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Chemistry Year 12 > Alcohols 3.3.5 > Flashcards

Alcohols 3.3.5 Flashcards

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1
Q

What is the boiling points of alcohols?

A
  • Low volatility
  • High boiling points due to their ability to form hydrogen bonds between alcohol molecules
  • Smaller alcohols can dissolve in water because they can form hydrogen bonds to water molecules
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2
Q

How can we figure out if it’s a primary alcohol?

A

Look at the carbon attached to the -OH
Has one alkyl group (CH3) around the carbon

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3
Q

How can we figure out if it’s a secondary alcohol ?

A

Look at the carbon attached to the -OH
Has 2 alkyl groups around the carbon

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4
Q

How can we figure out if it’s a tertiary alcohol?

A

Look at the carbon attached to the -OH
Has 3 alkyl groups around the carbon

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5
Q

What is the oxidising agent used ?

A

Potassium dichromate

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6
Q

What is the partial oxidation of primary alcohols?

A

primary alcohol => aldehyde

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7
Q

What are the conditions and reagent needed in partial oxidation of primary alcohols?

A

reagent : acidified potassium dichromate solution and dilute sulfuric acid
conditions : Warm gently and distil out the aldehyde

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8
Q

what is the observation when adding oxidising agent

A

orange to green (when oxidised)

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9
Q

what is the functional group of an aldehyde?

A

-HCO
Always has the C=O bond on the first carbon chain

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10
Q

What is the reaction of a full oxidation of primary alcohols?

A

Primary alcohol => carboxylic acid
aldehyde => carboxylic acid

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11
Q

What is the reagent and conditions needed in the full oxidation of primary alcohols?

A

Reagent : acidified Potassium dichromate solution and dilute sulfuric acid
Conditions : Use excess of potassium dichromate and heat under reflux

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12
Q

What is reflux?

A

Reflux is used when heating organic reaction mixture for long periods of time

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13
Q

what do we not do when doing a reflux reaction?

A

•Never seal the end of the condenser as the build up of gas pressure could cause the apparatus to explode .
• Anti-bumping granules are added to prevent vigorous boiling

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14
Q

What is the reaction of the oxidation of secondary alcohols?

A

secondary alcohol => ketone

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15
Q

What is the functional group of a ketone

A

C=O in the middle of a chain
When ketones have 5C’s or more in a chain then it needs a number to show position of the double bond

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16
Q

what is the reagent and conditions needed in the oxidation of secondary alcohols?

A

Reagent : acidified potassium dichromate solution and dilute sulfuric acid
Conditions : Heat under reflux

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17
Q

Why cant tertiary alcohols be oxidised at all?

A

No hydrogen atom bonded to the carbon with the -OH group

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18
Q

What is the reaction , conditions and observation used in Tollens’ Reagent

A

Conditions : heat gently
Reaction : Aldehydes only are oxidised by tollens reagent into a carboxylic acid
Observation : aldehydes = silver mirror
ketones = no visible change

19
Q

What are the conditions , reaction and observations of using Fehling’s solution ?

A

Conditions : heat gently
Reaction : aldehydes only are oxidised by fehlings solution into a carboxylic acid.
Observation : Aldehydes = Red precipitation
Ketones = No visible change

20
Q

what are the two reagents used to distinguish between an aldehyde and a ketone ?

A

Tollens reagent
fehlings solution

21
Q

What is a dehydration reaction ?

A

Removal of a water molecule from a molecule

22
Q

what is the reaction of the reaction of alcohols with dehydrating agents?

A

reaction : alcohol => alkene
type of reaction : Acid catalysed elimination

23
Q

what is the reagent and the condition needed for the elimination reaction of alcohols

A

reagent : Conc. sulfuric or phosphoric acid
conditions : heat and reflux
role of reagent : dehydrating agent / catalyst

24
Q

what are the two ways ethanol can be formed ?

A

Fermentation
Hydration

25
Q

what is the equation for fermentation?

A

Glucose => ethanol +Carbon dioxide
C6H12O6=> 2CH3CH2OH + 2 CO2

26
Q

what are the conditions needed in fermentation ?

A

•Yeast
•No air ( the presence of air can cause extra reactions to occur)
• temperature 30-40 •C
• anaerobic conditions

27
Q

What are some advantages of Fermentation?

A
  • Sugar is renewable source
  • Production uses cheap equipment
28
Q

What are disadvantages of using fermentation?

A

• batch process which is slow and high production costs
• ethanol made is it purr and needs purifying by fractional distillation

29
Q

What is the equation for hydration of ethene?

A

CH2 = CH2 (g) + H2O (g) => CH3CH2OH(g)

30
Q

what is hydration?

A

the addition of water to a molecule

31
Q

what are the conditions needed for hydration?

A

High temperature 300•C
High pressure 70atm
Strong acidic catalyst of concentrated H3PO4

32
Q

What are the advantages of hydration?

A

•Faster reaction
• Purer product
• continuous process (cheaper manpower)

33
Q

What are the disadvantages of hydration?

A

• high technology equipment needed
• ethene is non-renewable resource
• high energy costs for pumping to produce high pressures

34
Q

what does the term carbon neutral refer to?

A

an activity that has no net annual carbon emissions to the atmosphere

35
Q

why is it argued that ethanol is classed as carbon neutral

A

Any CO2 given off when the biofuel is burnt would have been extracted by the air by photosynthesis when the plant grew. There would be no net CO2 emission into the atmosphere

36
Q

What are equations to show no net contribution to CO2

A

Removal of CO2 by photosynthesis:
6CO2 + 6H2O => C6H12O6 + 6O2

Production of CO2 by fermentation and combustion :
C6H12O6 => 2CH3CH2OH + 2CO2
2CH3CH2OH + 6O2 => 4CO2 + 6H2O

37
Q

why do the equations show no net contribution to co2?

A

For every 6 molecules of CO2 absorbed , 6 molecules of CO2 are emitted.

38
Q

what are some mistakes that need to be avoided in a reflux apparatus experiment?

A

• Make sure there is no bung in the condenser or anything blocking it as it could increase gas pressure and lead to explosion
• Make sure flask is clamped
• Water out must be at the top and water in must be at the bottom
• No need for a thermometer

39
Q

What do the antibumping granuals do in the reflux apparatus?

A

• prevents large bubbles

40
Q

what is the technique used to separate a carboxylic acid from a reaction mixture containing a primary alcohol?

A

fractional distillation

41
Q

what’s a test tube reaction to show dehydration has occured

A

add bromine water
orange to colourless

42
Q

why do we use sodium carbonate solution to wash the distillate

A

Na2CO3 would neutralise the phosphoric acid

43
Q

Describe the apparatus used to remove the drying agent by filtration under reduced pressure. Your description could either be drawn or described (2)

A
  • Flat bottomed funnel containing filter paper
  • Büchner flask connected to vacuum pump
44
Q

what happens when a reaction mixture is refluxed

A

xture of liquids is heated to boiling point for a prolonged time.
- vapour is formed which escapes from the liquid mixture , is changed back into liquid and is returned to mixture .

Chemistry Year 12 (19 decks)

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