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✅Chemistry Unit 2 > đŸ”´đŸ”¸2.7 -Alcohols And Carboxylic Acids > Flashcards

đŸ”´đŸ”¸2.7 -Alcohols And Carboxylic Acids Flashcards

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1
Q

Define alcohol

A

A homologous series containing -OH as the functional group

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2
Q

Define fermentation

A

An enzyme catalysed reaction that converts sugars to ethanol

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3
Q

How is alcohol produced on a large scale? (2)

A
  1. Hydration of ethane

2. Fermentation

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4
Q

How is ethane produced on a large scale in the hydration of ethene

A

By cracking hydrocarbons produced from petroleum, reacting with steam to produce ethanol

Ch2=Ch2(g) + H2O(g) —<> CH3CH2OH(g)
đŸ”ºH = -45 (Exothermic)

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5
Q

What conditions are used in the hydration of ethene?

A

Compromise temperature of 300degrees, pressure of 60-70 atmospheres and a catalyst of phosphoric acid

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6
Q

What happens to the ethene not converted in the hydration of ethene

A

Only 5% converted and the remaining is recycled back to the reaction chamber

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7
Q

Basic description of fermentation

A

Dissolving sugar in water, adding yeast and leaving in warm place
(Process where sugars are converted to ethanol)

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8
Q

Why is yeast essential for fermentation?

A

It contain enzymes that catalyse the reaction :: C6H12O6 —> 2C2H5OH + 2CO2

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9
Q

C6H12O6 —> 2C2H5OH + 2CO2

How is ethanol separated?

A

Co2 is gas :: escapes :: 2C2H5OH remaining

Ethanol has boiling point of 80 degrees and :: to separate use fractional distillation

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10
Q

Why is fractional distillation rather than distillation needed to separate ethanol in fermentation?

A

Boiling temperatures of ethanol (80) and water (100) are quite close together

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11
Q

Define biofuel

A

A fuel that has been produced using a biological source

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12
Q

What are the two main forms of biofuel

Why can they be used as fuels?

A

Bioethanol and biodiesel

Can be used as fuels since both burn exothermically

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13
Q

How is bioethanol obtained?

A

From sugars in plants by fermentation

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14
Q

How is biodiesel obtained?

A

From the oils and fats present in the seeds of some plants

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15
Q

Name 3 advantages of using biofuels

A
  1. Renewable (grown and produced by animal waste)
  2. Carbon neutral (as plants use CO2 for photosynthesis, then produce CO2 when burnt) :: less overall greenhouse gases
  3. Economic and political security (countries that don’t have fossil fuels are less dependent on changes in price and availability)
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16
Q

Name disadvantages of biofuels

A

1) land use (land can’t be used to produce food + forests cleared for biofuel production)
2) resource use (needs large quantities of water and fertilisers to grow :: causes water pollution)
3) not carbon neutral as use Co2 to build/run factories for biofuel production

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17
Q

What forms when an alcohol is dehydrated?

Show an example equation

A

Dehydrated to form alkenes

E.g CH3CH2CH2OH —> CH3CH=CH2 + H2O

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18
Q

What are most commonly used to dehydrate alcohols

A

Concentrated sulphuric acid or heated aluminium oxide

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19
Q

Why is the dehydration of alcohol an elimination?

A

A double bond is produced by the removal of OH from one carbon atom and H from adjacent atom

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20
Q

Define classification of alcohols

A

Classification into primary, secondary or tertiary according to their structures

21
Q

What is a primary alcohol

A

Occurs when the -OH is joined to a carbon that is itself joined to not more than one other carbon atom e.g methanol or propan-1-ol (check book if unsure)

22
Q

What is a secondary alcohol

A

occurs when the -OH is joined to a carbon that is itself joined to two other carbon atom
E.g Propan-2-ol

23
Q

What is a tertiary alcohol

A

occurs when the -OH is joined to a carbon that is itself joined to 3 other carbon atoms
E.g 2-methyl butan-2-ol
(Check on pg 155 if unsure)

24
Q

What can be used to oxidase alcohols

How is this carried out?

A

Acidified potassium dichromate (VI)

Carried out by heating the alcohol with a mixture of aqueous potassium dichromate(VI) and sulphuric acid

25
Q

What is the oxidising agent usually shown by?

