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Higher Chemistry Unit 2; Natures Chemistry > Alcohols, Aldehydes & Ketones > Flashcards

Alcohols, Aldehydes & Ketones Flashcards

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1
Q

What do alkanols belong to?

A

a larger family called the alcohols

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2
Q

What is the structure of alkanols based on?

A

the alkanes with the distinctive hydroxyl functional groups

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3
Q

What is the common alkanol ethanol made by?

A

fermentation

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4
Q

What is the word equation for fermentation?

A

sugar or starch ——– > ethanol + carbon dioxide

yeast

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5
Q

What is the enzyme found in the yeast?

A

zymase

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6
Q

What is the maximum concentration of ethanol that can be produced by fermentation?

A

12-15%

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7
Q

At higher concentrations of ethanol what happens to the cells in the yeast?

A

they are destroyed

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8
Q

To meet the high market demand, how is ethanol made?

A

by the catalytic hydration of ethene

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9
Q

What is the chemical equation for the catalytic hydration of ethene?

A

C2h4 +H20 —–> C2H5OH

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10
Q

What other kind of reaction is the catalytic hydration of ethene?

A

addition reaction

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11
Q

What can the hydration of some alkenes yield?

A

isometric alkanols

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12
Q

What is the general formula for the alkanols?

A

CnH2n+1OH

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13
Q

What does the type of intermolecular bonding influence?

A

the physical properties of molecular substances e.g. melting / boiling point, viscosity and solubility.

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14
Q

In terms of intermolecular bonding what type of bonds do alcohols have between their molecules?

A

hydrogen bonds

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15
Q

When compared to alkanes (non-polar) of similar mass, what do alcohols have?

A 
a higher melting/boiling point 
higher viscosity 
water soluble (due to strong hydrogen bonds between the molecules)
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16
Q

What is a diol? (give an example)

A

an alcohol that has 2 hydroxyl groups e.g. ethan-1,2-diol

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17
Q

Why can the physical properties of ethan-1,2-diol (GFM 62g) be compared with the alkane butane (GFM 58g)?

A

because it has a similar mass

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18
Q

What is triol? (give an example)

A

an alcohol that has 3 hydroxyl groups e.g. propan-1,2,3-triol

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19
Q

Describe the relationship between the number of hydroxyl groups and the strength of hydrogen bonds?

A

The greater the number of hydroxyl groups the stronger the hydrogen bonds between the molecules

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20
Q

What effect does an alcohol with more hydroxyl groups have?

A

higher melting/boiling points
more viscous it will become
more soluble in water

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21
Q

Describe the combustion of alcohols?

A

burn in oxygen to produce carbon dioxide and water

22
Q

Describe the dehydration of alkanols?

A

Alkanols can be converted to alkenes by dehydration

23
Q

What alcohols be classed as?

A

primary
secondary
tertiary

24
Q

How can you identify a primary alcohol? (give an example)

A

The carbon atom bonded to the hydroxyl group is bonded to one carbon atom e.g. ethanol

25
Q

How can you identify a secondary alcohol? (give an example)

A

The carbon atom bonded to the hydroxyl group is bonded to two carbon atom e.g. butan-2-ol

26
Q

How can you identify a tertiary alcohol? (give an example)

A

The carbon atom bonded to the hydroxyl group is bonded to three carbon atoms e.g. 2-methylpropan-2-ol

27
Q

What is oxidation meant in terms of carbon compounds?

A

there is an increase in the oxygen to hydrogen ratio

28
Q

Give example of oxidation and explain it?

A

CH3CH2OH > CH3CHO
Ethanol > Ethanal
Loss of these hydrogen atoms brings about an increase in the O:H ratio, therefore oxidation has taken place.

29
Q

What is reduction meant in terms of carbon compounds?

A

There is a decrease in the oxygen to hydrogen ratio

30
Q

Give example of reduction and explain it?

A

CH3CHO > CH3CH2OH
Ethanal > Ethanol
Gain of hydrogen atoms brings about a decrease in the O:H ratio, therefore reduction has taken place.

31
Q

How can some alcohols be oxidised ?

A

by using a number of different oxidising agents

32
Q

Give two examples of oxidising agents and the observation on oxidation from them?

A

Acidified potassium dichromate solution = changes from : orange > blue/green
Copper oxide = changes from black> red/brown

33
Q

What are primary alcohols oxidised to?

A

alcohol> aldehyde> carboxylic acid

34
Q

What are aldehydes?

A

carbon compounds that contain a carbonyl group, C=O, at the END of the chain of carbon atoms

35
Q

What is the general formula for aldehydes?

A

CnH2nO

36
Q

What are secondary alcohols oxidised to?

A

alcohols > ketones

37
Q

What are ketones?

A

carbon compounds that contain a carbonyl group, C=O, on a MIDDLE carbon atom

38
Q

What is the general formula for ketones?

A

CnH2nO

39
Q

What are ketones based on?

A

an alkane structure and are referred to as alkanones

40
Q

What are tertiary alcohols oxidised to?

A

They do not oxidise

41
Q

How can unknown samples of aldehydes and ketones be distinguished?

A

They produce different results when mixed with oxidising agents

42
Q

Describe how you can distinguish between unknown samples of aldehydes and ketones?

A

A sample of X and Y are mixed with the mild oxidising agent (acidified potassium dichromate) and placed in a warm water bath. The samples are observed for any signs of a chemical reaction. This procedure is repeated using other oxidising agents. The samples are not heated directly using a Bunsen Bruner because they are flammable

43
Q

What is the colour change for acidified potassium dichromate?

A

orange > blue/green

44
Q

What is the colour change for Benedict’s solution?

A

blue > orange/red

45
Q

What is the colour change for Tollen’s reagent?

A

colourless > silver

46
Q

What happens when food is exposed to the air?

A

many of the chemicals in the food react with oxygen and the food is spoiled.

47
Q

What does oxygen which reacts with food do?

A

reacts with unsaturated edible oils to break them down

48
Q

What does oxidation of food cause?

A

the deterioration of flavour (rancidity)
loss of colour
loss of nutritional value
a health risk from toxic oxidation products

49
Q

What are antioxidants?

A

molecules which will prevent these oxidation reactions taking place

50
Q

What do antioxidants do?

A

Antioxidants are easily oxidised by giving away electrons. They protect other compounds from oxidation as they themselves are more likely to be oxidised in the first instance.

51
Q

Give 3 examples of antioxidants and state if they are natural and synthetic?

A 
Vitamin C = Natural 
Vitamin E = Natural 
Butylated Hydroxyanisole (BHA) = synthetic

Higher Chemistry Unit 2; Natures Chemistry (5 decks)

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