Carboxylic acids

0.200 mol of HOOCCH₂CH₂COOH is reacted with 0.300 mol NaOH.

How many water molecules are formed?

A 1.204 × 10²³

B 1.806 × 10²³

C 2.408 × 10²³

D 3.612 × 10²³

This question is about carbonyl compounds.

The three compounds below each contain a ketone and one other functional group.

Pyruvic acid
Methylglyoxal
Acetol

What is a functional group ?

A chemical test is carried out which gives a positive result for all three compounds.

Suggest the reagent and observation of this chemical test.

Reagent........

Observation........

A student is provided with three unlabelled sample tubes, containing either pyruvic acid, methylglyoxal or acetol.

The student carries out three chemical tests on each sample.

Complete the table with the expected observations, including ‘no change’ where appropriate.

Complete the flowchart for the reactions of pyruvic acid.

This question is about carboxylic acids and esters.

Short-chain carboxylic acids, such as methanoic acid, HCOOH, are soluble in water.

Explain, with a labelled diagram, how HCOOH interacts with water when it dissolves.

Ester F has the structure shown below.

What is the systematic name for this ester?

Ester F can be prepared from a carboxylic acid in two steps.

Step 1 The carboxylic acid is converted into an acyl chloride.

Step 2 The acyl chloride is converted into ester F.

Write equations for Step 1 and Step 2.

Show organic compounds as structures.

Step 1

Step 2

The repeat unit of a polyester is shown below.

Draw the structures of monomers required to form this polyester.

The compound below contains an ester and an amide group.

Draw the structures of the organic products formed by the complete alkaline hydrolysis of this compound using NaOH(aq).

Oil of wintergreen is a liquid used in medicine to relieve muscle pain.

Compound H is a component in oil of wintergreen and can be synthesised from compound G, as shown below. The boiling point and density of compound H are stated.

Compound G
Compound H boiling point = 222 °C density = 1.174 g cm⁻³

A student prepares a sample of compound H by the method below.

Step 1 Reflux 8.97 g of compound G for 30 minutes with an excess of methanol in the presence of a small amount of sulfuric acid as a catalyst.

Step 2 Add an excess of aqueous sodium carbonate, Na₂CO₃(aq). Two layers are obtained.

Step 3 Purify the impure compound H that forms from the resulting mixture.

The student follows this method and obtains 5.32 g of pure compound H.

Why does the student use reflux in Step 1 ?

In Step 2, Na₂CO₃(aq) removes the sulfuric acid catalyst and any unreacted compound G from the mixture.

Write equations for this removal.

Removal of sulfuric acid

Removal of unreacted compound G

Compound G

Another student suggests that adding aqueous sodium hydroxide would be more effective in removing the sulfuric acid catalyst than Na₂CO₃(aq).

Comment on whether the student’s suggestion is an improvement for the preparation of compound H.

Calculate the percentage yield of compound H.

Give your answer to three significant figures.

Describe how to purify the impure compound H from the two layers in Step 2.

This question is about aromatic compounds containing the –COOH and –OH functional groups.

Salicylic acid, shown below, is used in the manufacture of some important medicines.

Salicylic acid

Complete the flowchart for reactions of salicylic acid, by adding the organic products in each

PAS, shown below, is an antibiotic used to treat several diseases including tuberculosis (TB).

A student predicts that PAS could polymerise to form a polymer containing both ester and amide linkages.

Draw a section of this polymer.

The section should contain one amide and one ester linkage, which should be displayed.

For the treatment of TB, the maximum daily dosage of PAS that should be prescribed is 300 mg per kg of body mass.

A child weighs 20.0 kg.

Calculate the number of PAS molecules in the maximum daily dosage of PAS for this child.

This question is about compounds that contain the carboxylic acid functional group.

Carboxylic acids react with alkalis, metals and carbonates to form salts.

Write full equations for the following three reactions. Show structures for organic compounds.

• the reaction of propanoic acid with aqueous potassium hydroxide:

• the reaction of aqueous methanoic acid with magnesium:

• the reaction of the –amino acid, aspartic acid (R=CH₂COOH), with an excess of aqueous sodium carbonate, Na₂CO₃:

This part is about polymers derived from carboxylic acid monomers.

Poly(pent-3-enoic acid) is an addition polymer.

Draw the structure of pent-3-enoic acid and two repeat units of this polymer.

Butanedicarboxylic acid and 1,4-dihydroxy-2-methylbenzene react to form a condensation polymer.

Draw one repeat unit of this condensation polymer.

Three repeat units of a condensation polymer are shown below.

Draw the structure of the monomer required to form this polymer.

A polymer is formed from 400 molecules of 2-aminopropanoic acid.

Draw one repeat unit of this polymer.

What is the relative molecular mass, M_r, of the polymer?

Compounds 1, 2 and 3 are heated with NaOH(aq).

Which compound(s) react(s)?

A 1, 2 and 3

B Only 1 and 2

C Only 2 and 3

D Only 1

Which one of the following reacts with ethanoic acid and with phenol?

A Aqueous potassium hydroxide

B Bromine

C Calcium carbonate

D Methanol and an acid catalyst

Alcohols can be used to prepare organic compounds with different functional groups.

HO(CH₂)₄OH can be oxidised to form HOOC(CH₂)₂COOH.

State the reagents and conditions and write an equation for this oxidation.

In the equation, use [O] for the oxidising agent.

Reagents and conditions:........

Equation:

HOOC(CH₂)₂COOH is soluble in water.

Explain, using a labelled diagram, why HOOC(CH₂)₂COOH is soluble in water.

HOOC(CH₂)₂COOH and HO(CH₂)₄OH react together to form polymer E.

Draw one repeat unit of polymer E.

The functional groups should be clearly displayed.

Governments are encouraging the development of biodegradable polymers to reduce dependency on persistent plastic waste derived from fossil fuels.

Polymer E is a biodegradable polymer.

Suggest why polymer E is able to biodegrade.

This question is about aromatic carboxylic acids and their derivatives.

The concentration of ester K in the cosmetic product is 9.13 × 10⁻² g dm⁻³.

Using the results, calculate the concentration, in mol dm⁻³, of ester M in the cosmetic product.

Give your answer to two significant figures.

concentration of ester M =........ mol dm⁻³

0.1 mol of HOOCCH₂COOH are reacted with 0.1 mol of aqueous NaOH.

How many molecules of water are formed?

A 6.02 × 10²²

B 3.01 × 10²²

C 6.02 × 10²³

D 3.01 × 10²³