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Chemistry A - Level > Topic 6E - Alcohols (Organic Chemistry) > Flashcards

Topic 6E - Alcohols (Organic Chemistry) Flashcards

1
Q

What is a primary alcohol?

A

When there is an -OH functional group on a carbon attached only one other carbon

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2
Q

What is a secondary alcohol?

A

When there is an -OH functional group on a carbon which is attached to two other carbons

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3
Q

What is a tertiary alcohol?

A

When there is an -OH functional group on a carbon which is attached to three other carbons

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4
Q

What is the name of the primary, secondary and tertiary alcohol C4H9OH?

A

Primary - Butan-1-ol
Secondary - Butan-2-ol
Tertiary - Methylpropan-1-ol

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5
Q

Why are the boiling temperatures of alcohols higher than their corresponding alkanes?

A

Due to the addition of Hydrogen Bonding

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6
Q

Why is ethanol very water soluble?

A

Due to the ability of ethanol to form hydrogen bonds between the -OH and the water molecule

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7
Q

The solubility of alcohols decreases with…

A

Increasing carbon chain length

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8
Q

Why does solubility decrease with increasing carbon chain length?

A

This is because the large, insoluble hydrocarbon portion of the molecule outweighs the influence of the -OH group

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9
Q

Write the word equation and balanced symbol equation for the combustion of methanol

A

methanol (l) + oxygen (g) -> Carbon dioxide (g) + water (l)

2CH3OH + 3O2 -> 2CO2 + 4H2O

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10
Q

Write the word and symbol equation of the reaction of sodium with ethanol

A

Sodium + Ethanol -> Sodium ethoxide + Hydrogen

Na + CH3CH2OH -> CH3CH2O-Na+ + 1/2H

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11
Q

What is a way to safely dispose a small amount of unwanted sodium?

A

To react the sodium with ethanol

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12
Q

What is the name of reaction where the -OH functional group is swapped for a halogen?

A

A substitution reaction

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13
Q

In the Chlorination of primary and secondary alcohols what is the reagent?

A

PCl5 (Phosphorus Pentachloride)

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14
Q

In the Chlorination of primary and secondary alcohols what are the conditions?

A

No heating is required but the reaction should be done in a fume cupboard as HCl gas is produced which is toxic

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15
Q

Write a word and symbol equation for reaction of the primary alcohol ethanol and PCl5 in Chlorination

A

Ethanol + Phosphorus Pentachloride -> Chloroethane + Phosphorus oxychloride + Hydrogen Chloride

CH3CH2OH + PCl5 -> CH3CH2Cl + POCl3 + HCl

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16
Q

What is the reaction used to test for the presence of the -OH functional group in primary and secondary alcohols?

A

Chlorination

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17
Q

What is the positive result of the present of the -OH functional group, when testing for it with PCl5?

A

Clouds of misty fumes due to the HCl gas, these will turn damp blue litmus paper red

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18
Q

In the Chlorination of tertiary alcohols what is the reagent?

A

Shaken with Concentrated HCl

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19
Q

In the Chlorination of tertiary alcohols what are the conditions?

A

Room Temperature

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20
Q

Write a symbol equation for the reaction of the tertiary alcohol tert-butyl alcohol with HCl in Chlorination

A

(CH3)3COH + HCl -> (CH3)3CCl + H2O

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21
Q

In the Bromination of alcohols, what are the reagents?

A
  • Solid KBr
  • H2SO4 with a 50% concentration
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22
Q

In the Bromination of alcohols what are the conditions?

A

Heat under reflux (2nd step)

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23
Q

What are the 2 different equations for the first step of the Bromination of Alcohols?

A

KBr (s)+ H2SO4 (aq) -> KHSO4 (aq) + HBr (g)

2KBr (s) + H2SO4 (aq) -> K2SO4 (aq) + 2HBr (g)

24
Q

Write the general equation (using ethanol) for the second step of the Bromination of alcohols

A

CH3CH2OH + HBr -> CH3CH2Br + H2O

25
Q

Why is it important to use 50% concentrated sulphuric acid rather than fully concentrated acid?

A

As using a fully concentrated acid would cause all of the Br- ions to be oxidised to Br2 rather than Her which is what is needed

26
Q

Write an equation for the first step in the Iodination of alcohols

A

2P + 3I2 -> 2PI3

27
Q

What are the reactants and conditions in the first step of the Iodination of alcohols?

A

Reactants:
- Damp red phosphorus
- Iodine

Conditions
- Warmed

28
Q

Write an equation for the second step of the Iodination of alcohols using ethanol

A

3CH3CH2OH + PI3 -> 3CH3CH2I +H3PO3 (phosphonic acid)

29
Q

What are the conditions required for the second step of the Iodination reaction with alcohols?

