C10 - Organic Reactions Flashcards

1
Q

What are alkenes

A

A homologous series of unsaturated hydrocarbons due to them having 2 less hydrogen atoms than the alkane with the same number of carbon atoms. This is becuase of the carbon carbon double bond in them

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2
Q

General formula for alkenes

A

CnH2n

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3
Q

First four alkenes

A

Ethene, Propene, Butene, Pentene

Methene doesn’t exist as methane only has 1 carbon atom

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4
Q

Defenition of a functional group

A

The part of a molecule that determins how it reacts e.g. the alkenes carbon-carbon double bond

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5
Q

Combustion of alkenes

A
  • Produces unburnt carbon particles due to incomplete combustion
  • This means they burn with a smoky flame
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6
Q

Reaction of alkenes with hydrogen and conditions required

A
  • The two hydrogen atoms add ACROSS the double bond
  • The carbon-carbon double bond is converted to a single bond
  • So reacting an alkene with hydrogen produces an alkane
  • The conditions required are nickel as a catalyst and 150°C

(Hydrogenation reaction)

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7
Q

Reaction of alkanes with water and conditions required

A
  • The water must be steam
  • The temperature and pressure must be relativley high
  • Phosphoric acid is used as a catalyst
  • This is a reversible reaction and it produces an alcohol e.g. ethanol

(Hydration reaction)

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8
Q

Reaction of alkenes with the halogens

A
  • The two halogen atoms are added across the double bond
  • The double bond is opened up into a single carbon-carbon bond
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9
Q

Uses of alcohols

A
  • Fuels
  • Alcoholic drinks
  • Solvents
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10
Q

Functional group for alcohols

A

-OH (hydroxyl group)

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11
Q

first 4 alcohols and their structural formulas

A

Methanol - CH₃OH
Ethanol - CH₃CH₂OH
Propanol - CH₃CH₂CH₂OH
Butanol - CH₃CH₂CH₂CH₂OH

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12
Q

Two ways of making ethanol

A
  • Reacting ethene with steam
  • Fermentation of sugar cane
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13
Q

Conditions for fermentation

A
  • Temperature is around 30°C
  • Must have anaerobic conditions (no oxygen)
  • Add yeast
  • Slightly acidic conditions
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14
Q

Advantages and disadvantages of making ethanol by ethene and steam

A
  • Fast and continuous process
  • Produces pure ethanol
  • However, crude oil is the source for lots of the ethene which is non-renewable
  • Is an expensive process as energy is needed to increase the temperature and pressure
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15
Q

Advantages and disadvantages of making ethanol by fermentation

A
  • Low temperature - the reaction doesn’t require lost of energy
  • The sugar comes from plants so is renewable
  • Is carbon neutral
  • Produces an aqueous solution of ethanol (15%) so further fractional distillation needs to be done which is costly
  • Ethical concerns about using food sources to make alcohol
  • Is a batch process so is slow and laborious
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16
Q

Solubility of alcohols in water

A

The smaller chain alcohols up to and including propanol are all soluble in water and form neutral solutions
As the number of carbon atoms increases, the solubility decreases as the CH₃ part is hydrophobic

17
Q

Equation for the reaction of sodium with ethanol

A

ethanol + sodium —> sodium ethoxide + hydrogen

18
Q

Reaction of alcohols with an oxidising agent and give the name of it

A
  • The oxidising agent used is acidified potassium dichromate
  • The alcohol reacts to make a carboxylic acid and water
19
Q

Combustion of alcohols

A
  • They burn well with a clear flame
  • This forms carbon dioxide and water
20
Q

Functional group of carboxylic acids

A

COOH

21
Q

What happens when carboxylic acids dissolve in water

A
  • As they are weak acids, they ony partially ionise and this is shown by a reversbile reaction
  • This gives a solution with an acidic pH

CH₃COOH ⇌ CH₃COO⁻ + H⁺

22
Q

Reaction of a carboxylic acid witha metal carbonate e.g. ethanoic acid with sodium carbonate

A

ethanoic acid +sodium carbonate ⟶ sodium ehtanoate + carbon dioxide + water

23
Q

What is an ester and what are they used for

A

pleasant smelling compunds that are used in artificial flavourings and perfumes (as they are very volatile)

24
Q

reaction of ethanoic acid with ethanol
(carboxylic acid with an alcohol) and key points about the reaction

A

ethanoic acid + ethanol ⇌ ethyl ethanoate + water
* A sulfuric acid catalyst is needed
* The reaction is reversible

25
Q

General formula for an Alcohol

A

CnH2n+1OH