Organic Chemistry Flashcards

1
Q

Suggest a reason why some reactions occur by a mechanism involving a carbocation where others do not

A

Reactions involving carbocations tend to be tertiary carbocations since they are more stable than primary carbocations

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2
Q

Conditions of producing ethanol from ethene

A
  • CONCENTRATED phosphoric acid catalyst
  • high temperature
  • high pressure
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3
Q

Suggest and explain a reason why an alcohol might not be easily oxidised

A

Tertiary alcohol so has no hydrogens on carbon attached to -OH for oxygen to remove

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4
Q

Give reasons why a major product for a reaction is formed

A

Formed from a tertiary/secondary carbocation which is more stable because :

  • more alkyl groups bonded to carbon
  • donate electron density (inductive effect) for greater stability
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5
Q

Suggest what physical properties of a homologous series change as chain length increases

A

Boiling / Melting Point
Density
Viscosity

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6
Q

Reason for E/Z isomerism

A

Restricted rotation around C=C bond

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7
Q

Suggest why alkenes do not react with warm aqueous sodium hydroxide

A

OH- acts as a nucleophile so high electron density of double bond repels it

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8
Q

Suggest reasons why ethene is not made from elimination reactions of haloalkanes in industry

A
  • halogenoalkanes are expensive/ not readily available
  • low yield
  • slow reaction
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9
Q

What is meant by propagation step

A

Radicals formed and used

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10
Q

Suggest why haloalkanes are susceptible to attacks by nucleophiles

A

Bond between halogen and carbon is polar

Carbon atom is electron deficient/ partially positive

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11
Q

Features of a homologous series

A
  • gradual change in physical properties as relative molecular mass increases
  • same chemical properties
  • same functional group
  • same general formula
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12
Q

Suggest an economic reason for cracking fractions of crude oil

A

Meet high demand of more useful/ high value products which are in low supply using less useful products

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13
Q

Nucleophile + Electrophile

A
  • nucleophile = electron pair donor

- electrophile = electron pair acceptor

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14
Q

Production of ethanol by hydration

A
  • electrophilic addition reaction
  • continuous process
  • low percentage yield since reversible
  • high atom economy (no waste products/ ethanol only product)
  • unsustainable since ethene is finite (comes from crude oil)
  • requires energy to produce steam
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15
Q

Production of ethanol by fermentation

A
  • anaerobic respiration of yeast
  • high percentage yield
  • low atom economy since carbon dioxide water product
  • sustainable since crops are renewable
  • energy required for distillation
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16
Q

Suggest why distillation produces aldehydes

A
  • volatile components can escape / distill off

- partial oxidation

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17
Q

Suggest why reflux produces carboxylic acids

A
  • volatile components cannot escape so are refluxed

- complete oxidation

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18
Q

Suggest what the other product of oxidation of alcohols is

A

Water (always one mole - even when carboxylic acid is produced)

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19
Q

Conditions for production of ethanol by fermentation

A
  • enzymes (yeast)
  • anaerobic
  • 25 - 42 degrees C
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20
Q

Suggest how you can tell when fermentation of glucose is complete

A

No more bubbles suggesting carbon dioxide is not produced

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21
Q

Suggest role of H+ in hydration of alkenes

A

Catalyst since it is not used up

22
Q

Suggest properties of CFCs

A

Volatile
Non toxic
Non flammable
Inert

23
Q

Structural isomers

A

Same molecular formula but different structure / arrangement of atoms

24
Q

Uses of CFCs

A
  • aerosol propellant
  • dry cleaning solvent
  • refrigerant
25
Q

Suggest why a alkene might not have E/Z isomerism

A

One carbon atom is C=C bond is joined to two of the same groups

26
Q

Empirical formula

A

Simplest whole number ratio of the number of atoms of each element in a compound

27
Q

Molecular formula

A

Shows actual number of atoms of each element in a compound

28
Q

Displayed formula

A

Shows every atom and bond is a compound

29
Q

Structural formula

A

Shows unique arrangement of atoms in a compound without showing all bonds

30
Q

Free radical

A

Highly reactive species with an unpaired electron formed when a covalent bond breaks evenly (each atom has one electron)

31
Q

Suggest another reason for cracking

A

Alkene with can produce polymers

32
Q

Conditions for thermal cracking

A
  • high temperature

- high pressure

33
Q

Mechanism for thermal cracking

A

Free radical substitution

34
Q

Conditions for catalytic cracking

A
  • warm temperature
  • slight pressure
  • zeolite catalyst
    (silicon dioxide and aluminium oxide)
35
Q

Evidence of catalytic cracking

A
  • branched alkanes
  • cycloalkanes
  • aromatic compounds
36
Q

Plasticisers

A

Small molecules that get between polymer chains forming them apart allowing them to slide over each other

37
Q

Suggest why plastics are not biodegradable

A
  • long saturated alkane backbone
  • C-C and C-H bonds are non polar
  • unreactive so enzymes cannot attack
38
Q

Suggest what is meant by reflux and an advantage of it

A
  • condensing and re collecting solvent vapour

- allows mixture to be boiled indefinitely without significant loss in volume

39
Q

Suggest why gases are passed through sodium hydroxide in dehydration of ethanol using sulphuric acid

A

Remove carbon dioxide and sulphur dioxide from side reactions

40
Q

Suggest a drawback of using sulphuric acid in dehydration of ethanol

A
  • sulphuric acid is a strong oxidising agent

- oxidises alcohol into carbon dioxide and is reduced to sulphur dioxide

41
Q

Compare sigma and pi bond and hence suggest why alkene should are more reactive than alkanes

A

Sigma bond is stronger than pi bond since there is stronger orbital overlap. Alkene have a pi bond which is weak making them highly reactive.

42
Q

Conditions for electrophilic addition with ammonia

A

Excess ammonia
Reflux
High temperature/pressure

43
Q

Suggest why there needs to be an excess of ammonia in reaction between electrophilic addition

A

Otherwise amine group would react with haloalkane

44
Q

State which conditions favour elimination and substitution

A
Elimination 
- dissolved in ethanol 
- high temperature 
- tertiary haloalkane 
Substitution 
- aqueous 
- room temperature 
- primary haloalkane
45
Q

What are the mechanisms for hydration and dehydration reactions

A
Hydration = Addition 
Dehydration = Elimination
46
Q

Alternatives of CFCs

A
  • HFCs

- alkanes

47
Q

Stereoisomers

A

Same structural formula but different arrangement of atoms in space

48
Q

Functional Isomers Examples

A

Ether - Alcohol
Aldehyde - Ketone
Carboxylic acid - Ester
Alkene - Cyclic alkane

49
Q

Evidence of thermal cracking

A

MAINLY alkene produced

50
Q

Addition Polymerisation conditions

A
  • low temperature (exothermic)

- high pressure