A

Heat under reflux

30
Q

What is the definition of a dehydration reaction?

A

A dehydration reaction is a specific type of elimination reaction where water is removed form a saturated molecule to form an unsaturated molecule

31
Q

What is the definition of an elimination reaction?

A

An elimination reaction is when two atoms or a group of atom are removed from a compound to form two products

32
Q

What is the general equation for the dehydration of an alcohol?

A

Alcohol -> Alkene + water

33
Q

What are the conditions required for the dehydration of an alcohol?

A
  • Heat under reflux
  • Phosphoric acid catalyst (H3PO4)
  • Collect the product via distillation
34
Q

What is the oxidised dichromate (VI) ion?

A

Cr2O7 (2-)

35
Q

What is the reduced dichromate ion?

36
Q

What is the colour change you observe as the dichromate ion is reduced?

A

Orange to Green

37
Q

What are the conditions for the oxidation of primary alcohols?

A
  • Heat under reflux
38
Q

What is the oxidising agent/reagants required from the oxidation of primary alcohols?

A
  • Potassium Dichromate
  • Sulphuric acid
39
Q

Write an equation for the partial oxidation of the primary alcohol propan-1-ol to an aldehyde

A

propan-1-ol -> propanal + water

CH3CH2CH2OH + [O] -> CH£CH2CHO + H2O

40
Q

How would you collect the partially oxidised aldehyde product?

A

Distill off immediately

41
Q

Write the equation of the oxidation of the aldehyde propanal to a carboxylic acid

A

propanal -> propanoic acid

CH3CH2CHO + [O] -> CH3CH2COOH

42
Q

Write the full equation for when button-1-ol is completely oxidised to butanoic acid

A

CH3CH2CH2CH2OH +2[O] -> CH3CH2CH2COOH + H2O

43
Q

What is the oxidising agent/reagants required from the oxidation of secondary alcohols?

A
  • Potassium Dichromate
  • Sulphuric acid
44
Q

What are the conditions for the oxidation of secondary alcohols?

A
  • Heat under reflux
45
Q

Write the equation for the complete oxidation of propan-2-ol?

A

CH3CHOHCH3 + [O] -> CH3COCH3 + H2O

46
Q

How can you show that the oxidation product from secondary alcohols has been oxidised but not to a carboxylic acid?

A

The colour change from orange to green due to the reduction of the dichromate ion shows that the alcohol is being oxidised.

Test for the presence of a Carboxylic Acid functional group - Add Na2CO3 to your product. Bubble the effervescence through limewater and if CO2 is present the limewater should turn cloudy. Therefore a carboxylic acid would be present, or not.

NB - Carboxylic Acid + Metal Carbonate -> Salt + Carbon Dioxide + Water

47
Q

How could you test to se if an organic product is an aldehyde rather than a ketone or carboxylic acid?

A

Aldehydes are only partially oxidised, therefore if you were to heat it under reflux in the presence of H2SO4 and Potassium dichromate there would be a colour change of orange to green.

48
Q

What is a test that you can use to distinguish between an aldehyde and a ketone?

A

Fehlings/Benedicts test

49
Q

Describe how to test for the presence of an aldehyde using the Fehlings/Benedicts test?

A

Add a few drops of the aldehyde to the reagent and then warm gently in a hot water bath for a few minutes

50
Q

What is the positive colour change for a Fehlings/Benedicts test?

A

The blue solution produces a dark red precipitate of copper (I) oxide (aldehydes)

51
Q

What are the three reasons why it is unlikely that your product of any reaction in organic chemistry to be pure?

A
  • You often add excess of one reagent and so there will be unreacted starting material
  • There are often extra reactions during the one that you are doing, particularly inorganic ones
  • Water has been formed during the reaction or your solvent from the reaction
52
Q

Why do you need anti - bumping granules when heating an alcohol?

A

To prevent the formation of large gas bubbles that cause violent boiling by providing a large surface area for bubbles to form on

53
Q

What must you not do when distilling a solution?

A

Let the flask boil dry as otherwise there could be an explosion

54
Q

What are the observations when sodium reacts with alcohols?

A

The reaction is similar to when sodium is reacted with water. However, this reaction is:
- Much less violent
- Not as exothermic
The hydrogen gas is still produced but the sodium does not melt.

55
Q

What is produced when sodium reacts with alcohols?

A

Sodium alkoxide salts and hydrogen are produced. The salts are ionic and this is shown by including the charges of - on the oxygen o the alkoxide ion and the + of the sodium ion.

56
Q

What two organic products can be formed when butan-2-ol is dehydrated?

A

but-1-ene or but-2-ene

57
Q

What is the condition required for the dichromate ion to function as an oxidising agent?

A

The presence of H+ ions, therefore sulphuric acid is used to provide these

Chemistry A - Level (26 decks)

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