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OCR A A-Level Chemistry > Chapter 14 - Alcohols > Flashcards

Chapter 14 - Alcohols Flashcards

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1
Q

What is the functional group of an alcohol?

A

OH

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2
Q

What does the OH group in an alcohol determine?

A

The physical and chemical properties of it

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3
Q

Why is methanol used as a fuel?

A

It combusts efficiently

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4
Q

What is methanol used for? (2)

A

Fuel

Chemical feedstock - it can be made into polymers, solvents and adhesives

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5
Q

What is ethanol used for? (3)

A

Fuel
Drinks
Solvent

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6
Q

How are alcohols named?

A

-ol is added to the prefix and the position of the OH group is indicated using a number

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7
Q

Physical properties of alcohols compared to alkanes

A

Less volatile
Higher melting points
Greater water solubility

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8
Q

Why are the physical properties of alcohols and alkanes very different?

A

Whilst alkanes are on-polar, alcohols are polar. This means that whilst there are still weak London forces present in alcohols, there are also strong hydrogen bonds

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9
Q

Why are alkanes non-polar?

A

Hydrogen and carbon have very similar electronegativities

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10
Q

What forces are present in alkanes?

A

Weak London forces

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11
Q

Why are alcohols polar?

A

The O-H bond - oxygen and hydrogen have very different electronegativities

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12
Q

Why are alcohols less volatile than alkanes?

A

The strong hydrogen bonds in alcohol molecules require much more energy to overcome in order to turn the alcohol into a gas than the weak London forces in alkanes

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13
Q

Why are alcohols soluble in water but alkanes aren’t?

A

Hydrogen bonds form between the OH group of an alcohol and the water molecule. This can’t occur in alkanes because they are non-polar

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14
Q

Why does solubility decrease as the hydrocarbon chain increases?

A

The influence of the OH group decreases

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15
Q

What are the three types of alcohols?

A

Primary, secondary, tertiary

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16
Q

What is the general formula for an alcohol?

A

Cn H2n+1 OH

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17
Q

What are primary alcohols?

A

The OH group is attached to a carbon that is attached to two hydrogens and one alkyl group

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18
Q

What is a secondary alcohol?

A

The OH group is attached to a carbon that is attached to one hydrogen atom and two alkyl groups

19
Q

What is a tertiary alcohol?

A

OH group is attached to a carbon atom that is attached to no hydrogen atoms and three alkyl groups.

20
Q

What is produced when alcohols completely combust?

A

Carbon dioxide and water

21
Q

What type of reaction is combustion?

A

Exothermic - releasing large quantities of energy in heat.

22
Q

What happens to the amount of energy released when an alcohol combusts as chain length increases?

A

Increases

23
Q

How do you oxidise a primary or secondary alcohol?

A

Primary and secondary can be oxidised but tertiary cannot

24
Q

What oxidising agent do we use?

A

Potassium dichromate (vi) acidified with dilute Sillitoe acid

25
Q

What colour change occurs when an alcohol is oxidised?

A

Orange to green

26
Q

Why does the solution go green when an alcohol is oxidised?

A

As the solution is reduced

27
Q

What are the two products that can form when a primary alcohol is oxidised?

A

Aldehyde and carboxylic acid

28
Q

What is produced when a primary alcohol is heated and the product distilled immediately?

A

Aldehyde

29
Q

What is produced when a primary alcohol is heated under reflux?

A

Carboxylic Acid

30
Q

How to prepare an aldehyde?

A

The aldehyde is distilled out of the reaction mixture preventing further reaction with oxidation agents

31
Q

What is the general formula for both ketones and carboxylic acids?

A

C2nO

32
Q

How to prepare a carboxylic acid?

A

Heat the alcohol under reflux

33
Q

What is produced when secondary alcohols are oxidised

A

Ketone

34
Q

How to prepare a ketone?

A

Heat under reflux with oxidising agent

35
Q

Suffix for a ketone

A

-one

36
Q

Suffix for an aldehyde

A

-al

37
Q

What will happen when a tertiary alcohol is oxidised?

A

No reaction

38
Q

What is dehydration of an alcohol?

A

Any reaction in which water molecules is removed from the starting material

39
Q

What type of reaction is dehydration?

A

Elimination reaction

40
Q

How do you dehydrate an alcohol?

A

Heated under reflux in the presence of an acid catalyst (like H2SO4)

41
Q

What is produced when an alcohol is dehydrated?

A

Alkene

42
Q

What is produced when an alcohol reacts with hydrogen halide?

A

Haloalkenes and water

43
Q

How to prepare a haloalkane?

A

Alcohol is heated under reflux with sulphuric acid and sodium halide

OCR A A-Level Chemistry (28 decks)

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