CAIE A-Level Chemistry AS Organic Structure and Mechanism Conventions Questions

Practise CAIE A-Level Chemistry organic drawing conventions through unambiguous three-dimensional structures, optical isomers and wedge-dash notation.

Exam points

draw optical isomer pairs with wedge-dash bonds and correct three-dimensional arrangement

Covered syllabus points

Reference—Structural, displayed and skeletal formula conventions Reference—Organic reaction mechanism conventions

[Maximum number: 2]

C, D and E are isomers of each other.
They are made by passing an alcohol vapour over an aluminium oxide catalyst.

F is an organic molecule which has the molecular formula $\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}_{2}$ . When F is heated with NaOH(aq) followed by $\mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq})$ the products G and H are made.

\underset{\mathrm{C}_{3} \mathrm{H}_{6} \mathrm{O}_{2}}{\mathbf{F}} \xrightarrow[\text { by } \mathrm{H}_{2} \mathrm{SO}_{4}(\mathrm{aq})]{\mathrm{NaOH}(\mathrm{aq}) \text { followed }}+\mathbf{G}^{\mathbf{F}}+\mathbf{H}_{\mathbf{S}}^{\mathbf{F}}

Separate samples of G and H are added to
- $\mathrm{Na}_{2} \mathrm{CO}_{3}(\mathrm{aq})$
- sodium metal
- alkaline aqueous iodine.

The observations are described in the table.

Table for Question 1 — CAIE A-Level Chemistry AS

Draw the structures of G and H.

Figure for Question 1 — CAIE A-Level Chemistry AS

Correct structures:
$\mathbf{M1}\quad G = \mathrm{HCOOH} / \mathrm{HCO}_2\mathrm{H}$ $\mathbf{M2}\quad H = \mathrm{C}_2\mathrm{H}_5\mathrm{OH}$

G = \mathrm{HCOOH};\quad H = \mathrm{C}_2\mathrm{H}_5\mathrm{OH}

[Maximum number: 3]

$4\left(\mathrm{CH}_{3}\right)_{3} \mathrm{CCHO}$ is used in the synthesis of some antibiotics.

X, Y and Z are all isomers of $\left(\mathrm{CH}_{3}\right)_{3} \mathrm{CCHO}$ .

A summary of some of the reactions and properties of X, Y and Z is shown in the table.

Table for Question 2 — CAIE A-Level Chemistry AS

Draw the skeletal formula of Z.

[Maximum number: 2]

Calcium and its compounds have a large variety of applications.

Calcium ethanedioate is formed when calcium reacts with ethanedioic acid, $\left(\mathrm{CO}_{2} \mathrm{H}\right)_{2}$ . The compound contains one cation and one anion.

Draw the displayed formula of the anion present in calcium ethanedioate.

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Covered syllabus points

Question 1

Question 2

Question 3