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Higher Chemistry > 2.7 oxidation of food > Flashcards

2.7 oxidation of food Flashcards

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1
Q

What is oxidation in a carbon compound?

A

increase on the oxygen to hydrogen ratio

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2
Q

what is reduction in a carbon compound?

A

decrease in the oxygen to hydrogen ratio

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3
Q

What can hot copper(II) oxide or acidified dichromate(VI) solutions be used to oxidise?

A
  • primary alcohols->aldehydes->carboxylic acids

- secondary alcohols-> ketones

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4
Q

What happens to hot copper(II) oxide and dichromate (VI) solutions when oxidising primary and secondary alcohols?

A

copper(II)oxide
-black->brown solid
dichromate(VI)solution
-orange->green

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5
Q

explain the use of hot copper(II) oxide and dichromate (VI) solutions on tertiary alcohols

A
  • tertiary alcohols are not readily oxidised

- they cannot be oxidised using these oxidation agents

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6
Q

What is the functional group in aldehydes and keynotes?

A

carbonyl >C=O

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7
Q

what happens to aldehydes when oxidised?

A

oxidised to carboxylic acids

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8
Q

what happened to ketones when oxidised?

A

they can’t be oxidised to carboxylic acids. They are not readily oxidised

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9
Q

What is the reaction of blue Fehling’s solution with an aldehyde?

A

-brick red precipitate

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10
Q

what is the reaction of Tollens’ solution with an aldehyde?

A

-colourless/clear–>silver mirror

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11
Q

what is the reaction of acidified dichromate solution when there is an aldehyde present?

A

-orange->green

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12
Q

What causes the oxidation of food?

A

oxygen in the air

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13
Q

What happens when edible oils are oxidised

A

it gives food a rancid flavour

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14
Q

What are antioxidants?

A

-molecules that prevent unwanted oxidation reactions occurring
-substances that are easily oxidised
-oxidise in place of the compounds they have been added to protect
-they can be identified as the substance being oxidised in a redox equation
(preserving flavour in foods)

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15
Q

How do antioxidants work?

A

-they are substances that are easily oxidised, they oxidise in place of the compounds they haven been added to protect

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16
Q

What is the difference between and aldehyde and a ketone?

A

the carbonyl functional group is on an end carbon in an aldehyde and an intermediate carbon in a ketone.

17
Q

What is an isomer?

A

compounds with the same molecular formula but different structural formula

18
Q

What 3 oxidising agents can be used to differentiate between and aldehyde and a ketone?

A
  • acidified potassium dichromate solution
  • Fehling’s solution
  • Tollens’ reagent
19
Q

What can aldehydes be used for?

A

flavour and aroma molecules

20
Q

What is produced when primary alcohols are oxidised?

A

aldehydes

21
Q

What is produced when secondary alcohols are oxidised?

A

ketones

22
Q

What is produced when aldehydes are oxidised?

A

carboxylic acids

23
Q

What are 3 oxidising agents used to distinguish between aldehydes and ketones?

A
  • acidified potassium dichromate solution
  • Fehling’s solution
  • Tollens’ reagent
24
Q

describe the reduction of carboxylic acids

A

carboxylic acid–>aldehyde–>primary alcohol

25
Q

Explain how different cooking methods can alter the flavour and nutritional value of foods?

A
  • polar groups are soluble in water
  • if the vitamin is polar then cooking the food in water will remove the vitamin value from the food
  • non-polar groups do not dissolve in water and therefore by cooking non-polar molecules in water, the molecules do not dissolve
26
Q

What functional groups are polar?

A
  • OH
  • C=O
  • COOH
  • NH2
  • CONH
27
Q

What happens when aldehydes are oxidised in foods?

A

they produce carboxylic acids

-the food becomes spoiled and can have a very acidic taste (due to the carboxylic acids)

28
Q

How do food manufactures prevent oxidation of foods?

A
  • packages in an atmosphere of nitrogen

- addition of antioxidants

29
Q

What are flavour and aroma molecules in food often?

A

aldehydes and ketones

30
Q

What is the volatility of a flavour compound determined by?

A

its structure

Higher Chemistry (17 decks)

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