Carboxylic Acids And Esters

Question 1

What is the functional group for carboxylic acids

Answer 1

-COOH

Question 2

How do you name carboxylic acids?

Answer 2

• Find and name the longest alkane chain, take off the ‘e’ and add ‘-oic acid’.
• The carboxyl group is always at the end of the molecule and it’s more important than other functional groups so number starting from this carbon

Question 3

How many groups contains a carboxyl group contain? and name them

Answer 3

• Two
• Hydroxyl group
• Carbonyl group

Question 4

Draw the displayed formula of 4-hydroxy-2-methylbutanoic acid

Answer 4

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Question 5

Why are carboxylic acids known as weak acids and give the reaction

Answer 5

• in water, they partially dissociate into carboxylate ion and H+ ion
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Question 6

• What products are formed when carboxylic acids react with carbonates ?
• Give the equation reaction of ethanoic acid and sodium carbonate

Answer 6

• Carbon dioxide
• Salt
• water
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Question 7

What happens to carbon dioxide in the reaction between carboxylic acids and carbonates?

Answer 7

Carbon dioxide fizzes

Question 8

What is formed when carboxylic acids react with alcohols and describe this reaction

Answer 8

• Esters are formed
• functional group of -COO- group
• Frequently heating carboxylic acids with an alcohol in the presence of a strong acid catalyst
• Esterification reaction

Question 9

What is the strong acid catalyst used in an esterification reaction

Answer 9

Concentrated sulphuric acid

Question 10

What is another word for an esterification reaction and why?

Answer 10

• Condensation reaction
• Releases water

Question 11

Give an equation reaction of carboxylic acids and alcohols

Answer 11

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Question 12

How is an ester named?

Answer 12

• First bit comes from the alcohol- alkyl group
• Second bit comes from the carboxylic acid- ‘oate’

Question 13

What is the difference between the name of an ester and the displayed formula of an ester

Answer 13

The name is written the opposite way round the formula

Question 14

How is an oate and alkyl group numbered?

Answer 14

• Oate- backwards
• alkyl- forwards

Question 15

Give equations of how ethyl 2-methyl butanoate is formed

Answer 15

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Question 16

Give uses of esters of esters and why they are used in the manner that they are

Answer 16

• Food flavourings
• Perfumes
• Solvents
• Plasticisers
• Esters have a sweet smell

Question 17

Give some properties of esters

Answer 17

• Polar liquids
• Lots of polar organic substances will dissolve in them
• Low boiling points so they evaporate easily from mixtures

Question 18

Give other uses of esters and why they are used the way that they are

Answer 18

• Used in glued and printing inks because they evaporate easily

• Used as plasticisers, added to plastics during polymerisation to make the plastic more flexible. The plasticiser escapes though and the lattice becomes brittle and stiff

Question 19

How do esters form alcohols?

Answer 19

When they are hydrolysed

Question 20

What is hydrolysis?

Answer 20

When a substance is split up by water

Question 21

Why is an acid or alkali used in the hydrolysis of esters?

Answer 21

• It is used to speed up the reaction

Question 22

What are the two types of hydrolysis of esters

Answer 22

• Acid hydrolysis
• Base hydrolysis

Question 23

Describe acid hydrolysis

Answer 23

• Splits the ester into an acid and alcohol
• Reflux the ester with a dilute acid e,g hydrochloride or sulfuric
• It is a reversible reaction so lots of water is added to push equilibrium to the right

Question 24

Draw the diagram formula for the reaction of ethyl ethanoate and H2O under reflux and using an acid and give the products

Answer 24

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Question 25

• Describe the reaction of base hydrolysis • Give a diagram of the reaction of ethyl ethanoate with an hydroxide and what products are formed

Answer 25

• Refluxing the ester with a dilute alkali • E.g Sodium Hydroxide • A carboxylate ion and alcohol is formed • Check physical flashcards for answers

Question 26

What are fats and Oils ester of?

Answer 26

They are esters of Glycerol and fatty acids

Question 27

What are fatty acids? And how do thry form esters?

Answer 27

* Long chain carboxylic acids * They combine with propan-1,2,3-triol (glycerol) to make esters

Question 28

What are the two types of bonds fatty acids can possess?

Answer 28

* Saturated bonds (no double bonds) * Unsaturated bonds (double bonds)

Question 29

• What are most fats and oils made of? • What are the properties of fats in humans • What are the properties of oils?

Answer 29

• Most fatty acids are made from fatty acid chains • Animal fats have mainly saturated hydrocarbon chains which lead to increasing vander waals forces between them which require higher temperatures to melt them • Vegetable oils: have unsaturated hydrocarbons, the double bonds mean the chains are bent and don’t pack together well, decreasing the van der waals forces so they’re easier to melt and are liquids at room temperature

Question 30

What products are formed when Oils and fats are hydrolysed

Answer 30

Glycerol, soap and fatty acids

Question 31

What is a soap?

Answer 31

The salt of a long chain carboxylic acid

Question 32

• Draw the structure of a fat • Draw the structure of glycerol • Give the molecular formula of sodium salt

Answer 32

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Question 33

What is a biodiesel a mixture of? And how are they formed

Answer 33

• Biodiesel is a mixture of methyl esters of fatty acids • oils must be converted to biodiesel first • Reacting them with methanol, using potassium hydroxide as a catalyst

Question 34

Give the reaction of a triester and methanol to form glycerol and a methyl ester

Answer 34

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Question 35

Describe the bonding in the double bond of the carbonyl functional group

Answer 35

- The double bond in the carbonyl group compromises a S- bond and a pie bond. - The pie bond is formed by direct overlap of orbitals between the C atom and O atoms - The pie bond is formed by sideways overlap of p-orbitals on the carbon atom and oxygen atom. However, the carbonyl bond does not react in the same way as the double bond in an alkene because the oxygen atom is more electronegative than the carbon atom. - This creates a dipole in the C=O bond because the bonded electrons are attracted towards the oxygen atom

Question 36

Reaction of fat to form glycerol and salt

Answer 36

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