Questions I got wrong in F324

Question 1

Write the formula of the salt formed when H₂N(CH₂)₄NH₂reacts with an excess of HCl.

Answer 1

Cl^-H₂N⁺(CH₂)₄N⁺H₂Cl^-

Question 2

Knowing this reaction:

Write the product formed when benzaldehyde reacts with CH₃COCH_3.

Answer 2

Question 3

Benzaldehyde reacts with a solution of potassium hydroxide. In this reaction, benzaldehyde is both oxidised and reduced to form two organic products.

Suggest an equation for this reaction, showing clearly the structures of the two organic products.

Answer 3

Question 4

What does multiplet at 7.3 show about the structure?

Answer 4

Shows 5 aromatic hydrogens. Hence there is a benzene ring in the structure.

Question 5

What is meant by the term isoelectric point?

Answer 5

The pH at which the Zwitterion exists.

Question 6

Different R groups in a-amino acids result in different isoelectric points. Suggest the functional group, in the R group, that results in the iso electric point being lower than pH 3 and higher than pH 10.

Answer 6

A functional group resulting in isoelectric point lower than pH 3 would be COOH.

A functional group resulting in an isoelectric point higher than 10 would be NH_2.

Question 7

I know that if an R group contains an NH2 then it’ll have a higher isoelectric point and that the converse would apply for a COOH group being on the R group but why?

Answer 7

kay, so we know that the isoelectric point is the pH at which the amino acid has no overall charge, so there are NH2 groups and no NH3+ groups, COOH groups and no COO- groups.

If you add basic groups such as NH2 to the R side chain, there’s a greater chance of protonation at any given pH as there are now two proton acceptors in the amino acid. As a result, the pH needs to be higher to prevent any charges arising from protonation, hence the isoelectric point is higher.

If you add acidic groups such as COOH to the R side chain, there’s a greater chance of deprotonation at any given pH as there are now two proton donators in the amino acid. As a result, the pH needs to be lower to prevent any charges arising from deprotonation, hence the isoelectric point is lower.

Question 8

State methods that are used by manufacturers to synthesis pharmaceuticals containing just the required optical isomer.

Answer 8

• using enzymes or bacteria to produce them.
• Using (chemical) chiral synthesis Or using chiral catalysts.
• Using (natural) chiral molecules/bacteria.

(Also allow: Biological catalysts, ‘chiral pool’ , transition metal complex. )

Question 9

Answer 9

Question 10

Answer 10

Question 11

Chlorobenzene can be nitrated to form a mixture of products. Suggest why the reaction forms a mixture of products.

Answer 11

substitution/nitration/NO2 at different positions (on the ring)
OR
forms different isomers
OR
multiple substitution/nitration

Question 12

The student reacted an excess of C2H5NH2 with two different acids.
Write the formulae of the salts that would be formed when an excess of C2H5NH2 reacts

with:

Sulfuric acid.

Answer 12

(C₂H₅NH₃+)₂SO₄²–

Question 13

Some artificial sweeteners commonly available many years ago have now been withdrawn from use.

Suggest why.

Answer 13

(adverse) side effects
OR toxicity
OR irritation

Question 14

Explain what is meant by the term condensation polymerisation.

Answer 14

monomers join/bond/add/react/form polymer/form chain AND another product/small molecule e.g. H2O/HCl