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HIGH CHEM U2 Nature’s Chemistry > KA3- Oxidation And The Chemistry Of Cooking > Flashcards

KA3- Oxidation And The Chemistry Of Cooking Flashcards

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1
Q

Alcohols

A

Compounds that contain hydroxyl functional group -OH (so hydrogen bond)
CnH2n+1O/OH
Higher boiling points than alkanes because hydrogen bonds stronger
Soluble in water because contain polar hydroxyl group

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2
Q

Naming alcohols

A

Numbering from one side which gives the -OH the lowest number
Ensuring the -OH takes priority over any branches

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3
Q

Primary alcohol

A

OH group joined to the end of the carbon chain
-CH2OH

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4
Q

Secondary alcohols

A

OH group joined to an intermediate carbon atom
—CH—
|
OH

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5
Q

Tertiary alcohol

A

OH group joined to an intermediate carbon atom wich also has a branch attached
|
—C—
|
OH

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6
Q

Propane (alcohols)

A

Doesn’t have a hydroxyl group so cant from a hydrogen bond with other propane molecules
Much lower boiling point than other molecules as only weak London dispersion force have to be broken to change propane from a liquid to a gas

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7
Q

Adding hydroxyl groups (alcohols)

A

Molecules are held together by hydrogen bonding in the solid and liquid state
Much more energy must be supplied to overcome the hydrogen bonds which attract the molecules

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8
Q

Oxidation of alcohols

A

Primary and secondary alcohols can be oxidised by various oxidising agents
Tertiary alcohols don’t undergo oxidisation

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9
Q

Suitable oxidising agents (alcohols)

A

Acidified potassium dichromate
Hot copper (II) oxide

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10
Q

Primary alcohols oxidised

A

Produce aldehydes
Primary alcohol—> aldehyde—> carboxylic acid
O:H ratio can help
2/3 H- aldehyde
1/3 H- carboxylic acid

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11
Q

Secondary alcohols oxidised

A

Produce ketones
Secondary alcohol—> ketone (not readily oxidised)

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12
Q

Aldehydes and ketones

A

C=O (carbonyl group)

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13
Q

Aldehydes

A

The carbonyl group is at the end of the carbon chain and has a hydrogen atom attached to it
Prefixal (propanal)

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14
Q

Ketones

A

Carbonyl group is joined to 2 other carbon atoms and does not have a hydrogen atom attached to it
Prefixone (propanone)

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15
Q

Branched ketones

A

Position of carbonyl group changes
Position of branches-prefix of how many branches branch name chain prefix-position of carbonyl-one

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16
Q

Branched aldehydes

A

Carbonyl group position never changes
Position of branches-prefix of how many branches branch name chain name

17
Q

Oxidation of aldehydes and ketones

A

Oxidising agents can be used to distinguish between aldehydes and ketones since aldehydes can oxidise but ketones cannot

18
Q

Oxidising agents (aldehydes)

A

Fehling’s solution
Tollen’s reagent
Acified potassium dichromate

19
Q

When aldehydes are oxidised

A

Form Carboxylic acids
Eg
Ethanal —> ethanoic acid
CH3CHO —> CH3COOH

20
Q

Oxidation

A

Occurs when there is an increase in the oxygen to hydrogen ratio

21
Q

Reduction

A

Occurs when there is a decrease in the oxygen to hydrogen ratio

22
Q

Carboxylic acids

A

CnH2nO2
Produced from the oxidation of primary alcohols and aldehydes
Can react with bases to form salts

23
Q

Reduction of Carboxylic acids

A

The reverse of the oxidation of primary alcohols
Carboxylic acid —> aldehyde —> primary alcohol

24
Q

Vitamin C

A

Contains a number of polar -OH groups which can hydrogen bond to water so is soluble in water
Vitamin C dissolves in water (while cooking)

25
Q

Denaturing in food

A

Protein molecules which contain polar -NH and -C=O groups, bind to other protein molecules through hydrogen bonding which gives them a specific shape, when heated the hydrogen bonds break causing a complete change in shape- resulting in a change of flavour

26
Q

Polar

A

Hydroxy, carbonyl, carboxyl, amie, amide

27
Q

Flavour and aroma molecules in food

A

Are often aldehydes and ketones
Oxidation of these molecules can change the flavour, making foods taste unpleasant so antioxidants are used to prevent this oxidation and thus preserve flavour

28
Q

Chemical structure of a food molecule

A

Can be used to determine whether the molecule is likely to be soluble or insoluble in water o oil

29
Q

Volatility of a flavour compound

A

Determined by its strucure

HIGH CHEM U2 Nature’s Chemistry (6 decks)

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