A

[O]

26
Q

Write the word equation for the oxidation of a primary alcohol using ethanol as an example: Stage 1

What is the functional group of the main product of This reaction?

A

Ethanol + [o] —> ethanal + water
(LOOK AT DIAGRAM JESS)

O
||
C-H (an aldehyde)

27
Q

Write the word equation for the oxidation of a primary alcohol using ethanol as an example: Stage 2

What is the functional group of the main product of This reaction?

A

Ethanal + [O] —> ethanoic acid

```
Functional group
O
||
C-OH
carboxylic acid e.g ethanoic acid
~~~

28
Q

Write the word equation for the oxidation of a SECONDARY alcohol using propan-2-ol

A

Propan-2-ol + [O] —> propone (keytone with functional group (-C=O) and 2 hydrogens removes +water
(DIAGRAM)

29
Q

Write the word equation for the oxidation of a TERTIARY alcohol using 2-methylpropan-2-ol as an example

A

No reaction takes place as no hydrogen in the adjacent carbon that can be lost

30
Q

Write a summary of oxidation reactions (1,2,3)

A

1) Primary—> aldehydes—> carboxylic acids
2) Secondary—> ketones
3) tertiary alcohols are not oxidised

31
Q

What is the colour change of acidified potassium dichromate as an oxidising agent?

A

Orange—> green

Test for primary and secondary alcohols but not tertiary

32
Q

Define carboxylic acid

A

A homologous series containing -COOH as the functional group

33
Q

Name some carboxylic acids and where they’re present

A

1- Methanoic acid (formic acid) in venom from ant bites

2- ethanoic acid in vinegar

3-citric acid in lemons and other fruits

4-Malic Acid in many fruits

34
Q

Define a weak acid

A

An acid that is only partially ionised in aqueous solution

35
Q

Why are carboxylic acids acidic?

A

Because they release H+ ions when added to water

36
Q

Show the carboxylic acid dissociation equation

A

RCOOH —<> RCOO- + H+

When R is a variable group

37
Q

What kind of acids are carboxylic acids?

What does this cause?

A

Weak acids shown through pH and :: the ionisation needed to produce H+ is an equilibrium

38
Q

What reactions occur with carboxylic acids?

A
  1. As an acid

2. Esterification

39
Q

general word equation and example of carboxylic acid + base

Is there a visible change?

A

General: acid + base = salt + water
Example using base NaOH
Ethanoic acid —> sodium ethanoate

No visible change as all reagents and products are colourless and soluble in water

40
Q

General Word equation and example of carboxylic acid + carbonates and hydrogencarbonates

What is observed? How can this be tested?

A

General: acid + carbonate —> salt + water + co2

Effervescence is seen as co2 produced, gas can be collected and tested with limewater

41
Q

Give the general equation for esterification

A

Carboxylic acid + alcohol —> Ester + water

42
Q

What is esterification catalysed by?

A

Concentrated sulfuric acid

43
Q

Describe how esterification is carried out

A

Heat carboxylic acid with an alcohol and concentrated sulfuric acid

44
Q

How can you tell esterification is a test for an alcohol/carboxylic acid?

A

Esters produced gave a sweet fruity odour

45
Q

How do you obtain a pure sample of an ester?

A
  1. Carboxylic acid, alcohol and concentrated sulfuric acid are heated together in a flask
  2. Produces equilibrium mixture of Ester with some carboxylic acid and alcohol
  3. Flak is attached to allow the removal of the Ester as soon as it’s formed
    (DIAGRAM PG 159)
46
Q

How does le chatelliers principle support the distilling of Ester

A

The removal of Ester pulls the equilibrium to the right and more Ester is made

47
Q

Why can the Ester by distilled off by leaving the other organic substances in the reaction flask

A

The Ester has the lowest boiling temperature: alcohols, carboxylic acids and water all contain the -Oh group and can hydrogen bond, this increases their boiling temperatures. Esters can’t hydrogen bond

48
Q

Explain why 2-bromopropane is the main product opposed to 1-bromopropane

A
  • 2 bromopropane is formed from secondary carbocation (1 is from primary carbocation)
  • secondary carbocations are more stable than primary carbocations

✅Chemistry Unit 2 (8 decks)

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