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CHEMISTRY A LEVEL > 3.9 Carboxylic Acids and Derivatives > Flashcards

3.9 Carboxylic Acids and Derivatives Flashcards

1
Q

Draw the displayed formula for propanoic acid.

A

(see page 1 in the chemrevise revision guide)

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2
Q

Draw the displayed formula for ethanedioic acid.

A

(see page 1 in the chemrevise revision guide)

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3
Q

Are carboxylic acids weak or strong acids?

A

Carboxylic acids are only weak acids in water and only slightly dissociate, but they are strong enough to displace carbon dioxide from carbonates.

(see page 1 in the chemrevise revision guide for an equation)

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4
Q

Are carboxylic acids soluble in water?

A

The smaller carboxylic (up to C4) acids dissolve in water in all proportions but after this the solubility rapidly reduces. They dissolve because they can hydrogen bond to the water molecules.

(see page 1 in the chemrevise revision guide for a diagram)

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5
Q

Describe the delocalisation in carboxylic acids.

A

(see page 1 in the chemrevise revision guide)

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6
Q

What does increasing the chain length of a carboxylic acid do to its strength?

A

It pushes electron density on to the COO- ion, making it more negative and less stable. This makes the acid less strong.

Propanoic is less acidic than ethnoic acid.

(see page 1 in the chemrevise revision guide)

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7
Q

Why is chloroethanoic acid more acidic than ethanoic acid?

A

Electronegative chlorine atoms withdraw electron density from the COO- ion, making it less negative and more stable. This makes the acid more strong.

(see page 1 in the chemrevise revision guide)

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8
Q

What 3 things can carboxylic acids form salts with?

A
  • metals
  • alkalis
  • carbonates
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9
Q

acid + metal -> ?

A

acid + metal -> salt + hydrogen

see page 2 in the chemrevise revision guide for an example equation

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10
Q

acid + alkali -> ?

A

acid + alkali -> salt + water

see page 2 in the chemrevise revision guide for an example equation

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11
Q

acid + carbonate -> ?

A

acid + carbonate -> salt + water + CO2

see page 2 in the chemrevise revision guide for an example equation

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12
Q

The effervescence caused by production of CO2 with carboxylic acids with solid Na2CO3 or aqueous NaHCO3 can be used as a ________ for carboxylic acids.

A

The effervescence caused by production of CO2 with carboxylic acids with solid Na2CO3 or aqueous NaHCO3 can be used as a functional group test for carboxylic acids.

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13
Q

Draw the equation for the oxidation of methanoic acid.

A

(see page 2 in the chemrevise revision guide)

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14
Q

When a carboxylic acid reacts with an alcohol in the presence of a strong acid catalyst what does it produce?

A

carboxylic acid + alcohol ester + water

see page 2 in the chemrevise revision guide

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15
Q

Draw the displayed formula for methyl propanoate.

A

(see page 2 in the chemrevise revision guide)

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16
Q

When reacting ethanoic acid and ethanol:

  • Draw the equation
  • What are the conditions
  • What is the usual yield
A

(see page 2 in the chemrevise revision guide)

conditions - heat under reflux, acid catalyst (H2SO4)

yield - low, (50% ish)

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17
Q

What are 3 uses of esters?

A
  • PERFUMES, FLAVOURINGS - esters are sweet smelling compounds. Need to be non toxic, soluble in solvent such as ethanol, volatile (turns into gas), and not react with water.
  • SOLVENTS - for polar organic substances, used as a solvent in glues and printing inks.
    Although polar, they do not form hydrogen bonds (there is no hydrogen bonded to a highly electronegative atom)
    They have a lower boiling point than the hydrogen-bonded carboxylic acids they came from. They are almost insoluble in water.
  • PLASTICISERS - for polymers
    Often pure polymers have limited flexibility because the polymer chains cannot move over each other.
    Incorporating some plasticiser into the polymer allows the chains to move more easily and the polymer can become more flexible.
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18
Q

What are 2 ways esters can be hydrolysed?

A
  • heating with acid

- sodium hydroxide

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19
Q

When an ester is hydrolysed, what two compounds are formed?

A

When an ester is hydrolysed a carboxylic acid and an alcohol are formed.

(it is the reverse reaction of an ester formation)

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20
Q

When an ester is hydrolysed with an acid what are the:

  • reagents
  • conditions
A

reagents - dilute acid (HCl)

conditions - heat under reflux

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21
Q

Write the equation for the hydrolysis of ethyl propanoate with a dilute acid.

Does it give a good yield of the products?

A

(see page 3 in the chemrevise revision guide)

22
Q

Write the equation for the hydrolysis of methyl propanoate with sodium hydroxide.

Why is the reaction not reversible?

A

(see page 3 in the chemrevise revision guide)

23
Q

What 3 things can be made from hydrolysing vegetable oils and animal fats?

