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SQA Higher Chemistry Unit 2 > Unit 2(a) - Oxidation of Food and the Chemistry of Cooking - Alcohols, Carboxylic Acids, Aldehydes and Ketones > Flashcards

Unit 2(a) - Oxidation of Food and the Chemistry of Cooking - Alcohols, Carboxylic Acids, Aldehydes and Ketones Flashcards

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1
Q

What is the general formula for an alcohol?

A

CnH2n+1OH

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2
Q

How do alcohol isomers differ?

A

Position of hydroxyl group

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3
Q

What functional group is present in alcohols?

A

OH (hydroxyl group)

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4
Q

What is a diol/triol?

A

Diol - two hydroxyl groups

Triol - three hydroxyl groups

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5
Q

What are some properties of alcohols?

A
  • Polar liquids
  • Overall polar molecule
  • More viscous than similar sized liquid alkane
  • Evaporate more slowly than similar sized liquid alkane
  • Significantly higher melting and boiling points than similar sized alkanes
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6
Q

What are the three types of alcohols?

A
  • Primary
  • Secondary
  • Tertiary
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7
Q

What is a primary alcohol?

A

An alcohol with only one carbon atom joined to the carbon bonded to the hydroxyl group

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8
Q

What is a secondary alcohol?

A

An alcohol with two carbon atoms joined to the carbon bonded to the hydroxyl group

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9
Q

What is a tertiary alcohol?

A

An alcohol with three carbon atoms joined to the carbon bonded to the hydroxyl group

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10
Q

What is mild/severe oxidation?

A

Mild: affects just functional group
Severe: affects whole molecule

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11
Q

What do primary alcohols oxidise to?

A

Aldehyde, then Carboxylic acid

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12
Q

What does a secondary alcohol oxidise to?

A

Ketone

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13
Q

Why do tertiary alcohols not oxidise?

A

No hydrogens to lose

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14
Q

What is the general formula for an aldehyde?

A

RCHO, where R is an alkyl group

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15
Q

How are aldehydes named?

A

Corresponding alkyl name with ending replaced with -AL

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16
Q

What is the general formula for a ketone?

A

RCOR’, where R and R’ are alkyl groups

17
Q

How are ketones named?

A

Corresponding alkane name with the ending changed to -ONE

18
Q

What are some properties of aldehydes and ketones?

A
  • Very polar
  • Higher mps and bps than alkanes of a similar size
  • Smaller aldehydes/ketones are water soluble
19
Q

Give 3 oxidising agents for primary and secondary alcohols

A
  • Acidified potassium dichromate solution (orange to green)
  • Benedict’s/Fehling’s solution (blue to brick red
  • Tollen’s reagent (silver aqueous to silver solid)
20
Q

What is the general formula for a carboxylic acid?

A

CnH2n+1COOH

21
Q

What are some properties of carboxylic acids?

A
  • Colourless liquid
  • pH 2-3
  • Sharp smell
22
Q

When do foods oxidise?

A

When exposed to oxygen in the air

23
Q

What happens to fats and oils when oxidised?

A

Degradation of long fatty acid chains and formation of short chain products

24
Q

Which molecule mediates the oxidation of fats and oils?

A

Free radicals

25
Q

How can oxidation of foods be slowed down?

A
  • Reducing the temperature
  • Packaging under and vacuum or under an inert gas
  • Addition of antioxidants
26
Q

What are antioxidants?

A

Molecules that reduce the rate of oxidation

27
Q

What is a free radical?

A

A highly reactive species containing an unpaired electron

28
Q

How do antioxidants work?

A

They oxidise themselves to donate an electron to stabilise the free radical

29
Q

Give an example of a natural antioxidant

A

Vitamin C or vitamin E

30
Q

Give an example of a synthetic antioxidant

A

Butylated hydroxyanisole

31
Q

What is accurately known in a standard solution?

A

Concentration

32
Q

How is a standard solution prepared?

A
  • Dissolve weighed substance in deionised water
  • Pour solution through a filter funnel into a graduated flask
  • Rinse out beaker with deionised water to make sure all substance is used
  • Continue to add deionised water until desired volume is reached
  • Stopper flask and invert to ensure proper mixing
33
Q

Why is deionised water used for preparing standard solution?

A

Ensure that no other ions interfere with the reaction

SQA Higher Chemistry Unit 2 (5 decks)

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