete oxidation of a primary alcohol
RCH2OH + 2[O] → RCH2O + H2O
60
write the chemical equation for the oxidation of a secondary alcohol
RCH(OH)R + [O] → RCOR + H2O
61
what are possible alternative reagents and conditions for dehydrating alcohols
- react alcohol with hot, concentrated sulphuric acid (H2SO4), then distill off the product alkene - react alcohol with hot, concentrated phosphoric (V) acid (H3PO4), then distill of the product alkene - pass alcohol vapour over a Al2O3 catalyst (600K) and collect the alkene vapour over water
62
describe 2 tests to distinguish an aldehyde from a ketone
- add the aldehyde/ ketone to acidified dichromate solution and heat gently. If the solution is reacted with an aldehyde, there's a colour change from orange to green, as the aldehyde is oxidised to an acid and the dichromate is reduced from Cr(V) to Cr(III). If the solution reacts with a ketone, there will be no visible change, as the ketone is not oxidised - add the aldehyde/ketone some Benedict's solution in a test tube, and heat in a water bath for a few minutes. If the solution reacts with an aldehyde, there will be a colour change from blue to brick-red, as the copper (II) oxide will be reduced to copper (I) oxide, and the aldehyde will be oxidised into an acid. If the solution reacts with a ketone, there will be no visible change, as the ketone is not oxidised
63

Chemistry A-level (13 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions