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Nature's chemistry Flashcards

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1
Q

What is an Alkanol?

A

A homologous series based on the alkanes with on of the hydrogens replaced by OH (gf CnH2n+2O)

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2
Q

What is a primary alcohol?

A

When one other carbon is attached to the carbon atom to which OH is attached to (Except methanol)

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3
Q

What is a secondary alcohol?

A

When the carbon attached to the OH is also attached to two other carbon atoms

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4
Q

What is a tertiary alcohol?

A

When 3 carbon atoms are bonded to the carbon atom which has the OH attached to it

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5
Q

What is used as the oxidising agent for alcohols? (Give colour change for each)

A

Acidified potassium dichromate - Primary orange to light blue, Secondary orange to dark green, tertiary orange to orange

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6
Q

What does each class of alcohol oxidise into?

A

Primary = Aldehydes to Carboxylic acid
Secondary = Ketones
Tertiary = N/A
(look for increase in O2:H2 for oxidation)

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7
Q

What is oxidation?

A

Loss of an electron, addition of O2 or removal of H2

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8
Q

Name two advantages of Alkali hydrolysis

A
  1. The reaction is one way rather than reversible

2. It is easy to separate the products

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9
Q

What group do fats and oils belong to and how is it formed?

A

Triesters (triglyceride). Formed from the condensation reaction of one glycerol molecule and 3 fatty acid (long chained carboxylic acids) molecules.

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10
Q

When is a triglyceride a fat or oil?

A 
Fat = solid at room temperature (saturated as they can pack closely together)
Oil = liquid at room temperature (unsaturated as they can't pack closely together cos' of kinks)
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11
Q

What is the test for unsaturation?

A

Bromine solution (if unsaturated, bromine changes from brown to colourless)

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12
Q

Definition of surfactants

A

A substance, such as soap, that possesses a hydrophobic tail and hydrophilic head and which, on being made into a solution with water, reduces the surface tension of water and also reduces the interfacial tension between oil and water.

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13
Q

Explain how the addition of soap and other surfactants cleans fabric of grime etc.

A

The hydrophobic tails ‘burrow’ into the droplet of grease
Hydrophilic heads are left to face the surrounding water
This results in the formation of a ball-like structure (a micelle) which is suspended in the water and can be washed away.

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14
Q

What is hard water and how does it affect the cleaning action of soap?

A

Hard water contains calcium and magnesium ions which reduces the cleaning action of soap, leaving a ‘Scum’. It does not form lather with soap but rather a precipitate.

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15
Q

What is a detergent?

A

A compound which has soap-like structure that are used to break up and remove grease and grime. They are soluble in water and do not form precipitate.

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16
Q

What are emulsions?

A

When immiscible liquids like water and oil are mixed together, droplets of suspensions called emulsions are formed. This is unstable and the liquids seperate

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17
Q

What elements do all proteins contain?

A

Carbon, Hydrogen, Oxygen and Nitrogen

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18
Q

What are essential amino acids?

A

Amino acids our bodies cannot produce and therefore must be consumed in our diet.

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19
Q

What are the two classification of proteins and how is this obtained?

A

Fibrous proteins have their molecular chain interwoven to form multi-strand cables. They are soluble in water, fairly stable to changes in pH and temperature, tough and unreactive. Found in tendons, skin, hair, nails, cartilage and bones
Globular proteins operate inside cells and are soluble in water, sensitive to changes in pH and temperature and are generally reactive.

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20
Q

What type of protein are enzymes and how do they function?

A

Globular. Catalyse specific reactions according to the shape of a substrate and reactants. Enzymes can be denatured when heated or pH is changed as pattern of bonding between chains is altered.

21
Q

Which molecules are likely to be volatile when cooked?

A

Those with molecular mass <300 (type of bonding also impacts volatility)

22
Q

Functional group of ketones and aldehydes?

A

Carbonyl (C=O)

23
Q

Name two oxidising agents other than, dilute potassium dichromate, and the change observed when added to ketones and aldehydes

A

Tollen’s reagent - silver mirror precipitate in aldehydes, ketones = N/A
Fehlling’s solution - red precipitate in aldehydes, Ketones = N/A

24
Q

Name 4 effects of oxidation on food

A
  1. Deterioration of flavour
  2. Loss of colour
  3. Loss of nutritional value
  4. A health risk from toxic oxidation products
25
Q

Give definition and example of anti-oxidants

A

Chemicals that are added to food to prevent them from being oxidised. E.g Ascorbic acid (vitamin C)

26
Q

Give an example of an emulsifier

A

Lecithin is found in egg yolk

27
Q

Why are stabilisers used in food?

A

To give products texture and mouthfeel

28
Q

List 4 reasons why the food industry uses emulsifiers and stabilisers

A
  1. Quantities produced are much larger than at home
  2. Need for greater consistency between batches produced
  3. Foods are likely to be transported over long distances and for long periods of time
  4. Some additives allow for the production of food in large quantities which is not possible at home
29
Q

What are essential oils?

A

A mixture of organic compounds. The main organic compounds found in essential oils are Terpenes.

30
Q

What are terpenes?

A

Compounds made up of isoprene units (C5H8)

31
Q

List some uses of essential oils

A

Cleaning, flavours, perfumes, medical, insect repellent etc

32
Q

What are free radicals and name its three steps

A

Result of a breakdown of a diatomic bond which forms two highly reactive atoms, each having an unpaired electron.
Initiation, Propagation & termination

33
Q

What are free radical scavengers?

A

Compounds that combine with free radicals to form stable molecules. They are used in anti-aging cream (most common are vitamin C & E). They are initially esters but once they penetrate the skin, they hydrolyse to produce the vitamins which form stable molecules with the radicals.

34
Q

State the amide/peptide link

A

O=CNH

35
Q

With reference to hydrogen bonding, describe denaturing of enzymes

A

Heating a protein causes some, or all, of the hydrogen bonds to break, leading to a change in shape. This happens to enzymes as well.

36
Q

What is oxidation?

A

loss of an electron, removal of H2 or addition of O2

for oxidation, look for an increase in O2:H2

37
Q

What does the square brackets mean if featured in a reaction equation?

A

[O] = oxidation

38
Q

list 4 uses of esters

A
  1. flavouring agents and scent in food
  2. Organic solvents and thinners
  3. Plasticisers
  4. In perfumes
39
Q

If an ester is hydrolysed by Sodium Hydroxide, what does it form?

A

Fatty acid with COONa functional group (making sodium salt) + alcohol

To change into acid, add excess dilute hydrochloric acid, dilute sulphuric acid or any other strong acid

40
Q

Name three Amino acids and their ‘R’ chain

A

Glycine (-H), Alanine (-CH3) & Cysteine (-CH2-SH)

41
Q

How are enzyme active sites formed?

A

The long chains of amino acids are folded to form these active sites

42
Q

Why are volatile molecules important in food?

A

They contribute to the flavour of the food. This helps us to smell the food and taste it. One property to consider when cooking is the solubility of the flavour molecules

43
Q

What is the colouration of aldehyde oxidation?

A

Blue/green

44
Q

Give the equation of the oxidation of Vitamin C

A

C6H8O6 —-> C6H6O6 + 2H* + 2e’

45
Q

Give an example of an emulsifier

A

Lecithin in egg yolk

46
Q

When Terpenes oxidise…

A

They become Terpenoids

47
Q

Name two essential oils and their uses

A

Geraniol - Added to some cosmetics to balance and revitalise the skin
Citral - found in Melissa oil which is used to combat cold and sores

48
Q

How does UV radiation harm humans?

A

The high energy radiation can damage protein molecules and so enzymes may cease to function or cells may be broken. This can lead to skin cancer

49
Q

Apart from UV radiation and chlorofluorocarbons, name one other compound which catalyses the breakdown of the ozone layer

A

Nitrogen monoxide - formed during thunderstorms or aircraft break down - Although it doesn’t form free radicals

Chemistry (4 decks)

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