CAIE A-Level Chemistry AS 21 Organic Synthesis Questions

Practise functional-group analysis, multi-step route design and identification of reagents, conditions and by-products, checking each transformation against the target structure.

Covered syllabus points

21.1 Organic synthesis

[Maximum number: 1]

31 X is an organic compound containing the elements carbon, hydrogen and oxygen only.
The table shows the observations made from three chemical tests carried out on X .

Table for Question 1 — CAIE A-Level Chemistry AS

What is a possible structure of X ?

Figure for Question 1 — CAIE A-Level Chemistry AS — Option A

Figure for Question 1 — CAIE A-Level Chemistry AS — Option B

Figure for Question 1 — CAIE A-Level Chemistry AS — Option C

Figure for Question 1 — CAIE A-Level Chemistry AS — Option D

[Maximum number: 1]

2-bromopropane is converted to 1,2-dibromopropane in a pathway involving two reactions.

\text { 2-bromopropane } \xrightarrow{\text { reaction } 1} \text { compound } X \xrightarrow{\text { reaction } 2} \text { 1,2-dibromopropane }

What are the reagents and conditions for the two reactions?

reaction 1

reaction 2

heat under reflux with aqueous NaOH

$\mathrm{HBr}(\mathrm{g})$ at room temperature

heat under reflux with aqueous NaOH

$\mathrm{Br}_{2}(\mathrm{l})$ at room temperature

heat under reflux with ethanolic NaOH

$\mathrm{HBr}(\mathrm{g})$ at room temperature

heat under reflux with ethanolic NaOH

$\mathrm{Br}_{2}(\mathrm{l})$ at room temperature

[Maximum number: 1]

Each of the compounds below is treated separately with an excess of $\mathrm{NaBH}_{4}$ .
The product of each reaction is then heated with an excess of concentrated $\mathrm{H}_{2} \mathrm{SO}_{4}$ .
Which compounds give only one final product with the molecular formula $\mathrm{C}_{7} \mathrm{H}_{10}$ ?

1, 2 and 3 are correct

1 and 2 only are correct

2 and 3 only are correct

1 only is correct

[Maximum number: 1]

Crotyl alcohol, $\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{2} \mathrm{OH}$ , is a colourless liquid which is used as a solvent.
Crotyl alcohol will react separately with $\mathrm{Br}_{2}, \mathrm{~K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7} / \mathrm{H}^{+}$ , conc. $\mathrm{KMnO}_{4} / \mathrm{H}^{+}$ and $\mathrm{PCl}_{5}$ under suitable conditions.

Which row is correct?

reactant

conditions

main product

$\mathrm{Br}_{2}$

room temperature

$\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{2} \mathrm{Br}$

$\mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7} / \mathrm{H}^{+}$

heat under reflux

$\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCHO}$

conc. $\mathrm{KMnO}_{4} / \mathrm{H}^{+}$

heat under reflux

$\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCO}_{2} \mathrm{H}$

$\mathrm{PCl}_{5}$

room temperature

$\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCH}_{2} \mathrm{Cl}$

All question bank results loaded

Covered syllabus points

Question 1

Question 2

Question 3

Question 4