PL hkop: Organic functional groups; esterification

Question 1

Name this molecule:

HOOC-CH₂-COOH

Answer 1

Propanedioic acid

Question 2

What is the name of a benzene ring with one carboxyl group attached?

Answer 2

Benzoic acid (also benzenecarboxylic acid)

Question 3

Give the formula for ethyl ethanoate.

Answer 3

CH₃COOC₂H₅

C₂H₅OCOCH₃

Question 4

Name this compound:

COOCH(CH₃)CH₃

Answer 4

Methylethyl methanoate

Question 5

Name this compound:

HOOCCH₂CH₂COOH

Answer 5

Butanedioic acid

Question 6

Name this compound:

Answer 6

Benzene-1,3-dicarboxylic acid

Question 7

Name this compound:

CH₃CH(CH₃)COCH₃

Answer 7

Methylbutanone

Question 8

Write the molecular formula for ethanoic anhydride.

Answer 8

(C_nH_2n+1**CO)₂O

(CH₃CO)₂O

Question 9

Write the formula for hexanedioic acid.

Answer 9

HOOC(CH₂)₄COOH

Question 10

• Write an equation to show how ethanoic acid reacts with calcium carbonate.
• What type of reaction is it?
• Name the organic product

Answer 10

• CaCO₃ + 2CH₃COOH →Ca(CH₃COO)₂ + CO₂ + H₂O
• Acid-base
• Calcium ethanoate

Acid + base → salt + CO₂ + H₂O

Question 11

3 substances - ethanoic acid, phenol + ethanol - are each added to sodium carbonate. One solution fizzes. State and explain which reactant this is.

Answer 11

• Ethanoic acid, since carb acids react to produce gaseous carbon dioxide
• Phenol and ethanol don’t react with carbonates, as they don’t have a high enough [H⁺]

Question 12

How do the following react with metals? What type of reaction occurs in each case?

• Carboxylic acids
• Phenols
• Alcohols

Answer 12

• All react to form salts
• All redox reactions

Question 13

Write an equation to show how ethanoic acid reacts with magnesium.

Answer 13

Mg + 2CH₃COOH → Mg(CH₃COO)₂ + H₂

Question 14

• What is formed when an alcohol reacts with a carboxylic acid?
• Give two names for the reaction which occurs.
• How is it typically catalysed?

Answer 14

• Ester + water
• Condensation, esterification
• Conc. H₂SO₄ / conc. HCl

Question 15

What is a condensation reaction?

Answer 15

One in which two molecules react to form a larger molecule, with the elimination of a smaller molecule, such as water.

Question 16

Draw a mechanism to show how an alcohol reacts with a carboxylic acid. Use this to write a general equation.

Answer 16

ROH + R’COOH ⇌ R’COOR + H₂O

Question 17

What is esterification?

Answer 17

The process by which an ester bond is formed by the condensation reaction, typically of the hydoxyl group in an alcohol and the carboxyl group in a carboxylic acid.

Question 18

How can the equilibrium position of esterification be shifted to the right?

Answer 18

• Adding an excess of alcohol
• Distilling off the water as it forms
• If a sulfuric acid catalyst is used, it absorbs some of the water

Question 19

What is the name of the product when phenol and benzoic acid react?

Answer 19

Phenyl benzoate (an ester)

Question 20

Draw the repeating unit of the polymer formed by the reaction of these monomers:

Answer 20

Question 21

How does esterification compare between alcohols and phenols?

Answer 21

• OH group in phenols is less reactive than in alcohols
• More vigorous reactant, e.g. an acid anhydride, is needed to esterify phenols

OH group in phenols is less reactive since delocalisation in ring acts like an electron vampire, making the O a worse nucleophile

Question 22

• Write the formula for the monomer used to form this polymer: -(-OCH(CH₃)COOCH(CH₃)CO-)-_n.
• What is the name of the monomer?

Answer 22

Condensation polymerisation occured. 2 repeating units have been shown.

• HOCH(CH₃)COOH
• 2-hydroxypropanoic acid

Question 23

Write an equation, using skeletal formulae, to show how propanoic butanoic anhydride is formed.

Answer 23

Correction: + H₂O (as a product)

Question 24

Write the equation for the reaction that occurs when propan-2-ol and propanoic acid are heated under reflux in the presence of sulfuric acid.

Answer 24

C₃H₈O + C₂H₅COOH ⇌ C₂H₅COOCH(CH₃)₂ + H₂O

Question 25

Write the equation for the reaction that occurs when ethane-1,2-diol and ethanoic acid are heated under reflux in the presence of sulfuric acid.

Answer 25

*Because it is a diol, one acid molecule bonds to each side of it.* C₂H₆O₂ + 2CH₃COOH ⇌ CH₃COOCH₂CH₂OCOCH₃ + 2H₂O

Question 26

Draw two repeating units of the polymer formed between HOCH₂CH₂OH and HOOCCH₂COOH.

Answer 26

*Wrong - Os on right side of alcohol are derived from alcohol, not acid*

Question 27

* Write an equation to show the reaction of ethanol with ethanoic anhydride. * Explain why the reaction occurs in this way, making reference to the mechanism.

Answer 27

* C₂H₅OH + CH₃COOCOCH₃ → CH₃COOC₂H₅ + CH₃COOH * Nuclephilic substitution. Oxygen on alcohol acts as a nucleophile and attacks δ+ carbonyl carbon on acid anhydride. Remaining components bond together

Question 28

Polyesters are commonly synthesised using an alcohol and carboxylic acid as reactants. What could the acid be replaced with?

Answer 28

An acid anhydride ## Footnote *This is because it too has a carbonyl group (makes carbon δ+) with stable leaving group attached (prevents reverse reaction)*