OXIDATION OF FOOD Flashcards

1
Q

When chemicals in food are exposed to oxygen in air

A

chemical composition changes and they begin breaking down

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2
Q

animal and plant tissues contian

A

antioxidants molecules to prevent breaking down by oxygen exposure

slow down rate of discolour/break down

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3
Q

food left unattended

A

lose nutritional value and begin to break down and discolour

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4
Q

alcohol functional group

A

OH

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5
Q

what kind of series is alochols

A

homologous

CnH2n+OH

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6
Q

names end in

A

-ol

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7
Q

Types of alcohols

A

Primary
Secondary
Tertiary

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8
Q

Primary alcohols

A

hydroxyl group on a C with at least 2 H

AT END

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9
Q

Secondary alcohols

A

Hydroxyl OH attached to Carbon with at least 1 Hydrogen

Somewhere in middle of carbon chain

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10
Q

Tertiary alcohols

A

Hydroxyl OH attached to a carbo with no H attached

on branch with carbon that is attached to other carbon branch so no H

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11
Q

Oxidation of alcohol

A

Using oxidation agent

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12
Q

Oxidisation agent examples

A

acidified potassium dichromate

acidified potassium permanganate

hot copper (II) oxide (black solid)

Benedicts reagent

Tollens reagent (silver-mirror)

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13
Q

Oxidation of primary alcohol

A

Forms 2 products in 2 stage reaction

Oxygen Hydrogen ratio increases so O added or H removed

  1. Loses 2 H to form aldehyde
  2. Oxygen added to aldehyde to form carboxylic acid
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14
Q

oxidation of propan-1-ol

A

PROPANAL + WATER

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15
Q

oxidisation primary alcohol summary

A

Primary alcohol
Aldehyde
Carboxylic Acid

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16
Q

Oxidation of secondary alcohol

A

only once

form ketones (alkanones)

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17
Q

ketone

A

-one

carbonyl group never at end (c double bond O)

lose H gain double bond from secondary alcohol

propanone and butanone not need numbers as always number 2

18
Q

Tertiary alcohol oxidation

A

Not readily oxidised

19
Q

Many common flavours for cooking formed from

A

aldehydes and ketones

20
Q

group in both ketones and aldehydes

A

corbonyl group

21
Q

Aldehyde

A

Alkanal

Have carbonyl group at end of carbon chain

end in -al

when naming carbonyl number not needed as always 1

22
Q

carbonyl group

A

C double bond O

23
Q

how to tell ketone and aldehyde apart

A

using oxidising agent act different

24
Q

acidified potassium dichromate colour change

A

orange to green

25
Q

fehling’s soluton colour chnage

A

blue to brick red preticipate

26
Q

Tollen’s reagent colour change

A

Clear to silver mirror participate

27
Q

carboxylic acid

A

contain carboxyl group (-COOH))

always on C1

-oic acid

28
Q

Reactions with carboxylic acids

A

Undergo reduction reactions (opposite oxidation)

e.g. ethanol to ethanol to ethanoic acid when oxidised to opposite for reduction

29
Q

OH ratio for primary alcohol reactions

A

ethanol 1:6

Ethanal 1:4

Ethanoic acid 1:2

30
Q

Reduction carboxylic acid

A

Oxygen removed or hydrogen added

31
Q

Carboxylic acid reacting with base

A

form salt and water in neutralisation reaction

32
Q

neutralisation reaction carboxylic acid and base when long fatty acid used

A

the salt formed is soap

33
Q

butter going off

A

formation of butanoic acid as butter is hydrolysed

34
Q

What helps prevent food from spoiling

A

Antioxidants which are reducing agents

35
Q

Antioxidants in many brighly coloured fruits

A

antioxidant compounds called polyphenols - vitamin C

36
Q

Vitamin C reacts to form

A

dehydroascorbic acid by losing 2 H from the hydroxyl attached to ring part, forming 2 ketones

loss H indicates oxidation and 2e- lost - supply of electrons prevent oxidation in other chemicals, causing them instead to be reduced

37
Q

vitamin C reaction formula

A

C6H8O6 —–> C6H6O6 + 2H +2e-

38
Q

removal of H and loss electrons in vitamin C

A

indicate this is an oxidation reaction, showing that as an antioxidant, vitamin C itself is oxidised

39
Q

Why do diols have higher bo than alcohols

A

This is due to the presence of two hydroxyl groups which allow for more hydrogen bonding, contributing to a higher degree of intermolecular attractions.

40
Q

what kind of agent are antioxidants

A

reducing