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A Chemistry A-level > Mechanisms > Flashcards

Mechanisms Flashcards

1
Q

Primary alcohol –> Aldehyde
Reagent:
Conditions:
Equation:

A

Reagent: K2Cr2O7 + dilute H2SO4
Conditions: warm + distillation
Equation: propan-1-ol + [O] –> propanal + H2O

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2
Q

Primary alcohol –> Carboxylic acid
Reagent:
Conditions:
Equation:

A

Reagent: K2Cr2O7 + dilute H2SO4
Conditions: EXCESS Cr2O7 2- ions + heat under reflux
Equation: propan-1-ol + 2[O] –> propanoic acid + H2O

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3
Q

what is the colour change of potassium dichromate

A

orange to green

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4
Q

Secondary alcohol –> Ketone
Reagent:
Conditions:
Equation:

A

Reagent: K2Cr2O7 + dilute H2SO4
Conditions: heat under reflux
Equation: propan-2-ol + [O] –> propanone + H2O

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5
Q

how to distinguish between aldehydes and ketones

A
  1. Tollens’ reagent - aldehydes turn into silver mirror
  2. Fehlings solution - aldehydes turn blue to red ppt
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6
Q

how to test for carboxylic acid

A
  • adding sodium carbonate
  • effervescence of CO2 gas
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7
Q

Alcohol –> Alkene
Reagent:
Conditions:
Type of reaction:
Mechanism:

A

Reagent: concentrated H2SO4
Conditions: warm + under reflux
Type of reaction: acid catalysed elimination
Mechanism:

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8
Q

2 ways to form ethanol

A
  1. Fermentation
  2. Hydration of ethene
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9
Q

pros and cons of using fermentation to make ethanol

A

advantages:
1. sugar is renewable resource
2. cheap equipment

disadvantages:
1. batch processing is slow + high cost
2. ethanol is not pure so need to be purified via fractional distillation
3. deforestation to grow sugar

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10
Q

pros and cons of using hydration of ethene to make ethanol

A

advantages:
1. faster
2. pure product formed
3. continuous process so cheaper

disadvantages:
1. expensive equipment
2. ethene is non-renewable
3. high energy cost for high pressure

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11
Q

Hydration of ethene
Conditions:
Equation:
Mechanism:

A

Conditions: conc. H3PO4 catalyst, high temp, high pressure
Equation: CH2CH2 + H2O –> CH3CH2OH
Mechanism:

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12
Q

fractional distillation

A
  1. oil is heated and passed into column
  2. fractions condense at different heights
  3. the temp of decreases upwards (cooler at top)
  4. separation depends on boiling points which depends on size of molecules
  5. the larger the molecule the larger the van der waals forces to more energy needed to break them
  6. similar molecules condense together
  7. small molecules condense at the top at lower temps
  8. big molecules condense at the bottom at higher temp
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13
Q

economic reasons for cracking

A
  1. shorter chains are more in demand
  2. products of cracking are more valuable
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14
Q

thermal cracking
conditions and products

A

conditions: high pressure + high temp
products: alkenes + hydrogen

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15
Q

catalytic cracking
conditions and products

A

conditions: high temp + zeolite catalyst
products: branched + cyclic alkanes, aromatic hydrocarbons
cheaper than thermal cracking because no high pressure required

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16
Q

complete combustion

A
  • in excess O2
  • products: CO2 + H2O
17
Q

incomplete combustion

A
  • in limited O2
  • products: CO or C + H2O
18
Q

free radical substitution product and steps

A

product: haloalkane
steps:
1. initiation
2. propagation
3. termination

19
Q

free radical substitution of CH4 + Cl2 –> CH3Cl + HCl

A

steps:
1. initiation
2. propagation
3. termination

20
Q

what is a nucleophile

A

lone pair donor

21
Q

what is a electrophile

A

lone pair acceptor

22
Q

examples of nucleophiles

A

:OH- (NS or E)
:NH3 (NS)
:CN- (NS or NA)
Ethanolic NaBH4 (NA)

23
Q

Haloalkane –> Alcohol
Reagent:
Conditions:
Type of reaction:
Mechanism: bromoethane

A

Reagent: aqueous KOH
Conditions: heat under reflux
Type of reaction: nucleophilic substitution

24
Q

Haloalkane –> Nitrile
Reagent:
Conditions:
Type of reaction:
Mechanism: bromoethane

A

Reagent: ethanolic KCN
Conditions: heat under reflux
Type of reaction: nucleophilic substitution

25
Haloalkane --> Amine Reagent: Conditions: Type of reaction: Mechanism: bromoethane
Reagent: ethanolic :NH3 x2 Conditions: heat under reflux Type of reaction: nucleophilic substitution
26
Haloalkane --> Alkene Reagent: Conditions: Type of reaction: Mechanism: bromoethane
Reagent: ethanolic KOH Conditions: heat Type of reaction: Elimination Type of reagent: Base OH-
27
examples of elecrophiles
Br2 (EA) HCl (EA) HBr (EA) NO2+ (ES)
28
Alkene --> Dihaloalkane Reagent: Conditions: Type of reaction: Mechanism: ethene
Reagent: Br2 Conditions: room temp Type of reaction: electrophilic addition
29
Alkene --> Haloalkane Reagent: Conditions: Type of reaction: Mechanism: ethene
Reagent: HCl or HBr Conditions: room temp Type of reaction: electrophilic addition
30
Primary alcohol --> secondary alcohol --> tertiary alcohol --> reagent:
Primary alcohol --> aldehyde --> carboxylic acid secondary alcohol --> ketone tertiary alcohol --> does not oxidise reagent: K2Cr2O7 and conc. H2SO4
31
Aldehydes --> Primary alcohols reagent: conditions: type of reaction: mechanism:
reagent: Ethanolic NaBH4 conditions: room temp + pressure type of reaction: nucleophilic addition
32
Ketones --> Secondary alcohols reagent: conditions: type of reaction: mechanism:
reagent: Ethanolic NaBH4 conditions: room temp + pressure type of reaction: nucleophilic addition
33
Carbonyl (ketone/aldehyde) --> Hydroxynitrile
reagent: KCN + dilute H2SO4 conditions: room temp + pressure type of reaction: nucleophilic addition
33
why is KCN better than HCN for nucleophilic addition
1. HCN is toxic 2. KCN fully dissociates but HCN doesn't
34
how can 2 isomers be formed from ethanal + :CN-
1. planar carbonyl group 2. CN- can join from the front or the back 3. equal chance of each isomer being formed
35
how to distinguish between enantiomers in racemic mixture
1. shine plane polarised light 2. each enantiomer would rotate/reflect light in opposite directions
36
Benzene --> Nitrobenzene reagent: electrophile: type of reaction: mechanism:
reagent: conc. nitric acid + conc. H2SO4 electrophile: NO2+ type of reaction: electrophilic substitution
37
Benzene --> Phenyl ketone reagent: electrophile: conditions: type of reaction: mechanism:
reagent: acyl chloride + anhydrous aluminium chloride electrophile: [CH3CO]+ conditions: heat under reflux type of reaction: electrophilic substitution
38
Nitrobenzene --> Phenyl amine reagent: conditions: type of reaction:
reagent: Sn and HCl conditions: heating type of reaction: reduction

A Chemistry A-level (2 decks)

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