A
  • soap
  • glycerol
  • long chain carboxylic acids

(see page 3 in the chemrevise revision guide for an equation)

24
Q

Is glycerol soluble in water?

A

Glycerol forms hydrogen bonds very easily and is readily soluble in water.

25
Q

What 3 things is glycerol used for?

A
  • cosmetics
  • food
  • glues
26
Q

How does soap work?

A

(see page 3 in the chemrevise revision guide for an equation)

27
Q

What is biodiesel?

A

Biodiesel is a mixture of methyl esters of long chain carboxylic acids.

28
Q

How are vegetable oils converted into biodiesel?

Why can it be argued that this method is classified as carbon-neutral?

A

Vegetable oils can be converted into biodiesel by reaction with methanol in the presence of a (strong alkali) catalyst.

(see page 3 in the chemrevise revision guide for an equation)

29
Q

Draw the functional group for an acyl chloride.

A

(see page 3 in the chemrevise revision guide)

30
Q

Which is more reactive:

  • acyl chlorides
  • carboxylic acids
A

Acyl chlorides are much more reactive than carboxylic acids.

31
Q

Draw the displayed formula for ethanoyl chloride.

A

(see page 4 in the chemrevise revision guide)

32
Q

Draw the displayed formula for ethnoic anhydride.

A

(see page 4 in the chemrevise revision guide)

33
Q

Draw the functional group for an acid anhydride.

A

(see page 4 in the chemrevise revision guide)

34
Q

When acyl chlorides react with water, what:

  • Is the functional group change?
  • Is the reagent?
  • Are the conditions?
A

acyl chloride -> carboxylic acid

reagent - water
conditions - room temperature

35
Q

Draw the equation for the reaction of ethanoyl chloride with water.

A

(see page 4 in the chemrevise revision guide)

36
Q

When acid anhydrides react with water, what:

  • Is the functional group change?
  • Is the reagent?
  • Are the conditions?
A

acid anhydride -> carboxylic acid

reagent - water
conditions - room temperature

37
Q

Draw the equation for the reaction of ethanoic anhydride with water.

A

(see page 4 in the chemrevise revision guide)

38
Q

Draw the mechanism for the reaction of ethanoyl chloride with water.

A

(see page 4 in the chemrevise revision guide)

39
Q

When acid anhydrides react with an alcohol, what:

  • Is the functional group change?
  • Is the reagent?
  • Are the conditions?
A

acid anhydride -> ester

reagent - alcohol
conditions - room temperature

40
Q

When acyl chlorides react with an alcohol, what:

  • Is the functional group change?
  • Is the reagent?
  • Are the conditions?
A

acyl chloride -. ester

reagent - alcohol
conditions - room temperature

41
Q

Draw the equation for the reaction of ethanoyl chloride with ethanol.

A

(see page 4 in the chemrevise revision guide)

42
Q

Draw the equation for the reaction of ethanoic anhydride with ethanol.

A

(see page 4 in the chemrevise revision guide)

43
Q

Draw the mechanism for the reaction of ethanoyl chloride with ethanol.

A

(see page 4 in the chemrevise revision guide)

44
Q

When acyl chlorides react with ammonia, what:

  • Is the functional group change?
  • Is the reagent?
  • Are the conditions?
A

acyl chloride -> primary amide

reagent - ammonia
conditions - room temperature

45
Q

When acid anhydrides react with ammonia, what:

  • Is the functional group change?
  • Is the reagent?
  • Are the conditions?
A

acid anhydride -> primary amide

reagent - ammonia
conditions - room temperature

46
Q

Draw the mechanism for the reaction of ethanoyl chloride with ammonia.

A

(see page 5 in the chemrevise revision guide)

47
Q

When acyl chlorides react with primary amines, what:

  • Is the functional group change?
  • Is the reagent?
  • Are the conditions?
A

acyl chloride -> secondary amide

reagent - primary amine
conditions - room temperature

48
Q

When acid anhydrides react with primary amines, what:

  • Is the functional group change?
  • Is the reagent?
  • Are the conditions?
A

acid anhydride -> secondary amide

reagent - primary amine
conditions - room temperature

49
Q

Draw the mechanism for the reaction of ethanoyl chloride with a primary amine.

A

(see page 5 in the chemrevise revision guide)

50
Q

Give the equation for how aspirin is made.

Why is ethanoic anhydride used instead of acid chlorides?

A

(see page 6 in the chemrevise revision guide)

51
Q

Give the 6 steps used in purifying an organic solid though recrystallisation.

Give a reason for 5 on the steps.

Give 3 reasons why there could be a loss in yield.

A

(see page 6 in the chemrevise revision guide)

52
Q

Give one way of testing for the degree of purity of a sample.

Explain this method.

A

(see page 7 in the chemrevise revision guide)

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