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Wjec Chemistry Unit 2 > 2.7 Alcohols and Carboxylic acids > Flashcards

2.7 Alcohols and Carboxylic acids Flashcards

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1
Q

Two main methods of producing alcohols

A

Hydration and fermentation

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2
Q

Hydration of alkenes

A
  • produces alcohols from alkenes in the presence of an acid catalyst
  • very high percentage yield - 1 product
  • industrial process- high yield
  • catalyst - phosphoric acid - increases rate without affecting yield
  • 300 degrees celsius- compromise temperature as forward is exothermic so high yield would need a low temperature but would lead to a slow rate of reaction
  • high pressure (60-70atm)- less moles of product so high yield favoured by high pressure, increases rate of reaction expensive when too high
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3
Q

Fermentation - sugars are converted to alcohol

A

• catalysed by enzyme present in yeast
• sugar is dissolved in water
• yeast is added and mixture is left in a warm place
• production of alcoholic drinks
• cheaper than hydration - lower temperature needed
• lower percentage yield than hydration
Eg glucose –> ethanol and carbon dioxide

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4
Q

After fermentation describe and explain how ethanol can be separated from the aqueous mixture left in the fermentation vessel

A

By fractional distillation as it has a boiling temperature of 80 degrees C

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5
Q

What is a biofuel

A

Fuel that has been produced using a biological source

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6
Q

Advantages of biofuels

A
  • renewable - grow trees, animal waste material
  • greenhouse gases - although they produce CO2 when burned they take some in during photosynthesis- carbon neutral overall
  • economic and political security- countries without their own source of fossil fuels are affected bu changes in price + availability
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7
Q

Disadvantages of biofuels

A
  • land-use- deforestation to create land to grow plants for biofuels
  • use of resources- need lots of water and fertiliser , short supply of water and water pollution
  • carbon neutrailty?- building factories and transport raw material - CO2 production
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8
Q

Alcohol dehydration to form alkenes

A
  • water molecule is eliminated from the molecule and double bond is formed
  • need a dehydrating agent/catalyst eg heated Al2O3 or concentrated H2SO4
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9
Q

How can addition polymers be produced from fermentation without the need for crude oil?

A

Fermentation produces the primary alcohol which can be dehydrated to produce an alkene which is used in the production of addition polymers

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10
Q

Primary alcohol

A

-OH joined to C that is not joined to more than 1 other C atom

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11
Q

Secondary alcohol

A

-OH is joined to C that is joined to 2 other C atoms

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12
Q

Tertiary alcohol

A

-OH joined to C that is joined to 3 other C atoms

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13
Q
A

Primary

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14
Q
A

Primary

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15
Q
A

Secondary

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16
Q
A

Tertiary

17
Q

Oxidation of primary alcohol

A

Primary alcohol –> aldehyde–> carboxylic acid

18
Q

Oxidation of secondary alcohol

A

Secondary alcohol–> ketones

19
Q

Oxidation of tertiary alcohol

A

No oxidation

20
Q

Use of acidified potassium dichromate (V)

A

Behaves as oxidising agent of alcohol
Orange to green
Primary + secondary- positive
Tertiary- negative

21
Q

Formation of carboxylic acid

A

Aldehyde produced from primary alcohol will undergo further oxidation to form a carboxylic acid
Secondary won’t

22
Q

Testing for carboxylic acids

A

React as acids with sodium hydrogencarbonate
Produce CO2
CO2 collected and tested using limewater- cloudy if it is CO2

23
Q

Description of carboxylic acids as acids

A

Weak- slightly dissociate in solution

Form H+ ion and carboxylate ion RCOO-

24
Q

Carboxylic acids and carbonates reaction

A

Carboxylate salt, water and carbon dioxide

25
Q

Carboxylic acids and hydrogen carbonates reaction

A

Carboxylate salt, water and carbon dioxide

26
Q

Carboxylic acid and base reaction

A

Carboxylate salt and water

27
Q

Carboxylate salt eg Na

A

CH3COO-Na+

28
Q

Propene can be formed by a dehydration reaction

Name a suitable reagent for this reaction

A

Concentrated sulphuric acid

29
Q

Give an oxidising agent that can be used, in acid solution, to oxidise primary alcohols to carboxylic acids and state what is seen as the reaction proceeds

A 
Potassium dichromate (VI)
Colour change from orange to green
30
Q

State the conditions of temperature and pressure used in the preparation of ethanol from ethene

A

300 degrees C

60-70 atm

31
Q

Ethanol can be converted to ethanoic acid in an oxidation reaction.
Give suitable reagents for this reaction

A

Acidified potassium dichromate (VI)

32
Q

Ethene can be used as the starting material in the industrial preparation of ethanol
Name the catalyst used in this reaction

A

Phosphoric acid

Wjec Chemistry Unit 2 (8 decks)

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